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Ask Your PCA: How do codling moths affect NOW infestations?

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Issue Date: August 12, 2020
Justin Nay PCA, Integral Ag Services, Durham
Justin Nay

The 1-A flight of the codling moth came at the usual time this year, but it was very strong. One week during the 1-A flight showed double-digit and even triple-digit codling moth counts in some orchards.

High nut drop of codling moth-infested nuts from the first flight was an indication there would be problems with the 2-A and 2-B flights. Similarly, the trap numbers for the second flight in early July began increasing, with double-digit codling moth trap captures in a week.

Walnuts finished the second flight of codling moth in mid-July, with higher-than-average spray applications. The second flight codling moth-infested nuts were filled with nutmeats in several walnut varieties.

By the end of July/first of August, navel orangeworm females start laying eggs, and NOW start to cycle in walnuts with codling moth problems. They could build up to damaging numbers before harvest on these damaged nuts, so it's important to monitor traps and crack open damaged nuts to see if NOW has infested them.

For orchards with higher-than-average nut drop in the 1-A, farmers should be on the lookout for NOW in August or it could sneak up on them. The codling moth and NOW in walnuts seem to go hand in hand.

There has been concern for several years that pyrethroid resistance is building. There are other options to pyrethroids, but with lower nut prices this year, many growers may have opted to use pyrethroids instead. This could mean less control of the codling moth for orchards using only pyrethroids versus the newer Altacor or Intrepid chemistries.

Recent research has shown that birds—flickers, woodpeckers and nuthatches—will scour an orchard and feed on codling moth pupae over the winter. It's also been shown that riparian habitat close to walnut orchards reduces codling moth in those areas.

Permission for use is granted, however, credit must be made to the California Farm Bureau Federation when reprinting this item.

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