How will early blooms and light crop affect navel orangeworms?

By Justin Nay
Integral Ag Services, Durham

Due to an unseasonably warm March that led to an early pistachio bloom, the crop is small this year. Pistachios are alternate bearing, and 2026 is expected to be a light-crop year. The combination of a small crop and an “off” year could create challenges for growers. 

If prices are low, some growers may not shake, and this could present problems with the navel orangeworm, or NOW. A single shake could pose additional challenges because the nuts remain on the trees longer, increasing their exposure to the pest.

Off years generally have fewer early splits, but they still occur. Even with a light crop, some trees will produce enough nuts to develop early splits, providing entry points for NOW. The pest is very good at finding the splits, so it’s important to prevent populations from building in July when growers delay harvest for a single shake.

The level of NOW activity in the orchard and the number of early splits will determine the spray applications, which could begin as early as mid-July. 

Intrepid, Altacor and pyrethroids tend to be the most heavily relied upon products. If applied at the right time and rate, with high gallons of water per acre, they deliver good results.

Growers who harvest will generally invest in chemical treatments. However, when large numbers of moths are cycling through mummies on the orchard floor, sanitation may be a more cost-effective option. Using a sweeper instead of a blower and shredding more slowly can help destroy mummy nuts that serve as NOW breeding sites. 

Growers who decide not to shake because their crop is too small will need extra winter sanitation to prevent large NOW populations the following year, which will be an “on” year in the alternate-bearing cycle and could result in more early splits. Pruning crews and other orchard activities can knock many mummies from the trees, and Mother Nature frequently removes them as well.

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