Evaluation of Control of the RWW with the Nematode Steinernema Carpocapsae, 1989

Abstract

Abstract Experiments were conducted in the field and greenhouse at the Texas A&M University Agricultural Research and Extension Center at Beaumont. A basin (120 × 80 ft) with Beaumont clay soil was disced and rototilled in the early spring. On 21 Apr the basin was fertilized with urea at 68 lb nitrogen/acre and drill planted at 100 lb seed/ acre. Distance between rows was 7 inches. The basin was then flooded on the same date and drained 22 Apr. Another flush irrigation was applied 25 Apr and drained the same d. Thiobencarb was applied on 26 Apr at 4 lbs (AI)/acre before rice emergence which occurred 29 Apr. On 23 May propanil at 3 lbs (AI)/acre and bentazon at 0.5 lbs (AI)/acre were applied followed by an application of urea at 51 lbs nitrogen/acre on 26 May. Sixteen plots (each 13 × 6 ft) were arranged in a randomized complete block (4 treatments and 4 replications) within the basin. A metal barrier was placed around each plot to prevent treatment contamination among plots. As soon as the barriers were in place a permanent flood (4 inches deep) was applied to the basin on 26 May. The basin was flush irrigated when needed between rice emergence and the permanent flood. On 7 Jun (12 d after the onset of the permanent flood) Furaden 3 GF was applied, using a hand-held shaker, at 0.6 lbs (AI)/acre to selected plots. On 8 Jun the basin was drained and nematode #25 (Steinernema carpocapsae) was applied 9 Jun to selected plots at 250/inch2 using a 4-nozzle hand held sprayer (R&D Sprayers, Inc. Model AS) equipped with 800067 tips and 100 mesh screens. Finished spray vol was 66 gal/acre. Spray was propelled with CO2 at 22 psi. Application was made at dusk when conditions were calm and the boom was kept below the top of the metal barrier. Thus, drift and exposure to UV radiation were minimal at time of application. The basin was reflooded 12 Jun. Soil remained moist during the drain period. On 3 Jul 5 soil cores (4 inch diam × inches deep); each containing about 1 plant, were removed from each plot. Plants were washed in a 40-mesh screen bucket and RWW larvae and pupae were recovered and counted. In a greenhouse experiment, Beaumont clay soil, obtained from a fallow rice research basin, was sifted through an 8 mesh screen (8 squares/inch). Thirty-six paper cups (4.25 inch diam × 5.25 inch tall) were filled with the sifted soil to 1 inch from the top. The soil in each cup was fertilized with urea at 68 lbs nitrogen/acre. Each cup was planted with 6 seeds and flush irrigated from planting until plants were about 8 inches tall at which time rice was thinned to 1 healthy plant/cup. Weeds were removed by hand. Cups were arranged in a randomized complete block (6 treatments with 6 replications) after placement in a large metal pan which was filled with water to about 1 inch from the top of the cups. Cups were filled with water so that plants were exposed to about a 2 inch flood. On 21 Aug RWW adults were collected from late planted rice at the Texas A&M University Agricultural Research and Extension Center at Beaumont. Cylindrical transparent cages made of polyactetate were placed over selected plants which were in the 3-leaf stage and about 12 inches tall. Three female and 1 male RWW were placed in each cage on 21 Aug. The tops of the cages were covered with polyester netting to prevent escape of the insects. On 24 Aug (3 d after infesting plants) cages were removed and adult RWW were found and destroyed. On 20 Sep designated cups were drained and nematode #25 (Steinernema carpocapsae) was applied to designated flooded and drained cups at the rate of 250/inch2. Thus, nematodes were applied to flood water and moist soil containing plants infested and not infested with the RWW. Treatments were applied by pipette after proper dilution of a stock suspension of nematodes was prepared. Each treated cup received 7.7 ml of the proper dilution of nematode suspension. All drained cups were reflooded 22 Sep. On 27 Sep RWW infested plants from cups treated with nematodes were washed in a screen bucket and RWW larvae and pupae were recovered and counted. The soil from remaining cups (treated with nematodes but not infested with WW) was sent to BIOSYS for nematode bioassay. Data for field and greenhouse experiments were transformed using Vx + 0.5 and analyzed by ANOVA and where appropriate means separated by DMRT.