Plum Curculio (Coleoptera: Curculionidae) Adult Mortality and Associated Fruit Injury After Exposure to Field-Aged Insecticides on Tart Cherry Branches
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ECOTOXICOLOGY Plum Curculio (Coleoptera: Curculionidae) Adult Mortality and Associated Fruit Injury After Exposure to Field-Aged Insecticides on Tart Cherry Branches 1 2 3 ERIC J. HOFFMANN, CHRISTINE VANDERVOORT, AND JOHN C. WISE J. Econ. Entomol. 103(4): 1196Ð1205 (2010); DOI: 10.1603/EC10017 ABSTRACT Plum curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), adults were exposed to Þeld-aged residues of thiamethoxam, acetamiprid, thiacloprid, indoxacarb, or azin- phos-methyl on tart cherry, Prunus cerasus L. variety Montmorency. At 1, 3, 7, and 14 d postapplication, fruit were sampled for chemical residues, and bioassays were used to assess beetle mortality and plant tissue injury. Azinphos-methyl had lethal activity within1dofexposure at all postapplication intervals and signiÞcant fruit protection extended to 14 d postapplication. All of the neonicotinoids had lethal activity at 3 d posttreatment, with acetamiprid activity extending to 7 d. Antifeedant and oviposition deterrent effects were seen with thiamethoxam and thiacloprid; damage incidence was signiÞcantly reduced in the absence of signiÞcant beetle mortality or intoxication. Thiamethoxam and acetamiprid penetrated into leaf and fruit tissue and were detected in the interior tissues at 14 d postapplication, but interior thiacloprid residues were not detected after day 1. Indoxacarb provided some fruit protection out to 7 d postapplication, and 14-d-old residues intoxicated beetles, but the slow action of this compound allowed signiÞcant damage to occur before beetles were incapacitated. Indoxacarb was only detected as a surface residue after the Þrst day postapplication. These data on the plantÐ insectÐchemistry interactions will support use and management decisions as compounds with acute contact activity are phased out. KEY WORDS plantÐinsectÐchemistry triad, sublethal effects, antifeedant, oviposition deterrent Plum curculio, Conotrachelus nenuphar (Herbst) (Co- internal feeding of the larvae can cause fruit abscission leoptera: Curculionidae), is a key pest of eastern (Levine and Hall 1977), and the oviposition scar is North American tree fruit. Adult oviposition and larval sufÞcient to reduce the value of fresh market fruit, feeding on fruit are major causes of economic losses in regardless of any larval damage. The oviposition scar commercial tree fruit crops east of the Rocky Moun- is not a major issue in processed fruit, but there are tains. Adults emerge from their overwintering sites marketing mandates for infestation-free processed tart and mate in early spring, with most females mated well cherries at harvest (USDA Agricultural Marketing in advance of commercial crop fruit set (Smith and Service 1941a,b). There are no disinfestation proce- Salkeld 1964, Racette et al. 1992, Hoffmann et al. 2004). dures currently available for tart cherries, so growers Plum curculio adults have been observed to feed on are under signiÞcant pressure to keep their entire leaves, ßowers, and fruit structures as soon as they orchards free of plum curculio infestation at harvest. arrive in orchards in the spring (Chouinard et al. Current control tactics for plum curculio are cen- 1993). On fruit, feeding damage occurs as punctures tered on insecticide-based population control during with gouged-out subsurface ßesh, and oviposition in- the oviposition period. Fruit are monitored for evi- jury is readily identiÞable by the c-shaped incision dence of beetle activity (e.g., feeding damage and that the female chews into the fruit skin before ovi- oviposition scars), and controls are initiated at the Þrst position into the ßesh of the fruit. New oviposition sign or in anticipation of beetle presence, after the scars have been noted from May through early July if pollination period is completed. In apples and cher- appropriate hosts are present (Reissig et al. 1998). The ries, the organophosphate azinphos-methyl (Guthion, Bayer Cropscience, Research Triangle Park, NC) has provided excellent plum curculio control since the 1 Corresponding author: USDA Arid Lands Agricultural Research Center, 21881 N. Cardon Lane, Maricopa, AZ 85238 (e-mail: late 1950s (Bobb 1957, Smith and Fiori 1959, Snapp [email protected]). 1960, Forsythe and Rings 1965). However, this com- 2 Pesticide Analytical Laboratory, Michigan State University, 206 pound is being phased out as a result of the 1996 Food Center for Integrated Plant Systems, Michigan State University, East Quality and Protection Act; the registration is cur- Lansing, MI 48824-1311. 3 Center for Integrated Plant Systems, Michigan State University, rently set to expire in 2012 (USEPA 2006). A related East Lansing, MI 48824-1311. compound, phosmet (Imidan Gowan Co., Yuma, AZ), 0022-0493/10/1196Ð1205$04.00/0 ᭧ 2010 Entomological Society of America August 2010 HOFFMANN ET AL.: PLUM CURCULIO AND FIELD WEATHERED INSECTICIDES 1197 is also known to offer good protection against plum ticides were applied to experimental plots other than curculio (Forsythe and Rings 1965, Hagley and Chiba those described below. 1980). Phosmet registration is expected to continue Insect Source and Maintenance. Northern strain beyond that of azinphos-methyl, but rate restrictions plum curculio adults were collected from 5 May to 10 and increased preharvest intervals may reduce its util- June 2005 in cherry and apple (Malus spp.) orchards ity. at the TNRC by using beating trays or commercially There are nonorganophosphate compounds regis- available pyramid traps (Tedders and Wood 1994). tered for tree fruit that provide crop protection during Beetles were kept together for 1 wk after Þeld col- the plum curculio oviposition period. Applications of lection to ensure that females were mated, sexed ac- the neonicotinoids thiamethoxam and thiacloprid cording to Thomson (1932), and placed into gender- have shown Ͼ80% reduction in apple fruit damage separate screen cages (model 1450 B, BioQuip (Wise et al. 2006) and also show curative activity when Products Inc., Gardena, CA) lined with paper towels. applied to infested fruit (Wise et al. 2007a, Hoffmann Cages were kept outside in a shaded area near the et al. 2009). The neonicotinoids acetamiprid and imi- cherry orchard. Beetles were provided with untreated dacloprid are considered less effective tools but are cherry branches (P. cerasus variety Montmorency) currently labeled for plum curculio suppression. The with fruit and foliage in wetted ßoral foam (OASIS, oxadiazine indoxacarb (Avaunt, DuPont, Wilmington, Smithers-Oasis Co., Kent, OH). Plant material in cages DE) also has demonstrated fruit protection in Þeld was replaced every 2 to 3 d, and water was added daily. trials (Wise et al. 2006), and several pyrethroids are Insecticides. There were Þve formulated materials registered for plum curculio control. used in these Þeld trials: azinphos-methyl (Guthion Despite this array of tools, there are signiÞcant gaps 50W, 1,120 g [AI]/ha, Bayer CropScience), acet- in our understanding of how these various compounds amiprid (Assail 70WP, 167 g [AI]/ha, Cerexagri, King achieve fruit protection. The organophosphates are of Prussia, PA), thiamethoxam (Actara 25WG, 79 g well known for their acute adulticidal contact activity, [AI]/ha, Syngenta, Greensboro, NC), thiacloprid but it cannot be assumed that all classes and com- (Calypso 4F, 158 g [AI]/ha, Bayer CropScience), and pounds perform similarly. Sublethal antifeedant or indoxacarb (Avaunt, 126 g [AI]/ha, DuPont). Insec- repellent activities may be quite effective crop pro- ticides were tank mixed at 935 liters/ha concentrated tection mechanisms, but they can be overlooked in spray and sprayed with an FMC 1029 airblast sprayer. laboratory toxicity screenings. Antifeedant activity Field Application. Chemicals were applied on 31 has been reported in neonicotinoids (Nauen et al. May 2005 in a randomized, complete block design, 1998, Drinkwater 2003, Wise et al. 2007b, Tansey et al. with four blocks and one treatment replicate per 2008), and many botanical extracts are behaviorally block. Cherry fruit were at 8Ð10 mm in diameter at the active against insect pests (Isman 2006). time of application. Each treatment was separated Intensifying economic competition and increased from neighboring trees within rows by at least two attention to sustainability principles demand that ap- trees, with a row between treatments. Unsprayed con- plication recommendations for new compounds be trol trees were in an adjacent orchard section, sepa- optimized. To make the most complete assessment of rated by at least four trees or two rows from the area crop protection potential, plant-insect and plantÐ receiving insecticide treatments. High temperatures chemical interactions should be observed in parallel ranged from 18 to 31ЊC, and there were seven post- with the traditional insectÐchemical interaction stud- application days with rain events; Þve with a cumu- ies (Wise et al. 2007a). This article uses this framework lative total of under 0.25 cm and two of 0.5 cm. in describing the lethal and sublethal performance Bioassay. Terminal branches were harvested and characteristics of Þve compounds currently registered brought into the laboratory to evaluate lethal and for plum curculio control. sublethal effects of Þeld applications. One branch per tree was removed at 4 h, 3 d, 7 d, and 14 d postappli- cation. Undamaged shoots were pruned to 10 fruit and 10 leaves and placed in water-soaked ßoral foam Materials and Methods (Smithers-Oasis Co.) inside a clear plastic 946-ml con-