Evaluation of Dimilin and Benlate for Soybean Insect Pest and Disease Control, 1990

The experiment was conducted at the Texas A&M University Agricultural Research and Extension Center, Beaumont. The experimental design was a randomized complete block with 6 treatments and 4 replications. Soil type was a Midland silty clay loam. Plot size was 40 ft × 6 rows (32-inch row spacing) with 2 buffer rows on either side of each plot. Plots were planted 16 Jun at about 10 seeds/ft. On 18 Jun plots were treated with 2 pt Dual and 1 qt Roundup/acre in a finished spray volume of 20 gal/acre. Seedlings emerged 24 Jun but the stand was not uniform due to large amounts of partially decayed organic matter which arose from a heavy weed cover at the time of land preparation. On 3 Jul plots were treated with 1.5 pt Storm/acre in a finished spray volume of 20 gal/acre. On 28 Aug (when soybeans were in V13 R3) Dimilin, Benlate, and Dimilin + Benlate treatments were applied to 4 rows of each plot using a Solo backpack sprayer. Finished spray volume was 20 gal/acre. One day pre-application and 2, 7, and 14 day post-application samples of insects were taken; however, insect populations were too low on all sample dates for a meaningful evaluation. A repeat application of treatments was made (when soybeans were V15 R5) on 20 Sep. At this time target insect populations were evident and increasing. Pre-application (2 h before application) and 1, 7, 13, 20, and 32 d post-application insect samples were taken. Each sample consisted of shaking soybean plants along 9 ft of row over a vertical beat sheet. Insects were shaken and brushed from the vertical beat sheet into a plastic bag which was frozen for later inspection of the contents. One sample (9 ft of sampled row) was taken from each plot on each sample date. From time of application on 20 Sep to 14 d later no appreciable precipitation was recorded. On 6 Nov plots were visually rated for disease severity. Anthracnose was the predominant disease. At maturity, 40 ft of row in each plot was harvested with a small plot combine. Insect count data were transformed using Vx + 0.5 and all data analyzed by ANOVA and DMRT where appropriate.