Cause Watermelon mosaic virus 2 has been found in eastern Oregon. Zucchini yellow mosaic virus could be a problem also. Both are transmitted by aphids and also easily by mechanical means. Generally not a significant problem in the Northwest.
Symptoms A light mosaic pattern may be evident before distinct dark and light green areas develop on leaves. Dark green areas can be raised. Infected plants are lighter green than normal and are stunted. Other than being smaller, no fruit symptoms are evident.
- Reduce field activity to reduce spread by mechanical means.
- Highly tolerant varieties may be available soon.
Chemical control Applying insecticide to control aphids will not prevent the disease. Aphids that already have the virus still can move into the field and transmit the virus.