Plan for Early Hull Split Sprays in Pistachios to Manage NOW

Warm spring and rapidly mounting degree days could help pests get an early start.

Another mild winter and warmer-than-average spring on the West Coast means degree-day units are building at a rapid rate, and with them the potential for heavy pressures from pests such as navel orangeworm (NOW). An earlier start for the pests could also mean an extra NOW generation this season.

In many parts of California, development of this year’s pistachio crop is ahead of the normal pace – as much as two weeks in some areas, says Jeff Pacheco, DuPont Crop Protection technical sales agronomist. “In orchards with heavy NOW pressure, protecting pistachios as early as pea-split may be critical to preserving nut quality. And it’s better to err on the side of caution and make the first application a little early than a little late with newer insecticides.”

DuPont™ Altacor® insect control powered by Rynaxypyr® is a good first-spray option because its duration of activity provides some application flexibility, he adds. “Altacor® provides long residual and ovicidal,1 ovi-larvicidal, larvicidal and adult activity2,3 on navel orangeworm and is an important part of an effective NOW management program.”

Track Key Degree-Day Points
Research conducted by entomologist Joel Siegel, USDA San Joaquin Valley Agricultural Sciences Center, Parlier, California, has identified four important times to intensify scouting and make insecticide applications if needed—1,700, 2,200, 2,700 and 3,000 to 3,200 degree days (starting from January 1).

“These peak flight times for navel orangeworm in pistachios are good guidelines, since an effective application should be made before peak egg-laying of NOW” says Pacheco. “Based on these degree-day points, the first application may need to be made a little earlier than normal in some orchards due to crop phenology. That’s certainly a possibility this season.”

Start scouting trees early, he recommends. “When it comes to determining the best time to spray, crop development stages and pest pressure should always trump degree days.”

The first application should help to knock down the early NOW population and prevent a pest buildup, he says. “Second and third sprays that coincide roughly with 2,200 and 2,700 degree-day points might also need to be made a little earlier depending on pressure, climate conditions and days to harvest.”

With the threat of a possible fourth NOW generation, growers seeing higher pest pressures should consider a fourth spray timed between the 3,000 and 3,200 degree-day accumulation points, says Pacheco. “Later sprays are important for producers using two-shake harvesting, which can put some of the crop at greater risk for late-season damage.”

Manage Against Insect Resistance
Resistance management is an important element of an effective integrated pest control program and especially important with NOW. As more acres of pistachio trees come into production, the increase in tree nut acres is leading to increased pest pressures, says Pacheco. “We’ve already seen some types of insecticides, such as pyrethroids, become less effective against NOW following multiple applications during the season.

“It’s important to avoid treating successive NOW generations with the same insecticide or insecticides with the same IRAC group number,” he says. “Altacor®, an anthranilic diamide (Group 28) insecticide, fits well into a rotational program, providing long-lasting control of NOW and only a ten-day pre harvest interval.”

1 Significant ovicidal activity is observed at varying levels depending on pest species. Activity is maximized when eggs are laid onto treated surfaces.
2 Disruption of adult insect behaviors in some pest species is observed (e.g., codling moth, oriental fruit moth) such as mate finding, mating, oviposition, feeding, locomotion and orientation.
3 Adult mortality is species, application rate, exposure level and time dependent for NOW (based on lab and field studies).

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