Agriculture: Pistachio Pest Management Guidelines

Fruit Development

This year-round IPM program covers the major pests of pistachios in California.

About Fruit Development

What should you be doing at this time?

Avoid severe water stress in mid-May during stage one of kernel development (bloom through shell expansion) to reduce the incidence of early shell split and navel orangeworm infestations, which can introduce fruit molds that cause aflatoxin contamination.

Check pheromone and egg traps once or twice per week:

  • Obliquebanded leafroller. Hang pheromone traps by mid- to late April in Fresno and northward. Note biofix (the first date when male moths are consistently caught in traps). Continue monitoring traps to determine treatment timing if needed.
  • Navel orangeworm. Identify the first (May) and second (late June to early July) generations using egg or pheromone traps. In late July use degree-days, pheromone trap catches, and inspections for eggs on early split nuts to identify the beginning of the third generation for treatment.

Monitor weekly for bugs, small plant bugs, and stink bugs and treat if needed according to the Pistachio Pest Management Guidelines. Look for:

  • Plant bugs, stink bugs, and leaffooted plant bug nymphs, using a beating tray on clusters.
  • Black (darkened) nuts and epicarp lesions. Cut open nuts to confirm if there is bug feeding (stink bug, leaffooted plant bug, small plant bugs).
  • Stink bugs and leaffooted plant bug eggs on leaves or fruit.
  • Calocoris norvegicus and lygus bugs by sampling with a sweep net in weeds and groundcover. Once nut shells harden in late May, small plant bugs no longer cause damage.

In mid-May to early July, check trees where mealybug infestations were noted after harvest or at budbreak. Look for adult females on the rachises and manage as needed at peak crawler emergence (typically the first week of June) according to the Pistachio Pest Management Guidelines. If no treatment was made in June, continue monitoring.

In July, sample 100 nuts weekly for early splits. Apply an insecticide for navel orangeworm if more than 2 early splits per 100 nuts are found.

Monitor for fruit scabbing and rachis darkening caused by citrus flat mite. If detected, consider a pesticide application.

Manage orchard floor weeds:

Apply herbicides for weeds that escaped initial management using drift-reducing spray nozzles where possible. Apply herbicides only when environmental conditions are favorable.

Monitor and manage diseases:

  • Alternaria blight (lesions) on foliage starting in mid-July. Manage if needed according to the Pistachio Pest Management Guidelines.
  • Botryosphaeria panicle and shoot blight. Consider a fungicide application in early June or if rain occurs. Consider performing an ONFIT assay in June to predict blighted fruit at harvest. You may need to adjust your fungicide spray program accordingly.
  • Verticillium wilt. Note trees for future removal.

Look for vertebrates and their damage and manage if needed:

  • Ground squirrels
  • Jackrabbits
  • Meadow voles
  • Pocket gophers

Sporadic or minor pests and disorders you may see:

Invertebrates
  • Darkling beetles
  • False chinch bugs
  • Webspinning spider mites (particularly where soils are alkaline)
Diseases and abiotic disorders
  • Botrytis blossom and shoot blight
  • Epicarp staining (due to rain)
  • Nut collapse
  • Pistachio pop
Text Updated: 10/14