Pesky wasps could cause issue's for our crop- but our awesome farmers have a trick up their sleave!

In our last post of “Stories from the orchards”, we told you all about the process of pollination – the start of our wonderful pistachio’s journey in the orchards in Greece.

In this blog we are going to talk about the main threats the pistachios face.

Whilst insects are great for the Orchards assisting pollination, they’re also the biggest hinderance! It might come as a shock that the threat from insects starts very early in the crop cycle, in fact just weeks after pollination has happened and the pistachios are developing. The biggest threat comes from a type of pesky wasp and can cause major problems for the pistachios. Without good management the wasp can reduce production up to a staggering 90% each year. Our farmers have been growing pistachios for many many years and understand this threat and control infestation through their amazing sustainability program.

Over the winter months wasps like to make their home inside pistachios that have been left on the trees.  When temperatures start to rise at the beginning of spring the adult hatches into the pistachio, this happens between early May to early June, depending on weather conditions. Most of the adults are females and begin to lay eggs 3 days after they hatch on the newly pollinated and developing pistachio fruit. Once infected the new pistachio will wither and sadly become unusable.  

It’s essential to monitor the orchards closely throughout this time to pinpoint the date the first adult hatches, and therefore control practices take place at the right time. Good orchard management by our farmers clears old pistachios not harvested from the previous harvest so they will not become infected. Our farmers collect up to a thousand old un-harvested pistachios from surrounding trees and place them in cages on abandoned orchards. The cages are hung on the trees to mirror the same conditions that they have in their own orchard. The wasps then make these cages their home instead of the trees in active orchards. By checking the cages every couple of days, they can identify the date the first wasps hatch and become active.  

The threat from the wasp reduces from June when the pistachio shell starts to harden and the female can no longer lay her eggs inside the developing pistachio.

Cages containing infected pistachios from the previous year’s crop are hung in old and unused pistachio orchards to replicate conditions. Regular monitoring will identify when new wasps will arrive. The date is very dependent on the weather – hot weather brings forward hatching.