r state' I-.. .-V BOARD April 1942 ^ y ^ Nv £-566 \\ DEPARTMENT / AGRICULTURE \\ BUREAU or !l EMTOMOLOGY AND FLAiMT QUARANTINE •CONTROL OF THE BOLL WEEVIL ON SEA-ISLAKD COTTON UNDER FLORIDA CONDITIONS C. S. Rude, Division of Cotton Insect Investigations Experiments conducted by the Bureau of Entomology and Plant Quarantine of the United States Department of Agriculture in cooperation with the Florida Agricultural Experiment Station during the past 5 years show that the toll weevil may be profitably controlled on sea-island cotton. Proper cultural practices and direct control measures are important, and both should be used to obtain satisfactory control of the boll weevil. Cultural Practices Important in Weevil Control Cultural control practices, to be of the greatest value, should start in the fall with the early destruction of cotton stalks. The stalks should be cut or plowed out as soon as possible after the cotton is picked. This practice cuts off the weevils' food supply and stops late breeding by the weevils; it also causes the weevils already present to enter hibernation in poor condition and reduces their chances of survival. It is especially important to destroy, cut, or plow out the cotton plants so that there will be no winter or early-spring growth or fruiting. In the southern part of the sea-island area cotton grows and fruits all winter in some years. When this happens the weevils continue to multiply and are present in large numbers to attack the first squares that appear in the spring, or the old plants may sprout early in the spring and prdduce squares much sooner than the planted cotton. These early squares afford the overwintered weevils a place to feed and to deposit eggs for the production of an early brood of weevils which later infest the planted cotton. Select fields as far as possible from fields in which cotton was grown the previous season. Use good seed and plant on land that will produce a good crop in the absence of boll weevils. Prepare the land well in advance of planting to insure good moisture conditions. Apply a fertilizer, high in potash, at a rate of not less than 400 pounds per acre 10 days or 2 weeks before planting. Plant as early as weather conditions will permit without causing stunting by the cold. Apply a side dressing of fertilizer containing nitrogen and potash at chopping time. Leave 2 to 3 stalks per hill, 15 to IS inches apart. Cultivate frequently to keep the cotton in good growing condition. Observance of these cultural practices will do much to get cotton started quickly and reduce the amount of poisoning needed for weevil control. - 2 Direct Control Measures UNIVERSITY OF FLORIDA 3 1262 09230 3618 Examine the cotton for weevil dairage every few Cars after scvares have formed. When 15 percent of the squares are found to be punctured tv weevils, dust with calcium arsenate at the rate of 5 to 7 poun-^'s per acre at 5-c.ay intervals. In case rain washes the dust off within 12 cayUght nours after application, redust at once. Cotton may be dusted successfully at any time of day or night when the air is still enough so that the cust coes not blow away. For best results the nozzle of the duster should be about 5 or 6 inches above the tops of the plants so that the dust will be driven cownward through the plants. In this way all parts of the plant will receive a uniform light coverage of dust and it will also help to reduce drift of the aust. From 5 to 10 applications will usually be reeded to protect sea-island cotton from weevils. When dusting machinery is not availaole, somewhat less dependable results may be obtained by sprayin=. the cotton, using calcium arsenate in water (10 pounds to 50 gallons) applied at the rate of 25 to 30 gallons per acre. Sweetened poison mopped on the plants has not been effective for toll weevil control. How to Determine Percentage of Punctured Squares A simple and practical way of determining the percentage or boll weevil infestation is to walk across the cotton field and puH off 100 squares. Care should be taken to take about the same number o"f souares from the top, center, and bottom branches. Hold the souares in the hand or pocket until 100 have been pulled and then examine them for weevil feedin- and egg punctures. The number of punctured squares found will be the percentage of infestation. For greater accuracy several such counts may be taken m a field. When this is done, add the counts and take an average for the weevil infestation in the field. In small fields one count carefully made is sufficient. " ^ Control of Cotton Aphids Cotton aphids, or "lice," frequently become serious on cotton that has been dusted with calcium arsenate. The danger of aphid injury may be lessened by avoiding early or unnecessary applications of calcium arsenate To prevent aphid build-up, 1 percent of nicotine should be added to all the calcium arsenate used for boll weevil control. To prepare the calcium arsenate-nicotine dust, add 2i pounds (approximately 1 quart) of 40-percent nicotine sulfate (Black Leaf 40) to each ICO pounds of calcium arsenate and mix thoroughly in a barrel mixer such as is used for treating seed This dust mixture can be kept for several months in a steel calcium arsenate drum or other tightly closed container, but quickly loses its strenc^th if exposed to the air. If no suitable container is available, the mixture should be freshly prepared for each application. Damaging aphid ponulations can be checked by spraying or dusting with nicotine sulfate. For spraying use 1 pint of 40-percent nicotine sulfate and 4 or 5 pounds of laundry soap to ICO gallons of water. This spray should be applied at the rate of 20 to 30 gallons per acre while the plants are dry and the air calm. To check heavy infestations by dusting, it is usually necessary to uso approxi- mately 3 percent of nicotine in the dust. This can be made by adding approximately 8 pounds of nicotine sulfate to 100 pounds of lime or calcium arsenate.