The carrot weevil is the most economically important insect pest of carrot in the northeastern United States (Simonet and Davenport, 1981). In New Jersey, adults overwinter in and near hedgerows and fields where carrots were grown the previous year, emerging in late April to early May (Ryser, 1975). Adults feed directly on leaves and crowns of carrots, and females oviposit from early May through June in carrot roots (Ryser, 1975). Larvae tunnel extensively throughout the upper third of the roots, damaging 80% or more of the carrots in untreated fields (Zimmerman et al., 2004). Pepper (1942) reported two full broods with a partial third brood in northern New Jersey, and three full broods with a partial fourth in southern New Jersey.
Growers currently use multiple foliar sprays of diazinon, esfenvalerate, or cyfluthrin for control of carrot weevil; no other insecticides are labeled for use on carrot in New Jersey. Control of the carrot weevil is difficult because the female deposits her eggs directly in the roots, thus eliminating the potential for larval control. Consequently, pesticide applications are directed at adults to prevent or reduce oviposition. Carrot weevil damage has been increasing on New Jersey carrot farms during the past several years, and yield losses exceeded 75% on farms in Salem County in 2002 and 2003. These losses may partly be due to the cancellation of persistent broad-spectrum insecticides once labeled for carrot weevil control, such as parathion, azinphos-methyl, and phosmet, until the early 1990s. Additionally, the increase in carrot weevil damage may also be attributed to limited acreage for crop rotation, an important pest management tactic for carrot weevil (Grafius, 1984).
Seed treatment technologies have advanced rapidly during the past few years, and various seed treatments have effectively controlled a wide range of pests in many crops. There is evidence that fipronil, a relatively new phenylpyrazole insecticide that interferes with the gamma-aminobutyric acid (GABA) receptors of insect neurons, may be useful as a seed treatment for control of carrot weevils. Fipronil is highly toxic to Coleopterans, including weevils, and is systemic in plants (U.S. Environmental Protection Agency, 1996). In field trials, it has been successfully used as a seed treatment for control of the rice water weevil [Lissorhoptrus oryzophilus (Coleoptera: Cucurlionidae)] (Walsh and Johnson, 2002), cucumber beetle [Acalymma vittatum [Coleoptera: Chrysomelidae]) (Whalen and Spellman, 2005), onion maggot [Delia antiqua (Diptera: Anthomyiidae]) (Nault et al., 2005), and chironomid larva [Chironomus tepperi (Diptera: Chironomidae)] (Stevens et al., 1998).
The present trials were conducted to compare the effectiveness of a seed treatment of fipronil, an in-furrow application of thiamethoxam, and multiple foliar applications of spinosad or diazinon directed at the base of the plant for control of the carrot weevil in processing carrot.
Boivin, G. 1988 Effects of carrot developmental stages on feeding and oviposition of carrot weevil, Listronotus oregonensis (LeConte) (Coleoptera: Curculionidae) Environ. Entomol. 17 330 336
Grafius, E.J. 1984 Step-by-step management of the carrot weevil in carrots and celery in Michigan Pest Profiles, Michigan State Univ. Ext. Fact Sheet PP-9
Nault, B., Straub, R.W. & Taylor, A.G. 2005 Performance of novel insecticide seed treatments for managing onion maggot (Diptera: Anthomyliidae) in onion fields Crop Prot. 25 58 65
Pepper, B.B. 1942 The carrot weevil, Listronotus latiusculus (Bohe.) in New Jersey and its control New Jersey Agr. Expt. Sta. Bul. 693
Ryser, B.W. 1975 Investigations regarding the biology and control of the carrot weevil, Listronotus oregonensis (LeConte) in New Jersey Rutgers Univ New Brunswick, NJ MS thesis
Simonet, D.E. & Davenport, B.L. 1981 Temperature requirements for development and oviposition of the carrot weevil Ann. Entomol. Soc. Amer. 74 312 315
Stevens, M.M., Helliwell, S. & Warren, G.N. 1998 Fipronil seed treatments for the control of chironomid larvae in aerially-sown rice Field Crops Res. 57 195 207
United States Environmental Protection Agency 1996 New pesticide fact sheet: Fipronil; EPA-737-F-96-005. U.S. Environ. Protection Agency, Office of Prevention, Pesticides, and Toxic Substances U.S. Government Printing Office Washington, DC
Taylor, A.G., Eckenrode, C.J. & Straub, R.W. 2001 Seed coating technologies and treatments for onion: Challenges and progress HortScience 36 199 205
Whalen, J. & Spellman, M. 2005 Insect management in cucumbers with seed treatments 4 7 University of Delaware integrated pest management results, 2005 Univ. Delaware Newark
Zimmerman, M., Hitchner, E., Ghidiu, G.M. & Rossell, E. 2004 Control of carrot weevil in processing carrots 2 3 Vegetable entomology research results New Jersey Agr. Expt. Sta. Bul. 104M