Bt Applications for Leafrollers

Saturday Feb 04, 2023

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.

Factors Affecting Bee Pollination of Tree Fruits

Saturday Feb 04, 2023

Nearly 1,000 species of bees occur in the Pacific Northwest, but only a small number of species are useful in the pollination of orchard crops. Pesticide use and loss of appropriate nesting habitat have reduced the numbers of wild bee pollinators, leaving most of the pollination for commercial orchards dependent on honeybees. The success of honeybee pollination in tree fruits is affected by a number of factors, which in part can be manipulated by orchardists and beekeepers.

Apply Mating Disruption Dispensers Before First Moths Fly

Wednesday Feb 01, 2023

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?

Monday Jan 02, 2023

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 for Leafrollers

Monday Jan 02, 2023

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.