Monday, July 24, 2017

There’s Smoke and Fire in the Hot Air Across the Valley

Where there’s smoke, there’s fire.

Well, in this hot, dry post rainy season, this trite phrase is more than cliché around these parts.  In recent days, thick, brown choking smoke has enveloped the Valley.

Coupled with the summertime triple-digit temperatures, the smoky conditions make it tough for growers, farm-hands and others who earn a living working outdoors. It’s also rough for folks with respiratory conditions.

The fire: A massive, out of control blaze in Mariposa County, east of Merced, and other locales around the Golden Brown State.

“The smoke is really bad,” says almond field scout Jenna Mayfield. “It also has been really hot.”

The Fresno region, for instance, recorded triple-digit temperatures for 16-straight days this month, before dropping to 98 “cool” degrees last Wednesday. Ah, 100-degree weather returned over the weekend.

In almonds, there could be a different kind of fire smoldering in orchards: namely pests.

Peach twig borer numbers on the rise.

“Peach twig borer was getting a lot higher last week, more than previous weeks,” Jenna said. The spate of very hot weather triggered the uptick.  We’ll see how the numbers shape up this week.

Peach twig borer, or PTB, produce four generations each year. The larvae, or small caterpillars, damage the nuts as well as growing shoots. They cause shallow channels and surface groves. Sometimes, PTB damage can be masked by navel orangeworm damage. The reason: NOW will feed on earlier damage caused by PTB.

In some instances, growers have no other choice but to treat their orchards for the pests. Here are some monitoring tips from UC IPM:

Natural enemies can keep PTB larvae in check in the orchards.
  • Use past history, including results from harvest samples from the previous year, to determine if your orchard will require treatment.
  • Preferred treatment timing is during the dormant period (combined with oil sprays if there is concern for San Jose scale, European red mite, or brown almond mites) or at full bloom and petal fall (may be combined with bloomtime fungicide sprays, but check restrictions on compatibility).
Of course, exploring biological controls before determining whether to treat the orchard is a good management practice. PTB doesn’t have lots of friends – the pest boasts some 30 natural enemies.
Almond kernels damaged by PTB.
“In some years and orchards, these natural enemies destroy a significant portion of larvae, but they may not reduce twig borer populations below economically damaging levels. Ants also can be found preying on peach twig borer larvae.”

Right now, PTB isn’t a major threat as almond hulls begin to split. But, Jenna warns, “it’s something to look out for.”

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