- Fruits: grapes
- Pest Management: integrated pest management, traps
After low MALB populations in 2011, we continued the study one more year into 2012 via an extension to attempt and collect further data on the efficacy of the push-pull strategy. However, 2012 proved to be an even lower density year than 2011. In addition, the first detection of a new invasive pest in MN grapes was made and confirmed as the spotted winged drosophila (SWD), Drosophila suzukii. Based on the new pest identification, insecticide sprays were applied to the entire vineyard to protect the grape clusters from infestation. In an early ripening variety, Leon Milot, levels of grape cluster infestation with maggots reached 80%. Our study had just commenced prior to the discovery of SWD and with a very low MALB catch on sticky cards, despite the usual high level of fresh splitting damage in Leon Milot, and the insecticide sprays, we decided to end the MALB trial as we would not be able to collect data for the push-pull strategy against MALB.
Overall we believe that the data collected over the course of these studies demonstrate the concept of the push-pull strategy has potential to be successful. Critical aspects of the strategy that must be in place to achieve a successful design include an effective trap coupled with an effective lure and a repellent that can aid in moving the insects toward the traps and the perimeter of the cropping area. In addition, the timing of deployment of the strategy is critical to influence insect populations, and for MALB specifically, both prior to infesting the crop and prior to harvest of the crop.
The focus of this project will be the development of a sustainable management plan to manipulate populations of H. axyridis to simultaneously repel beetles (push) from grape clusters within a vineyard, and also attract, trap and kill beetles (pull) at the perimeter of the vineyard. This approach builds on previous and ongoing research at the University of Minnesota, in cooperation with several grape and wine producers in Minnesota and Wisconsin. Moreover, this approach, recently referred to as a “push-pull” strategy is gaining acceptance worldwide as an effective pest management strategy in many cropping systems. For grapes, and particularly those grown for the increasingly popular Midwest wine industry, most growers prefer to avoid, or use less pesticide. With H. axyridis this is a major challenge, as this beetle has the potential to build up to very high levels near the end of the growing season, usually within 7-14 days before harvest. Although new insecticides have been approved for use near harvest, growers are reluctant to spray this close to harvest, due to the possibility of detectable residues on grapes, negative effects on farm workers who usually hand-harvest grapes, or potential impacts on final juice and wine product.
Harmonia axyridis has emerged as an economic, contaminant pest of wine throughout the eastern U.S., because it produces a foul defensive substance when they are crushed or disturbed; the process is known as “reflex bleeding”. Chemicals found in this liquid (methoxypyrazines) give the wine an unpleasant flavor and odor, often referred to as “burnt-peanut butter” affect. Recent work in our lab, in cooperation with the UofM Enology lab, and the Dept. of Food Science and Nutrition’s Sensory lab, has confirmed that the detection threshold (odor and taste) suggests that in-field infestations of just 3-5% of the clusters, infested with1 or more beetles/cluster, is sufficient to contaminate the wine and cause losses of entire lots of wine. Our previous field work, has confirmed that inexpensive yellow sticky cards can be used to monitor MALB in the field, to verify when populations migrate to the vineyard, typically late-August in Minnesota and Wisconsin. We have also developed rapid, reliable methods for sampling MALB in grape clusters.
The proposed research will benefit growers of wine grapes and grapes for juice. MALB has easily caused million dollar losses throughout the eastern U.S. in recent years in both industries, wine and juice grapes. We believe our approach is appropriate for this audience given their need for non-insecticidal alternatives. More important, we believe this technology is particularly suited to many of the relatively small grape growers in the NC Region, who currently only produce 1-4 acres each. The placement of repellents and traps in vineyards, is initially labor-intensive, but can be completed in ca. 2 hrs/acre and thus is feasible for smaller operations.
- 1)— Four-arm olfactometer to complete identification of most active attractants and repellents to H. axyridis under laboratory conditions (preliminary data for 6 compounds complete).
2)— Determine retention times (i.e., half-life) of candidate semiochemicals used for attractants and repellants placed on sticky traps under field conditions.
3)— Field assessment and efficacy of candidate “pull”-attractants (based on those found to be most efficacious from laboratory studies), using sticky cards (e.g. Galvan et al. 2006). This will be done at the Rosemount, UofM Agric. Experiment Station (UMORE Park), near soybean fields.
4)— In-field “push”-repellent studies to assess if volatiles can effectively repel H. axyridis.
5)— Combine the best push-pull compounds into a complete IPM program in vineyards.