Filbert aphid (Myzocallis coryli)
Hazelnut aphid (Corylobium avellanae)

Pest description and crop damage Medium to small aphids that feed on leaves and husks and produce honeydew. Filbert aphid is typically more problematic in Willamette Valley hazelnut orchards. It is a green aphid primarily found on undersides of leaves where it feeds on phloem along leaf veins, while hazelnut aphid is primarily found on husks. Filbert aphid is typically green or pale yellow and lacks well-developed cornicles, which are tube-like projections that emerge from the abdomen. Hazelnut aphid by contrast has well-developed cornicles, longer legs, and also may have reddish coloration. Experimental evidence indicates that heavy infestations of aphids should be controlled to prevent reduced fill and smaller nut size. Damage caused by aphids is cumulative; benefits might not be seen during the first season of treatment but become evident after two years or more of aphid control. Honeydew produced by aphids is colonized by sooty mold fungus. Sooty mold fungus can impede photosynthesis and severely devitalize plants and retard growth.

Biology and life history Aphids overwinter as eggs in crevices in bark and on twigs, and around buds and leaf scales. Eggs turn from a greenish color to black as they mature. In early spring, eggs hatch in synchrony with budbreak, and the aphids feed on swelling buds and leaflets before moving to the leaves. The population can increase rapidly, and there are 8 to 10 generations per year. In the fall, sexual males and females are formed. These mate and females lay overwintering eggs.

Pest monitoring The sampling period is April 1-Sept 30. Check three terminal branches per tree and three leaves per terminal. Count the number of aphids per leaf and treat when the following thresholds are reached: April: 20 per leaf, May: 30/leaf, June: 40/ leaf, and July: 40/ leaf with an increasing population. If there are signs of the parasitoid, Trioxys pallidus, hold off on treatment and check back on population levels in a week. Mummified aphids indicate that the parasitoid is active. The mummies appear swollen, rounded and darker and may have an exit hole chewed by the wasp. Note that populations of aphids typically peak by June and will decrease substantially by July regardless of management action.

Management-biological control

An introduced parasitoid wasp (Trioxys pallidus) targeting this aphid has become well established in the Willamette Valley. This biological control makes aphid sprays unnecessary in many hazelnut orchards. Learn to recognize mummies and avoid treating when biological control is active. The aphid has a lower temperature threshold for development than the wasp, which typically emerges about two weeks after the aphids. As a result, there is typically some lag time between population increase of aphids and the response of the wasp. Pest management that is detrimental to the wasp population can aggravate aphid problems. Note also that broad-spectrum insecticide applications made against other pests can free the aphid from biological control causing its population to surge. There are a number of important predators of aphids that occur in hazelnut orchards including ladybird beetles (larvae and adults), syrphid fly larvae, Geocoris (big-eyed bugs), Deraecoris (plant bugs), and lacewing larvae. Yellowjackets also prey on aphids.

Management-cultural control

Aphid populations tend to be higher in plants that are fertilized liberally with nitrogen. Home orchardists: Wash aphids from plants with a strong stream of water or by hand-wiping. Avoid excessive watering which, together with nitrogen applications, produces flushes of succulent growth. Control ants, which "farm" the aphids for their honeydew and protect them from predators.

Management-chemical control: HOME USE

  • acetamiprid-Do not make more than one application a year. PHI 7 days.
  • azadirachtin (neem oil)-Some formulations are OMRI-listed for organic use.
  • bifenthrin (as a mix with other ingredients)
  • carbaryl
  • esfenvalerate
  • gamma cyhalothrin
  • imidacloprid-PHI 7 days.
  • insecticidal soap-Some formulations OMRI-listed for organic use.
  • kaolin-Some formulations are OMRI-listed for organic use.
  • mineral or vegetable oils-Dormant or delayed dormant applications can kill aphid eggs. Use caution not to interfere with active pollination.
  • plant-derived essential oils-Some formulations are OMRI-listed for organic use and have shown efficacy against aphids.
  • pyrethrins (often as a mix with other ingredients)-Some formulations are OMRI-listed for organic use.
  • zeta-cypermethrin

Management-chemical control: COMMERCIAL USE

  • acetamiprid (Assail 70WP) at 0.57 to 1.0 oz/100 gal water (2.3 to 4.1 oz/a). PHI 14 days. REI 12 hr. No more than 4 applications per season.
  • azadirachtin (neem oil)-Some formulations are OMRI-listed for organic use.
  • chlorpyrifos- Generic labels for chlorpyrifos are also available.
    • Lorsban Advanced at 3 to 4 pints/100 gal. PHI 14 days. REI 1 day. No more than three applications per season. Do not graze livestock in the treated area. Extremely toxic to fish. Toxic to birds and wildlife. RESTRICTED USE IN OREGON.
  • chlorpyrifos+gamma-cyhalothrin (Cobalt) at 6.5 to 14.2 oz/100 gal (26 to 57 fl oz/a). PHI 14 days. REI 1 day. Do not make more than 3 applications per season of Cobalt or other product containing chlorpyrifos for hazelnuts. RESTRICTED USE IN OREGON.
  • clothianidin (Belay) at 3 to 6 oz/100 gal water. Use the low rate for smaller infestations or smaller trees. Apply no more than 0.2 lb a.i/acre per year.
  • diazinon (Diazinon AG 500) at 1 pint/250 to 400 gal water/a. No more than one application per season. PHI 45 days. REI 18 days. Washington and Oregon only.
  • flupyradifurone (Sivanto) at 7.0 to 10.5 fl oz/a. PHI 7 days. REI 4 hr. Use no more than 28 fl oz/acre/year.
  • imidacloprid (Provado 1.6, Admire Pro, generics) at 3.4 to 7 fl oz/a. PHI 7 days. REI 12 hr. imidacloprid+beta-cyfluthrin (Leverage 360) at 2.8 oz/a. PHI 14 days. REI 12 hr.
  • imidacloprid+cyfluthrin (Leverage 2.7) at 3.8 to 5.1 oz/a. PHI 14 days. REI 12 hr.
  • spirotetramat (Movento) at 6 to 9 fl oz/a. PHI 7 days. REI 1 day.
  • sulfoxaflor (Closer SC) at 1.5 to 2.75 oz/a. PHI 7 days.

Management-chemical control: COMMERCIAL USE

There are no chemicals registered for this pest on hazelnut. Registered materials with high residual activity could be used as trunk sprays during periods of beetle flight.