Last week, WSU invited Professor Emeritus Alexander Purcell from UC Berkeley, an entomologist who was a key component for the California X disease abatement program in the 1980’s, to tour orchards in Wenatchee and Yakima and meet with researchers and representatives of the Washington cherry industry. After joint discussions, we think leafhoppers are moving into orchards while feeding on orchard broadleaf weeds in the groundcover before moving onto cherry or stone fruit trees. Indeed, last week we did find leafhopper vectors while sweep net sampling orchard groundcover weeds. Therefore, groundcover is likely an important part of X disease transmission. There is a wide range of potential methods to combat this problem, and we encourage you to treat the problem of the groundcover as a source of leafhoppers within the philosophy of your orchard management program. Any herbicide treatments to remove ground cover weeds should be paired with insecticide treatments to kill leafhoppers that are stimulated to move from the groundcover to trees.
As a reminder, X disease infects trees for the life of the tree, so all orchard blocks should be treated for leafhoppers, including non-bearing blocks. Sampling can be conducted with yellow sticky cards to monitor effectiveness of treatments.
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