Cucurbit Yellow Vine Disease (Serratia ureilytica)

Symptoms of cucurbit yellow vine disease

Symptoms begin with plant decline (fig. 1), interveinal yellowing leaves (fig. 2), followed by the yellowing of entire vines. Plant wilting may begin as soon as two weeks after the first symptoms appear. Other symptoms include stunting and plant collapse (fig. 3A). The bacterium moves systemically in the vascular tissue of the plants. The vascular tissue of affected plants can sometimes have a honey-brown color when looking at the cross-section of the stem at the crown of the plant.

Symptoms may be similar to those caused by bacterial wilt, which is caused by the bacterium Erwinia tracheiphila and transmitted by the striped cucumber beetle (Acalymma vittatum) and spotted cucumber beetle (Diabrotica undecimpunctata). Although both diseases can be seen as wilting and scorching of leaf margins, the main difference between them is the yellow appearance in CYVD compared to bacterial wilt (no yellow appearance, fig. 3).

Management of cucurbit yellow vine disease

Current disease management practices aim to control the squash bug vector. Squash bugs usually aggregate on the underside of leaves or at the base of cucurbit plants (fig. 2), allowing them to escape from foliar-applied insecticides. Although plastic mulch can help control other pests, it gives the squash bug a place to shelter, which can increase its population. 

Therefore, managing the first generation of squash bugs during their nymphal stage (end of June in New York State) is crucial to reducing the size of the adult population. Cultural practices to control the squash bug include crop rotations with non-cucurbit plants or at a sufficient distance from where previous cucurbits were, removing crop debris and old fruit that will not be harvested, so that the overwintering population can be reduced. Using Hubbard squash as a trap crop on plot edges can help reduce disease in the main plot. Although squash bugs are challenging to manage, insecticide use remains one of the most effective control strategies. Refer to your local Cornell Cooperative Extension guidelines or your state guidelines when applying insecticides to crops. 

Any time you use a pesticide, you must read and follow the label directions and comply with all applicable laws and regulations related to pesticide use. Also be sure that any pesticide used is approved for use in your country and state/province.