Rice Stink Bug Control with Selected Insecticides

Transcription

1 PEST MANAGEMENT: INSECTS Rice Stink Bug Control with Selected Insecticides D.R. Johnson, G.E. Studebaker and H. Robertson ABSTRACT A small-plot trial was conducted to evaluate the efficacy of selected insecticides on the rice stink bug. All insecticides provided significant control and improved quality. Low rates of lambda-cyhalothrin, resolved zeta-cypermethrin, gama-cyahalothrin, and methyl parathion proved to be effective alone and in combination. The new insecticides, gammacyhalothrin and resolved zeta-cypermethrin, provided similar control to the previously labeled products. Methyl parathion applied in combination with lambda-cyhalothrin and resolved zeta-cypermethrin gave improved control of adult and immature stink bugs in rice. INTRODUCTION The rice stink bug, Oebalus pugnax (Fabricius), is a major pest of rice production in Arkansas. Rice stink bug damages rice by feeding on the flowering rice and on kernels as they develop. Economic injury to rice results from yield reduction and the discoloration of rice kernels as a result of feeding. Discoloration is commonly related to rice stink bug feeding activity. Discolored, or pecky, rice kernels reduce the commercial value of rice. Riceland estimates that Arkansas rice producers lost $30 million due to rice stink bug damage in Damage occurs when the insect inserts its mouth parts into the developing rice kernel and extracts some or all of the contents, resulting in a discolored area due to fungi introduced at the time of feeding (Lee et al., 1993). Insecticides are the main control agents utilized against the rice stink bug. Some new insecticides are being developed that may aid in the control of the rice stink bug. Evaluation of these and current products remains necessary for maintaining control procedures. 182

2 B.R. Wells Rice Research Studies 2003 PROCEDURES A stink bug management study was conducted in 2003 at the University of Arkansas Northeast Research and Extension Center (NEREC) located in Mississippi County, and at the University of Arkansas Pine Tree Branch Station (PTBS) located in St. Francis County. At both locations a single spray application of selected insecticides was applied to each test followed by three individual rating evaluations. Eleven replicated treatments were applied at each location using a Mud Master and CO 2 - powered boom using TX6 hollow-cone spray tips in 9.4 gallons of total solution per acre. Plots consisted of two 7 ft by 60 ft strips on 7-in. row spacing, with a 3 ft wide gap between each strip. The variety at each location was Cocodrie, planted on 30 April at NEREC and 23 May at PTBS. The treatments were arranged in a randomized complete block with four replications at each location. Each evaluation consisted of ten sweeps using a 15-in. sweep net throughout each plot. These sweeps were taken at the tops of the plants after the plant population had achieved full heading. At PTBS, the test consisted of single chemical applications of selected insecticides. These applications were low and reduced rates of Mustang Max 0.8 EC (resolved zeta-cypermethrin), Karate Z 2.08 CS (lambda-cyhalothrin); Malathion 5 EC, methyl parathion; and XDE CS (gamma-cyhalothrin). Treatment rates are listed in Table 1. This spray application took place on 2 September Evaluations for each of these treatments were taken at 6, 9, and 12 DAT. At the NEREC, the test consisted of both single chemical applications and tank mixes of selected insecticides. The single chemical applications were of low and reduced rates for Mustang Max 0.8 EC (resolved zeta-cypermethrin); Karate Z 2.08 CS (lambda-cyhalothrin); Malathion 5 EC (malathion); and Methyl Parathion 4 EC. The tank mix application consisted of Mustang Max 0.8 EC with Methyl Parathion 4 EC, and Karate Z 2.08 CS with Methyl Parathion 4 EC. Treatment rates are listed in Table 3. This spray application took place on 5 September Evaluations for each of these treatments were taken at 4, 6, and 14 days after treatment (DAT). RESULTS AND DISCUSSION At the PTBS, the test consisted of only single chemical applications of selected insecticides. Again, with the exception of malathion 5 EC, all of the treatments significantly reduced the stink bug population (Table 1). The other treatments were effective in control of stink bugs with resolved zeta-cypermethrin providing 72% reduction across all rates, lambda-cyhalothrin and gama-cyhalothrin with a 77% reduction, methyl parathion with 70% control, and malathion only providing a 24% reduction in the population. Overall, yields were not significantly different in the test (Table 2). However, the percent peck was significantly lower in all treatments compared to the untreated check with the exception of one rate of the resolved zeta-cypermethrin that had slightly more peck that other treatments. Lambda-cyhalothrin at the highest rate and methyl parathion had the lowest percent peck with 0.92% and 0.90%, respectively, compared to 2.5% in the untreated check. 183

3 AAES Research Series 517 At the NEREC location, the test consisted of both single chemical applications and tank mixes of selected insecticides. With the exception of malathion 5 EC (0.94 lb ai/ acre) all of the treatments significantly reduced the stink bug population (Table 3). The tank mixes of resolved zeta-cypermethrin plus methyl parathion and lambda-cyhalothrin plus methyl parathion resulted in the most efficient control providing a 93% reduction in the population when compared to the untreated check. The most efficient single chemical spray was the lower rate of methyl parathion 4 EC (0.375 lb ai/acre) providing 89% control compared to resolved zeta-cypermethrin at 70% and lambda-cyhalothrin at 80%. Consideration should be given to the fact that the single treatments were the lowest label rates and the test was designed to see if combinations would give more efficient use of these insecticides. No significant difference was observed in yield for the treatments or quality factors (Table 4). However, as expected, a trend for lower peck was seen in rice that was treated for rice stink bug. SIGNIFICANCE OF FINDINGS Although all treatments provided control of the rice stink bug, these data suggest that rice producers can use lower rates of some insecticides, thus saving money in control costs. Low rates of these insecticides will be evaluated next year in large-block trials to see if new recommendations can be made. Resolved zeta-cypermethrin provided similar control to the best performing, previously labeled products; it was available to producers in 2003 and has proven to be an effective control method. Also, the developing insecticide, gamma-cyhalothrin, provided similar control to existing products and will be a valuable tool for controlling the rice stink bug in the future. ACKNOWLEDGMENTS Funding for this research was provided by rice grower check-off funds through the Arkansas Rice Research and Promotion Board. We would also like to express our appreciation to Riceland Foods for evaluating the rice milling quality. We greatly appreciate the help of Mr. Roger Eason, Mr. Shawn Clark, and the staff of the University of Arkansas PTBS. LITERATURE CITED Lee, F.N., N.P. Tugwell, S.J. Fannah, and G.J. Weidemann Role of fungi vectored by rice stink bug (Heteroptera: Pentatomidae) in discoloration of rice kernels. J. Econ. Entomol. 86(2):

4 B.R. Wells Rice Research Studies 2003 Table 1. Evaluation of insecticides for control of stink bugs at the Pine Tree Branch Station, Number of stink bugs 6 DAT z 6 DAT 9 DAT 9 DAT 12 DAT 12 DAT Average Average Treatment Rate nymph adult nymph adult nymph adult nymph adult (lb ai/ace) (no./10 sweeps) Untreated check Resolved zeta-cypermethrin Resolved zeta-cypermethrin Resolved zeta-cypermethrin Lambda-cyhalothrin Lambda-cyhalothrin Lambda-cyhalothrin Malathion Gamma-cyhalothrin (XDE-225) Gamma-cyhalothrin (XDE-225) Gamma-cyhalothrin (XDE-225) Methyl Parathion LSD (P=.05) Z DAT = days after treatment. 185

5 AAES Research Series 517 Table 2. Effect of insecticides for control of stink bugs on yield and quality of rice at the PTBS, Treatment Rate Milling yield Peck Yield (lb ai/acre) (%) (lb/acre) (bu/acre) Untreated check Resolved zeta-cypermethrin Resolved zeta-cypermethrin Resolved zeta-cypermethrin Lambda-cyhalothrin Lambda-cyhalothrin Lambda-cyhalothrin Malathion Gamma-cyhalothrin (XDE 225) Gamma-cyhalothrin (XDE 225) Gamma-cyhalothrin (XDE 225) Methyl Parathion LSD (P=0.05)

6 B.R. Wells Rice Research Studies 2003 Table 3. Evaluation of insecticides for control of stink bugs at the Northeast Research and Extension Center, Number of stink bugs 4 DAT z 4 DAT 6 DAT 6 DAT 14 DAT 14 DAT Average Average Treatment Rate nymph adult nymph adult nymph adult nymph adult (lb ai/ace) (no./10 sweeps) Untreated check Resolved zeta-cypermethrin Resolved zeta-cypermethrin plus Methyl parathion Resolved zeta-cypermethrin plus Methyl parathion Resolved zeta-cypermethrin Lambda-cyhalothrin Lambda-cyhalothrin Lambda-cyhalothrin plus Methyl parathion Lambda-cyhalothrin plus Methyl parathion Methyl parathion Methyl parathion Malathion LSD (P=0.05) z DAT = Days after treatment 187

7 AAES Research Series 517 Table 4. Effect of insecticides for control of stink bugs on yield and quality of rice at the Northeast Research and Extension Center, Treatment Rate Milling yield Peck Yield (lb ai/acre) (%) (lb/acre) (bu/acre) Untreated check Resolved zeta-cypermethrin Resolved zeta-cypermethrin plus Methyl parathion Resolved zeta-cypermethrin plus Methyl parathion Resolved zeta-cypermethrin Lambda-cyhalothrin Lambda-cyhalothrin Lambda-cyhalothrin plus plus Methyl parathion Lambda-cyhalothrin plus plus Methyl parathion Methyl parathion Methyl parathion Malathion LSD (P=0.05)