Raspberry plants with yellowing leaves are a sign of trouble and need a gardener's attention to restore them. Yellow leaves indicate a problem with the growing conditions an external threat, such as a pest or disease. Solving the problem keeps raspberries healthy and encourages berry production.
Causes include pest and disease problems. Aphids and other pest insects, such as mites and scale insects, feed on the leaves, causing them to yellow. Soil conditions also affect raspberry health. These plants require well-drained, loamy soil with plentiful organic matter, according to the University of Maine. Raspberry leaves may yellow if they are not growing in full and direct sunlight.
Applying pesticides keeps the plants healthy. Reducing the population of harmful insects, such as aphids, keeps the leaves strong and green, and repairs damaged leaves. Releasing biological controls for natural pest control also helps raspberries with yellow leaves. Ladybirds feed on aphids, organically reducing the aphid population.
Taking care of the soil helps keep the plant healthy. Add organic compost made of vegetable matter to the soil around the raspberry bush in addition to fertiliser. Mixing the compost and fertiliser into the soil adds nutrients to the earth that the plant uses. A lack of nutrients, such as nitrogen, iron, phosphorus and potassium, contributes to yellow leaves.
Raspberry plants not receiving enough water are more likely to have yellow leaves. Grow them in moist soil. The top several inches of soil should remain damp throughout the growing season, so that the plant takes in water and nutrients. Water the raspberry plant at least once a week. Keeping it hydrated prevents its leaves from yellowing due to a lack of water.