Pests

• Pest problems turn the leaves of a raspberry bush brown over a short period of time, especially if infestations are especially severe. Aphids, raspberry cane borers, Japanese beetles and mites all feed on the flesh of the leaves or the stems of the raspberry plant. As the plant loses nutrients and is wounded by the feeding insects, the edges of the leaves will start to turn brown. Browning will sometimes be accompanied by wilt. Apply pesticides to control pests.
  
  

Rust Fungi of Raspberry Plants

• Rust is a fungal disease that affects a wide variety of plants. When it grows on the leaves of a raspberry bush, it will turn them a reddish or orange brown, similar to the color of rust on metal. The rust spreads over the leaves in patches, causing the leaves to turn brown, wilt and die as the fungus grows. Apply a fungicide to the raspberry bush to stop the progression of the disease and prune severely damaged portions of the raspberry bush.
  
  

Verticillium Wilt

• Verticillium wilt is a fungal disease that grows in the soil. It affects raspberry bushes that are growing in or near standing water, which provides the moisture necessary for fungal growth. According to Michigan State University Extension, black raspberries are particularly susceptible to this disease. Symptoms like yellowing and browning leaves begin toward the bottom of the raspberry bush and gradually spread upward. Use disease-resistant plants and apply fungicides to the raspberry plants to protect them from wilt.
  
  

Growing Location

• The location where a raspberry bush is planted plays a major role in its health. A lack of full sun will lead to brown leaves, weak growth and fewer raspberries. Raspberries grow best in moist, nutrient-rich soil that drains water easily. Sandy soils are best, according to Michigan State University Extension. Prune the raspberry bush in the early spring to keep it healthy and make it less likely to attract pests and disease.