Alternaria late blight, a fungal disease affecting both leaves and fruit, can lower the quality of pistachios and reduce grower profit. High humidity in orchards increases the magnitude and severity of the blight infections. One cause of high orchard humidity is the evaporation of water from the soil surface, which in turn is enhanced by irrigation systems that wet the surface. In this study, we tested the use of buried drip irrigation, which reduces orchard floor wetting, to see how well it controlled the disease. When compared with a traditional flood irrigation system, the buried drip system reduced orchard humidity and dew duration and increased temperature. This significantly reduced leaf symptoms of the disease and fruit infection at harvest. Additionally, more shells split open with the buried drip method, resulting in a higher yield of marketable pistachios.

This web page will provide certain Plant Pathology and Nematology educational materials to growers, Farm Advisers, Pest Control Advisers and to the public. This information would aid in disease diagnosis, proper sampling procedures for submission to diagnostic labs, and the principles of epidemiology and disease management that underlie the University’s Pest Management Guidelines.

In addition, we will broadcast disease alerts (including outbreaks of new diseases, tracking of new pathogen races, tracking of fungicide-resistant strains, etc.) and disseminating information relating to research advances, poisonous mushrooms, and other issues of importance to Pest Control Advisers, Master Gardeners and other professional and volunteer groups.

Abnormal pistachio nuts, known as “early-split nuts,” have both the hull and shell split while still on the tree, exposing the kernel to invasion by insects and molds. Deficit irrigation of pistachio trees in April and May resulted in substantial increases in the formation of early-split nuts in late summer, while extreme deficit irrigation in July and August resulted in decreased formation. However, deficit irrigation during the period of shell hardening, mainly in June, did not affect early-split formation.