The 2024 Statewide Pistachio Day attracted over 600 attendees to the Visalia Convention Center on January 17, 2023. This annual event is designed to extend research conducted by University of California scientists to the growers, ranch managers, PCAs, and other members of allied industries, who translate the information into tangible practices affected production.

The 2024 meeting was hosted by Elizabeth Fichtner, Farm Advisor, UCCE Tulare County and David Haviland, Farm Advisor, Kern County. The event was divided into three sessions moderated by Jorge Angeles, Farm Advisor UCCE Tulare County, Tobias Oker, Farm Advisor UCCE Kern County, and David Haviland, Farm Advisor UCCE Kern County. Coffee, breakfast, and luncheon were sponsored by the California Pistachio Research Board and numerous corporate sponsors.

            Robert Klein, manager of the California Pistachio Research Board, provided updates from the California Pistachio Research Board on pistachio production and consumption. During the morning session, researchers from the University of California provided information on different aspects of pistachio culture including economics, climatic considerations, breeding, fertility, cover cropping, satellite remote sensing, and mechanical harvesting. The afternoon session focused on pest management issues, including disease and insect management, as well as nematode management.  Researchers discussed implementation of sterile insect technique for management of navel orangeworm, monitoring programs for leaffooted bug, insecticide programs for Gill's mealybug and insights on Carpophilus, a recently-identified pest in California. During the coffee and luncheon breaks, participants interacted with the sponsors hosting booths in the trade show area. The event concluded with a Pest Management Question and Answer session that facilitated conversation between researchers and the grower and PCA communities. 

Within the past decade a wood decay fungus with no prior record in North America has emerged as a pathogen of almond, prune, and peach (rootstock) in the San Joaquin Valley. Since 2016, Ganoderma adspersum, has been associated with decay symptoms on almonds in Kings, Tulare, Kern, and Madera counties. Unlike other endemic species of Ganoderma that were previously recognized in California almond orchards, G. adspersum appears to be aggressive on young trees, particularly those on ‘Nemaguard' rootstock. Additionally, G. adsperum infection appears to be prevalent in orchards with high incidence of crown gall caused by Agrobacterium tumefaciens, leading plant pathologists to suspect that the bacterial disease may predispose infected almond trees to the decay fungus. After a recent farm call with almond growers and crop consultants, UCCE Advisors Mohammad Yaghmour, Elizabeth Fichtner, and Raymond Mireles have initiated a series of studies to further investigate the potential relationship between crown gall and G. adspersum in the field, as well as evaluate techniques to limit the spread of G. adspersum in orchards.

Ganoderma adspersum is a wood decay fungus that infects the roots and butts of trees causing white rot and leading to tree blow-over and mortality especially after windy and rainy storms, hence, it is also called butt rot. Infected trees may appear healthy but are more likely to collapse during storms or harvest activities than uninfected trees.

 Infection by G. adspersum can be identified by the fruiting bodies, known as conks. The conks are thick-based, semi-circular, or hoof-shaped, shelf-like fruiting bodies found on tree trunks mainly at the base of the tree. Once fruiting bodies are visible, the fungus has already colonized the tree; consequently, removing fruiting bodies has little potential to affect the health of infected trees. Because Ganoderma fruiting bodies may produce 30 billion spores a day, the removal of fruiting bodies may reduce disease spread by limiting the inoculum level in affected orchards. Fruiting bodies generally regrow three to four months after removal; therefore, repeat removal of conks will be necessary to maintain reduced inoculum levels in orchards. Recent studies indicate that sporulation is highest in August and September, suggesting that harvest related activities may also contribute to spore dispersal.

In February 2024, Yaghmour, Fichtner, and Mireles established new research studies in Tulare County orchards to address the hypothesis that G. adspersum infections are more prevalent on trees infected with A. tumefaciens. With the assistance of Santosh Bhandari, Associate Specialist with UC ANR, over 6,000 trees were surveyed across two orchards and rated for incidence of each disease. Both orchards were on ‘Nemaguard' rootstock and included ‘Nonpareil,' ‘Monterey,' and ‘Fritz' varieties. Results of statistical analyses indicate a significant association between G. adspersum and crown gall infection on all varieties in both orchards.  For each incident of crown gall, the probability of infection with G. adspersum increased by over 80-fold across all varieties in both orchards.

Studies conducted by Daisy Hernandez, a PhD student in the Department of Plant Pathology at UC Davis, suggest that stem infections with crown gall do not alter the tree's susceptibility to future infection with G. adspersum at another location on the stem. This work suggests that the association of the two diseases may not be related to a physiological change in the plant resulting from prior infection with A. tumefaciens; however, it does not rule out other mechanisms of predisposition. Mireles, Yaghmour, and Fichtner are interested in studying whether the crown gall itself presents a unique infection court (ie. opening) that facilitates infection with windblown spores of G. adspersum that may encounter the gall years after crown gall development.

In 2024, new studies will be initiated to evaluate the potential benefit of phosphites (ie. K-Phite^®) in limiting the progression of new infections of G. adspersum in affected almond orchards. Phosphites offer a cost-effective approach at managing several plant diseases, including Phytophthora on almonds. Phosphites are known to induce plant defense responses to disease and are often better at preventing than curing disease. Additionally, some growers have expressed interest in using conk-removal as a strategy for reducing G. adspersum inoculum in orchards. UCCE Advisors plan to evaluate the influence of phosphite treatment on the rate of fruiting body regrowth with the anticipation of identifying multiple techniques that growers may employ to mitigate the economic effects of these diseases in California orchards.