Sponsored by...



Summer is at hand. Temperatures on Monday and Tuesday will climb well into the 90s across a wide portion of our coverage area. Water demand will pick up and some wilting may occur as trees try to transition from a mild spring to the first real blast of summer.


Rain fell through parts of our coverage area late in the week. Some fungicide applications – particularly for blight in walnuts – went out ahead of the rain.


Put brown marmorated stink bugs on your watch list. This is a relatively new insect in almonds and in California, although it’s been well established back east for a couple of decades. See comments by David Doll.



The 2018 Lake County Spring Walnut Field Meeting is set for Thursday, May 31, from 8:30 a.m. to noon. The event is sponsored by U.C. Cooperative Extension. Connect to more info in our Links section.




Franz Niederholzer, UC Farm Advisor, Sutter/Yuba Counties:

“It started raining last night and into this morning (5/25), and enough fell to make you nervous – or at least pay attention – if you didn’t spray. At the Chico State farm, it’s rained 0.58 of an inch so far, which is a significant amount of rain there for May. The total at Red Bluff was 0.6 of an inch and 0.4 at Yuba City.


“If you’re farming walnuts and more than a quarter-inch falls, that’s the rainfall criteria for the botryosphaeria predictive model, with temperature being a factor, too. On the west side of the valley and along the I-5 corridor, the totals I saw were under that quarter-inch mark.


“We actually had mild weather this week, but forecasts say highs could move into the low to mid 90s early next week. Right now, it’s in the 60s. In places, one model says we could see 97 on Monday and Tuesday in areas on the west side.


“With almonds, that kind of rain does raise concerns, depending on location, how long rain lasted and how long trees remained wet. This kind of rainfall event can trigger rust outbreaks if trees aren’t protected.


“Where people have had hull rot issues, they should be done with nitrogen by now. If hull rot hasn’t been a factor, you should be winding down nitrogen by early June.


“Growers who’ve had hull rot issues in the last couple of years ought to consider a spray in early June that targets monilinia hull rot, the brown rot disease. The timing for that is 3 to 4 weeks before hull split, based on recommendations from Jim Adaskaveg (UC Plant Pathologist). The treatment targeting monilinia is different from the fungicide application at hull split, which is aimed at the bread mold form of hull rot.”


Dan Prentice, Prentice Ag Consulting, Bakersfield:

“Stink bug numbers have crept up in an isolated area, and we did treat for those. It’s been really hard to find mites. Now and then we’ll come across a leaf with a few mites and that’s been it.


“Some alternaria is starting to show up, maybe a little later than normal. In our areas where alternaria is a factor, we made our second application 7 to 10 days ago (from 5/25).


“Pistachios are quiet. We sprayed for plant bugs early on but have not detected any reemergence since then. Our mealy bug sprays are going out this week in areas where we have them. Those treatments started on Tuesday and, depending on the area, will continue through next week.



“We’re getting into the early set in tomatoes. No worm issues. Where we’re seeing curly top, it’s what we normally expect.”


Rick Foell, Field Manager, Capay Farms, Hamilton City:

“We’ve gotten rain in places this morning (5/25) but it was spotty and variable. I heard thunder at my house at 6 a.m. but no rain fell. Not too far away, though, enough rain fell that it was too wet to work this morning on that ranch. On another ranch, we got a third of an inch by 7 a.m.


“In almonds, we’re finishing potassium applications and the rest of our nitrogen. We’re trying to make sure irrigation is going on everything and making the last mowing, plus setting up to apply ant bait. Ant colonies seem to be larger this year, based on mound size, and we’re seeing more mounds. These are pavement ants.


“We made preventive mite sprays and hope that holds until hull split sprays start. We’re anticipating the first hull split sprays beginning in the last week of June. At least that’s the plan right now. Where we’re picking up higher numbers of NOW eggs, we might start in the third week of June, but we should be rolling on all fields by the last week of June.


“In walnuts, we did a hurry-up spray this week for codling moths and included a blight material. About a week ago one of the forecasts we follow had a hint of rain for today and Saturday. Everything fit close enough together that we decided to treat our Howards for sure and any acreage in the area where we normally see a little more blight or bot. In a couple of cases, we didn’t spray fields in a drier area where I wasn’t as concerned.


“We made the decision to spray on Monday, going with the idea that it was better to spray and then not get rain than to skip spraying and then get rain and end up with blight. Spraying started Tuesday and we treated everything that needed it.


“The treatment was at the end of the 1B codling moth flight and at the beginning of the 2A flight. In fact, the day after we started spraying, all of our codling moth trap numbers jumped up. So, it was good timing as things worked out.”


Aaron Beene, PCA, Simplot, Merced:

“Some rain fell last night (5/24), probably the first measurable rain in the whole month of May, and it’s been cloudy and cool all day. Next week, though, the highs are supposed to move into the upper 90s, so spring is done and summer is starting.


“We’re finishing our May sprays, which have been going on for about the past 7 to 10 days. The majority of my growers have been adding something for rust and scab, plus a preventive miticide and foliar nutrients. It’s kind of the last shot through the field before hull split timing unless something comes up.


“The trees are fairly clean. With this cool spring, there’s still a lot of vegetative growth and things look good. Nut fill is probably 90% done, and that’s just about what we expect in late May and the first of June. With this spring’s cool weather, nuts have had time to size out.


“We’re finishing our last nitrogen applications if needed. Otherwise, we are monitoring and treating weeds and ants as needed and checking for late leaf diseases that can pop up, like rust, scab and alternaria. Otherwise, we’re in a holding pattern until hull split.


“In walnuts, we’re pretty much finished with the 1B codling moth flight. Guys started treating about a week ago. I made the first nitrogen shot in walnuts 1 to 2 weeks ago and nuts are sizing. Blight hasn’t been that bad of a problem, which points back to the lack of May rain.



“In that 1B spray, I did include something for botryosphaeria where we have a history of it. I’m glad now that I did, considering this rain. No signs of aphids or any disease in walnuts so far.”


David A. Doll, Pomology Farm Advisor, Merced County:

“I seem to be reaching a conclusion about some of the drop that’s happening around the county in Butte-Padre blocks. In places, I think we’re seeing the effects of brown marmorated stink bugs (BMSB). It’s a relatively new insect in almonds. If nuts are turning yellow and dropping, check for signs of insect feeding. Cut open nuts and look for damage.


“Evidently, this insect can do a number on almonds, and it evidently accounts for some nut drop that I’m seeing and people are reporting. The first report of it in Merced County was last year but it was known to be around Modesto County, too. I was in almonds this week where this appeared to be the case and the farmer said he had observed that kind of drop for a couple of years, so BMSB may have been in isolated pockets and went undetected.


“The feeding occurred earlier. By the time nuts started dropping, we couldn’t find a single insect, but it looked like 600 to 700 pounds of nuts were on the ground. We do know that at least one beneficial insect will work over BMSB and parasitize a significant percentage of the population. But BMSB is so new that viable populations of that beneficial haven’t become established yet.


“Next week the highs are supposed to move into the 90s, so water use will pick up. After this relatively long and cool spring, we may see some wilts set in as things heat up. Generally speaking, it will be the first hot week of the year.


“Hit-or-miss showers fell today (5/25). I think most people are fine without spraying fungicides but there may be a bit of a concern where they haven’t treated in a couple of months. Overall, the crop is proceeding normally. This has been one of the better Mays that I can remember.”




California: Walnut Spring Field Meeting, Upper Lake, May 31 5-21


Subscribe To This Weekly Report

AgFax Tree Crops, formerly AgFax Almonds, is published weekly during the crop production season.

AgFax Tree Crops span> is published by    

AgFax Media LLC

142 Westlake Drive

Brandon, MS 39047-9020.   


Owen Taylor, Editor and Publisher.

For subscription inquiries, please contact Laurie Courtney -

© 2018, AgFax Media LLC