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Title: Surface-Applied Insecticide Treatments for the Elimination of Larval Japanese Beetle (Coleoptera: Scarabaeidae) From Field-Grown Nursery Plants

item Reding, Michael - Mike
item Klein, Michael

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/26/2008
Publication Date: 1/22/2009
Citation: Oliver, J., Reding, M.E., Youseff, N., Klein, M.G., Bishop, B., Lewis, P. 2009. Surface-Applied Insecticide Treatments for the Elimination of Larval Japanese Beetle (Coleoptera: Scarabaeidae) From Field-Grown Nursery Plants. Pest Management Science. 65:(4)381-390.

Interpretive Summary: The Japanese beetle (Popillia japonica) is an important horticultural and quarantine pest of agricultural commodities including nursery crops, capable of utilizing 430 known host plants. The annual cost of controlling adult and larval (hereafter referred to as grubs) Japanese beetle is estimated at > $460 million / yr. The Japanese beetle, continues to be a quarantine issue for nurseries shipping plants from the eastern U.S. to states west of the Mississippi River. Currently, the only two pre-harvest treatments approved by the U.S. Domestic Japanese Beetle Harmonization Plan for field production nurseries. The objective of the current study was to evaluate a variety of new reduced-risk insecticides to find additional treatments to add to the Harmonization Plan. Over a 6-year period, we tested seven insecticides at different rates and application timings comparing them to currently acceptable treatments. Celero, Flagship, and Mach 2 reduced the numbers of Japanese beetle grubs compared to untreated trees, and provided control comparable to the Harmonization Plan standards Marathon 60W and Discus. Insecticides applied in July and at the full labeled rate were consistently the most effective at reducing numbers of Japanese beetle grubs. Our data shows that Celero, Flagship and Discus are effective enough to seriously be considered as treatments in the Harmonization Plan.

Technical Abstract: The Japanese beetle, Popillia japonica Newman, continues to be a quarantine issue for nurseries shipping plants from the eastern U.S. to states west of the Mississippi River. Currently, the only pre-harvest treatments approved for field-grown nurseries in the U.S. Domestic Japanese Beetle Harmonization Plan (DJHP) include Marathon (60WP and 1G) (Active ingredient [AI] = imidacloprid) and Discus (AI = imidacloprid + cyfluthrin). The current study examined alternative pre-harvest treatments for the DJHP in field nursery settings over a 6-yr period, including Celero 16WSG (AI = clothianidin), Dylox 80 T&O (AI = trichlorfon), Flagship 25WG and 0.22G (AI = thiamethoxam), Mach 2 (AI = halofenozide), Precise Acephate (AI = acephate), Safari 20SG (AI = dinotefuran), and Sevin 4F (AI = carbaryl). Treatments were applied at multiple timings at either 1x (labeled broadcast) or higher (2x and 3x) rates. Nursery plants were mechanically harvested during October and the soil examined for scarab and curculionid larvae. All insecticides provided significant reduction of larval Japanese beetle populations from the untreated control with the exception of Dylox 80 T&O, Precise Acephate, Safari 20SG, and Sevin 4F. With the exception of Safari 20SG, neonicotinoid treatments and halofenozide had statistically equivalent grub control to the DJHP approved Marathon 60WP 1x and Discus 1x standards during most test years. During 2005, 1x rates of Celero 16WSG (June and August) and Flagship 25WG (June) provided greater (P < 0.05) grub control than DJHP Marathon 60WP and Discus standards. Across all test years and timings, percentage grub reduction from the non-treated control ranged as follows: Marathon 60WP (1x: 59.2'100; 3x: 78.9'100), Discus (1x: 60.7'100; 3x: not tested), Celero 16WSG (1x: 96.1'100; 3x: 97.4'100), Flagship 25WG (1x: 75.0'100; 3x: 80.0'100), Mach 2 2L or 2SC (1x: 70.0'100; 3x: 90.0'100), and Safari 20SG (1x: 13.2'88.2; 3x: 71.1'93.4). July-applied treatments generally had more consistent grub control than other timings and were significantly greater than June and August applications for several treatments in 2003 and 2005. The use of higher 2x and 3x rates did not statistically increase Japanese beetle control over 1x broadcast rate, except for a July-applied Flagship 25WG and Mach 2 2L treatment during 2003 and a June-applied Marathon 60WP and Safari 20SG treatment during 2005. With the exception Celero 16WSG June 3x, Flagship July 3x, and Mach 2 2L July 3x treatments, all insecticide treatments exceeded the DJHP Nursery Accreditation threshold of one grub during one or more tests in this study. The addition of a surfactant (Suffusion) to Discus and Marathon 60WP treatments did not increase grub control. Most treatments allowed significant infestations of other scarabs (e.g., Phyllophaga spp., Cotinis nitida L., Anomala spp., Cyclocephala spp.) and unidentified curculionid larvae. Overall, the study found Celero 16WSG, Flagship 25WG, and Mach 2 2L provided grub control equivalent to Discus and Marathon 60WP DJHP standards during most test years. Safari 20SG was as effective as imidacloprid standards during August. These insecticides may be suitable for treating field-grown nursery stock destined for DJHP Category 2 states, but since no treatment is 100% effective all of the time, their use will require an assessment of the risks and benefits by regulatory agencies. New insecticides in the DJHP would increase grower options and potentially lower costs.