A bacterium, Serratia marcescens. The bacteria survives the winter in squash bugs and is spread to the young plants in the spring when the bugs colonize and feed on cucurbit crops.
Curcurbits (cantaloupe, pumpkin, squash, and watermelon)
Symptoms of the disease normally appear 10 to 15 days prior to fruit maturity and are similar in cantaloupe, pumpkin, watermelon and squash. Leaves change from green to lime-yellow, and then to bright yellow. Affected plants gradually decline and exhibit a blighted appearance within 7 to 10 days. In some cases, immature plants may not turn yellow, but wilt and collapse in 1 day. Fruit and flowers on affected plants are not distorted, but watermelon fruit lose their chlorophyll very quickly. The distinguishing characteristic of YV-affected plants is that the phloem, which normally has a clear translucent appearence, becomes honey-colored, particularly in the crown area. Although foliar symptoms of YV are similar to vine decline symptoms caused by soilborne pathogens, root degeneration occurs only in the later stages of YV development.
Please contact your local county extension office for current information.