Includes
Hop aphid (Phorodon humuli)
Mealy plum aphid (Hyalopterus pruni)
Thistle aphid (Brachycaudus cardui)
Grape mealybug (Pseudococcus maritimus)
Pest description and crop damage Several aphid species attack apricots, including the hop aphid, mealy plum aphid, and thistle aphid. Aphids tend to be teardrop-shaped, translucent green insects that measure less than 0.1 inch long. Adults of the thistle and mealy plum aphids are pale bluish green to brownish green; mealy plum aphid has a white, powdery coating. Hop aphid is pale yellowish green, winged forms are green to black. Both adult and immature aphids feed on plants by injecting their needle-like mouthparts into green tissues and sucking out plant juices. Early in the season, aphid feeding can stunt and deform shoot growth. Later in spring, feeding can lead to leaf curling, or, at high aphid abundances, shoot dieback and damaged fruit. Aphids excrete large amounts of sticky honeydew that can cover surfaces of leaves and fruit. Fungi and molds colonize the honeydew and can leave dark spots on the surface of the fruit, compromising appearance and quality.
Newly hatched mealybug nymphs, or crawlers, are about 0.06 inch long, pink-to-salmon colored, coated with a white powder wax, and very mobile. The more mature, sedentary nymphs are pink-to-purple with waxy filaments giving them a whitish cast. Adult females resemble nymphs and are about 0.2 inch long and mobile. Later in the season, mealybugs may produce copious amounts of honeydew. This honeydew may be colonized by black sooty mold that can discolor leaf and fruit surfaces.
Biology and life history Aphid species associated with apricots tend to overwinter in fruit trees as dark rice-shaped eggs hidden in cracks and crevices along tree bark, twigs, and buds. There are multiple aphid generations each year. Later generations reproduce asexually and bear live young (foregoing the egg stage). In the late spring and early summer, most aphid populations develop wings and leave fruit trees for a multitude of summer hosts like vegetable crops and weed species.
Grape mealybug overwinters as crawlers in egg sacs beneath bark scales and in cracks. Crawlers start emerging from egg sacs at the beginning of bud swell and begin feeding on the bases of buds. As buds open, the crawlers go directly to new shoots and leaves. Once settled, the crawlers start feeding, become progressively sedentary and harder to kill. First generation nymphs mature during late June and July in the Northwest. Adult males appear first, mate with last instar nymphs or adult females and die. Receptive females release a pheromone to attract males. Mated females migrate to sheltered areas, lay eggs and die in the egg sac. A partial second generation matures in late August and September.
Pest monitoring Observe shoots for aphid and mealybug presence prior to budbreak. Effective management is best undertaken while the aphid and mealybug populations are at their lowest density early in the spring.
Management-biological and cultural control
Several parasitic wasps, predatory lacewings, lady beetles, syrphid fly larvae, and other insects play an important role in controlling aphids and grape mealybugs.
Management-cultural control
Wash aphids from plants with a strong stream of water or by hand-wiping. Aphid populations tend to be higher in plants that are fertilized too liberally with nitrogen. Avoid excessive watering, or late season nitrogen applications that produce flushes of succulent growth. Most aphid species leave apricots in June-July for summer hosts and return to fruit trees in the autumn.
Management-chemical control
Dormant to delayed dormant applications target overwintering eggs and newly emerged aphid populations when their abundance in the fruit trees is lowest; spray coverage of exposed fruit tree surfaces is essential. Sprays applied during the growing season are meant to target rapidly increasing aphid populations and should be applied before leaves curl to avoid protecting aphid populations from spray residue. These applications may reduce mealybug and leafroller abundance as well. Applications to mealybugs during earlier life stages can be more effective due to a reduced quantity of protective wax covering their bodies.
Management-chemical control: HOME USE
Dormant to delayed-dormant season spray
- horticultural mineral oil-Some formulations OMRI-listed for organic use.
Growing-season spray
Warning: Many pesticides are hazardous to bees. Look for bee precautionary statements on product labels and do not use these products during bloom or if bees are foraging in the orchard.
- azadirachtin (neem oil)-Some formulations are OMRI-listed for organic use.
- carbaryl-Highly toxic to bees.
- esfenvalerate-Aphids only. Highly toxic to bees.
- gamma-cyhalothrin-Highly toxic to bees.
- horticultural mineral oil-Some formulations are OMRI-listed for organic use.
- imidacloprid-Soil drenches may have residual activity in woody plants lasting for 12 or more months. If short-term management is the goal, consider other approaches.
- insecticidal soap-May require several applications. Some formulations are OMRI-listed for organic use.
- kaolin-When sprayed on leaves, trunks, and fruit, kaolin acts as a repellant to insects. Some formulations are OMRI-listed for organic use.
- lambda-cyhalothrin-Highly toxic to bees.
- malathion-Highly toxic to bees.
- plant-derived essential oils-Some have shown efficacy against aphids and mealybugs. Some formulations are OMRI-listed for organic use.
- pyrethrins-Highly toxic to bees. Some formulations are OMRI-listed for organic use.
- zeta-cypermethrin-Highly toxic to bees.
Management-chemical control: COMMERCIAL USE
Delayed-dormant spray
- horticultural mineral oil (rates vary; check product label)-REI varies; check product label. Some formulations are OMRI-listed for organic use.
Prebloom and in-season sprays
In some cases, these products have caused more damage than good by reducing beneficial insects. For best results, apply insecticides before leaves begin to curl, and before petal fall.
- diazinon (Diazinon 50W) at 1 lb/100 gal water (4 lb/A). REI 4 days. Diazinon is toxic to bees. Do not use if bloom is present and/or bees are foraging in the orchard. Note: Diazinon is limited to one application as a foliar spray per season.
- horticultural mineral oil (rates vary; check product label)-REI varies; check product label. Some formulations are OMRI-listed for organic use.
- phosmet (Imidan 70W) at 0.75 to 1 lb/100 gal water (4.25 lb/A). REI 7 days. Extremely toxic to fish; avoid spray drift and surface runoff.
Petal fall spray
- acetamiprid (Assail 30SG) at 5.3 oz/A. REI 12 hr. PHI 7 days.
- diazinon (Diazinon 50W) at 1 lb/100 gal water (4 lb/A). REI 4 days. PHI 21 days. Diazinon is toxic to bees. Do not use during bloom or if bees are foraging in the orchard. Diazinon is limited to one application as a foliar spray per season.
- imidacloprid (Prey 1.6F, Nuprid 1.6) at 2 fl oz/100 gal water (4 to 8 fl oz/A). REI 12 hr. PHI 0 days. Do not apply during pre-bloom, bloom, or when bees are actively foraging.