Growing raspberry bushes in your backyard allows you to harvest fresh fruit you can eat raw or add to elegant desserts. If the leaves of your plants appear to be browning and drying, take action immediately to identify and control the problem before it affects fruit production. A number of cultural and environmental factors are responsible for leaf problems.
Insect pests cause the foliage of a raspberry bush to turn brown and eventually die, especially if the infestation is large. Pests including Japanese beetles, aphids, spider mites and raspberry cane borers feed on the foliage and stems of the plant and sap essential nutrients. Initial symptoms of damage include browning leaf edges that spread to cover the entire surface unless treated. Infected leaves also droop as they lose nutrients, then die and fall off. Spray infestations with horticultural or neem oil, or use a registered insecticide to tackle large problems. Repeat applications for stubborn pests.
A number of diseases cause browning and drying foliage on raspberries. Symptoms of spur blight include brown markings on floricane and primocane leaves along with damaged buds. Trim off infected canes or leaves to control spread. Anthracnose, a fungal disease, causes tiny purple-red spots on the leaves of a raspberry bush that develop into light brown or grey patches, along with cracked canes. Trim infected parts of the plant and apply a registered fungicide to control spread. Mosaic virus causes the tips of raspberry leaves to turn brown, along with limited fruit production. Proper cultural practices prevent the damaging disease.
Root rot and verticillium wilt are two root problems that cause the leaves to turn brown and die. Overwatering raspberries or causing them to stand in pools of water for prolonged periods suffocates the roots, thus developing root rot. The condition causes the roots to appear black and slimy as opposed to creamy-white and leaves turn brown and eventually fall off. Raspberries planted in poorly draining soils with excessive moisture become susceptible to verticillium wilt, a fungal disease in the soil. Initial symptoms include browning or yellowing leaves that start at the base of the plant and gradually spread upward. Grow disease-resistant varieties of raspberries, especially black raspberries that are particularly susceptible to the disease. Prune infected canes and apply a registered fungicide.
Improper growing conditions cause the leaves of the plant to turn brown. The planting site plays a vital role in its health and vigour. Raspberries thrive in well-draining, moist, nutrient-rich soils with full sunlight exposure. Failure to provide the plant its optimal growing conditions increases plant stress that manifests itself as brown leaves, premature leaf drop and stunted growth, along with other symptoms. Spring pruning keeps the plant healthy and less likely to succumb to pests and diseases.