By John Wood, Certis USA Regional Manager

Signs of post-harvest and fall are evident. Temperatures are dropping. Almond harvest is 50 percent completed, pistachio collection is starting, walnuts are in the finishing stages of maturity and pecans are about half-filled.

While most pests are controlled by now, tree nut growers can still encounter worm infestations. Application of Bt sprays is an effective strategy. The Bts Agree^®, Deliver^® and Javelin^® have zero-day PHIs, 4-hour REIs, are residue exempt and can be used on conventionally or organically produced tree nuts.

Counting mummy nuts is the next chore in almonds to reduce the overwintering of navel orangeworm (NOW). Also check for late-season Alternaria strikes. Proper orchard sanitation from now through early winter will help reduce NOW infestations next season.

As walnuts come in, be sure to sample them so you can evaluate your pest management practices. Note that NOW and codling moth leave frass and webbing inside the shell, and brown, crescent-shaped marks behind the leaves. Husk fly infestations result in mushy black hulls, black stained shells and no kernel damage.

Examine pistachio orchards for Alternaria late blight lesions, or strikes; Botryosphaeria panicle and shoot blight to get ahead of them for next year’s management.

Once harvest is complete, one of the first tasks for all tree nut growers is to examine weeds that did not get controlled this year with a pre-emergent product. A weed survey is in order to identify grasses and broadleaf weeds. You’ll also want to look for winter weed species that may be cropping up. Weeds typically can be controlled with a tank mix of pre-emergent and contact herbicides. The University of California Integrated Pest Management Program offers crop-specific weed survey forms at ipm.ucanr.edu.

Be sure to irrigate after harvest, too. Root activity increases and continues through fall and winter as trees work to store carbohydrates, nutrients and water for emergence next season.

In the next issue we will discuss late-season and post-harvest nematode control. Until next time.