Impact of foliar-applied insecticides for control of the invasive rice delphacid in Texas rice, 2024

The rice delphacid (RD) is a planthopper native to South and Central America; it has become an invasive pest in Texas rice. First detected in Texas in 2015, RD populations have since spread throughout the Texas rice belt. The objective of this field trial was to assess the efficacy of 1-time applications of 8 different foliar insecticides labeled for other sucking/hemipteran insects, including 2 emergency exemption labels (Endigo ZCX and Tenchu 20SG) in controlling RD. This study was conducted in a rice field (main crop; variety CL153) naturally infested with RD at a grower’s location in Galveston County, Texas, in Aug 2024. A total of 9 treatments including an untreated check were arranged in a randomized complete block design with 4 replications. The 8 insecticide treatments were Dimethoate LV-4 (AI: dimethoate), Endigo ZCX (AI: thiamethoxam and lambda-cyhalothrin), Flonicamid (research product), Malathion 57 EC (AI: malathion), Orthene 97 (AI: acephate), Sevin XLR Plus (AI: carbaryl), Sivanto Prime 200 SL (AI: flupyradifurone), Tenchu 20SG (AI: dinotefuran). Plots measured 4 ft wide × 20 ft long. RD populations were determined by conducting sweep samples (10 sweeps per plot) with a 15-inch sweep net. Pretreatment RD samples were collected from each plot before foliar insecticide treatments were applied on 10 Aug using a hand-held CO₂-pressurized 3-nozzle spray rig (800,067 tips, 50 mesh screens, 28 gpa final spray volume), using 2-liter plastic bottles. Insecticide efficacy on RD was evaluated 4 (Aug 14), 6 (Aug 16), 9 (Aug 19) and 12 (Aug 22) days after treatment (DAT). Sweep samples were placed in zip-top gallon bags, frozen, RD were sorted (adults, nymphs, and total) and recorded. Untransformed data were analyzed using ANOVA, and means were separated using a Fisher’s Protected LSD (P < 0.05).

At 4 DAT, RD adult populations were significantly higher in the Tenchu 20 SG treated plots compared to the untreated check (Table 1). Total RD numbers at 4 DAT were significantly lower in plots treated with Endigo ZCX, Flonicamid, or Orthene 97 compared to the untreated check (Table 3). At 6 DAT, RD adult numbers were significantly lower in the Flonicamid and Orthene 97 treated plots compared to the untreated check (Table 1). RD nymph populations were significantly reduced in the Endigo ZCX and Orthene 97 treated plots at 6 DAT compared to the untreated check (Table 2). Total RD populations were significantly lower in the Endigo ZCX, Flonicamid, and Orthene 97 treated plots compared to the untreated check (Table 3). At 12 DAT, only the Orthene 97 treatment resulted in significantly lower populations of adults, nymphs, and total RD compared to the untreated check (Table 1, 2, and 3). Although the results of this study show promise for Flonicamid, Orthene 97, and Endigo ZCX as potential chemistries for RD control, further research is needed to determine the optimal timing for insecticide application.¹

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