Black Pests on Citrus Leaves
The home citrus orchard brings beautiful, fragrant blooms that slowly ripen into sweet, succulent fruit fresher than any produce that can be found in a supermarket. Citrus management can be time intensive, though, since insect pests are common visitors -- knowing the insects you're up against makes the job significantly easier. Luckily, there are only a few black insect pests that feed on citrus, the major offenders being aphids, scale, sharpshooters and moth caterpillars.
Black Citrus Aphid
Black citrus aphids (Toxoptera aurantii) are tiny, black, soft-bodied insects that feed on the juices inside of citrus leaves. Their feeding causes young leaves to curl toward the stem. Rarely do black citrus aphids feed on hardened, mature leaves, so control is not warranted. Since aphid feeding activities rarely affect citrus fruit yields, the black citrus aphid is often allowed to persist on citrus trees to provide honeydew for other insect pests that would otherwise feed on fruits.
The black scale insect (Saissetia oleae) appears as a dark grey or black mottled growth on citrus trees, primarily grapefruit. After their second molt, young black scales attach permanently to their citrus host and do not move again. Black scale have several natural parasites, but ants will protect the scale in order to farm their honeydew. Control ants first by baiting them and wrapping the trunks of affected trees with sticky traps. If natural predation cannot control scale once ants are gone, apply a horticultural oil when scale larvae are in the crawler stage and still relatively vulnerable.
Closely related to leafhoppers, glassy-winged sharpshooters (Homalodisca vitripennis) are 1/2-inch long, brown to black insects with distinguishing white to yellow spots on their heads. While heavy populations of feeding glassy-winged sharpshooters will reduce fruit quality and yield, the smaller populations that are normally seen only cause cosmetic damage on fruit and foliage. Generally, glassy-winged sharpshooters are tolerated in small numbers, unless grapes are nearby (they can vector Pierce's disease). When control is necessary, apply imidacloprid to the soil around affected trees, but wait until the blooms of citrus have faded, since this chemical will harm bees. Pyrethrins are also effective control and much less dangerous to pollinators during bloom time.
Western Tussock Moth Caterpillars
The young larva of the Western tussock moth (Orgyia vetusta) are distinctly black, bristled caterpillars that feed on tender, young fruit and new growth. High numbers of caterpillars will consume all new growth, destroying entire crops. Parasitic wasps are natural predators of the Western tussock moths; they can keep small populations under control. Control large populations of Western tussock moth caterpillars with sprays of Bacilius thuringiensis.
- Unviersity of California Statewide Integrated Pest Management Program: Citrus Pest Management Guidelines
- Unviersity of California Statewide Integrated Pest Management Program: Aphids on Citrus
- Unviersity of California Statewide Integrated Pest Management Program: Black Scale on Citrus
- Unviersity of California Statewide Integrated Pest Management Program: Glassy-Winged Sharpshooters on Citrus
- Unviersity of California Statewide Integrated Pest Management Program: Western Tussock Moth on Citrus
Kristi Waterworth started her writing career in 1995 as a journalist for a local newspaper. From there, her meandering career path led to a 9 1/2 year stint in the real estate industry. Since 2010, she's written on a wide range of personal finance topics. Waterworth received a Bachelor of Arts in American history from Columbia College.