Bt Applications for Leafrollers

Sunday Feb 04, 2024

Bacillus thuringiensis (Bt) is a bacterium that must be eaten by lepidopteran larvae (caterpillars) to be effective. Bt is a great material for leafroller control because it is specific and has little effect on natural enemies. However, it must be applied 2-3 times to be effective when leafroller populations are high. Experience has also shown that in the spring, the high temperatures need to be above 65°F for 3 or more days so that larvae have a chance to feed on it before sunlight breaks it down. DAS provides forecast temperatures for all stations in the "Weather Forecast" and in the "Show Data Grid" table so that you can decide whether or not to use Bt or other recommended chemicals.

Apply Mating Disruption Dispensers Before First Moths Fly

Thursday Feb 01, 2024

Mating disruption dispensers work by releasing synthetic pheromone which prevents or delays males from finding and mating with females. Therefore, dispensers need to be placed in your orchard before the first moths fly and mate. First moth flight (= biofix) occurs at around 175 DD. We recommend to place pheromone traps before first apple blossoms open or by 100 DD whichever comes first.

Which Leafroller Species is in Your Orchard?

Tuesday Jan 02, 2024

There are two leafrollers commonly found in Washington orchards: Pandemis leafroller (PLR) and Obliquebanded leafroller (OBLR). The phenology of the two species is quite different and you need to be sure which species you have for proper management and use the correct model on DAS. PLR used to be more common, but in the past 10 years, OBLR has displaced PLR from many of the production areas.

Delayed Dormant Sprays

Tuesday Jan 02, 2024

Dormant sprays are important for management of a wide range of pests including European red mite, woolly apple aphid, rosy and green apple aphids, and San Jose Scale. Most of these are easily controlled using a variety of materials, but if you are using oils, remember that good coverage is essential because they work by covering the egg stage and preventing respiration.

Delayed Dormant Sprays for Leafrollers

Tuesday Jan 02, 2024

Pandemis leafroller (PLR) and oblique-banded leafroller (OBLR) have different phenologies which are well documented on DAS. Delayed dormant sprays can work well for PLR, but are generally too early in the season for efficacy against larvae of OBLR.