f A q t u r a I S c i e U N I V E.R S I. T Y OF CALIFORN "I PlillIM ■ y lllfiiil LI ilflllr'-' 1 ■' v:'j*i :alifornia agricultural Experiment Station W Extension Service CIRCULAR 554 THIS CIRCULAR DESCRIBES • what Ladino is, and what you should know about certification of seed • what varieties offer what advantages to growers + • how to prepare land and manage crops for maximum yields 4 • basic principles of weed control * • how to recognize major diseases • important insect pests w Harvesting and post-harvesting techniques are discussed and illustrated, and major insect pests are pictured for easier identification. AUGUST, 1970 THE AUTHORS: Vern L. Marble is Extension Agronomist, Davis. Luther G. Jones is Associate in the Experiment Station (Agronomy), Davis John R. Goss is Professor of Agricultural Engineering, Davis. Roy B. Jeter is Farm Advisor, Glen County. Vernon E. Burton is Extension Entomologist, Davis. Dennis H. Hall is Extension Plant Pathologist, Davis. The authors wish to thank M. D. Miller, L. G. Jones, V. P. Osterli, and A. D. Reed, authors of circular 182, Seed Production of Ladino Clover, for valuable assistance in producing this publication. [2] LADINO CLOVER SEED PRODUCTION IN CALIFORNIA INTRODUCTION JLadino (Trifolium repens var. latum), believed to be a naturally developed large form of common white clover, was first brought to the U. S. from northern Italy in about 1891. Since then selections have been made from the original introduc- tions at various locations in the U. S., and several Experiment Stations have pro- duced improved varieties better adapted for local requirements. Today, Ladino is the basic legume in California's irrigated pastures and the state now produces most of the nation's Ladino seed. Ladino is a rapid-growing, long-lived, true clover, spreading by means of creep- ing stems (stolons) which elongate rapidly and take root at the joints if soil is moist. Leaves, stems and flower heads of Ladino generally are from two to four times as large as common white clover, but they are similar in shape, color, and markings of leaves and flower heads. The plants usually have most of their roots in the top 18 to 24 inches of soil, and obtain most of their moisture from the upper 12 inches. However, on deep, open soils La- dino may send roots down as far as 5 feet. Young or thin stands thicken rapidly, and grazed or clipped stands will produce another mature crop in 21 to 28 days. Ladino clover is palatable and adapta- ble, and when grown with grasses and other legumes provides highly produc- tive and nutritive pasturage; although primarily a pasture crop, it can also be used for hay and silage. Ladino is ex- tensively planted in the more humid eastern half of the U. S. and in the west's irrigated areas. It survives the winters of most northern states if properly man- aged in the growing season. Good man- agement includes fertilization, well-timed grazing or mowing, and a compatible grass association. Ladino can be expected to become even more widely used as new varieties of the plant are developed to meet needs of local areas. Fig. 1. Characteristic growth pat- tern of Ladino clover stem. The creeping stems elongate and take root at the joints in moist soil. Note the growing point of hori- zontal stem at extreme right. Blos- soms of increasing maturity are shown to the left of the first flower bud in this photograph. [3] Table 1. Ladino clover seed production in California Year Acres harvested Yield per acre Production (cleaned seed) Price per pound received by farmers pounds pounds dollars 1969 16,000 305 4,880,000 0.70 1968 12,500 295 3,688,000 0.71 1967 12,000 300 3,600,000 0.63 1966 14,500 290 4,205,000 0.48 1965 14,500 340 4,930,000 0.46 1964 16,000 320 5,120,000 0.53 1963 17,000 365 6,205,000 0.49 1962 18,500 305 5,642,000 0.61 1961 19,000 230 4,370,000 0.58 1960 21,000 205 4,305,000 0.60 1959 16,000 260 4,160,000 0.55 1958 13,000 315 4,095,000 0.49 1957 11,000 280 3,080,000 0.28 1956 18,000 310 5,580,000 0.35 1955 15,000 275 4,125,000 0.53 1954 14,000 245 3,430,000 0.52 1953 24,000 245 5,880,000 0.33 1952 46,000 195 8,970,000 0.90 1951 46,000 120 5,520,000 1.20 1950 35,000 120 4,200,000 1.20 1949 14,000 107 1,500,000 1.30 1948 13,000 90 1,200,000 1.60 1947 7,000 80 560,000 1.50 1946 7,000 83 580,000 1.25 1945 10,000 52 520,000 1.40 1944 7,000 60 420,000 1.75 1943 2,000 85 170,000 1.00 1942 2,800 75 210,000 0.85 1941 2,800 100 280,000 0.40 Certification requirements. Nearly all Ladino clover seed grown in Califor- nia is certified by the California Crop Improvement Association, whose office is on the Davis campus of the University of California. Detailed certification stan- dards listing all requirements with which a seed grower must comply are available from your local University of California Farm Advisor's office. Certification of any seed crop is de- signed to maintain genetic purity without mixture with other varieties or crops, and to insure the consumer that seed is of known variety and quality. To produce certified Ladino seed a grower must: • Become familiar with California Cer- tification Standards for Ladino Clover (see your Farm Advisor for standards) . • Plant approved seed stock on eligible land. • File applications required by the cer- tification standards. • Meet all cultural requirements as to weed control, field history, and iso- lation as prescribed in the certifica- tion standards. • Pass field inspection and clean-seed sample inspection. • Have all harvesting equipment in- spected by the Agricultural Commis- sioner's office. <*■ - 4] Where seed is grown. California clover seed production is concentrated in irrigated areas of Glenn, Sacramento, and i Tehama Counties, but counties with a seed-growing history include Butte, Co- lusa, Madera, Mendocino, Placer, San Joaquin, Siskiyou, Stanislaus, Sutter, Yolo, and Yuba. Satisfactory seed crops can be grown in most of the state, but not in areas having temperatures of 100 to 110° F for 5 or more days in a row, as such heat tends to significantly retard seed production. High winds at harvest time (July, August, and September) can severely damage windrowed seed crops. Bad weather or snow at harvest time will \ interfere with harvesting and will lower seed quality. Soil and irrigation requirement. Heavier soils are well-suited for Ladino seed production. Ladino does well on shallow soil underlain by a tight clay layer or a hardpan, even if the restricting layer is within 12 to 18 inches of the sur- face. Tight soils, and soils having rela- tively impervious hardpan or tight clay layers, tend to keep irrigation water in the plants root zone. Saline soils are un- favorable for Ladino. On deep, open, fri- able, fertile soils seed production is seldom successful because of difficulty in irriga- tion management — over-irrigation fre- quently occurs, causing excessive vegeta- tive growth that lodges and promotes germination of seeds in the head. Irrigation requirements depend on soil type, soil depth, and prevailing tempera- ture. Gravelly or sandy soils require an irrigation schedule of 5 to 10 days, and heavy clay or deep loam soils require a 7 to 17 day schedule for good seed produc- tion. Water percolation losses on well- drained soils results in a demand for two to three times more water than is needed on heavier soils. LADINO CLOVER VARIETIES Until recent years, commercial Ladino clover seed was sold as certified or com- mon Ladino clover because improved varieties had not been developed. Today, several new varieties have come into pro- > duction and have been tested at the Ex- periment Station and in county trials. Ladino. This is the basic pasture leg- ' ume in most humid or irrigated areas of the U. S. — 85 to 90 per cent of the La- dino clover seed grown in California is of 1 this variety. It comes from original Lan- dino introduced from Italy and grown in selected foundation seed fields in Califor- nia and Oregon. Leaves are trifoliate, and normal petiole length is 9 inches or more; the plant is hairless, and seeds vary in color from brown to yellow. Espanso. Espanso (formerly called Granladino) was selected from the most 4 desirable plants from a natural giant-type found at Lodi, Italy. The selected plants were grown under severe drought condi- tions and only surviving plants were com- bined to produce the variety. In the U. S., it appears to be inferior to existing com- mercial varieties in seed production but similar in forage yield. Espanso's distinc- tive characteristics are vigorous spring and fall growth, persistence in the sum- mer, and noticeably longer petioles and larger leaves. Planting stock produced under OECD (Organization for Eco- nomic Cooperation and Development) regulations is supplied from Italy. Merit. This 30-clone synthetic variety was developed and released by Iowa State University in 1961 from selections made from California and Oregon certi- fied seed. Merit looks like Ladino but is more uniform for the true type (charac- terized by large leaves and long peti- oles) ; it has shown superior yield, good winter survival, and summer drought tolerance in the states of Iowa, Illinois, Wisconsin, and Minnesota. [5] Regal. This was developed by the Alabama Agricultural Experiment station and released in 1962 to a private com- pany for exclusive production. It is a syn- thetic of five clones selected for stand persistence and yield under conditions found in the southeastern U. S., where it is more persistent and consequently more productive than any commercially avail- able Ladino or white clover. Pilgrim. Pilgrim, which was released in 1953, is a synthetic variety of 21 clones originating from seed collected from older Ladino pastures in the northeastern states and Canada. The principal objectives in the development of Pilgrim were to purify seed stock of the large type, and to establish a continuing source of breeder seed of the same genetic composition. Breeder seed is produced and maintained by the Washington Agricultural Experi- ment Station. Tillman. This is a six-clone synthetic variety developed by the South Carolina Agricultural Experiment Station and the U.S.D.A. Parent plants were selected for profuse branching of stolons, sparse flowering, persistence of stands, general disease resistance, and improved forage production in South Carolina. Released in 1969, the probable areas of adaptation are the areas in the southern states adapted to Ladino. It is superior to other Ladino varieties in persistence of stand and forage production in South Carolina. PREPARING LAND Land should be prepared so as to provide for the most economic and uniform appli- cation of irrigation water and to facilitate cultural and harvesting operations. The contour check system of irrigation is suc- cessful for irrigated pastures when prop- erly modified, but is rarely used in La- dino seed production (except where each contour check can be immediately and completely drained following irrigation to avoid seed damage from germination and drowning of plants). Sprinkler ir- rigation may be used where land leveling is not practical. Clover seed fields require frequent irrigation, and so it is important that land be properly prepared to mini- mize labor costs. (Additional informa- tion on preparing land for irrigation can be found in University of California cir- cular 408, The Border Method of Irriga- tion.) Strip-check irrigation The most widely used and probably the best method of land preparation for pro- ducing Ladino seed is the strip-check system, although more land leveling is required for this than for any other type of flood irrigation. Strip checks require grade only in the direction in which water flows down the check, and this grade may or may not be uniform. Grades of 0.2 to 0.5 foot per 100 feet are desirable for covering the ground quickly. Steeper slopes are used where soil resists erosion, and where it would be inadvisable to level the field uniformly because of cost, soil structure, and soil depth. The first step in preparing land is earth moving. This should be based upon a contour map of the field showing the direction and percentage of slope and the location of cuts and fills indicating the amount of grading, hauling, and filling required to level the field. After land is leveled, it should be plowed or disced and smoothed with a float or land plane be- fore border levees are built. It is best to plane diagonally across the field first, and then lengthwise down the field. After levee building, the field is irrigated to settle the fills, and then it is important to harrow or disc and plane the checks to obtain a uniformly smooth field surface. [6] Road graders, or special custom-built attachments for tractors which build the borders and level the ground between them in one operation, are used in some areas for levee building. Disc ridgers, crowders, or alfalfa checkers are also used, but with these it is necessary to work strip checks a second time to cross- level the land between borders. The size and shape of levees is impor- tant: they should have a base width of about 4 feet and a settled height of about 6 inches. Such levees will be covered with clover plants so that the entire field will be productive and harvesting equipment can easily move across them. When levees are first constructed they are composed of loose earth and are irregular in shape. Before being seeded they should be com- pacted and smoothed with a ring roller. Width, length, and grade of checks will depend upon shape of the field, topog- raphy, amount of water available, and type of soil. Checks are usually directed so that water moves down the steepest natural slope; this reduces the amount of cross- leveling needed, but if the field has a water-penetration problem the practice may not be desirable. Water penetration is generally increased when the slope is reduced; this can be accomplished by further land leveling or by altering direc- tion of the checks. If the land has con- siderable side fall, strips should be made narrow. The difference in elevation be- tween any two adjacent checks should not be over 2% inches. Length of strips depends on the shape of the field and the rate at which water penetrates soil. In sandy soil, much water may be wasted by deep percolation at the upper ends of the strips if they are too long. This can sometimes be partly cor- rected by increasing the amount of water turned into each check. Table 2 gives recommended lengths for checks of different widths and for various rates of flow on clay and clay loam soils. If slopes are steep, strips longer than 800 feet should be limited in width to 15 feet or less. For porous loams and sandy loams, delivery rates for the sizes of checks given in the table should be in- creased from two to five times — or shorter checks should be used. This permits water to cover ground quickly without much water being applied at any one irriga- tion (water velocity should be kept low enough to prevent erosion). The first 8 to 12 feet of the checks may be left per- fectly level so that water will be uniformly Table 2. Proper sizes of strip-checks for clay loam and clay soils Flow delivered Length of check to each strip for various widths of strip Cubic feet Gallons 10-feet 15-feet 20-feet 25-feet per second per minute wide wide wide wide Feet 0.2 90 440 0.3 135 660 440 . . . 0.4 180 880 660 440 . 0.5 225 880 660 440 440 0.6 270 1,320 880 660 440 0.7 315 1,320 880 660 440 0.8 360 1,320 880 660 0.9 405 1,320 880 660 1.0 450 1,320 880 1.2 540 . . . . . . 1,320 880 1.5 657 ... 1,320 [7] distributed between levees before it moves down the checks. To insure uni- form coverage over full width of checks, land between borders must be carefully cross-leveled. The unit head (rate of de- livery of water into each check) may vary from 0.2 to 1.0 cubic foot per second (90 to 450 gallons per minute) ; this head can be regulated by changing the number of checks irrigated at one time. The lower end of the checks should be left open to drain off excess water. Pond- ing at the lower end of the runs rapidly drowns the clover and causes growth of such weeds as dock, plantain, sedges and water grass. Adequate drainage should be provided for collecting and removing sur- plus water from the low end of the field. Surplus water may be used for irrigating other fields. Strip-check irrigation is not recommended for seed production on sandy soils, steep slopes, or where only small flows of water are available; if seed is grown under these conditions, sprinkler irrigation is advisable. Fig. 2. Immediately below: good leveling, even distribution of water with surplus running to drainage ditch. Fig. 3. Bottom of page: improper leveling of land causes drowning of plants. ^maammi Sprinkler irrigation Preparation for sprinkler irrigation is similar to that for strip-check irrigation except that levees are not constructed. Sprinklers are used in sandy soil or on steep slopes, or on unleveled land, and where only a small flow of water is avail- able. The sprinkler system must be de- signed to fit the existing water flow and land conditions. Where feasible, the strip- check system is preferred. Seedbed preparation The same fine, firm seedbed used in planting irrigated pastures is recom- mended. Such a seedbed has a firm, moist zone covered by 2 to 3 inches of moist well-worked soil free from big clods and large air pockets. The surface soil should be firmed by cultipacking before seeding — a loose, cloddy seedbed filled with air pockets may result in a patchy, thin stand. A preliminary irri- gation before planting settles fills and re- veals low areas and other irregularities that can be corrected before seeding; it also firms the soil and provides an even moisture supply for germinating seed. If it has rained just before seeding, pre- liminary irrigation can be omitted. After irrigation or rain the field should be planed if irregular settling has occurred. A final harrowing should be given just before seeding. A broadcast application of 25 to 30 pounds per acre of nitrogen and 13 to 17 pounds of phosphorus per acre (that is, 30 to 40 pounds per acre of P 2 5 ) just before final harrowing is recommended for establishing a stand. On many Cali- fornia soils where clover is grown for seed, Ladino responds to applications of phospohrus. The amount needed for max- imum yields may vary considerably with area and soil type; when needed, it is estimated that a normal crop of Ladino seed of 300 to 500 pounds will use about 26 pounds of phosphorus (60 pounds of P 2 5 , or 300 pounds of single superphos- phate) as fertilizer. The complete fertil- izer requirement for the first year should be applied before seeding. It is important to use a material containing sulfur, as this is often deficient in soils suited for clover seed production. MANAGEMENT OF NEW SEEDINGS Time to plant. Depending upon local conditions and the current weather pat- terns, seeding should be done between September 15 and November 15. Plant- ing in the early fall insures larger and more productive Ladino plants in the first crop year, with seed yields approach- ing normal for established fields in the area. Spring seedings are preferable if fields are foul with winter-growing weeds. Satisfactory yields may be attained from seedings made from February 15 to March 20. Seed yield gradually decreases to uneconomic levels from seedings made after March 20, through April 30. In areas of severe winter frosts, planting should be completed early enough in fall to insure seedling establishment before the first hard freeze is likely to occur. Inoculating seed. Before being sown on newly-leveled fields, Ladino clover should be inoculated with nitrogen-fixing bacteria. Companion crops. The use of a companion or nurse crop is not recom- mended when planting a Ladino clover seed field unless the soil is blowsoil, peat, or very sandy. Planting stock required. Only reg- istered or foundation seed (available from local seedsmen) may be used to grow certified seed. Fields seeded with common Ladino are not eligible for cer- [9] tification; on such fields, 2 years of pro- ducing other crops is required to insure destruction of all white clover. Seeding rates, equipment, and methods. The recommended seeding rate is 3 to 4 pounds per acre by airplane or ground equipment; airplanes are gen- erally used to seed fields bigger than 15 acres and are especially useful in seeding fields having wet seedbeds. One pound of seed is equivalent to about 17 plants per square foot, and 10 to 15 seedlings per square foot is considered an accept- able seedling stand — very thick stands delay the onset of spring bloom as much as 10 to 20 days. Early fall planting (September 15 to October 15) usually requires light irrigations every 4 to 10 days until fall rains eliminate this need. When a dry field is seeded subsequent fall and winter rains dissolve the clods covering the seed, but best results are usually obtained if the dry field is culti- packed after seeding. Harrowing gives less satisfactory results if it barely cov- ers the seeds. Discing should never be employed, as seeds will be buried too deeply. Ground-seeding equipment in- cludes: tractor- or trailer-mounted broad- case seeders, grain drills with special grass-seeding attachments, alfalfa drills, and hand-operated cyclone seeders. These can be used satisfactorily, if properly adjusted. Seed-covering precautions rec- ommended in airplane seeding apply equally to these methods of seeding. Care of new stands. Surface soil should not be allowed to dry out during the germination period — such drying ac- counts for more unsatisfactory stands than any other single factor. Early fall and late spring seedings require frequent and light irrigations timed to keep sur- face soil moist; this prevents crusting and enables germinating plants to emerge. Fall seeding is best, as rains may be ex- pected to help the germination process. Regardless of date of planting, however, surface soil should never be permitted to dry out for more than a day or two until a satisfactory stand is attained and the plants have at least four or five true leaves. In general, Ladino is slow in get- ting established. New stands intended for seed produc- tion should not be grazed during their first year because grazing then frequently results in reduced first-year seed yields. If weeds become a problem at this time, forage should be shredded or chopped with a flail machine; mowing or rotary- shredding are not recommended as they tend to concentrate or windrow the de- bris. Selective herbicides are available for control of most weed problems. Weed control in seedling Ladino. If weeds are numerous in new stands they may thin out the clover because of weed competition and contamination of clover seed with weed seed. Where annual weeds such as ryegrass, burclover, ca- narygrass, knotweed, and oxtongue thistle are so prevalent that they prevent estab- lishment of a satisfactory stand of clover, spring sowing of clover is recommended. Weeds germinate and emerge during the winter when moisture is available, but they can be destroyed during spring seedbed preparations, thus minimizing the competition for the ensuing clover crop. Weed prevention is the first step in weed control in new seed fields, and can be accomplished by selecting only clean fields or by practicing rotational pro- grams that will insure weed-free land. Weed control around irrigation outlets, fences, and on adjacent land is especially important. Effective herbicides for new stands are available. Weed control recommendations are published each year by the University — see your local University of California Farm Advisor for these. [10 Fig. 4. Above: Russian knapweed. Fig. 5. Left: Yellow star thistle seedling. Fig. 6. Below: Yellow star thistle. Fig. 7 (top left). Ladino clover infested with Fig. 8 (top right). Buckhorn (narrowleaf plan- dodder, tain) seedling. Fig. 9. Buckhorn (narrowleaf plantain). Fig. 10. Oxtongue thistle seedling. [12] Fig. 11 (above). Oxtongue thistle. Fig. 12 (top right). Curly dock. Fig. 13. Young curley dock. CARE OF ESTABLISHED STANDS Grazing or shredding established stands. Grazing or shredding early lush spring growth in established stands helps to control weeds and promotes a rapid, even, abundant flowering growth and a more uniform set of seed. Grazing should begin about May 5 and be completed by May 15, and a 3- to 4-inch stubble should be left. If a field has been grazed heavily as a substitute for clipping, it also must be clipped to increase uniformity of flower formation. Fields pastured in the winter and early spring should be allowed to regrow at least one month after grazing before clipping in early May. Spring cleanup in preparation for a seed crop is best accomplished by graz- ing and clipping, shredding, or removal of green forage by chopping and ensiling. Grazing wet stands results in a rough field surface which causes greater than normal seed losses at harvest time (live- stock should not be pastured in wet Ladino seed fields) . Because Ladino is slow to dry, making hay is not compatible with seed produc- tion; haying may reduce seed yields by delaying irrigation; this will cause stunt- ing of the clover and will increase grassy weed establishment. [13] Fig. 14. Harvesting wilted forage in windrow n during spring cleanup. Htlk \J ',*>* '* }\ rri > : ife Fig. 16. Spring cleanup with self-unloading van for hauling forage or green feed. Weed control in established stands. Preventive weed control should be continued through the life of the stand. Weeds should not be allowed to seed on irrigation borders, ditches, fence rows, service areas, etc. Rogueing should be continued every year to prevent the invasion of new or noxious weeds such as dodder, dock, buckhorn, johnsongrass, etc. Herbicides for controlling weeds must be coordinated with a program of grazing, shredding, rogueing, crop rota- tion, and proper irrigation. In established Ladino seed fields some of the troublesome broadleaf weeds are: dodder, buckhorn (narrowleaf plantain) , white top (hoary cress), oxtongue thistle, yellow star thistle, and dog fennel. Trou- blesome grassy weeds included: water- grass, ryegrass, sedge, johnsongrass, Fig. 15. Spring cleanup: self-propelled swather (top) and custom-made chopper (bottom). dallisgrass, perennial pigeongrass (knot- root bristlegrass), and lovegrass. No seed field containing any primary noxious weeds such as hoary cress, camel- thorn or Russian knapweed is eligible for certification. Any infestation should be treated and regularly checked to prevent regrowth of noxious plants — a list of such weeds is available at your Farm Ad- visor's office. All equipment used to apply herbicides should be checked for proper functioning and accurate calibration. Fertilizers. Field strip tests, soil tests, and plant tissue analysis will help to de- termine fertilizer requirements, but full- scale application should be made only after field tests show the type of response to fertilizers. See your Farm Advisor [14] fpfe«#* J> Fig. 17. This shows results of proper weed control around irrigation outlets and roadway. about procedures for making and inter- preting such tests. Nitrogen should never be required on established stands of well-inoculated clover, but seedlings may be benefited by an application of 25 to 30 pounds per acre applied just before seeding. Such an ap- plication is best made as a mixed fer- tilizer containing 13 to 17 pounds per acre of phosphorus (30 to 40 pounds per acre of P 2 5 ) in addition to the nitrogen. Many soils adapted for Ladino clover culture are deficient in phosphorus, and a soil analysis may help determine if a soil would be more productive with added phosphorus. Soils containing less than 10 to 15 ppm of phosphorus (sodium bicar- bonate extraction method) should receive 26 to 43.5 pounds per acre of phosphorus (60 to 100 pounds per acre of P 2 5 ) disced into the seedbed before planting, and annual topdressings of 26 pounds per acre of phosphorus (60 pounds per acre of Po0 5 ). Because Ladino clover is shallow rooted, available phosphorus and sulphur may be rapidly depleted in the active root zone. Decreased availability of these nutrients in unfertilized clover seed fields may account for diminishing seed yields in the second or third season. Sul- phur can often be supplied as a fertilizer component of a phosphorus fertilizer. Soil in most California seed-growing areas has enough available potassium to grow a Ladino clover seed crop, and po- tassium or so-called complete fertilizers are rarely used on established seed fields. Potassium deficiency can be easily iden- tified by the appearance of small white- yellow spots, usually near the margins of the leaflets; the edges later turn yellow and in severe deficiency may turn brown. Irrigation. Plants should be watched closely for clues as to proper timing of irrigations: when leaves begin to cup to- [15 Fig. 18. Ladino clover leaves showing typical potassium deficiency. gether, it is time to irrigate. This may occur in only a few spots (the sandy or hard spots at first) but if these areas con- stitute an important proportion of the field they should be used as guides. Apart from this, plant symptoms in the whole field should be the guide. Do not with- hold irrigation until the entire field is wilting. Irrigation water will usually have to be applied every 7 to 12 days in late spring and summer. On sandy or gravelly soil it may have to be applied every 5 to 10 days; on heavy soils of high mois- ture-holding capacity, the interval may be 7 to 17 days. In most seed-producing areas of California, Ladino requires from 3 to 5 acre-feet of water per acre annu- ally; in interior valleys on open, perme- able soils as much as 6 to 9 acre-feet may be required annually. Each irrigation should be sufficient to replenish soil moisture to root depth. A soil tube is excellent for determining the depth at which moisture ends, but grow- ers should also know the depth of soil and the zone of root distribution. From Fig. 19. Soil tube for checking field moisture. 1 to 3 acre-inches of water per irrigation will usually be sufficient to replenish moisture, as larger applications will be wasteful and possibly harmful. Good drainage is essential for high seed-pro- duction of Ladino clover. Ponding of water at lower ends of fields in hot weather results in drowning large areas. Tail-water return systems are an eco- nomic way of conserving water and are recommended. Ladino clover seed fields must be kept growing slowly through the production period. Too much water produces lush growth which will lodge; this exposes mature seedheads to moisture, and causes seeds to germinate in the head. Upright clover can be irrigated after seedheads have matured without damage, but lodged stands irrigated after 60 per cent to 70 per cent of the heads are mature produce lower yields. Seed fields that are to continue produc- tion the following year must be irrigated immediately after harvest because stand reduction will occur after 30 to 40 days without water (reduction increases after harvesting because stolons are exposed to the hot sun). The first irrigation should be in late afternoon or at night to avoid serious injury to stolons. [16] „ .y. Fig. 20. Typical placement of beehives for Ladino production. Note the row of beehives in background of photograph. POLLINATION Ladino clover flowers are highly self- incompatible and therefore must be cross pollinated to produce seed. Wind is not an effective pollinating agent. Bumble- bees and other wild bees, though helpful, are usually so few and so sporadically distributed that they cannot be relied upon for effective pollination. Honeybees are effective pollinators, and most seed growers now use a mini- mum of one "strong" honeybee hive per acre; a few use 3 or 4 such hives per acre. (A strong hive has brood in not less than seven combs, and bees enough to cover no less than 15 frames in a 2- story hive.) Results of recent tests strongly indicate that 1 to 1% strong hives per acre are sufficient for complete pollination. Pollination service. Because honey- bees are important in seed production, it pays seed growers to time applications of insecticides so as not to injure them. If harmful insecticides are to be used, there should first be an understanding between the seed growers, applicators, and beekeepers involved so that the bees can be protected or removed from the field. Various financial arrangements for the special use of bees as pollinators can be made between seed growers and bee- keepers. Usually, the more hives supplied per acre the higher the charge per hive. Seedsmen, beekeepers, Farm Advisors, and Agricultural Commissioners are usually informed on current financial ar- rangements for honeybee pollinating service. Any agreement between seed pro- ducers and beekeepers should be on the basis of strong hives. Bees should be moved into seed fields as soon as blossoming starts, usually within 10 to 14 days after spring grazing or clipping is completed. In most Cali- fornia seed fields, bees are moved in about May 15 to 25 and are kept through the blooming period, which may be as late as September. Beehives should be well distributed around and through the fields; they must be placed where they will remain dry during irrigation, and where beekeepers can easily reach them for maintenance. [17] IMPORTANT INSECT PESTS Recommendations for chemical control of insect pests are subject to frequent change, so growers should consult the current pest control program available at their Farm Advisor's office. Because many pesticides are highly toxic to honey bees and beneficial insects, the farmer, the beekeeper, and the pest control operator must cooperate closely in order to minimize losses from chemicals. Whenever possible use material that is least toxic. When bees are present, the safest time and method of application of pesticides is at night with a ground ap- plicator. Avoid drift of pesticides onto bee colonies or nearby crops and weeds in bloom. Do not contaminate water avail- able to bees for consumption. Important insect pests affecting Ladino clover seed production are discussed below. Your County Farm Advisor and seed company representative will help you identify these insects. Lygus bugs. The lygus bugs, Lygus hesperus Knight and L. elisus Van Duzee, are sucking insects which feed on buds, flowers, and developing seeds, with re- sultant bud blast, flower drop, and shriv- eled seed. These bugs are usually the most serious pests of Ladino because they may be present throughout the entire time of seed set. Lygus adults are approximately % inch long, and are greenish to yellowish- brown with a raised light-colored V on the back. Young lygus bugs (nymphs) are greenish-gray with prominent black spots on the back in the later stages of development. Immature lygus bugs may be confused with aphids, but are readily distinguished from them by their red antennae and rapid movements. Lygus bug treatments in Ladino clover fields are based on 2-sweep counts taken in 10 to 20 places throughout a field. Three or more 2-sweep counts are made in each place, and are taken with the standard sweep net having an opening 15 inches in diameter and a handle 26 inches long — each sweep is an arc of 180°. One step should be taken between each sweep so that each arc covers a se- ries of plants undisturbed by the previous sweep. The borders of the field, and areas of heavy, lush growth, may have a sig- nificantly higher count than the re- mainder of the field, but all counts in a field are usually averaged and treat- ments are based on this. It is rarely prac- tical to treat only portions of the field. \ """"* [18] Spider mites. Spider mites com- monly found on Ladino clover include the Atlantic mite, Tetranychus turkestani Vgarov and Nikolski; the Pacific mite, T. pacificus McGregor; the two-spotted spider mite, T. urticae (Kock) ; and the clover mite, Bryobia praetiosa Koch. These species occur singly or in combi- nations, and their relative numbers and over-all abundance varies from field to "* field and from season to season. The clover mite does not normally cause economic damage in Ladino clover ** fields, but Tetranychus mites cause seri- ous damage when abundant. Generally, infestations are not of any consequence on first-year stands, but damaging in- festations are common in older stands, particularly in fields lacking enough water. Margins of fields subject to heavy dust accumulation on the plants are most susceptible to outbreak populations. In- fested leaves become cupped, yellowish, and spotted. Heavily-infested fields rap- idly take on a dried-out, reddish-brown appearance. Spider mite treatments are usually ad- visable early in the season when 10 per cent of the leaves on the irrigation levees show mite injury. In June and early July, the stand should be treated when 25 per cent of the leaves on irrigation levees show spider mite injury. Rapid devel- oping late-season infestations may dam- age a maturing heavy bloom, but control treatments 20 days or less before harvest are rarely profitable. If stands are se- verely attacked late in the season, it is best to start harvesting when the seed is mature. Regular and adequate irriga- tions tend to reduce the mite problem. Ground sprayers are the most effective means of applying miticides to Ladino Fig. 21. Adult lygus bug (top) and lygus bug nymph (bottom). The adult has a light-colored "V" area on its back; the nymph is characterized by reddish an- tennae, dark spots on the back, and rapid movements. ►Nymphs are often mistaken for pea aphids. clover; aircraft applications are less ef- fective because of inability to obtain coverage under the leaves. Ground-rig applications should be made at rates of 50 to 60 gallons of spray per acre (at 200 to 300 pounds per square inch pressure) to insure proper coverage. Aphids. Aphids are usually minor problems in Ladino clover seed produc- tion. The pea aphid, Acyrthosiphon pisum (Harris), is a large, green aphid most abundant in spring before seed pro- duction begins; in recent years, however, populations have continued throughout summer. When abundant it causes the stems to wilt and flower heads to shrivel. The clover aphid, Aphis bakeri (Cowen) , is a dirty yellow-green color and is much smaller than the pea aphid; it is found in flower heads and on the stem beneath the stipules. This aphid prefers red clover and alsike clover but occasionally attacks Ladino clover. Pea aphids produce little honeydew, but clover aphids produce large amounts. Natural control by predators and para- sites of both of these aphids is common particularly from early spring through June. The factors causing such control should be carefully evaluated before aphid control measures are undertaken. Several predators (the most common being lady beetle and syrphid fly larvae) are active against aphid populations. A small wasp parasite, Aphidiws smithi, frequently becomes an important control agent during late May and early June — large golden brown aphid mummies on the upper surface of the leaves indicate the presence of this beneficial insect. Under proper conditions a fungus dis- ease (indicated by the presence of moldy pads on the plants) may decimate an aphid population. The clover aphid should not be con- fused with the spotted alfalfa aphid, Therioaphis maculata (Buckton), which is a major pest of alfalfa but does not at- tack Ladino clover, red clover, or trefoil. [19 ' ' > Fig. 22. Leaves (top two rows) and heads (third row from top) damaged by spider mites; the bottom row of heads shown here are from plants which were not damaged by spider mites. Weevils. The clover root curculio, Sitona hispidula (Fabricius), attacks al- falfa and all clovers, particularly in young or declining stands. Major damage is caused by the larvae; these feed on roots and their damage is characterized by ir- regular longitudinal channels and pits on the roots. The larvae (which may be dif- ficult to find) are minute, skin-pink, and have dark heads. Adults (weevils) feed on leaves and cause ragged-appearing leaflets; this damage is seldom serious. [20 n Fig. 23. The green pea aphid, Acyrthosiphon pisum (Harris), shown feeding on a leaf. Other weevils occasionally found in Ladino clover include the clover leaf wee- vil, Hypera punctata (Fabricius), which is i/4 inch or more long, and the clover seed weevil, Miccotrogus picirostrus (Fabricius), which is slightly less than Vs inch long and is a slate gray color. Grasshoppers. Damaging numbers of these pests usually result from migra- tion from surrounding fields and uncul- tivated areas, and control is easiest when grasshoppers are young and before they move into the clover fields. Grasshoppers can, however, develop in the clover field, especially when seed production is re- peated in the same field; in such cases, it is best to control them before the field comes into bloom. Because they feed on the flower heads and seed, even low num- bers of grasshoppers may cause serious damage. Highest numbers occur in La- dino clover fields in late May and in June, but severe crop damage sometimes occurs as late as July. The proper insecticide and dosage de- pends on the size of the grasshoppers and whether or not bees are present. In gen- eral, sprays give higher initial kill, con- tinue to kill over a longer period, and re- quire less insecticide per acre than do dusts. Armyworms and cutworms. The western yellow-striped armyworm, Pro- denia praeftca Grote, is the most impor- tant caterpillar attacking Ladino clover stands in California. It is usually black, and has two prominent yellow stripes and many fine bright ones on each side; at maturity it is approximately 1% to 2 inches long. Armyworms may be abund- ant from June to early September and are highly destructive because they feed on flowers. Damaging numbers may develop within a Ladino clover field, or move in from surrounding alfalfa fields being cut; insecticide barriers can prevent such in- vasions. The beet armyworm, Spodoptera exi- giia (Hubner), occasionally becomes abundant in Ladino clover fields, but 21 controls for other pests usually keep it below serious damage levels. Night-feeding cutworms may become a serious problem in spring or after har- vest. These pests hide underground dur- ing the day and feed on plants at night. For best control, fields should be irrigated before applying insecticides. Clover case bearer. The clover case bearer, Coleophora spissicornis (Ha- worth), is mainly associated with Ladino clover but occasionally attacks other clovers. These shiny, metallic black moths are found from early May until late August. The female lays eggs on freshly- opened flowers, and the larvae eat their way through the developing seeds and flowers. The larger larvae move about with their bodies encased in dried flowers, and thus are hard to detect in the flower heads. Chemical control does not appear to be practical. To reduce damage from the clover case bearer, seed fields should be shredded, or pastured and shredded, in the spring and the seed crop should be * started about May 15. H Miscellaneous pests. Thrips, leaf- < hoppers, and other insects occasionally become abundant on clovers grown for seed. They are not considered serious and ( usually are eliminated by treatments for other pests. Slugs, sowbugs, and pillbugs may be- come abundant in fields with heavy growth, and may cause severe damage by feeding on new buds. These pests can „ usually be kept at low numbers by fre- quently shredding spring growth or by # removing it from the field. DISEASES Several diseases of Ladino clover are discussed here, chiefly to enable the grower to recognize them. Those caused by fungi do not appear to be of economic importance, but those caused by viruses and a mycoplasm may decrease high seed yields. (Mycoplasms are minute organ- isms and are classified as the smallest bac- teria.) Crown and root rot. Crown and root rot caused by the fungus Sclerotinia scle- rotiorum occurs in winter and early spring, usually following rain, and symp- toms vary with weather conditions and the type of plant tissues invaded. The fun- gus infects leaf and stem tissue, causing a soft, watery rot, and grows downward into the roots. During periods of high hu- midity masses of white fungus growths are visible, and these are soon followed by the appearance of black, irregularly- shaped bodies (sclcrotia) whose presence is the best means of identifying the dis- ease. Sclcrotia are deposited on soil and serve as a means of survival for the fun- gus. During cool, moist weather in winter and early spring, sclcrotia germinate and produce saucer-shaped fruiting structures about the color and diameter of a pencil eraser. These fruiting bodies produce numerous spores that are ejected into the air and help spread the fungus. Pepper spot. This disease, caused by the fungus Pseiidoplea trijolii, occurs abundantly in spring. Symptoms are nu- merous pinpoint-size, sunken, black le- sions on leaves and petioles (the spots seldom increase in size on Ladino clover) . Infected leaves soon die and often remain attached to the stems. The fungus survives in dead, infected plant debris and pro- duces numerous spores when cool, moist conditions occur. Because there is little economic loss from the disease, no con- trol is practiced. Rust. Rust is caused by the fungus Uromyces trijolii, and is recognized by raised reddish-brown pustules on the un- derside of leaves. The disease may occur in early fall and late spring, but it is [22 H^^pi |P "*^M ^^r^ywfk ^^^m 3 Hf W>\ *• ■<+%% • kJ% WtiHHt"*'** 4 * « * v.^B H^^HKrilP f ,- ^ ■JL v '*i ^ wm&iSW*' - LU UJ CO < LU -J O 800 ■ EARLY LODGING LOSS _ FIELD HARVEST □ HARVESTED DATA PLOT HARVEST DATA ■ 1 i 700 600 500 400 300 200 100 , 1 _ _| . „ iHUItNIIAL [SEED 1 PRODUCTION l 1 \ F 1 ' f JULY AUGUST 15 21 29 5 13 DATE OF HARVEST 18 Fig. 30. Actual (harvested) and potential (harvested plus lost) seed yield at several harvest dates during last month of production showing seed lost by poor water and harvest management. [27] o £40 cr. < co 20 O ^ 10 O 3 • • Bloom Count . Accumulated Seed Production o o Harvested Seed ,*800 600 cc < a: LU o_ CO o Z> O Q. 400 o 200 Q LU LU CO MAY JUNE JULY AUGUST 2\ 29 29 > \\ 17 23 I 8 14 2\ OBSERVATION DATES Fig. 31. Ladino clover bloom and seed production curves showing yield potential. \3 18 < O 90 per cent of their total potential yield in 90 to 100 days following cut-back. Ir- rigation cut-off and harvest must be timed correctly in order for harvestable seed yields to approach the potential produc- tion. Where considerable lodging is evi- dent, its is advisable to stop irrigation in preparation for harvest when 60 to 70 per cent of the seed heads are mature. In stands where plants are upright and 80 to 90 per cent of the heads are mature, light, rapid irrigations may be continued 10 to 20 days to permit late-blooming heads to mature. Thus, vigorously-grow- ing fields may be irrigated longer and harvested later because seed heads usu- ally have not lodged and germination in them has not begun. For maximum yields, irrigation must be stopped before germination of seed in heads becomes extensive. The harvest should be scheduled accordingly, usually within 90 to 110 days following cut-back. The top 2 feet of soil should be checked to ascertain how long soil moisture will support the crop after final irrigation, in order that harvesting can be completed and irrigation resumed to prevent stand loss from moisture-stress. Harvesting methods. In California, harvesting is done by one of two methods : spray-curing followed by direct combin- ing and no subsequent harvesting opera- tion, or combining from the windrow, with straw and chaff from the combine blown into vans. Collected material is re- threshed at a central location, and the field is vacuumed after the first combin- ing operation. The second method re- quires much specialized equipment which established seed growers have built up over the years, so new seed-growers are encouraged to spray-cure and direct-com- bine the seed crop. If the combine is equipped with a specially-built cutter bar mounting to permit harvesting across ir- rigation borders, and the field surface is very smooth, 90 to 95 per cent of the potential seed yield can be harvested. Large-scale field tests for the second method under ideal conditions indicated that approximately 85 per cent of the potential yield was harvested. Spray curing. If soil is shallow and uniform and the amount of water in the soil can be controlled, drying the stand to cure for direct combining is some- times done. However, fields must dry uni- formly before direct combining after field drying can be accomplished with any sue- [28] I****. sJi Fig. 32. A modified cutter-bar mounting permits cutting across irrigation borders within IV2 inches of soil surface. With such a mounting, up to 95 per cent of the crop can be harvested. cess. The most successful method of con- ditioning for direct combining is applica- tion of pre-harvest sprays. (See your local Farm Advisor for information about chemicals registered for use as pre-har- vest sprays.) Mowing and windrowing. Most La- dino clover cut for seed is windrowed with a self-propelled windrower; if a mower is used it should have a bunching attachment. In either case, clover should be cut as close to the ground as possible; occasionally a side-delivery rake is used for windrowing immediately after mow- ing. Enough space should be left between swaths or windrows to provide room for harvesting machinery. Some growers prefer swath drying, in which case windrowing is done a night or two before combining. To prevent shat- tering, raking should be done slowly and when the material is tough from high hu- midity or dew. Because Ladino is usually difficult to cut, cutter bars should be sharp, adequately powered, and kept in top-notch operating condition. Normally, clover plants are dry and ready for com- bining 4 or 5 days after mowing. Curing may be hastened by turning the windrows; this should be done at night when losses from shattering will be at a minimum. Turning should be done slowly, with only enough acreage turned each night to keep ahead of combine operations. Some growers do not turn swaths or windrows if curing conditions have been particularly favorable. Threshing. Ladino clover-seed thresh- ing requires skill, experience, and pa- tience. However, newi growers should be able to spray-cure and direct-combine seed crops under most conditions. To reduce the possible spread of weed seeds, all machines should be cleaned thor- oughly before entering a field. There are wide variations in methods [29 Fig. 33. Weedy grass rows resulting from moving combine into the field without first thoroughly cleaning it of straw and chaff containing weed seeds. of threshing the Ladino seed crop. If the crop is not spray-cured and direct-com- bined, most methods can be fitted into the following pattern: • Mowing and partially raking or windrowing seed Crop with self-pro- pelled windrowers. • Combining windrows and collecting straw from rear of the combine. • Rethreshing of straw and chaff from the first threshing, usually with a sta- tionary thresher. (Equipment to me- chanize feeding of stationary thresh- ing unit is available.) • Vacuuming the field and threshing material picked up by the vacuum machine with a stationary thresher. (An alternate method is to vacuum and thresh with a self-propelled vac- uum-combine unit.) Self-propelled combines are equipped with regular or locally adapted forage pickups and straw blowers; the latter facilitate moving straw into tightly cov- ered and screened vans behind the com- bine. Material accumulated from the com- bine is usually rethreshed by a stationary thresher located at one corner of the field. The combine shoe is usually equipped with a %2 _ i ncn round hole screen, and cyclinder speeds of about 6,000 feet per minute are used. To calculate the cylin- der seed in feet per minute, multiply the cylinder diameter in feet by 3.14 and the cylinder (revolutions per minute). When the windrowed clover has been picked up, the field is vacuumed with a custom-made locally-adapted machine; seed recovered from material picked up in vacuuming ranges from 10 to 40 per cent of total seed harvested per acre. Many vacuum machines simply blow the suctioned material into a covered van, and the material is threshed by stationary threshers. Recently, custom-made suction ma- chines have been built into self-propelled combines in which the suction unit re- places the entire header assembly. In most such machines, material from the cyclone of the suction unit feeds directly into the cylinder of the threshing unit. After threshing, debris from the rear of the machine is discharged back onto the field. This feature is considered to be a distinct advantage over the system in which the suctioned material is hauled off the field for threshing. Some California farmers have built their own clover combines and threshers [30] *&*&*%$? z ■> »/'.„z- --" Fig. 34. Combining from windrows with a self-propelled harvester (top), and collecting straw and chaff for rethreshing (bottom) with a stationary thresher. with greatly increased screening capacity. In a few instances, seed cleaners have been mounted on field threshers. Because of the smallness and smooth- ness of Ladino clover seeds, they can easily escape from inside the combines — so combines should be equipped with a seed-collecting pan under the main har- vester body. A large collecting pan sus- pended under the machine can return as much as 50 to 100 pounds of clean seed per day; pans are particularly important in the direct combining operation, but should also be used when the field is going to be vacuum harvested (free seed on the ground is difficult to pick up even when brushes are used at the entrance of the vacuum nozzle). Seed damage. Ladino clover seed can be damaged by excessive threshing cylin- der or vacuum-fan speeds, protruding sharp edges in the ducting to the cyclone, or by the cyclone itself. Holes in the duct- ing or cyclone wall must be immediately patched with a flush patch — failure to do so has resulted in sufficient seed damage to lower the germination well below the minimum of 85 per cent for certified seed. If the crop is being direct-combined with- out rethreshing, the cylinder speed should be between 6,000 and 6,500 feet per min- [31] Fig. 35. Left: vacuuming seed. Below: unloading vacuumed seed and trash from seed-tight van with automatic cable-pulley rig. Seed will be recovered with a stationary thresher. Fig. 36. Right: a custom-made, self-propelled vacuum-combine. ■ * ■"' '■*"■* [32] ute (1040 to 1130 for a 22-inch cylinder) . Cylinder speeds as low as 5,450 feet per minute (950) can be used if the straw is rethreshed. Importance of post-harvesting management. To revive drought- stricken clover fields, they should be ir- rigated immediately after harvesting is completed (in fact, irrigators and har- vestermen will often be seen together in the same field) . If this is done, damage to the stand because of harvest drying-out will be minimized and growers will get greatly increased fall pasturage. Irriga- tions should be frequent in autumn until regular rains begin. When a seed field is directed-combined without collecting the straw and chaff from the combine, all debris should be removed from the field. Where severe frosts occur, clover-seed fields should enter the cold season with not less than 6 to 8 inches of growth — good clover protects against excessive frost and reduces weed competition. In milder areas, seed fields can be success- fully grazed well into the winter without serious damage to the stands, provided that animals are moved out of the fields when soil is wet and over-grazing is not allowed. Processing and selling seed. Threshed seed is sent directly to seed warehouses, where it is cleaned and pre- pared for marketing. California Ladino seed-producing districts are fortunate in having efficient, well-staffed, commercial seed-processing facilities available. Proc- essed seed is sold by growers under two systems: California seed-growers associa- tions, which are recognized as farmer- cooperatives market Ladino seed for grower members; or reputable seed firms with national outlets who annually con- tract with local growers for their crops. Production costs. Production costs for Ladino clover seed are quite variable, depending in large part on yield and the method of harvest. Your local Farm Ad- visor can supply you with current infor- mation on these topics. To simplify the information, it is sometimes necessary to use trade names of products or equip- ment. No endorsement of named products is intended nor is criticism implied of similar products not mentioned. Co-operative Extension work in Agriculture and Home Economics, College of Agriculture, University of California, and United States Department of Agricul co-operating. Distributed in furtherance of the Acts of Congress of May 8, and June 30, 1914. George B. Alcorn, Director, California Agricultural Extension Sep 17m-8,'70(N7398L)VL i > T ME! A FARM PRODUCT r Well, not exactly — you can't grow auto- mobiles on farms, but farm products are essential in manufacturing them. Consider the annual agricultural needs of just one major automobile company. 900,000 bushels of corn 736,000 bushels of flax- seed 74,000 bales of cotton | or, in terms of approximate acreage: 15,000 acres of corn 80,000 acres of flax 78,000 acres of cotton During the same period this company used products derived from 364,000 sheep and 36,000 cattle — plus many other items such as hog bristles and beeswax. In all, produce equivalent to the output of 1,000 good-sized farms is needed yearly. No wonder a top executive in the automotive industry has said: "Our plants, here and throughout the world, would have to close their doors in a few days if their flow of agricultural materials were to stop." Supplying America's countless industries — and feeding the nation bountifully — makes agriculture America's biggest and perhaps most important business. That is one reason why anything which affects agriculture affects everybody.