Spring 2014: Light brown apple moth update on regulations and research
Regional Report for Santa Cruz and Monterey Counties by Steve Tjosvold
The Animal and Plant Health Inspection Service (APHIS), the regulatory arm of the USDA, announced in early February 2014 that they will maintain their current classification of light brown apple moth (LBAM) as a quarantine pest. This announcement and the analysis that preceded it was a result of petitioners requesting the deregulation of LBAM. APHIS announced, “By maintaining a regulatory program for LBAM, APHIS is seeking to minimize the further spread of the moth in the United States and maintain foreign trade markets for our producers.” The announcement is available at: http://www.aphis.usda.gov/newsroom/2014/02/pdf/fr_lbam_quarantine.pdf.
Light brown apple moth leafroller larvae are commonly found in shelters (leaf rolls) composed of leaves pulled together with silken webs. A mature larva such as this one can be up to 18mm (3/4 inch) long with a light to medium green body, yellow to light brown head, light to medium green segment just behind the head, and light-colored hairs and legs. Photo by S. Tjosvold.
We have been conducting research in Santa Cruz and Monterey counties to aid in LBAM detection and management. In the UCNFA News Spring 2013 issue, I described one of those research projects where we are evaluating the importance of LBAM in areas around the perimeter of nursery and berry fields because we suspect that LBAM may be migrating from natural vegetation and weeds into these production areas. (See: http://ucanr.edu/sites/UCNFAnews/Regional_Report_Santa_Cruz_Monterey_Cos/Spring_2013__LBAM_field_data_available_for_Monterey_Bay_Area_growers/.)
Trapping for LBAM on nursery perimeter. Scout checks commercially-available Jackson trap and pheromone bait that specifically attracts and traps male LBAM moths. Photo by S. Tjosvold.
The eight monitored production sites are grouped into five generalized regions in Santa Cruz County and north Monterey County. Our data shows a relatively synchronized peak moth emergence in early November in all monitored areas in 2011 and 2012. But in 2013, there is a noticeable decline in the numbers of LBAM adults that we have trapped and larvae found on the nursery-perimeter hosts. We believe that the drought in 2013 is taking a toll on LBAM because their plant hosts are either not as prevalent or not as suitable for colonization. The period from February 19, 2013 (the last significant rainfall) to just before the recent February 2014 rains has proven to be one of the longest periods with significantly below-normal rainfall. Young growth on perennial hosts and some annual hosts have just not been readily available for LBAM to thrive. To date, the greatest numbers of larvae have been found on French broom (Genista monspessulana)(19%), coyote bush (Baccharis pilularis )(16%), dovefoot geranium (Geranium molle)(10%),buckhorn plantain (Plantago lanceolata)( 7%) and wild radish (Raphanus raphanistrum) (7%). There are 31 different host species that have been identified so far. The data for moth emergence and a complete host list is updated every 2 weeks and can be accessed through the UCCE Santa Cruz homepage: http://cesantacruz.ucanr.edu/.
Another project was to evaluate California Department of Food and Agriculture official regulatory insecticides and other newer insecticides in field conditions. Insecticide treatments were applied before and after egg deposition and the efficacy was evaluated based on the survival of the brood to attain adulthood. In addition, residual activities of the insecticides were evaluated to help make management decisions on the timing and frequency of field applications. Treatments did not affect egg laying except for lambda-cyhalothrin (Scimitar), which repelled moths and greatly reduced egg laying and the size of egg masses for 3 to 4 weeks. Diflubenzuron (Dimilin) was not effective. All other treatments reduced survivorship, with Bacillus thuringiensis (Dipel) and indoxacarb (Provaunt) lasting up to 1 week, spinosad (Conserve) lasting 1 to 2 weeks, and chlorantraniliprole (Acelepryn) and emamectin benzoate (Enfold) lasting 2 to 3 weeks. Horticultural oil (Pure Spray Green) did not improve control when combined with Bacillus thuringiensis, spinosad, or methoxyfenozide (Intrepid). Methoxyfenozide, a registered insect growth regulator targeting moth larvae, lasted 3 to 4 weeks, and could be a very useful integrated pest management product in nurseries.
This research was funded by a Specialty Crop Block Grant (CDFA/USDA).
Steven A. Tjosvold
Farm Advisor, Environmental Horticulture
UC Cooperative Extension Santa Cruz County
1432 Freedom Boulevard
Watsonville, CA 95076-2796
(831)763-8013 phone, (831) 763-8006 fax