California Almonds: Pests Will Enjoy The Warming Weather Trend – AgFax Tree Crops

Almonds after rain. ©Sara Savary, AgFax Media

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Owen Taylor, Editor
Jenny Holtermann, Contributing Editor


Wet weather over the last few weeks has mostly been a positive development, considering the dry winter across much of the state.

Wet and cooler conditions stalled pest activity to an extent. Moths were less likely to fly, and a combination of rain and predators held spider mites in check in places. But the forecast calls for warmer conditions going into April, so pest populations could build quickly.

Nutlets started to drop in some areas. Hail, a natural drop of unfertilized bloom and wind have all contributed to the drop.

Pistachio bloom is underway in places, with buds measuring a half to one inch.

Walnuts are also starting to release pollen and show small nuts in certain areas.

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Franz Niederholzer, UC Farm Advisor, Colusa, Sutter and Yuba Counties

“It has been a cold week, with highs only in the upper 50s and low 60s. Around the Sacramento Valley, the maximum temperatures have mostly run below average for this time of year.

“Morning temperatures have been close to or below freezing the last couple of mornings, with a few areas dipping just below 30. Most temperatures in the north state yesterday morning (3/26) were 30 to 34 degrees. I have not heard of any damage. Temperatures were similar this morning.

“The forecast, beginning early next week, is for temperatures in the 70s.

I’ll take it.

“In almond orchards I’ve been in, I have seen quite a bit of drop of pea-sized nutlets still in the jacket. The heaviest blooming varieties are showing the most drop, Aldrich, in particular.

“Of course, we only need 25% of all flowers to set a good crop, so the drop shouldn’t be a concern. These are flowers that weren’t pollinated or fertilized.

“With rain in the forecast for this week, growers have been putting out fungicides in almonds and early walnut varieties. Many sprayed late last week and should be good for this weekend.

“With the cool weather, degree days have been slow to accumulate. We made a biofix at the Nickels Soil Lab in Arbuckle on March 13. As of yesterday, March 26 – almost two weeks later – only 26-degree days had accumulated. It takes 100-degree days for navel orangeworm eggs to hatch.”


Dan Prentice, Prentice Ag Consulting, Bakersfield

“Growers are gearing up for the 5-week post-petal-fall spray, which should start in the week of April 6.

“Growers who are seeing a significant amount of mite activity will commonly include a miticide in the post-petal-fall spray. Right now, mite activity varies, so not all growers will use a miticide.

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“We haven’t needed a miticide in April for a few years, but this year it may be necessary, so we may be reverting to a more normal scenario. The bulk of our orchards today have fewer mites than a few weeks ago due to rain and predator activity.  We are seeing thrips larvae populations. 

“Orchards are wet now, but over the next ten days, higher temperatures will help dry out fields for the upcoming sprays. Across the area, three-quarters to over an inch of rain fell from the larger storm through last Monday.

“A few growers haven’t started fertilizer yet. However, most are nearing the end of their current cycles.

“Pistachios are starting to push bloom. Leaves are out in Golden Hills. In Kermans, we’re finding one inch to 1.5-inch-long buds.

“We are setting navel orangeworm traps this week in pistachios. A few growers set them out last week, and we have already scouted for eggs. It’s relatively normal to get high activity in the first week.

“A limited amount of tomato planting started before the last storm, and a preventive fungicide application went on for bacterial speak.”


Nathan Stewart, PCA, AgVantage Consulting, Inc., Visalia

“This week of rain has helped the trees but also prevented us from getting in the field. Scattered rain varied by location across the region over the last couple of weeks, with two-plus inches in places.

“Yesterday, people reported hail from Tipton to Reedley. The hail lasted from 10 to 15 minutes on the west side of the valley and maybe 10 minutes on the east side. The size of the hailstones was larger on the west side, as well.

“Hail had the potential to knock down developing almonds. When coupled with wind, it could be devastating. Damage assessments in stonefruit are underway. We did not see a large amount of nut drop before. However, I expect to find more now.

“Considering the warm-up in the forecast for next week, diseases will likely pop up. Before the rain, leaffooted plant bug was showing up. We will see populations grow as the weather warms up, but we will hold off on treatments until pressure builds.

“We will be monitoring for shot hole. We scouted for navel orangeworm moths before all the rain. With the change in weather, we will likely see an uptick in flights again.

“Another round of fungicides will probably go on before the 5-week post-petal-fall window.

“I’m reminding growers to keep up with fertilizer applications regardless of rain. Weeds are popping up again, so we will need another herbicide to maintain control. We had a lack of rain early, but all this later rain is increasing weed growth.

“Pistachio budswell sprays are going on early varieties. Kerman is pushing and will have buds showing in 7 to 10 days. Pistachio growers will be fertilizing with boron over the next 7 days.

“Ivanhoe walnuts are progressing as well as Serrs. Growers are applying ReTain with blight sprays in earlier varieties of Ivanhoe and Serrs. Nutlets are becoming visible with both varieties.”


Chris Cucuk, Cucuk Consulting Inc., Bakersfield

“Rain is helping to hold mite populations on the lower limbs, and pressure seems low. The odds of needing a mite spray before April are minimal at this point.

“As soon as we can get in the orchards again, the next round of fungicide will start for alternaria, rust and scab. April 1 to April 15 will be the ideal spray window for prevention in our area.

“Fertilizer applications continue, and irrigation is needed to incorporate them.

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“Navel orangeworm moths were flying before the rain. Once it warms up, we expect to see more flying. High temperatures of 80 degrees are in the forecast for the middle of next week.

“Pockets of rain were scattered over the last 7 to 10 days and measured three quarters to over an inch. Roots continue to take up the rain, and soil probes still show dry zones in places.

“Grapes are on their first or second round of copper sprays. No spider mites are showing at this point, and we’re only finding minimal amounts of leaf botrytis spots. Mildew will start to show up as temperatures increase. Vine mealybug is apparent along vine cordon and spur wood.”

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