Hot Times a Time for Almond Growers to Stay Ahead of Game

 Hot, hot, hot and hot. 

Make it sweltering. Over the weekend and today, we had triple-digit temperatures – well above the normal 90-degree weather we get around these parts in late spring.

Young almond trees were whipping in the wind last week.

Sweltering weather, including more 100-degree weather Tuesday through Thursday, is taxing growers trying to stretch their water supplies. But what do you expect after the Valley experienced a wacky week of weather – hot temperatures, a little cooling, some gusty winds and a bit of precipitation.

Almond field scout Jenna Horine thought some young trees were going to snap in half as sustained winds on the Westside one day last week had them bending almost like towering palms caught in a Florida hurricane.

This heat wave can be problematic for almonds. Jenna notes the heat can trigger a mite outbreak. Already, she is finding some mite pressure on newer orchards on the Westside. These trees have a smaller canopy than the more mature trees and can be stressed even more by the hot weather.

During her scouting rounds, Jenna has spotted some orchards with “Do Not Enter” warning signs along the margins, an indication that these growers have treated their orchards. However, she says almond growers participating in the San Joaquin Sustainable Farming Project have held off pesticide treatment, opting to closely monitor their orchards for signs of pest pressures.

Heavy canopies can increase humidity in almond orchards.

However, some growers have applied fungicides to prevent diseases, indicating they are worried about scab and rust issues. Generally, late spring and summer rains, sprinkler irrigation and nearby waterways can create humid conditions in orchards. That’s because thick canopies caused by trees planted close together essentially trap the moisture underneath, Jenna points out. Unlike drip systems, micro-sprinklers will create a kind of mist and the warm conditions create humid conditions under the canopy.

Mist from sprinklers also can create orchard humidity.

Rust and scab are common diseases tied to excessive moisture.

Here’s what UC IPM says about rust: “The development of rust is favored by humid conditions, and the disease becomes worse when rain occurs in late spring and summer. Trees can be defoliated quickly when rust becomes severe. The rust fungus survives from one season to the next in infected leaves and possibly also in infected twigs. The disease causes leaves to fall prematurely and will weaken trees, reducing the following year's bloom if not controlled. Rust is often observed in second- and third-leaf nonbearing orchards where fungicides have not been applied.”

Rust is caused by humid conditions.           - UC IPM photo

UC IPM points out that orchards with a history of rust, should “apply sulfur or manebfive weeks after petal fall and follow four to five weeks later in late spring and summer with a Quinone outside inhibitor fungicide (FRAC Group number 11) to control leaf infections. Two or three applications may be needed in orchards that have had severe rust problems.”

On scab, UC IPM says: “severe scab infections cause early defoliation; if left uncontrolled for several years, infected trees become weakened. The disease often occurs in sprinkler-irrigated orchards where water reaches foliage.”

Scab can cause early defoliation in almonds    - UC IPM photo

“Scab may be controlled by shot hole sprays. However, a scab treatment may be required if rain occurs into mid- to late spring. One application as late as five weeks after petal fall can protect against scab, but an earlier application (two weeks after petal fall) may improve control. Scab resistance to quinone outside inhibitor fungicides (also known as strobilurins) has been documented; do not use FRAC mode of action Group number 11 fungicides in these orchards.”

Jenna reminds growers to be proactive and monitor their orchards regularly. “Stay ahead of the game,” she says. That investment in time will yield dividends at harvest time.

Field Day Alert: Here’s a final reminder about Tuesday’s Cotton Field day scheduled from 10 a.m. to 12:30 p.m. at the D&V McCurdy Farm, Highway 33 in Firebaugh. Cotton growers can learn valuable insights about insects and water and weed management from these speakers: Dr. Pete Goodell of UC Statewide IPM, Dan Munk of UCCE Fresno County, Kurt Humbree of UCCE Fresno County and Bob Hutmacher of the Westside Research and Extension Center. Mark the date on your calendar. For more information, contact Marcia Gibbs of the San Joaquin Sustainable Farming Project at (530) 370-5325. See you there.