University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln U.S. Department of Agriculture: Agricultural Publications from USDA-ARS / UNL Faculty Research Service, Lincoln, Nebraska 2010 Efficacy of Methoprene for Control of Five Species of Psocids (Psocoptera) on Wheat, Rice, and Maize Christos G. Athanassiou University of Thessaly, [email protected] Frank H. Arthur USDA-ARS, [email protected] James E. Throne USDA-ARS, Manhattan, KS, [email protected] Follow this and additional works at: https://digitalcommons.unl.edu/usdaarsfacpub Athanassiou, Christos G.; Arthur, Frank H.; and Throne, James E., "Efficacy of Methoprene for Control of Five Species of Psocids (Psocoptera) on Wheat, Rice, and Maize" (2010). Publications from USDA-ARS / UNL Faculty. 2046. https://digitalcommons.unl.edu/usdaarsfacpub/2046 This Article is brought to you for free and open access by the U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Publications from USDA-ARS / UNL Faculty by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. 2244 Journal of Food Protection, Vol. 73, No. 12, 2010, Pages 2244–2249 Copyright G, International Association for Food Protection Efficacy of Methoprene for Control of Five Species of Psocids (Psocoptera) on Wheat, Rice, and Maize CHRISTOS G. ATHANASSIOU,1,2* FRANK H. ARTHUR,2 AND JAMES E. THRONE2 1Laboratory of Entomology and Agricultural Zoology, Department of Agriculture, Crop Production and Rural Environment, University of Thessaly, Phytokou Str., 38443, N. Ionia, Magnisia, Greece; and 2U.S. Department of Agriculture, Agricultural Research Service, Center for Grain and Animal Health Research, 1515 College Avenue, Manhattan, Kansas 66502, USA MS 10-203: Received 11 May 2010/Accepted 30 August 2010 ABSTRACT The insect growth regulator methoprene was evaluated for control of Liposcelis bostrychophila Badonnel, Liposcelis decolor (Pearman), Liposcelis entomophila (Enderlein), Liposcelis paeta Pearman (Psocoptera: Liposcelididae), and Lepinotus reticulatus Enderlein (Trogiidae) at application rates of 1, 5, and 10 ppm on maize, wheat, and rice. Methoprene did not completely suppress progeny production during the 40-day test period, but did cause a significant reduction in adult progeny in all psocid species at the application rates of 5 and 10 ppm. At 1 ppm, numbers of adults were reduced for all species on wheat and maize, but only for L. paeta on rice. Nevertheless, the numbers of nymphs present after 40 days generally were not reduced, relative to the controls. Methoprene applied at rates of 1 to 10 ppm to stored grain would not provide adequate control of psocids. Psocoptera (psocids) have become pests of stored with other reduced-risk insecticides, can control stored-grain products in Australia, China, and the United States during insects, including those populations that are resistant to the last two decades (20, 29). Psocids can feed on grain organophosphorus insecticides (4–11, 19, 21, 24). kernels and cause quality loss; they can also be cause for There are few reports in the scientific literature rejection of export grain and a health hazard (17). Many regarding efficacy of IGRs against psocids. Bucci (3) psocid species are tolerant to contact insecticides, and they evaluated both methoprene and fenoxycarb against L. can survive exposure on grains treated with concentrations bostrychophila by mixing different doses of these insecti- of insecticides that will control other insect species in stored cides in the psocid rearing media. The author found that grains. For example, Nayak et al. (22) reported that methoprene reduced the numbers of adults produced, but Liposcelis bostrychophila Badonnel, Liposcelis entomophila not the numbers of nymphs. Although the tested rates were (Enderlein), and Liposcelis paeta Pearman (Psocoptera: as high as 190 ppm, complete progeny production was not Liposcelididae) were tolerant to the pyrethroids deltamethrin achieved but adult fertility and egg hatch were reduced. and bioresmethrin and the carbamate carbaryl. The latter Nayak et al. (21, 22) obtained similar results on efficacy of two species were also tolerant to the organophosphorus methoprene at 1 ppm on wheat, which is the registered rate insecticides chlorpyriphos-methyl, pirimiphos-methyl, and in Australia, against L. bostrychophila, L. decolor, L. fenitrothion. Daglish et al. (12) reported that L. entomophila entomophila, and L. paeta, with little to no adult mortality was tolerant to bifenthrin, while spinosad was only and little progeny suppression. However, there are no data moderately effective against L. bostrychophila, L. paeta, available on methoprene for control of psocids at the higher and Liposcelis decolor (Pearman) (23). registered rates in the United States, such as 2.5 and 5 ppm, The use of insect growth regulators (IGRs) as grain and on other commodities including rice and maize. In protectants has certain advantages over traditional neuro- addition, previous studies have shown significant variation toxic insecticides, including low mammalian toxicity, in efficacy of grain protectants on different commodities (2, residual persistence, and reduced risks to applicators (1, 7, 16, 27). The objective of our study was to evaluate efficacy 9–11, 13). Methoprene is currently the only IGR that is of methoprene at different application rates on wheat, rice, registered as a grain protectant in the United States at the and maize for control of the stored-grain psocids L. label rates of 1, 2.5, and 5 ppm. It is a juvenile hormone bostrychophila, L. entomophila, L. paeta, L. decolor, and analogue, and it can confer egg toxicity as well as disruption Lepinotus reticulatus Enderlein (Psocoptera: Trogiidae). We of normal development of the immature stages. Several tested the label rates of 1 and 5 ppm; we also tested twice studies indicate that methoprene, alone or in combination the label rate of 10 ppm to determine whether this rate would have greater efficacy for psocids. Label rates for * Author for correspondence. Tel: z30-2421093195; Fax: z30-2421093195; grain insecticides are based on rates required to kill beetle E-mail: [email protected]. pests, and psocids often are not susceptible at these rates. J. Food Prot., Vol. 73, No. 12 METHOPRENE EFFICACY FOR STORED-GRAIN PSOCIDS 2245 TABLE 1. Number of adults and nymphs of Liposcelis bostrychophila per vial 40 days after the introduction of 10 female parental individuals on untreated commodities (0 ppm) or commodities treated with methoprene at three dose ratesa Stage Dose (ppm) Wheat Rice Maize F value P value Adultb 0 102.6 ¡ 18.0 ac 75.8 ¡ 13.0 a 48.2 ¡ 14.6 a 3.1 0.06 1 6.3 ¡ 1.4 A b 66.7 ¡ 15.3 B a 4.2 ¡ 0.9 A b 15.9 ,0.01 5 4.2 ¡ 0.7 b 5.8 ¡ 1.4 b 3.1 ¡ 0.8 b 2.2 0.14 10 4.5 ¡ 0.5 b 5.8 ¡ 0.9 b 2.8 ¡ 0.7 b 3.3 0.06 F value 29.1 14.1 9.3 P value ,0.01 ,0.01 ,0.01 d Nymph 0 48.0 ¡ 11.4 A 21.6 ¡ 5.8 B 9.0 ¡ 1.7 B 7.1 ,0.01 1 39.1 ¡ 13.9 18.2 ¡ 5.5 10.0 ¡ 2.4 2.9 0.07 5 34.9 ¡ 6.7 A 26.7 ¡ 6.7 A 5.8 ¡ 1.7 B 6.3 ,0.01 10 38.2 ¡ 7.7 A 26.3 ¡ 3.6 A 3.5 ¡ 1.4 B 15.6 ,0.01 F value 0.3 0.5 2.5 P value 0.83 0.65 0.07 a Values are means ¡ SE. b Two-way ANOVA results for adults: dose, df ~ 3,96, F ~ 42.6; commodity, df ~ 2,96, F ~ 7.4; dose | commodity, df ~ 6,96, F ~ 5.9; in all cases P , 0.01. c Within each row, means followed by the same uppercase letter(s) are not significantly different; within each life stage and column, means followed by the same lowercase letter(s) are not significantly different; where no letters exist, no significant differences were noted; in all cases for rows df ~ 2,24, for columns df ~ 3,32; HSD test at 0.5. d Two-way ANOVA results for nymphs: dose, df ~ 3,96, F ~ 0.2, P ~ 0.88; commodity, df ~ 2,96, F ~ 23.1, P , 0.01; dose | commodity, df ~ 6,96, F ~ 0.5, P ~ 0.81. MATERIALS AND METHODS taking new aliquot samples from the treated lots. The vials had a plastic lid with a hole in the center covered with fine mesh. The Commodities and formulation. Untreated, clean, and internal neck of the vials was covered by Fluon (Northern infestation-free wheat (Triticum aestivum L., a mixture of the Products, Woonsocket, RI) to prevent psocids from escaping. All var. Fuller and Santa Fe), rice (Oryza sativa L., var. Francis), and vials were then placed in black plastic boxes with saturated salt maize (Zea mays L., hybrid Golden Harvest H-8713) were used in solutions of sodium chloride to maintain the relative humidity level the tests. The moisture contents of the grains were adjusted to at 75%, as suggested by Opit and Throne (25), and the boxes were 13.5% before the beginning of the experiments. The methoprene placed in incubators set at 27.5uC and 75% relative humidity. The formulation used in the tests was Diacon II (Wellmark Interna- vials were opened after 40 days, and the numbers of live tional, Schaumburg, IL), a formulation that contains 33.6% active individuals were recorded separately for adults and nymphs. The ingredient of (S)-methoprene. entire procedure was replicated two times more by preparing new 1.6-kg lots each time, which gave a total of nine vials for each Insects. Five psocid species were used in the tests, L.