My Bougainvilleas Are Turning Yellow

Sap-feeding Pests

• Sap-feeding insects use needle-like mouth parts to pierce plant tissue and feed on the sap inside. They are found on all parts of the plant including leaves, stems and flowers. Common pests include aphids, whiteflies, thrips, scales and mealybugs. As they feed they cause spotting, deformation, yellowing, wilting and eventual leaf drop. Apply a strong jet of water to your bougainvillea weekly. Sap-feeding insects are weak and easily killed by this method. Insecticidal soaps and horticultural oils are also effective against insect pests.

Leaf Spots

• A number of bacteria and fungi cause leaf spotting on bougainvillea. Spots can range in color from yellow to black and may grow and coalesce as the disease progresses. Moist conditions favor the spread of pathogens so avoid wetting foliage when you water. Prune and destroy heavily infested branches and keep leaf litter cleaned up as well. Thin or remove plantings if infections persist.

Root Rot

• Over-watering is a serious problem for the bougainvillea. Soggy roots decay rapidly and are susceptible to root rot fungi. Infected roots cannot move water to the rest of the plant causing eventual death. Initial symptoms of root rot are yellow leaves and wilting. As root death increases, leaves become brown and the entire plant eventually dies. Use well-drained soil and only water when your bougainvillea is dry. According to a webpage on the Texas A&M website, bougainvilleas flower best when they are drought-stressed.

Chlorosis

• Yellow leaves can be caused by nutrient deficiencies in the soil. If the new growth on your bougainvillea is turning yellow, it is likely a magnesium or iron deficiency. Apply a micronutrient blend or chelated spray to correct the deficiency. Ensure you follow the manufacturer's directions carefully to avoid overdosing the plant with nutrients. If the old growth on your bougainvillea is turning yellow, apply 1 to 2 teaspoons of Epsom salts per 1 gallon of water as a drench or foliar spray.