“A small number of fungicide applications went out before the rain. Alternaria, rust and anthracnose can be a concern in blocks with a history of these diseases. We’re close to the tail end of treatment timing effectiveness with these diseases, especially with warm weather in the forecast since their last treatments. Growers in the area were applying fungicides this week after the rain. However, effectiveness may be questionable.
“Monitoring continues for stink bug and leaffooted plant bug, and spot treatments occurred in areas with high pressure. It’s important to remember these hot-spot locations when scouting and planning treatments next year and beyond.
“We are putting together our hull split programs with an emphasis on effectively rotating chemistry. We are tracking navel orangeworm flight activity towards week 27 or that last week of June.
A storm rolls through the upper San Joaquin Valley on May 18, 2020. Photo: Aaron Heinrich, Independent Crop Advisor, AgriWest, Inc., Escalon
“In walnuts, we’re between codling moth flights. Many traps had a fair amount of 1A activity, while others had nothing. For growers, that underscores the important of placing traps in all their orchards.
“Right now, traps are reasonably quiet as we watch for 1B activity, which tends to occur between 600- and 700-degree days from the biofix. We’re treating in places, based on a field’s history, how significant the 1A damage turned out to be and how heavy those first-generations flights were in a specific walnut orchard.
“Next week, we will begin hanging husk fly traps and then begin monitoring those on June 1.
“We are easily finding walnut aphid in nearly every block we are scouting. Right now, we see low numbers, but they are present, so we’ll watch for rapid increases that would warrant treatments.
“We are just starting to see spider mites in low numbers. We treated a few blocks for European red mites in an early stage. We are monitoring a few more blocks that could justify treatments if the numbers continue to build. Double-sided sticky tape monitoring for scale crawlers showed a significant amount of walnut scale and frosted scale this week. Next week, we plan to treat a few of those blocks at the crawler stage.
“Overall, we see more scale pressure this year than in previous years. This possibly is due to more reliance on mating disruption, which results in fewer of the worm applications that previously would have provided scale control. Without treatments, scale pressure leaves opening sites for secondary infections, such as botryosphaeria.”
Dan Prentice, Prentice Ag Consulting, Bakersfield
“A slight shower fell Monday morning (5/18), and then another developed that evening and it was just enough to settle the dust in our area.
“In several places across Kern County, we are fighting rust as well as alternaria. The tissue diseases showed up early and remain significant concerns as we head into the final growing stages. Growers are spraying in an attempt to keep leaves on the trees until harvest. The majority of growers have been playing catch up, trying to bring it under control.
“Insects have been quiet lately, with no plant bug issues since we treated in the middle of May.
“Spider mites are starting to show up along field edges. We do expect that mite pressure will increase as temperatures heat up next week, and we will closely monitor to see how quickly populations build. We’re less than five weeks away from that first planned hull-split spray at the end of June, and growers would prefer not applying a miticide before then.
“Traces of alternaria began to show in spots where pressure was evident in previous years. Mealybug treatments started this week as populations increased.”
Jhalendra Rijal, Area IPM Advisor, Northern San Joaquin Valley
“Monday’s rainstorm brought a quarter of an inch to the Modesto area and higher amounts in the northern part of the valley. The main issue was with cherries as they finish ripening now, and they tend to split after a rain. Rain favors the growth of spotted wing drosophila populations, too, which could lead to control measures in areas with more rainfall.
“Navel orangeworm eggs are present in traps. There’s always activity, although sometimes it’s sporadic. Yesterday, we counted 50-plus eggs in one specific trap. Peak adult trap counts usually occur at the end of April through the first week of May. Growers who are diligent with winter sanitation can limit their May spray programs and focus more on hull split programs. Infrequent May sprays have been made in the area, mostly where growers already were going to treat for peach twig borer.