The pistachio seed wasp
Scientific name: Εurytoma plotnikovi
Family: Eurytomidae

These insects are 4-5 mm long, and the females are larger than the males, with a brown-black head and thorax, red-yellow abdomen and red eyes; males are black with yellow-red legs and resemble small wasps. The have one generation per year. They overwinter as full-grown larvae (worms 6 mm long, off-white, cone-shaped, humpbacked) in the mummified pistachio nuts remaining on the tree after harvest, or on the ground. From late May to late June, larvae pupate and turn into adults which emerge at the same time as the nut, opening a hole at its base. Females insert one egg inside each unripe pistachio near its tip, leaving the nut vulnerable to fungi that impact production. The pistachio seed wasp reproduces by thelytokousparthenogenesis (only females are produced from unfertilized eggs), whereas males are very scarce.

Pathogens often invade through the point of entry and further affect yield.

Damage is mostly caused by larvae that initially feed on the still-tender inner walls of the nut and later on the developing seed. The infested nuts turn black and remain on the trees even after leaf fall, unlike blank or fungus-infested nuts that fall earlier. Damage can be as high as 95% of the yield.

CONTROL

ORGANIC

Gathering and burning of all nuts remaining on the trees after harvest no later than April (along with cluster prune out).

CHEMICAL

Placement of cages covered with fine muslin and filled with infested nuts into field conditions. Treatment with suitable pesticides 3 days after the appearance of adults in the monitoring cages or as soon as the nut appears (from mid-April). Treatment is repeated every week for 4 weeks or until nut-shell hardening.

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Athanasia Chatziperi, Agronomist, Attica Region