Walnut phylloxera

Taxonomic position: Walnut phylloxera (Phylloxera subelliptica) belongs to the order Hemiptera and the family Phylloxeridae. It is a highly specialized insect pest that has evolved to feed exclusively on the tissues of specific walnut species.

Host plants: The primary host for this pest is the common walnut tree (Juglans regia). The insect attacks the foliage, leading to the development of characteristic malformations that serve as both a food source and a habitat for the pest.

Biology and life cycle: The life cycle is strictly synchronized with the growth stages of the walnut tree. Overwintering occurs primarily in the egg stage, tucked away in the crevices of the tree bark. As soon as the buds burst in spring, the larvae emerge, migrate to the young leaves, and begin feeding, which triggers the plant to form protective galls.

Damage and economic impact: The damage is characterized by the formation of subelliptical galls on the leaves. Heavy infestations significantly impair the photosynthetic ability of the trees, causing foliage discoloration, premature leaf drop, and overall reduction in tree vigor. Prolonged stress can decrease fruit production and increase the tree's vulnerability to secondary infections and severe winter temperatures.

Control measures: Integrated pest management (IPM) is essential for controlling this pest.

• Applying contact or systemic insecticides during the dormant stage or early budding phase.
• Maintaining healthy orchard sanitation by removing and destroying heavily infested leaves.
• Encouraging the presence of natural predators, such as lady beetles and lacewings.
• Monitoring orchards regularly to detect early signs of gall formation.