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Home , Acrolepiidae, Acrolepiopsis, Leaf miner, Leek moth

Evaluation of Chemistries Against the (: ), a New in Author(s): Daniel L. Olmstead and Anthony M. Shelton Source: Florida Entomologist, 95(4):1127-1131. 2012. Published By: Florida Entomological Society URL: http://www.bioone.org/doi/full/10.1653/024.095.0443

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BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research. Olmstead & Shelton: Chemical Control of the 1127

EVALUATION OF INSECTICIDE CHEMISTRIES AGAINST THE LEEK MOTH (LEPIDOPTERA: ACROLEPIIDAE), A NEW PEST IN NORTH AMERICA

DANIEL L. OLMSTEAD* AND ANTHONY M. SHELTON State Agricultural Experiment Station, Department of Entomology, Cornell University, 630 West North Street, Geneva, NY 14456, USA

*Corresponding author; E-mail: [email protected]

Abstract

The leek moth, assectella (Zeller), is a newly introduced micro-lepidopteran pest in North America that attacks crops, including , leek, and . Eggs are laid on and emerging larvae may cause extensive damage by mining leaves, feed- ing on surfaces and feeding directly on bulbs. Little is known about existing natural enemies for this pest in North America, but classical biological control introductions are underway in . However, other management options are needed because the threat to the onion production industry in New York State and the Great Lakes Region is imminent. Laboratory studies showed that lambda cyhalothrin (Warrior® II), spinetoram (Radiant® SC), methomyl (Lannate® LV), chlorantraniliprole (Coragen®), and spinosad (Entrust®) significantly increased larval mortality, compared to the control, at 2, 4, and 8 days after treatment, while Bacillus thuringiensis and azadirachtin did not. These results are explained in part by the behavior of the .

Key Words: Acrolepiopsis assectella; leek moth; onion ; teigne du poireau; onion; leek; allium

RESUMEN

La polilla del puerro, Acrolepiopsis assectella (Zeller) es un micro-lepidóptero plaga reciente- mente introducido en América del Norte, que ataca los cultivos de Allium incluyendo cebolla, puerro y ajo. Los huevos son puestos en las hojas y las recién salidas pueden causar daño severo por las minas que hacen en las hojas, la alimentación sobre la superficie de las hojas y la alimentación directa a los bulbos. Se sabe poco sobre los enemigos naturales existentes para esta plaga en América del Norte, pero están realizando introducciones del control biológico clásico en Canadá. Sin embargo, otras opciones de manejo son necesarias debido a su amenaza inimente a la industria de producción de cebolla en Nueva York y la región de los Grandes Lagos. Ensayos de laboratorio mostraron que el cialotrina lambda (Warrior II), spinetoram (Radiante SC), metomilo (Lannate LV), clorantraniliprol (Coragen) y spinosad (Entrust) aumentó significativamente la mortalidad de larvas, en comparación con el control, a los 2, 4 y 8 dias después del tratamiento, mientras que insecticidas Bacillus thuringiensis y azadiractina no lo hizo. Estos resultados se explican en parte por el compor- tamiento del insecto.

Palabras Clave: Acrolepiopsis assectella, la polilla de puerro, cebolla, minador de la hoja; teigne du poireau, cebolla, puerro, Allium

The Leek moth, Acrolepiopsis assectella Zeller Jenner et al. 2010b). In North America, A. as- (Lepidoptera: Acrolepiidae), also called the onion sectella was first discovered in , Canada leaf miner or teigne du poireau (Garland 2002), is in 1993 (Garland 2002; Allen et al. 2008; Mason a micro-lepidopteran pest of Allium crops, includ- et al. 2010). Range expansion has continued and ing onion, leek, and garlic (Allison et al. 2007). A. assectella is presently established through- Eggs are laid on leaves and emerging larvae can out southeastern and western cause damage by mining leaves or feeding on leaf (Landry 2007; Jenner et al. 2010b). In 2009, A. surfaces and bulbs (Allen et al. 2008; Garland assectella was first found in the 2002). near Plattsburg, northern New York State along Acrolepiopsis assectella has been a pest of Al- the St. Lawrence Seaway less than 230 km from lium crops in Western , especially Bel- Ottawa. In 2012, A. assectella was present in Jef- gium, , and the Netherlands, for hundreds ferson, St. Lawrence, and Clinton Counties of of years. The range of A. assectella extends across northern New York (Ivy 2011), but found only in the Europe from to and North Af- small-scale production areas and home gardens rica (Asman 2001; Garland 2002; Landry 2007; containing , , and garlic. However, 1128 Florida Entomologist 95(4) December 2012 large commercial onion production occurs in Os- 15 cm deep plastic pots from seeds. Slow release wego County, NY, located 300 km to the south. A. fertilizer (Scotts Osmocote, 15-9-12) was applied assectella represents a threat to this area and oth- twice at 3-mo intervals initiated at planting. er onion production areas in New York that report Acrolepiopsis assectella were reared in a labora- annual harvest values of greater than $54 million tory colony that originated from field-collected pu- (USDA-ERS 2011). If A. assectella becomes estab- pae and late instar larvae found in a home garden lished in New York, it may also spread to other in Essex County, New York in August 2011. Pupae states in the northeast where Allium vegetable of this population were placed in clear acrylic cylin- production is important. ders (11 cm diam × 15 cm high) fitted with screened Acrolepiopsis assectella has few known natu- caps (i.e. oviposition chambers) and a flask of 10% ral enemies in North America and pest pressure sucrose solution for adult nutrition. When adults is often more severe than in Europe (Jenner et emerged, a 10 cm × 3 cm piece of fresh leek leaf, al. 2010b; Jenner et al. 2010c). Biological control rubbed with masticated leek pulp (Garland 2002), with a has worked well in Europe, and was hung from the oviposition chamber lid for a introduction of Diadromus pulchella (Wesmael) is 24-h period during which adults were given the op- underway in Canada (Jenner et al. 2010a; Jen- portunity to lay eggs on the leaf. Egg-laden leaves ner et al. 2010c). These efforts are important but were collected daily. To facilitate handling and col- additional options are needed because of the im- lection of larvae, freshly collected leaves were cut mediate threat to onion production in New York into 0.6 cm squares and allowed to dry to prevent State and the Great Lakes Region (Mason et al. leaf mining by emerging neonates. 2011). Cultural control options have been evalu- Dried egg-laden leaves were checked daily for ated for A. assectella. Intercropping has not prov- neonate larvae. Acrolepiopsis assectella larvae en effective, but trap cropping shows promise (As- were collected using a size 0 round tip paint- man 2002; Asman & Ekbom 2006). brush dipped in water to prevent static charge. Insecticides will play an important role in a Individual larvae were transferred to single flat- control strategy for this pest of high value veg- bottom 6mm diam wells of a 96-well plate (Falcon etable crops, and this has been demonstrated in 3912 MicroTest III Flexible Assay Plate, Becton the case of swede midge, Contarinia nasturtii Dickinson Labware, Oxnard, California) contain- Kieffer (Diptera: Cecidoymiidae) (Chen 2011), ing a small amount of leek pulp. Leek pulp was another newly introduced pest of vegetables prepared by adding 100 mL of distilled water to from Canada. Cornell University petitioned the 25 g of fresh, washed leek leaves in an Osterizer New York State Department of Environmental Model 471 blender set to high for 2 min, and then Conservation (NYSDEC), and was granted 2(ee) drained of liquid with a small strainer. A sheet emergency exemptions, for 5 insecticides for con- of Parafilm M was firmly pressed over the entire trol of A. assectella in 2010 based on the immedi- plate to form a seal over all individual wells con- ate threat of A. assectella. Requests for Entrust® taining to retain moisture and humidity, (spinosad) and DiPel® DF (Bacillus thuringiensis but allow gas exchange. Plates were held at 20 °C var. kurstaki) were approved for homeowners and and 16:8 h L:D. Larvae were transferred to clean organic growers in affected regions. Approvals trays with fresh leek pulp every 2 to 3 d. Insect for Warrior® II (lambda-cyhalothrin), Lannate® stage was calculated using head capsule size. LV (methomyl), and Radiant® SC (spinetoram) When larvae were 2nd or 3rd instars, they were were granted for large-scale conventional grow- individually placed in designated 96-well plates ers. Continued registration of these products is at 10 °C and 16:8 h L:D. important to prevent crop damage, and proven Insecticide treatments were applied at a stan- efficacy against A. assectella is key to this process. dard volume of 285.2 L per ha and 2.8 kg per cm2 Other insecticides might also be effective but of pressure through a single Teejet flat fan 8002 a literature review indicated a lack of research nozzle tip with an Allen Track Sprayer (Allen Ma- on efficacy against A. assectella for many chem- chine Works, Midland Michigan). A single potted istries, including those with the 2(ee) exempted leek plant, as described above, was placed into products mentioned above. This laboratory study the spray chamber and treated. Maximum label was conducted to provide preliminary efficacy da- rates, indicated on New York State registration ta for a variety of insecticides in different chemi- labels, were applied with a surfactant at 1% v/v cal classes that could be suitable against A. as- (Dyne-Amic®, Helena Chemical Co.) (Table 1). A sectella. single leaf of sufficient size was marked on each leek with a small pin and positioned during ap- MATERIALS AND METHODS plication to receive an even dose of insecticide. Treatments were replicated 3 times for use in bio- Mature leek plants, var assays completed at 2, 4, and 8 d after treatment ‘Lincoln’ (Bejo Seeds Inc., Geneva, New York), (DAT). were grown in a greenhouse at a constant 15 °C Bioassays were completed using 7, 8, or 9 discs and 16:8 h L:D. Plants were grown in 15 cm diam, (3.2 cm diam), cut from a treated leaf, and placed

1130 Florida Entomologist 95(4) December 2012 assectella mortality in the pyrethroid-sprayed Bt (Agree® WG and DiPel® DF) and azadirachtin plants was initially high but decreased as time (Neemix® 4.5) did not provide high levels of mor- progressed. Pyrethroids degrade quickly and tality of A. assectella and are not likely to be suit- the active ingredient in Warrior®, lambda cyha- able control agents. lothrin, has a half-life of 5 d on plant surfaces, More work is needed because some of our breaking down readily in sunlight (National findings contradict current recommendations Pesticide Information Center 2001). Our results about the effectiveness of Bt products (e.g., Allen showed that insects exposed to the plant surface et al. 2008). Neonate larvae burrowed into the shortly after treatment were controlled before en- host within min to h of hatching and 2nd instars tering the plant. As time between application and placed on fresh leaf material also burrowed into insect exposure increased, the treatment became mesophyll quickly (personal observation). It is significantly less effective and declined by 29.6% unlikely they ingested sufficient amounts of Bt (Table 1). proteins to be harmed, despite the use of good Spinetoram (Radiant® SC) and spinosad (En- foliar spray technology. Of the other options we trust®) both belong to the spinosyn class of in- tested for organic producers, only spinosad (En- secticides and had longer residual activities. Spi- trust®) provided decent control. Conventional nosad has a unique mode of action, acting quickly growers have more effective options. Based on on the insect nervous system through contact and these tests and our knowledge of spinetoram (Ra- ingestion (Thompson et al. 2000). This is suitable diant® SC) and chlorantraniliprole (Coragen®) for A. assectella because of the short time period for other Lepidoptera, field tests should be con- larvae are exposed to the plant surface. These ducted with these newer insecticide chemistries, positive results suggest more work should to be as well as pyrethroid and carbamate insecticides. done to evaluate spinosyn products. Methomyl (Lannate® LV) and chlorantranilip- ACKNOWLEDGMENTS role (Coragen®) were also effective at controlling A. assectella. Unlike lambda-cyhalothrin (War- Thanks to Amy Ivy, Executive Director and Horti- rior®), they were effective through 8 DAT. The ex- culture Educator at Cornell Cooperative Extension of act exposure pathways of these chemicals are not Clinton County for collecting populations of A. assectel- known. Both insecticides have contact and inges- la for our lab. Special thanks to Sue Coonrad, Clinton County, New York, USA homeowner and gardener who tion activity against (DuPont 2007). sacrificed her 2011 onion crop for A. assectella collec- Methomyl does not persist long on plant surfaces, tions. Finally, thanks to Dr. Jozsef Fail and Jun-ce Tian having a half-life of 3 to 7 d (Extension Toxicology who reviewed an earlier draft of this manuscript and Network 1993). provided useful comments and suggestions. The bacteria Bacillus thuringiensis (Bt) must be ingested to reach target sites in the digestive REFERENCES CITED tract and have an effect on the target organism. Neither of the Bt treatments (Agree® WG and ALLEN, J., FRASER, J. H., AND APPLEBY, M. 2008. Leek DiPel® DF) effectively controlled A. assectella. moth: a pest of allium crops. http://www.omafra.gov. on.ca/english/crops/facts/08-009.pdf. This contradicts the literature in which Bt was ALLISON, J., JENNER, J. 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