Here is this week's issue of AgFax Tree Crops.
Our thanks to BASF’s California team for once again sponsoring our coverage of tree crops in the Central Valley.
Owen Taylor, Editor
The very earliest hull split sprays in the lower San Joaquin Valley are about a week away.
Brown marmorated stink bugs have been noted in Merced County in our last two issues. This week you will find an expanded overview on how this invasive pest is developing in the upper SJV. See comments by Jhalendra Rijal, Area IPM Advisor.
Spider mites remain mostly in the background, even in Kern County, which is an historic hotbed for web spinners. See comments from Kern County PCAs John Moore and Jack Gonzales. This week’s contacts in other areas also report low to nonexistent mite numbers.
The upper SJV’s annual Mid-Season IPM Field Meeting for almonds is set for Monday, June 18, near Escalon. Connect to more info in our Links section.
Franz Niederholzer, UC Farm Advisor, Colusa and Sutter/Yuba Counties:
“We’re still in a rollercoaster weather pattern, which is good for bio-control of mites since beneficials have time to build their populations and keep the pest mites in check. Today (6/8), it warmed to around 90 but it’s been very comfortable this week otherwise. We’re supposed to hit another temperature spike next week but then a cooler pattern will come in by Friday and Saturday.
“Hull split will be here before we know it, so we need to start making plans, especially considering all the problems we had last year. Unlike 2017, when NOW egg counts on traps were at zero up until the last week of June, we have found eggs in at least one of the 12 egg traps at Nickels Soil Lab every week since early May.
“As things turned out in 2017, it was a heavy NOW year, despite low egg counts ahead of hull split. At Nickels, we sprayed multiple times but still had double the damage as we normally expect.
“At the end of the day, whether to spray at hull split is a decision that a grower has to make with his PCA. If you decide to spray, it is suggested that you go early to protect the first sound nuts as they split. Dr. Joel Siegel with USDA says that spraying too early is better than spraying too late, especially with longer residual materials.
“Of course, it’s not like you have to treat the whole orchard with that first application since in many orchards you’re going every other row to spray the Nonpareils. When you spray, make sure sprayer speed is slow enough to get material into and just above the tree tops. If the sprayer's fan can't push air through the entire tree canopy, spray won't get there, either, and you may not get the kind of coverage and protection you want.
“Spray when relative humidity is higher than 40% to avoid spray evaporation. UC research has shown 50% reduction in spray landing in the upper canopy when temperatures are in the upper 80s and relative humidity is approaching 40%. In research in the San Joaquin Valley, spray volumes at 150 to 200 gallons per acre at 2 MPH have delivered the coverage needed to give the best possible NOW control.
“Finally, growers and PCAs should check almond orchards for protein feeding ants -- pavement and/or southern fire ants -- to determine if treatment ahead of harvest is needed. Ant damage can be as bad as that from NOW, especially if nuts are on the orchard floor more than a week.
“In walnuts, no husk fly have turned up in our traps yet. We’re checking for mites, too, but really aren’t finding any. So far, aside from the once-in-a-lifetime freeze in February, this has been a nice spring.”
Jack Gonzales, PCA/CCA, Supervised Control Service, LLC, Bakersfield:
“Like other PCAs have reported recently, we’re having stink bug problems in almonds. I sprayed a couple of blocks last Saturday (6/2) and then recommended an aerial application for about 300 acres. This is the green stink bug. It’s an isolated problem but we definitely have to be looking for them right now.
“Spider mites remain pretty quiet – just a few flareups here and there. On the bulk of our acres, I think we can make it to hull split without applying a miticide. This is the third year in a row when we’ve had relatively low mite pressure this far into the season.
“As we’ve seen, that can change in July and suddenly growers have to treat. By then, they assume they’re through spraying and maybe they’ve unhooked sprayers from tractors so the machines can work in harvest. It’s a huge inconvenience when that happens. Considering Kern County’s history with mites, this also a very unusual mite situation.
“A couple of growers are talking about June 25 for starting hull split applications. That’s a little on the early side, but those clients have enough acres that they need to begin about that time to get across all their orchards. But for the bulk of our growers, treatments will get underway in a more normal time frame, around July 4. That’s all tentative, of course, depending on how hull split shapes up in individual fields. The trees do look beautiful.
“Pistachios are pretty quiet. Growers wrapped up their mealy bug sprays this week. I did write up my first alternaria spray in pistachios this year. This is a preventive treatment in just a few acres with a history of alternaria. I haven’t seen any yet, although it usually doesn’t turn up in pistachios until July.
“Cotton looks great. On the acres I personally check, lygus counts are very low – nothing higher than a 2 and most are at zero. Plants are setting squares quite nicely. The only high counts we’ve found were in some isolated acres. This is certainly a far cry from last year when we had heavy lygus pressure. No mite or aphid problems have developed.”
Brian Gogue, PCA, Helena Chemical Co., Hanford:
“This week I pulled the trigger on spraying one field for mites. A little population was beginning to appear. We’re going into another round of heat, and I decided to go ahead and clean it up. I sprayed one other field out west 10 to 14 days ago. It had been sprayed with abamectin early on and we had to spray it again.
“Those are the only blocks I’ve treated for our traditional web-spinning mites, but I did treat 2 other blocks near Hanford for brown mites and European red mites, which seem to be an up-and-coming issue for us. They’re hard to find. They like to stay down in the stems and the woody part of the tree and apparently come out at night and feed.
“They leave a silvery finish on the leaf and turn parts of the tree yellow. Last year was the first year I’ve ever had to treat for them, and that was in one block. They came back this year in that same block and one other block, as well.
“I’ve only treated 2 blocks for leaffooted bug this year. I could find a few stings in most blocks during most weeks but I saw very few bugs and no significant damage. Even where they were stinging, they were not penetrating nuts.
“We’re just watching now and are making sure things are cleaned up ahead of hull split. I think we’re roughly 4 weeks to hull split at this point (from 6/8). That’s probably close to a 30-year average. The heat unit numbers I saw recently put us spot-on for the 30-year average. We finished all the fertility in the last 7 to 10 days.
“In walnuts, we’re gearing up to do a spray around June 20. That’s somewhat for codling moths and a little for NOW and botryosphaeria, plus some foliars. This weekend we’re applying sun block on a few blocks. Next week the forecast says we will have multiple days in triple digits for highs, so we want to remove some potential stress from the trees.
“NOW has become more of an issue in walnuts in the last several years, even while codling moths seem to have become less of an issue.
“In pistachios, shells are all hardening quite a bit. You can pop a few nuts with your hands but most of them you can’t, and they resist being cut with a knife. Bug pressure has still been quite minimal. I’ve only treated a handful of blocks for true bugs. We’re just ramping up on fertility as we move into nut fill in the next 3 to 4 weeks.
“Cotton is moving a little on the slow side as far as growth goes, and we didn’t get a lot of the growth I expected. My average is probably 10 or 11 nodes. Lygus are ramping up this week. I’ve made a few treatments and I will line up a few more, as well. A little aphid activity developed in spots, too, and we’re going after them at the same time.
“A few mites are around in cotton but I’m not jumping into any mite treatments at this point. We’ve finished our first irrigation on furrow-irrigated cotton.
“Tomatoes still look really good. I’ve been treating basically everything for thrips over the last 3 to 4 weeks. Hoppers still aren’t much of an issue. Some random curly top is out there but it’s mostly insignificant. But in the last couple of weeks I’ve seen more and more spotted wilt, especially in my most western fields in the Cantua area. I have fields out there that are a bit concerning. Until now, we’ve only found leaf symptoms, but we’re now finding symptoms on the fruit.
“No worms at all. Powdery mildew has been showing up in the last couple of weeks and we’ve treated the majority of our acres for it. Alfalfa remains very quiet. Grapes are growing well. We have to look hard for powdery mildew. We’re on a 2-week rotation on fungicide but it’s still very clean at this point.”
Jhalendra Rijal, Area IPM Advisor, Northern San Joaquin Valley:
“In almonds, we are finding a lot of NOW eggs on egg traps and a relatively consistent number of females every week, and the moth catches also are relatively high. In the northern SJV, this is a little unusual.
“Normally, we see numbers decline between the first and second flights. The counts typically go down around the last week of May and don’t begin increasing until the start of the second flight. That isn’t happening this year. There hasn’t been a break – the counts are high and it’s still not even time for the second flight. All of that is a little concerning.
“Not much activity yet with spider mites, based on what I’m seeing and what growers and PCAs are saying. With stink bugs, pressure looks higher this year. A good deal of nut drop was reported in the beginning of the season and in some locations, we’re still seeing that.
“In many cases we don’t know whether this is the regular stink bug and/or the leaffooted bug. With stink bugs, it’s a little early to see this, so it’s probably the leaffooted bug. But we’re also finding the brown marmorated stink bug (BMSB) in places in Stanislaus and Merced Counties. In 4 orchards I’m monitoring, I’m picking up BMSB in all the traps in those orchards.
“I have seen BMSB damage in 3 orchards and a couple of PCAs have sent photos of BMSB in their orchards, too. So, it seems that BMSB has spread more than what we initially thought. Some people may have had BMSB damage but assumed it was caused by other bugs.
“Last year, I found BMSB in a single orchard, which was the first evidence that they were damaging almonds in the SJV. But this year it’s in multiple orchards. Frankly, I was surprised to see this much damage. I have not heard of our regular stink bugs putting as many nuts on the ground as I’ve seen when checking behind BMSB.
“This feeding started in April. Early season feeding caused nut abortion and nut drop. Feeding this time of the year may not necessarily cause significant nut drop, although gumming can be seen on fruits. We also don’t know how that will translate into damage that you’ll find after harvest.
“This insect has numerous hosts, unlike a lot of bugs we deal with that feed on a narrow range of plants. One place we’ve seen a lot of BMSB adults and damage is on the north side of Merced County in the Delhi area. On one side of that orchard we found a Tree of Heaven, which is a host, and it was certainly contributing to the damage to that adjacent orchard.
“That end of the orchard was sprayed in the first week of May and you could easily find a lot of dead stink bugs under the almond trees in border rows. When we checked again 3 weeks later, we found several live stink bugs on almond trees, and my student collected about 25 BMSB from a couple of border trees on that orchard. I think they moved back to the orchard from the nearby Tree of Heaven grove.
“BMSB overwinters in houses and other structures, and sometimes in the dry barks of dead trees. When they emerge in the spring, BMSB go to the first available host and then move to subsequent hosts. It takes about 45 days to progress from an egg to an adult and the adult lives about 45 days. With all that, BMSB could possibly turn into a bigger problem than leaffooted bugs and other stink bugs.
“If PCA and growers suspect unusual stink bug type of damage, scout for the BMSB in trees. Also, put some traps out. Sticky panel traps that can be used with BMSB lures are now commercially available.
“In walnuts, codling moth activity in our area has been mild, but you never know how they will finally trend. In 2016, activity was very low in the first flight and the second flight but then the third flight was huge. In 2017, we had high pressure in the first and second flights but then very low numbers in the third flight.
“We are currently (6/9) around the tail end of the first flight, based on an April 1 biofix. It is important to do trapping as well as nut damage evaluation to assess codling moth pressure. Check out the UCIPM codling moth guidelines in walnuts for details.”
John Moore, PCA, Growers Crop Consulting, Bakersfield:
“I’ve written some hull split recommendations that will actually go out on June 14 and then more recommendations for around June 26. Those are the dates that kind of fit with my model and the treatments don’t have to go out precisely on those dates.
“Some of my growers have really strong feelings about trying to time a PTB spray and this year that will fall about 10 days ahead of the NOW spray. So, they will spray PTB and then come back 10 days later with that NOW application.
“I’ve been finding empty stink bug egg casings over the last 3 or 4 weeks, but I’m not detecting any new damage or strikes. I did find some twospotted mites this week, which parallels the weather, but there weren’t enough yet to justify treating. We may see a few more next week. But temperatures have been unusual for this time of the year, with these rollercoaster swings. When highs are in the 80s, the threat of mites isn’t nearly as high as when temperatures range from 95 to 100.”
Nathan Stewart, PCA, AgVantage Consulting, Inc., Visalia:
“In almonds, kernels have hardened off across almost all varieties. Any plant bug issues are mostly behind us. It will be hot next week, approaching the high 90s, so we’re closely watching for mites. Some fields had an initial application of abamectin, some nothing, but we’re making sure mites don’t outweigh our beneficials.
“So far, the weather has been pretty mild. I guess we will call this summer and it seems like we’ll hit a heat wave soon. So, we’re making sure soil profiles are carrying adequate moisture.
“Aside from that, we’re kind of holding off until NOW time. My moth traps are picking up a touch this week after pretty much being at rock bottom. We will be thinking about NOW sprays toward the end of the month. That’s on my radar in a big way, trying to get ahead of the next flight and making sure we have the proper timing during hull split.
“In pistachios, shells are becoming rigid. We haven’t quite hit kernel fill yet but I am still looking for large plant bug strikes. Any treatments will be very site-specific, nothing broad. I will be applying my bud retention sprays as we approach July 1 – a nitrogen and boron application to help with next year’s buds.
“With walnuts, I’m expecting codling moth applications coming up between June 15 and June 22, depending on location. I’m watching for mites and a miticide may be included. That would be our 2A spray. Walnuts are sizing rapidly and I’m also lining up the next shot of nitrogen and/or potassium.”
California Almonds: Upper SJV Annual IPM Field Meeting – Escalon, June 18 6-10
California Almonds: Spotlight on Irrigation – Will Martin 6-4
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