FIELD AND FORAGE CROPS Insecticide Toxicity to Adelphocoris lineolatus (Hemiptera: Miridae) and its Nymphal Parasitoid Peristenus spretus (Hymenoptera: Braconidae) YONG-QIANG LIU, BING LIU, ABID ALI, SHU-PING LUO, YAN-HUI LU, 1 AND GE-MEI LIANG State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China. J. Econ. Entomol. 108(4): 1779–1785 (2015); DOI: 10.1093/jee/tov144 ABSTRACT In China, Adelphocoris lineolatus (Goeze) (Hemiptera: Miridae) is an important pest of alfalfa, cotton, and other crops, while Peristenus spretus (Chen & van Achterberg) (Hymenoptera: Bra- conidae) is the dominant nymphal parasitoid of this mirid bug. In the present study, the toxicity of 17 common insecticides to A. lineolatus was evaluated, and the susceptibility of P. spretus to the insecticides with high toxicity to A. lineolatus was tested under laboratory conditions. Of the 17 insecticides tested, 12 (beta cypermethrin, deltamethrin, carbosulfan, acetamiprid, emamectin benzoate, imidacloprid, phoxim, chlorpyrifos, acephate, profenophos, hexaflumuron, and abamectin) had a highly toxic effect on second-instar nymphs of A. lineolatus, with LC 50 values ranging from 0.58 to 14.85 mg a.i. (active ingredi- ent) liter 1 . Adults of P. spretus were most sensitive to chlorpyrifos, with LC 50 values of 0.03 mg a.i. liter 1 , followed by phoxim, acetamiprid, profenophos, carbosulfan, acephate, deltamethrin, emamectin benzoate, imidacloprid, beta-cypermethrin, and abamectin, with LC 50 values ranging from 0.06 to 3.09, whereas hexaflumuron exhibited the least toxicity to the parasitoid, with LC 50 values >500 mg a.i. liter 1 . A risk quotient analysis indicated that beta-cypermethrin, emamectin benzoate, abamectin, and hexaflu- muron when applied against A. lineolatus were the least toxic to P. spretus. KEY WORDS mirid bug, parasitoid, acute toxicity, risk assessment The mirid bug Adelphocoris lineolatus (Goeze) (Hemi- ptera: Miridae) is an Old World species (Wheeler 2001) widely distributed in western Europe, northern Africa, the Middle East, and much of Asia; it is adven- tive in North America (Scudder and Foottit 2006). This pest has a wide host range and feeds mainly on plant inflorescences and flowers, causing the premature petal fall. Feeding can reduce the yield of seed crops by 50% or more (Wheeler 2001). A. lineolatus is a serious pest of alfalfa in Poland, Hungary, France, Canada, the Czech Republic, and elsewhere in Europe and many countries in the former USSR, such as Tajikistan (Wheeler 2001, May et al. 2003). In the United States, A. lineolatus often occurs together with Lygus spp. at high densities in alfalfa fields, and its feeding results in bud blast, flower abortion, and missing or shrunken seeds, which can greatly reduce seed yield (Soroka 1991). Moreover, A. lineolatus also damages many other plants, such as asparagus in Canada, peach trees in Italy, legume seed crops and sunflower seed plants in the former USSR, and birdsfoot trefoil in the United States (Wheeler 2001). In China, A. lineolatus has 125 recorded host plants from 29 families, including cotton, alfalfa, potato, sun- flower, and many other crops (Lu and Wu 2008). In China, it was previously considered to be only a sec- ondary pest of various crops. Since the late 1990s, how- ever, with the widespread cultivation of Bt (Bacillus thuringiensis) cotton and the associated reduction in use of broad-spectrum pesticides, A. lineolatus and other mirid bugs [mainly Apolygus lucorum (Meyer- Du ¨r)] emerged as major pests of cotton and adjacent crops (Wu et al. 2002, Lu et al. 2010). Insecticides are the major form of pest control against mirid bugs in China (Lu and Wu 2011). To date, while various stud- ies have been conducted on the chemical control of Ap. lucorum, a widely distributed and frequently domi- nant mirid bug found on cotton and fruit trees (Liu et al. 2008; Dang et al. 2012; Tan et al. 2012a,b), less attention has been devoted to the management of A. lineolatus. A. lineolatus is the most important pest mirid in regions with mixed plantings of alfalfa and cotton (Lu and Wu 2008). Alfalfa is its preferred host throughout the year. From May to September, alfalfa plants are harvested as forage once a month. After cutting, A. lineolatus adults in alfalfa move into cotton and other crops, in which large adult populations accumu- late. About 10 d after cutting, alfalfa plants have regrown sufficiently that A. lineolatus adults return to alfalfa fields. Thus, alfalfa fields are the source of A. lineolatus populations found on many crops within an entire farming system (Lu and Wu 2008). A. lineola- tus adults and nymphs both occur in alfalfa fields, while 1 Corresponding author, e-mail: yhlu@ippcaas.cn. V C The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com Downloaded from https://academic.oup.com/jee/article/108/4/1779/2380132 by guest on 24 February 2023