Diaphorina citri
Common name: ACP
The Asian citrus psyllid is native to Asia but has become one of the most feared invasive pests in citrus-growing regions worldwide, having spread through much of Asia, the Americas, and, more recently, parts of Africa. It has now been confirmed in several East and West African countries, including Kenya, Nigeria, and Benin. While South Africa's citrus industry currently deals primarily with the related African citrus psyllid (Trioza erytreae), the continuing spread of the Asian citrus psyllid across the continent makes it a serious quarantine concern and a priority for early-detection monitoring in South African citrus regions.
Asian citrus psyllid on green leaf.
Asian citrus psyllid on green leaf.
Egg: Eggs are elongated and oval, pale yellow when freshly laid and turning bright orange with two small red eye-spots as they near hatching. They are laid on the tips of growing shoots, tucked between unfurling young leaves.
Nymph: Nymphs pass through five growth stages before reaching adulthood, feeding on tender new growth throughout their development.
Adult: The adult is a small, mottled brown-and-white insect that feeds at a distinctive 45-degree angle to the leaf surface, with its head down and body angled upward.
Development from egg to adult takes roughly two to seven weeks, depending on temperature, and the psyllid can complete numerous generations a year in warm climates, with population growth slowing but not stopping over winter.
ACP feeds almost exclusively on citrus and other plants in the Rutaceae family, including ornamental and hedge species such as orange jasmine (Murraya paniculata), which can act as a reservoir host near commercial orchards.
Direct feeding by nymphs and adults injects toxic saliva into growing shoots, causing leaf curling and distorted new growth, while heavy honeydew excretion promotes sooty mould that blackens leaves and reduces photosynthesis. However, the psyllid's real significance lies in its role as the primary vector of the bacteria that cause Huanglongbing (citrus greening disease), which is currently the most destructive disease affecting citrus production worldwide. Once a tree is infected, there is no cure; affected trees decline steadily, producing small, bitter, lopsided fruit before eventually dying, making vector control the front line of defence against the disease.
Because Huanglongbing has no cure, keeping psyllid populations low and detecting incursions early is essential, particularly in a country where the disease is not yet established. Regular monitoring of new flush growth, removal of neglected or abandoned citrus and reservoir host plants, and coordinated area-wide control all help limit the psyllid's spread.
