Assessing Reduced-risk Insecticides and Refining Distribution and Phenology Models to Improve Management of Oriental Fruit Moth (OFM) in Apples and Peaches

The Oriental fruit moth (OFM), Grapholitha molesta, is a serious pest of peaches and apples, and populations of this pest in several areas are resistant to pyrethroids and organophosphates. We used SARE support for expanding evaluations of reduced-risk insecticides and expanding OFM and degree-day monitoring. Additionally, we requested support for grower participation in educational programs. Our overall goals were to develop and provide essential information in a timely manner so that small farmers involved in apple and peach production could profit from improved insect management practices.

To assess the effectiveness of reduced-risk insecticides, we worked with 8 apple and peach growers to evaluate rynaxypyr (Altacor), acetamiprid (Assail), novaluron (Rimon), and spinetoram (Delegate) used per EPA labels in plots of at least 2.5 acres. We also evaluated the effectiveness of these and other reduced-risk insecticides in small-plot trials at the University of Illinois Pomology Research Farm near Urbana, IL, and we conducted concentration-mortality bioassays to assess the baseline susceptibility of two OFM populations to reduced-risk and pyrethroid insecticides. To better understand the distribution and phenology of OFM in peach and apple orchards in Illinois, we worked with growers to use pheromone traps,temperature sensors, and degree-day software to monitor in-orchard temperatures and degree-day accumulations in comparison with the timing and relative density of OFM flights.

All of the reduced-risk insecticides tested (Altacor, Assail, Rimon, and Delegate) effectively controlled Oriental fruit moth in grower-applied trials in Illinois apple and peach orchards (including populations considered to be resistant to pyrethroid insecticides). These reduced-risk insecticides also effectively controlled Oriental fruit moth and codling moth in small-plot trials at the University of Illinois orchard near Urbana, IL, but only Assail adequately controlled concurrent infestations of apple maggot, a key pest in apples in the northern Midwest. Oriental fruit moths were captured in pheromone traps at orchards as far north as the area surrounding Peoria, IL, but not at locations near Rockford (near the Wisconsin border). Captures in pheromone traps at locations north of Urbana, IL, were too sporadic to allow comparisons of flight timing with published degree-day models. At two orchards where mating disruption was used (in far southern IL and in western IL), no Oriental fruit moths were captured in pheromone traps – evidence of successful disruption of mating and control within those orchards. Counts of moths from pheromone traps in other orchards have been added to a multi-year database to validate/refine degree-day models of seasonal patterns of Oriental fruit moth occurrence. Concurrent work established baseline dose-response relationships that describe the toxicity of rynaxypyr, acetamiprid, spinetoram, spinosad, novaluron, esfenvalerate, and lambda-cyhalothrin to susceptible populations of Oriental fruit moth; these results provide a basis for future monitoring of insecticide resistance in this pest.

Gross incomes for fresh-market sales of peaches can exceed $18,000 per acre (300 bushels per acre X $60.00 per bushel). In areas where pyrethroid resistance led to culling nearly 20 percent of the crop in 2005 and 2006, losses were estimated at greater than $3,000 per acre. The reduced-risk insecticides evaluated in this research reduced losses to less than 1 percent – therefore reducing monetary losses by $2,970 per acre.

Introduction:

Specialty crops such as fruits and vegetables offer opportunities for diversification and increased profitability. Fruit and vegetable producers contribute to rural and urban economies and quality of life by providing jobs, local produce, and direct contact between producers and consumers at on-farm and farmers markets. However, fruit and vegetable production often involves significant use of pesticides to prevent scarring and contamination of produce. Negative impacts of pesticides can include unwanted residues on foods, environmental contamination, and development of pesticide resistance. To reap the broad benefits of fruit and vegetable production on diversified farms and minimize negative impacts of pesticide use, effective, reduced-risk pest management alternatives must be developed and used.

The Oriental fruit moth (OFM), Grapholitha molesta, has been a serious pest of peaches and other fruit crops since its introduction into North America in 1916. In the 1990s, infestations in apples increased markedly in the eastern US, and severe infestations were reported from apples in IL in 2006. OFM populations in southwestern IL and elsewhere are resistant to pyrethroids and organophosphates. Recent increased losses to OFM threaten the viability of apple and peach production in southern and southwestern IL and the lower Midwest.

To contribute sustainable peach and apple production via improved pest management, our overall research on OFM has two broad objectives:
1) Describe baseline susceptibility of OFM populations to key insecticides, including newly available reduced-risk and OMRI insecticides; identify any cross-resistance potential for the reduced-risk insecticides; and evaluate the effectiveness of reduced-risk insecticides in field trials.
2) Refine our knowledge of the geographic distribution and relative density of OFM in IL and its seasonal occurrence in relation to degree-day accumulations (phenology models) to better identify the need for and timing of management practices.

We requested SARE support for specific aspects of these objectives: 1) expanding evaluations of reduced-risk insecticides
2) expanding OFM and degree-day monitoring.

Additionally, we requested support for grower participation in educational programs. Our overall goals are to develop and provide essential information in a timely manner so that small farmers involved in apple and peach production can profit from improved insect management practices.