Why is fruiting important in an IPM program?
Fruit development generally occurs between mid-April and the start of shaking, but dates may vary according to region, variety, and weather. This is an important time to monitor irrigation practices, hull split, invertebrates, diseases and weeds.
Fruiting is also a time to take into account pesticide residue levels at the time of harvest before a treatment is made.
While it is important to avoid severe water stress during rapid shell growth in order to reduce the incidence of early shell split and thus navel orangeworm infestations, it is also important to adjust irrigation if Alternaria blight is serious so that the period from August 1 to 10 is irrigation-free.
It is important to look for "early splits". Typically the internal pistachio shell splits before harvest while the protective outer hull stays intact until after harvest. Early split nuts are when both the outer hull and internal shell split while still on the tree, exposing the kernel to invasion by insects and molds, including Aspergillus flavus which produces aflatoxins.
To make navel orangeworm treatment decisions, consider early splits, historic navel orangeworm problems, the abundance of old "mummy" nuts, the projected harvest date, and the presence and condition of surrounding orchards, especially almonds. More than 2 early splits per 100 nuts signals potential problems from navel orangeworm and treatment is recommended. If harvest is planned for mid-September to October, a second application will be needed.
Citrus flat mite, navel orangeworm, leaffooted plant bugs, and stink bugs are key pests at this time. If unchecked, increasing citrus flat mite populations can arrest fruit development and growth. Navel orangeworm infests the nut meat and leaffooted bugs and stink bugs can transmit stigmatomycosis under moist conditions.