E-470 April 1939 United States Department of Agriculture a-^BRARY Bureau of Entomology and Plant Quarantine rATE l^LANT 80AR0 PRACTICAL METHODS OF MORMON CRICKET CONTROL By Claude Wakeland and W. B. Mabee, Division of Domestic Plant Quarantines, and Frank T. Cowan, Division of Cereal and Forage Insect Investigations Contents Page Introduction 2 Historical 2 Geographical distribution 2 Damage 2 Type of damage 2 Crop damage 3 Range damage 3 Seasonal and life history 3 Stages of cricket development 4 Natural control 5 Climatic factors 5 Parasites and predators 5 Direct methods of control 5 Dusting 5 Materials used 6 Power dusting 6 Hand dusting 8 Danger to operators 8 Danger to livestock 9 Effect of dust on crickets 10 Oil-on-water barrier ; 11 How and where to use it 11 The use of water from oiled ditches 12 Effectiveness 12 Metal barriers 12 Where and how to use them 12 Effectiveness 14 Care of barrier : 14 Less effective methods 16 Trench barrier 16 Poison barrier ; 16 Water barriers. 17 Baits not recommended 17 Importance of organization 17 - 2 - INTRODUCTION Useful facts concerning the Mormon cricket (fig. 1), its life his- tory, habits, and thoroughly tested control practices for it are presented in this circular, which will serve as a source of information and instruction for supervisors, foremen, and others engaged in control of Mormon crickets. There are included facts concerning crickets, their hosts, and their control, obtained from foremen and workmen and from the field experience of the writers, that should be of value to men who may be engaged in control cam- paigns. The illustrations referred to in the text will be found at the back of the circular. There are several species and geographical varieties of the Mormon cricket, all of which have not yet been determined. Their life histories and habits are quite similar, and the control practices are identical. Life history and habits mentioned in this circular refer particularly to Anabrus simplex Hald. HISTORICAL The first recorded occurrence of Mormon crickets in outbreak numbers dates from 1848. Bancroft, in his "History of Utah," describes very vividly the outbreak of crickets which did considerable damage and threatened crops of the early Mormon colonists in the spring of 1848. Since then Mormon crickets have appeared periodically as a serious pest to agricultural and range crops at various places throughout the Western Great Plains and Rocky Mountain States. Mormon crickets normally develop and breed in foothill areas, but they appear in tremendous numbers and migrate far from their native breeding grounds. GEOGRAPHICAL DISTRIBUTION The accompanying map (fig. 2) shows the known distribution of Mormon crickets as determined by the fall survey of 1938. At present these crickets are a major insect problem in 10 States. They are now more widely distrib- uted, in outbreak numbers, than at any time in their history, seriously infesting, at the present writing, some 18,919,340 acres. DAMAGE . Type of Damage The kind of damage that crickets may do is extremely variable, de- pending upon local conditions, the plants or crops available, and weather conditions, as well as on the stage of development of the food plants or of the crickets themselves. Cricket damage may be divided into two classes, (1) injury to young plants and vegetation and (2) damage to native and cultivated seed crops. Although preferring certain plants as food, crickets may feed on almost any type of available vegetation. Often their feeding is erratic. - 3 - depending upon temperature or weather conditions. Frequently a band of crickets is observed moving through a field without doing any appreciable damage, only to stop in the next field and destroy the crop. Crop Damage During 1938 Mormon crickets were responsible, according to estimates submitted by qualified observers, for causing destruction of crops on more than 12,900 acres. Crop losses averaging 5.4 percent were also sustained on approximately 236,000 additional acres. Cereal and forage crops suffered the greatest loss, but garden crops were also damaged or destroyed. Range Damage Crickets normally inhabit and damage extensive areas of range land. In 1938 359 species of known range plants were listed as damaged by Mormon crickets. Damage in such areas varied with the intensity of the infestation in each area, but in certain cases closely studied in 1938 this damage amounted to startling reductions in livestock-carrying capacity. Mormon crickets are indigenous to the mixed prairie range areas east of the Continental Divide and of the sagebrush type west thereof. It has been determined that crickets in some localities prefer range plants of the higher forage values, and it is apparent that they may be responsible for greater range damage than has heretofore been realized. They undoubtedly are a serious factor in the rehabilitation of the range areas in some parts of the West. Early in the growing season and while the crickets are still im- mature, damage is confined principally to succulent vegetation. Later, as the plants and the crickets mature, the crickets turn their attention to the seed. In the cultivated crops, such as small grains, damage to the seed is of variable importance, depending upon the depletion of the particular range on which crickets are feeding or whether the principal range forage is an- nual or perennial. In cases where range is seriously depleted through overgrazing or drought, the destruction of the grass seed may be of major importance. SEASONAL AND LIFE HISTORY There is one generation of crickets annually. Only the eggs remain over the winter, hatching very early in the spring at low temperatures. The newly hatched crickets remain near the egg beds for several weeks, feeding on very young vegetation, clustering for protection from cold, or basking in the sunlight for warmth. As they gain size, the bands of crickets grad- ually disperse and soon begin migrating. Later they are in continuous migration throughout the summer. They stop only for feeding, molting (shed- ding their skin), mating, and egg laying. The Mormon cricket matures early in the summer. In reality a long- horned grasshopper, it has only rudimentary wings and can travel only by - 4 - walking or hopping. The males use their rudimentary wings to make a chirp- ing sound, but the females make no noise. These insects are cannibalistic and greedily devour any weakened individuals. The females begin laying eggs early in the summer. The eggs are normally laid in groups of about 40 to 50 over a period of 1 to 3 days, followed by a nondeposition period of from 5 to 7 days. Mating usually occurs during this latter period. Each female will mate several times during the egg-laying season. Not always, but generally, they prefer for egg lay- ing soil that is rather compact but not too hard, and usually they select areas that are reasonably free of vegetation. This selectivity of egg beds varies some in different localities. A little preliminary search, however, should soon indicate the specific conditions that are attractive in any particular location. Under adverse conditions the crickets attempt to de- posit eggs anywhere. The long ovipositor of the female is worked into the ground to its full length, and the eggs are deposited singly, never in pods like grass- hopper eggs. Sometimes many eggs are laid within a very small area, but at other times they are scattered. Female crickets have been known to lay as many as 298 eggs in a season, although the average under field conditions is probably nearer 150. Most of the egg laying is concentrated in "egg beds" on sunny slopes, where the soil is suitable. Eggs are laid from early in the summer until cold weather arrives, but do not hatch until early the following spring. During 1938 there was apparently more variation in the hatching dates of crickets than had been previously observed. In some areas crickets hatched as early as late in February and in other areas they were observed hatching as late as July 4. Crickets normally have seven periods of development or instars before becoming mature. The skin is shed between instars. Technical Bulletin No. 161, of the U. S. Department of Agriculture, indicates the easily seen differences between these instars. The early stages of crickets are rather difficult to distinguish, especially those of the males. Stages of Cricket Development The first and second instars are difficult to distinguish without the use of a binocular or strong hand lens. The ovipositor is just starting to develop and is not visible to the naked eye. When the crickets first hatch, they are light colored but soon darken until they are uniformly dark brown or black with a few white markings. When the female reaches the third instar the ovipositor is visible but still does not extend beyond the tip of the abdomen. When it reaches the fourth instar the ovipositor definitely extends beyond the tip of the abdomen. Until this stage the crickets have been nearly uniformly black. Color variations first appear during the fourth stage. In the fifth instar the ovipositor is twice as long as it was in the fourth, being now about one-third the length of the hind femur (large part of hind leg). Color is more in evidence, ranging from tan and pastel shades through the greens to dark browns. In the sixth instar the - 5 - ovipositor again is twice as long as it was in the previous instar and three-fifths as long as the hind femur. In the seventh instar the ovi- positor has reached its full length and is now a little longer than the hind femur or twice as long as it was in the sixth instar. The mature cricket has no longer ovipositor than in the seventh in- star and is practically the same size. However, the seventh-instar female can be distinguished from the adult because the stubby wing pads on her back do not meet in the center. In the adult stage the wing pads on the female definitely meet in the center, and the wing pads of the male overlap. Bright color variations in the adult tend to disappear. They darken with age from dark brown to black. NATURAL CONTROL Climatic Factors It is believed that the greatest natural factor in the control of crickets is a combination of weather conditions. Just what circumstances tend to reduce the cricket population to normal numbers has not yet been determined. Large outbreaks of crickets usually follow prolonged periods of drought, but they may extend into the better crop seasons. It is hoped that these climatic factors may be determined so that outbreaks may be forecast with accuracy. Parasites and Predators Many birds, mammals, and insects feed upon crickets, but none to such an extent as to be an important factor in natural control. Only one species of parasite is known to attack cricket eggs. This is a small wasp (Sparaison pilosum Ashra.) which develops within the cricket egg, the larva feeding upon the egg contents and emerging as an adult wasp late in the summer in time to infest the new crop of cricket eggs. This parasite has been observed in many areas, but in only a few has it occurred in sufficient numbers to affect the cricket population materially. Another insect (Palmodes laeviventris Cress.), a large black digger wasp, is predacious upon crickets. In a few instances this has been numerous enough to effect slight cricket reductions, but it, in turn, is parasitized by another insect. DIRECT METHODS OF CONTROL In this circular only control practices which have proved to be effective for general field use are discussed. Dusting The most satisfactory and outstanding method of cricket control now known is dusting with arsenical mixtures. - 6 - Materials used. — The use of sodium arsenite as a dust for cricket control was first tried and developed by Frank T. Cowan during 1926. Sodium arsenite dust proved so successful in experimental work that it was used extensively in Montana in 1927, on control operations in Lake and Sanders Counties. At first the dust was composed of 1 pound of sodium arsenite to 4 pounds of lime. During recent years, however, diatomaceous earth, a cheaper material and much less irritating to the skin of the operator, has replaced lirae. Diatomaceous earth is mixed with sodium arsenite at the rate of 3 pounds of the earth to 1 pound of sodium arsenite. The arsenite is the poisonous ingredient and the lime or diatomaceous earth acts only as a diluent. The purpose of the diluent is to facilitate even distribution of the small quantities of sodium arsenite, The amount of the mixed dust used will vary somewhat with the population of crickets, from 5 to 7 pounds per acre being sufficient in most cases. These ingredients mix readily. Mixing usually is accomplished in a cement mixer, an abandoned creamery churn, or, in small quantities, in a barrel which has been mounted diagonally on an axle. To adapt the cement mixer for this work a tight cover for it is constructed so that dust cannot escape while the mixer is in operation. If the mixer is not overloaded or not run too fast, 10 minutes' time is sufficient for combining these in- gredients satisfactorily. Power dusting. — In the past dust was applied by hand-operated dusters. Recently, however, power dusters have been introduced and have been found far superior to hand dusters, both in quality of work and efficiency of operation. One power duster (costing about ^100) mounted upon a small pick- up truck and operated by one man and a driver does as much work and does it better than a crew of 20 men using hand dusters. New methods of mounting power dusters make it possible to take these machines into country that formerly was considered too rough for their operation. One of the most satisfactory ways of mounting a power duster is to mount it in front of a car or truck, as illustrated in figure 3. Mounted as in figure 3, the duster can be operated by one man. As the booms and nozzles are in clear view, the operator can avoid obstacles and damage to his machine. This mounting has the added advantage of not flushing or alarm- ing the crickets before the dust is applied. Another very satisfactory method of mounting this duster is on the rear of a pick-up truck. Care should be exercised in the construction of the booms in this mounting so that damage will not result from accidental striking of obstacles. Figures 4, 5, and 6 illustrate a satisfactory way to construct the booms to avoid damage and to allow them to be folded for transportation to and from the field. - 7 - Another method of mounting a power duster, which has been used very satisfactorily in Wyoming, is on a two-wheeled trailer. The boom construc- tion is the same as illustrated in figures 5 and 6. However, this trailer is equipped with a coupling so that it can be attached to the back of a car or truck. It is also equipped with a substitute tongue that can easily be attached so that the duster can be pulled by a team. This is a decided advantage in rough country, as it can be operated wherever the team can be driven. Care should be taken, however, in using horses to pull dusters late in the season, especially where vegetation is scarce. The reason for this is that as the crickets grow large they are easily disturbed, and the slow movement of the team may cause a high percentage of them to go out of reach of the duster. Considerable difficulty v/as previously encountered in the use of power dusters, because vibration damaged various parts and caused break- downs. Every duster should be very firmly mounted on a substantial base to prevent twisting or vibration when operated in rough country. All duster operators should be instructed to keep these machines tightly fastened at all times, and each operator should be equipped with a wrench, pliers, screw driver, and a special set-screw wrench. This latter is necessary to keep the set-screws tight on the shaft which operates the agitator. When these set- screws become loose, they soon cut the shaft and repairs become more dif- ficult. Very little oil should be placed in the air-cleaner of these power dusters. The bottom of this filter should not be filled with oil to the indicated line. If this quantity of oil is used in rough country it will get into the carburetor and choke the engine. The result is a lot of extra cranking to restart the engine, and often the oil then becomes diluted with gas and penetrates the magneto, causing further difficulties. These filters are equipped with an air-cleaning material which is usually sufficient in itself. If oil is used, it should be sparingly applied in the removable top part of the filter and not poured into its stationary base. Another difficulty encountered with power dusters has been that operators have attempted to apply more dust than the machine is capable of discharging. Some operators have made the grave error of enlarging the ports in the feed mechanism. This has caused overloading of the engine, spilling of material from the fan-housing, and irregular discharge of dust. A satisfactory quantity of dust, sufficient for control, (5 pounds per acre) can be most evenly and effectively distributed by the use of a flaring, flat nozzle. No port enlargement is necessary. The diagram and pattern for the ready construction of such a nozzle are shown in figure 8 and the completed nozzle in figure 7. Practically all power dusters in the past have operated without nozzles on the ends of the discharge tubes. Without a nozzle the dust comes out in a round stream and does not cover a very wide area. In order to UBRARY STATE PLANT BOARD - 8 - produce the cloud of dust which is necessary, operators sometimes increase the discharge. This in turn overloads the equipment, and a considerable proportion of the dust that does emerge drifts away with the wind and may be wasted. This nozzle as illustrated should be on all dusters. The flat, fan shape, with the two baffle plates, seems to distribute the required amount of dust in the proper direction (laterally). It is thus easy to secure even distribution from the small power dusters over a width of about a rod. Nozzles also prevent streaking of the ground with dust, which frequently occurs when dusters are used without them. This streaking is an unnecessary waste of dust and also increases the hazard of livestock poisoning. The use of a suitable type of nozzle almost entirely prevents streaking and gives better distribution of dust and better control of the crickets. Hand dusting. — Where there are rough areas infested with crickets on which it is impossible to use a power-operated duster the hand-operated gun is of most value, and for efficiency's sake the use of hand dusters should be confined to such areas as coulees and arroyos where it is impossible to use power dusters. Hand dusters are very effective for use in the early part of the season on cool mornings. Advantage may be taken of the clustering habits of crickets by using hand guns to dust such concentrations. Hand dusting should be considered only as supplementary to power dusting. Danger to operators. — Where common sense is exercised there is slight danger nf any internal poisoning occurring when working with sodium arsenite. However, certain precautions should be taken for the prevention of external injury among the workers. Medical examination is required for laborers employed on Federal funds. Any individuals who show a predisposition to skin rashes, irritations, or respiratory disorders and those who may have dia- betes, tuberculosis, or syphilis should be rejected. Duster operators working should wear shoes or boots high enough so that the pant-legs can be tied down over them to prevent dust from gaining access to the bare skin and causing irritation. Operators of hand dust guns should wear aprons of tightly woven material that will prevent any excess dust from working into the clothing. Operators, of course, should take every advantage of wind direction and avoid, as much as possible, breathing the dust. Where they are continually exposed to the dust, they should wear a respirator and goggles. Most of the commercially made respirators are not satisfactory because they have a tendency to chafe the face at the points of contact. The most commonly used dust mask and one that is very satisfactory is a home-made affair, constructed of a simple wire clamp in which are placed strips of cellocotton. This material excludes the dust, will not chafe, and can readily be replaced. The most common source of cellocotton, if it cannot be purchased locally in rolls, is from sanitary absorbent padding sold by druggists. -9- Sodium arsenite causes skin irritation, particularly at any points where chafing may occur due to perspiration. Such conditions should be guarded against by the operators. Tight clothes, tight belts, or dust masks that rub or chafe cause the most difficulty. Where an individual is exposed to much dust, the exposed surfaces of the skin should be well covered with zinc oxide powder, talcum powder, or diatomaceous earth when the others are not available. All operators working continually with this material should take daily baths, and their clothing should be frequently washed. An operator who develops any skin irritation or arsenical burns should immediately be laid off and treated until the irritation disappears. Plenty of soap and water is the best preventive. The most satisfactory treatment is a saturated solution of photographer's hypo (sodium hyposulphite) applied to the irritated places and allowed to dry. If "hypo" is not available, a solution of common baking soda may be used. Any cuts or abrasions on the skin should be covered and entirely protected from the dust. Danger to livestock. — There is practically no danger of livestock poisoning from dusting for Mormon cricket control iX the dust is applied properly. Almost without exception, cases of poisoning observed have been due to the carelessness of the operators. The danger involved is entirely confined to spilling the dust in quantities upon the ground or leaving dusting equipment or dusting supplies exposed in places accessible to livestock. It may readily be seen that where the dust is uniformly applied at the rate of about 5 pounds per acre, the mixture would contain actually 1^ pounds of the poisonous sodium arsenite per acre, the remainder of the 5 pounds being made up of the harmless diatomaceous earth. Obviously it is extremely difficult for livestock to eat sufficient vegetation to secure an injurious amount of poison where so little poison is distributed on an acre of land. Crews applying poison are usually supervised by Federal, State, or county agencies. These crews are well trained and careful in the applica- tion of dusting materials. For the protection of trained crews, working under the supervision of public agencies, release of liability should be secured from land owners. These releases should conform to the laws of the State in which the dusting is being done. Although it may be unnecessary, ranchers should be given the opportunity to move livestock from areas to be dusted previous to dusting, if they so desire. Livestock in control areas should be kept well salted, as salt-hungry cattle and sheep are likely to search out and lick up any sodium arsenite that may have been carelessly spilled. Every dust gun operator should be carefully and definitely instructed to operate his gun in such a way as to prevent ground streaking and spilling of dust. When any materials are spilled by accident, the operator should be held responsible for throughly disposing of the poison so that it is in- accessible to livestock. Any employee careless in this respect should be severely disciplined. - 10 - When not in use, all dusting equipment, machines, trucks, trailers, and containers should be stored under lock and key in buildings safe from children or livestock. As soon as operations have been completed, all equipment should be thoroughly cleaned of poison and the residue destroyed by burying it deeply in the ground or by scattering it so thinly over the ground that animals cannot pick up a poisonous dose of it. Paper or burlap containers should be buried rather than burned, because burning does not destroy the arsenic. Effect of dust on crickets. — Crickets are killed by sodium arsenite apparently principally as a result of cleaning the material from their feet and antennae by their mouths. In this v/ay the dust is taken into the digestive tract and acts as a stomach poison. In the cases of early-instar nymphs the arsenite acts also as a contact poison. When dust is applied to crickets, they show marked signs of irrita- tion, become very nervous, and continue their migration almost continuously until the poison kills them. Advantage may be taken of this knowlecge in clearing a field of crickets or driving them into oil or metal barriers. It is often possible to rid a grain field of crickets without dusting the entire field. Where grain is nearly ripe and considerable shattering would result from complete dusting of the field, it may be protected by dusting several swaths through one side or around two sides of the field. The crickets immediately start moving, and this induces others to migrate, so the whole field soon may be vacated. Advantage may be taken of this behavior by dusting the rear and flanks of cricket bands to hasten their march into oil or metal barriers. Because the sodium arsenite is slow in action, crickets, especially when fully grown, do not die immediately. Some die within about 12 hours, but the total kill is not secured until the third or fourth day. Often, then, the results of dusting may appear discouraging until a more detailed search is made. Dusting as a control practice is most effective in the early stages of development when crickets cluster, and such control is most easily accom.plished early in the season previous to migration. Hatching beds and the closely clustered bands of very young crickets can be dusted by the coverage of much smaller acreages and with smaller quantities of material and labor than is possible later after migration has begun. Dusting is effective, however, against crickets throughout the season, although con- siderably larger territory must be covered to obtain equally satisfactory results. In some cases late dusting has interfered with mating and egg laying to a sufficient degree to reduce subsequent infestation. Dusting during high winds is not effective, as the dust does not pene- trate deeply enough into the vegetation to come in contact with the crickets, but drifts away in the air and is wasted. Dusting during wet weather or when excessive dew is on the foliage is likely to cause severe burning to the vegetation. - 11 - The use of nozzles on power dusters, as described previously, directs the dust under higher pressure so that dusting may be done effectively in windy weather. The dust distribution produced by these nozzles also prevents excess quantities of the dust from being discharged in any one spot; there- fore, there is less danger of burning vegetation. Under certain con- ditions, when air movement is not too rapid, advantage of the drift may be taken to cover a larger swath than the actual width of the booms. Oil-on-Water Barrier The use of oil on irrigation ditches and streams is one of the oldest methods of control, but was developed and used extensively in Wyoming in 1936 and 1937. It has proved an excellent means of cricket control where the circumstances permit, Crickets in their migration disregard irrigation streams or ditches and do not hesitate to march into the water and swim or float along until they can secure a footing and proceed on the other side. In this way streams and irrigation ditches ordinarily are a source of distribution of crickets and may carry them for great distances into new areas. Thus these ditches, when covered with a thin film of oil, form an excellent barrier which not only stops the progress of the crickets but kills them. How and where to use it.- — Oil drippers, consisting of an oil barrel with a shingle-nail hole punched in it, may be distributed at intervals of a half mile to Ij miles along ditches, depending upon the size and rate of flow of the particular ditch and the number of crickets entering it. The important point is to maintain a very thin, continuous film of oil on the surface of the water. Of course, after migration has passed, the oil should be shut off, to be turned on again when another band approaches the stream. The important qualities required of the oil are cheapness and ability to form a film quickly on the water's surface. Oil that floats in large globules without filming is unsatisfactory. The best oil yet found has been a low-grade distillate. This oil is straw-colored, is thin, and does not clog the openings in the barrel. It runs freely, continues running with very little attention, and quickly forms a film on the surface of the water, a small amount covering a very large area. There has been a tendency on the part of some workers to favor the use of a heavy crude oil because of its very low price. The sludge and sediment in these low-grade oils are a constant source of vexation, contin- ually clogging the oil drippers and necessitating an undesirable amount of attention. As these heavy oils do not form a film readily, much more oil must be used upon the water. The use of these excessive quantities of crude oil on irrigation ditches, with their attendant disagreeable odors and un- sightliness on the vegetation, causes many growers to be prejudiced against oil as a means of control. The use of the more expensive distillate is a genuine economy when all points are considered. - 12 - The use of water from piled ditches. — The question has often arisen about the danger to crops from water that is covered with a film of oil or the use of oiled ditches as a source of water for stock. Where the oil is applied, as it should be, in only a thin film, it does not interfere in the slightest degree with stock-watering purposes nor does it injure the livestock in any way. In cases where animals have received unusual amounts of oil owing to carelessness, this acts only as a laxative. At the cut-outs, where the water is to be removed for irrigation purposes, the following two methods of removing the water from the canal without taking the oil into the fields may be used: (1) Put a board cover over the cut-out so that all the water going into the lateral comes from below the surface. (2) Place a baffle plate (a board) so that it extends out into the stream just above the cut-out. When this has been done, a film of oil on the surface is by-p:ssed around the cut-out and no oil enters the lateral. In rare instances objections have been made to oiling because certain residents secure drinking water from the ditches. In such a case oil-free water may be secured by inserting some type of frame which directs the oil film around the point where the water intake is located. Effectiveness. — Oil barriers, a cheap method of control, should be employed wherever there are irrigation ditches, canals, or streams across which crickets are migrating. For irrigated areas of intensive farm crops threatened with invasion, there is no more effective protection than oiled ditches as just described. As in the case of metal barriers, too much de- pendence should not be placed on oiled ditches alone. They have their place in a control program but they must be supplemented with well-planned dusting operations. Metal Barriers Many types of fencing have been used to stop the migration of cricket bands. Wooden boards having a narrow strip of tin or oilcloth tacked along their top edges at right angles have been used with varying degrees of suc- cess. Recently, however, galvanized sheet iron has been reduced in price and has proved so far superior in actual field control that it is well worth the additional cost over the above-mentioned substitutes. Where and how to use them. — The metal barrier most commonly used con- sists of 10-inch strips of 28-gauge galvanized sheet iron which is sold either in 100-foot or 50-foot rolls. For most purposes the 50-foot rolls are advis- able on account of ease and convenience in handling them. In placing this barrier across the path of migrating bands it is necessary to clear the ground of vegetation along a narrow strip where the barrier is to be erected so as to prevent the vegetation from forming a ladder for the crickets to climb. The barrier is then erected along this - 13 - cleared strip and staked down. Metal stakes, each of which is U-shaped at the top, are preferable. These are placed on the side of the barrier away from the advancing crickets. A small quantity of soil is then shoveled and packed against the barrier on the same side as the stakes to fill any holes or uneven places in the ground which might permit the crickets to crawl under the barrier. In placing a barrier across a road it is necessary to form some type of gate or trench to prevent crickets from following the road or crossing bridges. The simplest and most effective way of preventing crickets from crossing a bridge is to dig a narrow trench, about 10 inches deep, across the road. This should be dug preferably along the abutment of the bridge. Then it is only necessary to insert one 10-inch plank within this ditch, as the abutment forms one side of it. The front opening of this trench is then faced with metal barrier which continues on out to the regular line of bar- rier or down into the oiled stream, as required. This trench is constructed narrow enough so that cars may easily pass over it. Such trenches need little attention to keep them free of dirt. Crickets, approaching one side or the other, pass on through the trench and across the road. Migrating up the road, they enter the trench and, failing to climb the barrier on the other side, progress along the trench across the road and on along the barrier or into the oiled stream. Where this road crossing is not located at a bridge, it is necessary to place planks on each side of the trench across the road to prevent traffic from caving in its sides. It must be borne in mind that metal barrier merely stops the migration of crickets and must be accompanied by some form of trap. In order to collect and destroy crickets as they accumulate along the barrier, many types of traps have been devised. Pits and various forms of pit traps are satisfactory, but considerable labor is required to construct and maintain them. The metal pen trap has proved the most satisfactory. The advantages of this are that very little labor is required to construct it and a minimum amount of attention thereafter. Figures 9 and 10 and the diagrammatic "floor plan" and cross section in figure 11 show the proper construction features of a good pen trap. There are a few points that should be strictly observed in the con- struction of the trap illustrated (see fig. 11). The most important feature is to have narrow entrances (not less than 12 or more than 18 inches wide). Crickets enter more readily where they are crowded and the force of the flow pushes them over the incline into the trap. Where an entrance is too wide and the crickets are not crowded, when they come to the edge of the drop- off and survey the situation, they attempt to go back and around the edge of the trap. Where the entrance is narrow and the crickets are crowding in rather rapidly, they have no alternative but to proceed over the incline and into the enclosure. - 14 - The v/ings of the trap should be relatively long and funnel-shaped in order to collect the crickets into a crowded condition so they will proceed inward. The reverse curve at the ends of the wings has been found an added advantage in preventing a backward wave or rT^vement, When crickets are startled or scared, the shape of this curve has a tendency to check this backward movement and to direct them toward the entrance. The piece of metal located at the front center of the trap is to direct the crickets out of their line of march into the large area of the enclosure, thus preventing them from proceeding directly to the opposite entrance and clogging it up. Because of the crowded conditions, crickets die rather quickly when confined in these traps. The trap entrances should be cleaned frequently and dead crickets shoveled either out of or to the center of the enclosure. Where but one trap is used continuously for a long period, its inside walls should occasionally be cleaned with a brush and water to prevent the crickets from gaining a foothold and climbing out. One point that should be stressed with all workers is that no dusting or other activity which would scare the crickets should be carried on in front of the barrier, as this may interfere with the free march of crickets along the barrier and into the traps- Effectiveness . — Another point that should be brought to the attention of all workers is that the barrier in itself merely stops migrations. To be of greatest advantage, the barrier must be supplemented with a dusting pro- gram. Where crickets are migrating, dusting should be done at the rear and flanks of the band in order to force them all into the traps and thus destroy the whole band. Without this supplementary program, barriers often have acted merely as concentration points for crickets and have not killed or prevented them from laying eggs along the barrier. Metal barrier is best used as follows: (1) Mobile units can be placed in front of migrating bands until the band is destroyed, then moved to a new location for a similar purpose. (2) Where there is a definite continued movement of crickets through- out the season in small areas, metal barrier, with the proper up-keep and attention to the traps, may be used to excellent advantage. (3) Metal barrier is excellent for use in connecting breaks between irrigation ditches or streams or in directing the crickets around siphons or underpasses in irrigation canals or ditches, thus supplementing an oil- barrier control operation. In every case where metal barrier is used, it should be supplemented with a well-planned dusting program or a combination of oiling and dusting. Care of barrier. — Metal barrier, purchasable for about $210 a mile '1938), lasts for a long time if properly cared for. The material is too - 15 - expensive to be handled carelessly by workers, and it is advisable that the following instructions for its care be given: (1) In laying metal barrier the same edge should be placed in the ground each successive year. The contact with the ground causes a certain amount of pitting and corrosion which roughens the metal. If both edges become corroded, as occurs when one edge is put in the ground one year and the opposite edge the next, the crickets may climb over the roughened sur- face. (2) Metal stakes with hooked tops are best, as it is then unneces- sary to drive nails throug the barrier metal, which would cause additional rough places and provide more footholds for climbing crickets. (3) When building a trap it is advisable to use one complete 50- foot roll for the main border of the trap rather than to cut a roll. (4) In cutting pieces of metal for trap entrances, cut all short pieces from the same roll and use these repeatedly for this purpose. This practice has not always been adhered to, and this has caused unnecessary work in making up uniform 50-foot rolls from the odd pieces remaining at the end of the season. (5) In taking up the barrier to move it from one point to another, or at the end of the season's operations, it should not be pulled out of the ground with trucks or teams of horses. This procedure stretches and distorts the tin so that it becomes extremely difficult to roll, to handle, or to run it through the barrier conditioning machine. The barrier should be removed carefully to prevent this distortion. (6) All nails should be removed from the metal. (7) To facilitate handling and later operations, the metal strip should be rolled uniformly on some type of winder with a diameter of not less than 7 inches. Where the barrier is wound too tightly it becomes bent, causing waves that are difficult to remove, thus making cleaning much harder at the end of the season. Figure 12 illustrates a simply constructed winder that any crew can put together quickly. (8) Barrier should always be stored in a dry place and preferably upon a floor of some type that will not absorb or hold moisture. Much bar- rier metal has been damaged by being stored on dirt or cinder floors that accumulated moisture and caused corroding and pitting on one edge. (9) All barrier metal should be cleaned at the end of each season's work so that it will be free of dirt and corrosion and ready for the folllow- ing season's operations. Old barrier that has not been properly cleaned is not nearly so effective in stopping the march of crickets. - 16 - (10) Care should be taken to keep the metal as clean as possible throughout the season. A few precautions taken during the summer will save an untold amount of work at the time of fall clean-up. If metal barrier is used around oiled ditches, guard against crude oil or heavy greases coming in contact with it, as they are extremely hard to remove. If burners are used to kill crickets in traps or for other purposes, by all means keep the flame away from the metal. Burned metal will not clean satisfactorily and is practically useless in stopping cricket migrations. Almost any type of device that will wind the metal barrier into rolls with a diameter of not less than 7 inches will suffice. The diagram in figure 12 may serve as a guide for its construction. When a 50-foot roll has been completely wound, a piece of baling wire is tied loosely around it. The metal then is unwound by hand until this wire becomes tight. This loosens the metal roll from the cylinder. The hinged end support is then dropped and the roll removed. Less Effective Methods During past outbreaks a variety of devices and materials have been used. Other methods than those explained in this circular in detail have not proved practical, so only brief mention is made of a few that have proved partially effective. Trench barrier. — Trench barriers have been used effectively in some areas to stop migrations of crickets. The success of a trench barrier is dependent upon the presence of a light sandy soil. There are few soils in which such a barrier can be cheaply dug where it will maintain its shape without too much repair. The trench barrier, to stop crickets, must be at least Z feet deep and maintain a clean-cut, perpendicular wall facing the advancing crickets. The trench should be at least 18 inches wide, and the soil which is removed therefrom should be piled on the side away from the advancing crickets. In order to prevent the trench from becoming filled, pits should be dug at intervals the full width of the trench and at least 2 feet deep. As these pits fill with crickets, they should be coverd with soil and new pits constructed. Although the trench barrier is one of the oldest means of stopping migrating crickets, its use has been largely abandoned because of the tremendous labor cost involved in construction and particularly in maintenance. The use of this barrier is limited to areas of the proper type of soil and has been largely replaced by the metal barrier, which is easily moved from place to place. Poison barrier. — Poison barriers have occasionally been constructed by placing a streak of poison dust along the ground or in furrows. These barriers are only partially effective and then only for a short period or until the poison becomes caked from moisture. Because they are such a great danger to livestock, their use should be forbidden. - 17 - Water barriers . — Before the extensive use of oil on ditches and streams, barriers were floated on the top of the stream for the purpose of collecting and directing the floating crickets into traps at the edge of the stream. These barriers v/ere constructed of heavy pieces of timber upon which an upright piece of tin was tacked. Crickets floating down the stream would crawl upon the timber and, failing to climb the tin at its back, would then progress along it to the edge of the ditch or stream, where they were directed into pits or traps. This type of water barrier has been largely discontinued since oil has been found so effective when used on irrigation ditches and streams. However, there may be unusual circumstances where oil- ing is undesirable and where these barriers would serve to good advantage. Baits not recommended. — Many bait formulas have been experimented with in the past in an attempt to secure a bait that would be as effective as grasshopper bait. Under certain conditions baits have proved valuable, but until further research work is done, baits are not recommended. Many mechanical devices, including burners, have been used, but their effectiveness has been so limited that their use has been discontinued. IMPORTANCE OF ORGANIZATION Cricket control is primarily not a problem for the individual farm operator, even though it has been repeatedly demonstrated that an individual, by the use of proper methods and much diligence, can save his crops. Crick- ets breed on and disseminate largely from range areas and nonagricultural lands. They usually cover such large acreages and migrate so rapidly that their control is logically a problem for a whole community and, in larger areas, control becomes a Statewide and Federal problem. All agencies con- cerned have a definite responsibility in control operations. In the States where crickets occur there are large areas of Federal, State, and county lands, in addition to the lands of nonresident, corporate, and resident owners. If cricket control is to be efficient, all agencies must contribute a share to control operations, and it is only through such cooperation that large-scale control can be accomplished >. / Figure 1, — Male (upper) and female (lower) Mormon crickets (natural size) • Figiire 3. — Front mounting of power d\ister. This duster is mounted on a wooden frame which is bolted to two heavy angle irons which, in turn, are bolted to the frame of the car. To be most effective, this machine should be equipped with nozzles. Figure U* — Rear mounting details of a power duster. This is a 5-horsepower duster mounted on the rear of a pick-up truck. In this picture the outlets are located closer to the ground than they should be in actual operation. »«.. Figure 5« — Side view of rear moimting. Side view of mounting in figure 4^, showing the details of boom supports and method of folding booms for transportation. Figure 6. — Boom construction. Details of eye-bolt attachment of booms. This method of mounting permits flexibility of booms. They are held forward in place by springs, and supported by ropes knotted and run through notches in the tops of the uprights as seen in figures U and 5. These features prevent breakage in case the booms strike obstacles. Jlgnre 7. — The completed nozzle. This picture shows the cofflpleted home-made nozzle attached to the outlet hose. Explanation of figure 8. — Pattern for nozzle construction. This pattern is acttial size and may be used as a template for cutting the nozzle from tin. The construction of this nozzle requires no particular skill. It is merely cut out of tin with a pair of tin- anipSy folded as indicated, and soldered together. A. The part in the diagram marked "A** forms the main body of the nozzle. Two pieces should be cut, as illustrated, and the edges bent as indicated. One piece forms the top, and the other forms the bottom of the nozzle. B. Two pieces should be cut, as indicated, the exact shape and size of "B." These pieces act as baffle plates to divide the air and dust stream erenly through the nozzle. These two pieces, when cut, should be bent and fitted into the holes marked "b" between the top and bottom of the nozzle; in other words, between the two pieces marked "A." ThQ projecting lugs are then clinched and soldered in place. £• The piece "C," when bent to form a tube, forms the entrance to the nozzle and the connection for Joining the nozzle to the outlet hose. "C** is fitted into the nozzle at "c-1," and when all parts aoce fitted properly the seams are soldered. The opening or lip of this nozzle should be not more than three-sixteenths of an inch in width » Figure 9. — A pen trap in operation. Figure 10. — Details of construction of pen entrances, Figure 11. — DlagraiB showing construction details of pen trap* Figure 12. — A barrier-metal winder. A. Hinges are used as indicated by "A" on the first support so that this support may be dropped out of the way for remoTal of the finished roll of metal. The other supports for the axle are similar to the one in "A** but not hinged. B. "B" indicates a groove that is sawed into the cylinder of the winder. The end of the sheet metal is fitted into this groove and rolled on the cylinder by turning the crank. This cylinder may be meule of the end of a straight fence post or a block sawed from a log, its principeO. specification being that its diameter should be uniform and not less than 7 inches. £. The axle is fastened rigidly to the wooden cylinder of the winder, by a collar and lag screws. This collau: is fastened rigidly upon the axle by a bolt which runs through both the collar and the axle. D. The axle and crank are made from any pipe of suitable diameter that may be on hand, inch-and-a-quarter pipe being preferred. UNIVERSITY OF FLORIDA 3 1262 09224 6742 ill