Mold Continued from Page 7
and promotes early leaf fall. Eventually trees succumb. Cook is conducting field trials this year to test the effectiveness of Orondis, a newly registered fungicide from Syngenta, as well as the older fungicides Fosphite, Ridomil and Aliette against Phytophthora. He applied the materials through irrigation to infected tree roots during the spring root flush and plans to reapply them in the fall during the second flush. The products don’t cure Phytophthora but instead are designed to stop further root infection. Along with a strong nutri- tional program, Cook said he hoped the treated trees will generate new roots to re- place those damaged by the water mold and will remain productive. The Almond Board of California also is funding research led by UC Riverside that is looking at Orondis and two unreg- istered products, Presidio and Elumin, which could potentially help manage Phytophthora strains that have grown re- sistant to phosphites. “We’re just trying to get the trees back into producing so they can give some eco- nomic return to the grower. That’s all we’re after,” Cook said. “For some of the trees we’re looking at, they’re pretty far gone and aren’t going to make it.” (Vicky Boyd is a reporter in Modesto. She may be contacted at vlboyd@att.net.)
“The roots in some areas were under 10 inches of water, and they couldn’t breathe,” Cook said. “You have huge disease issues with any type of vascular problem, and it exponentially gets worse.” Water-saturated soils reduce the abil- ity of oxygen to infiltrate the root zone. Because roots require oxygen, long peri- ods of flooding can lead to asphyxiation, with fine feeder roots being the first to be affected. During the winter when trees are dor- mant and have lower respiration rates, they can withstand up to seven days of standing water. But as they begin to leaf out and root activity picks up, standing water in orchards of as few as five days can kill mature trees, according to University of California studies. In light of saturated soils this spring, Holtz recommended almond growers wait on their first irrigations until soil moisture sensors or pressure bombs in- dicated they were needed. He noticed in his family’s own almond orchard that they had already made four irrigations in 2022 by the time they applied the first irrigation this year. “The worst thing you can do is wa- ter too much or too early. You’ll cause Phytophthora on you’re own,” he said. “By holding off and using the pressure chamber or some type of soil monitoring
Almond trees that were blooming during flooding were more susceptible to disease issues. Prolonged periods under water can asphyxiate trees, with danger higher for those starting to leaf.
and only watering when your tree real- ly needs it, that’s the best Phytophthora (management) tool.” Phytophthora crown and root rots are caused by a handful of naturally occurring water molds that favor wet soil conditions. Of the two, crown rot is more rapid and kills trees by damaging plant tissue that carries water and nutrients from the roots. With the first hot spell in May, trees
tried to tap those soil nutrients and mois- ture for respiration and leaf growth. But a compromised plumbing system prevent- ed their movement, causing some trees to quickly collapse and die. One of the telltale symptoms of Phytophthora crown rot is leaves on infected trees wilt and dry but remain attached. Root rot, on the other hand, is a chron- ic problem that slowly plugs root vascu- lar tissue. As a result, it decreases tree vigor, stunts tree growth, reduces yields
2023 Health & Safety on the Farm and Ranch
California Farm Bureau is pleased to offer this year-long program of training sessions presented by Nationwide. Select topics will be presented in both English and Spanish. Members, enjoy access to free classes! Register for the upcoming training webinars. Trainings will be presented via Zoom. The Hazardous Agricultural Materials (HAM) training must be attended in person at a participating County Farm Bureau office or at the California Farm Bureau office in Sacramento. For a list of class dates and to register, visit cfbf.com/FBE or call (800) 698-FARM for assistance. You will receive a Zoom link and details two days prior to your selected webinar date.
8 Ag Alert July 19, 2023
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