Control of Aphids in Cotton in Mississippi, 1985

A small plot field study was conducted to measure the relative efficacy of several insecticides for control of aphids on cotton in the Delta region of MS. Since the species of aphids was not determined, we assumed that the population was predominantly composed of Aphis gossypii. The study was conducted on a grower farmer where aphids were found at measurable severs. According to the grower the field had previously been treated several times with pyrethroid insecticides. Plot size was 4 rows × 50 ft. Applications were applied with a John Deere high clearance sprayer equipped with 2 TX-4 nozzles/row that delivered a spray volume of ca. 3.0 gpa. Each treatment was replicated 4 times in a randomized complete block design. Pretreatment observations indicated that the aphid population was between 10-20 aphids/upper leaf. Posttreatment observations were made by randomly collecting 10 leaves from the upper, mid, and lower canopy levels in each plot at 2, 7, and 14 days after application. Each collected leaf was classified as having (1) 0 aphids, (2) 1-5 aphids, (3) 6-15 ;iphids, (4) 16-25 aphids, or (5) 25+ aphids. For purposes of comparing the various treatments, the data were converted to estimated number of aphids/leaf by multiplying the mid-point of each classification by the number of observations for that classification. Data were subjected to AOV and means were separated by Duncan’s multiple range test.