New Technologies for a Stubborn Insect Pest of Apples
Three pheromone release systems take on the obliquebanded leafroller
Microsprayers, microencapsulated sprayables, paraffin-based emulsions–no, this is not a chemistry professor’s shopping list. It’s a list of the latest in techniques for managing insect pests. These new delivery systems or formulations can be used to spread pheromones (hormone-like chemicals that enable male insects to locate the females of their species at mating time) in crop foliage. Ideally, pheromone releases have the effect of disorienting male insects. They stop searching for females, and the mating process is disrupted. A microsprayer and an applicator used for applying the paraffin-based emulsion are pictured below. Microencapsulated sprayables look a lot like vitamin capsules and are applied using standard sprayers.
Paraffin-based emulsions can be placed on trees by
"tree-marking gun applicators" like this one.
This microsprayer releases pheromones in puffs of atomized
liquid from pressurized canisters.
Cornell entomologists Art Agnello and Harvey Reissig tried these three types of pheromone releases–along with a new, IPM-compatible insecticide–in two commercial apple orchards last summer. They were attempting to manage the obliquebanded leafroller (OBLR), an insect that has caused costly damage to western New York apples for the past 25 years. According to Agnello, "The OBLR is the insect to beat in western New York apple orchards. We’ve got to keep looking for alternatives." The leafroller has developed resistance to many of the standard insecticides.
The orchards used for this project have typically withstood 15-30 percent damage by the OBLR if left untreated. What happened in the 1998 season?
At orchard #1, where leafrollers were not very numerous, the addition of a pheromone treatment to a standard pesticide spray did not make much difference. There was three percent damage with either the microsprayer or the emulsion plus the new biorational pesticide, and four percent damage with the grower’s standard treatment.
At orchard #2, where leafroller populations were high, the damage spread was significant: 5 percent with microsprayers plus the alternative pesticide versus 30 percent with the grower’s standard treatment.
The three pheromone release systems performed well. The paraffin-based emulsions and the microsprayers showed somewhat better results than the encapsulated sprayables, perhaps because the latter cannot provide a stable release of pheromone for prolonged periods and so is more dependent on a careful reapplication schedule. Further testing of these devices will be necessary to compare their effectiveness in orchards with various levels of OBLR infestation.