Scouting for Cranberry Fruitworm

Friday, July 29, 2011

Hi folks,

Thought I should post a little reminder on scouting for cranberry fruitworm and how to calculate the percent out of bloom! Happy Scouting!

Decisions on when to apply control measures for Cranberry Fruitworm requires a variety of scouting methods. Pheromone traps can determine when adults are active in the beds. Most importantly you need to determine the growth stage of the plant and time the first insecticide application around 50% out of bloom. In order to calculate ‘% Out of Bloom’ – you need to start checking as soon as ‘pinheads’ start to form. For each acre of bog (make sure you sample the entire bed avoiding any bare areas), randomly collect 10 uprights and record the number of hooks, flowers, pinheads and fruit. Calculate % out of bloom using the following equation:

% out of bloom = (total # pinheads and fruit)/(total number of hooks, flowers, pinheads and fruit) X 100

Apply 1st treatment 7-9 days after 50% out of bloom for Howes and Early Blacks, 5-7 days after 50% out of bloom for Ben Lear and 3-5 days after 50% out of bloom for Stevens.

Five days after the first treatment, randomly collect 50 fruit per acre (or a minimum of 200 per bed for smaller acreages), and use a microscope to record the number of eggs. On beds sized 1-5 acres, the threshold is 1 egg, on larger beds add 1 egg per every 2 acre increase, for example, the threshold on a 7 acre bed would be 2 eggs. If egg numbers trigger a spray, spray immediately, if no eggs are found, continue to scout for eggs every 3-4 days until mid august.