Cucurbit Yellow Vine Disease

• Curcubit yellow vine disease is an infection resulting from the Serratia marcescens bacteria. Squash bugs spread the disease to butternut squash and other plants. Curcubit yellow vine disease clogs the plant's vascular system, causing yellowing leaves and leaf drop. Insecticides prevent squash bug infestations that spread the disease.
  
  

Powdery Mildew

• Powdery mildew is a disease that causes the leaves on butternut squash plants to turn yellow. The first symptom is small white dots on the underside of leaves, followed by general leaf yellowing and leaf drop. To treat, use fungicides recommended for this particular disease.
  
  

Root-knot Nematodes

• Root-knot nematodes are microscopic worms that settle in the roots of butternut squash plants. The bugs lay eggs and feed on the roots, resulting in root distortion, yellowing of leaves and leaf drop. A wide variety of nematicides are available to treat root-knot nematode infestations, such as chloropicrin and methyl bromide.