Navel orangeworm (NOW) counts in southern San Joaquin Valley have been low so far this year, but that could change and cause concern by harvesttime, warns Donald Thomas, owner of Advanced Agricultural Services. Based in Hanford, Calif., the company provides organic and conventional pest management services from Madera County south to Kern County.
Here’s his assessment of this and several other almond and pistachio pests.
“Navel orangeworm started slow, but moth activity has really picked up the past few days,” says Thomas, based on his observations in Kern, Kings and Tulare counties in early July.
The low numbers this past spring, he suspects, were due to heavy amounts of rain followed by cool temperatures. The winter mummies that he collected in the soil and on the trees in almond and pistachio orchards yielded very few surviving navel orangeworms. Worms he did find in mummies were not viable. He found fungal organisms feeding on the kernels and larva.
Early almond splits started the last week of June, while pistachio pea-sized split began in some orchards the first week in July. Second generation flights started in his area July 7 and moths are now laying eggs.
“Despite the low count, navel orangeworm is resilient,’ Thomas says. “This second generation is weak, but the pests have an amazing ability to show up at kernel exposure.”
Even if you haven’t seen navel orangeworms so far, don’t count them out just yet, he cautions. The cool spring has delayed some crops and related pest activities by about 12 days. As temperatures increase, so will the pest pressures.
The key to preventing a NOW outbreak at harvest is controlling the population. Winter sanitation, mummy and early split inspections, moth and egg trapping inspections, temperature degree day monitoring, and choosing the best spray tools to fit your farming practices are some of the actions growers are taking to control NOW pressures, Thomas notes. Spray technologies such as insect growth regulators offer long residual protection and a relatively safe environment for many beneficial insects.
By the end of June, Thomas was beginning to see new stink bugs and leaffooted plant bugs feeding in almond and pistachio orchards.
“It hasn’t been across the board, but you can easily walk into pockets of activity,” he says.
April and May flight activity of the larger plant bugs was low. But, even though the June flight wasn’t as active as in previous years, activity has been picking up, Thomas reports.
Almond growers who have had problems with plant bugs in the past have included contact chemicals to kill the pest with hull split sprays, he says. He expects pistachio growers with higher populations of stink bugs and leaffooted plant bugs will clean them up with navel orangeworm sprays this month.
Thomas and his staff are also becoming concerned about the increasing threat of Gilli mealybug. It can cause problems in almond and walnut orchards, but can be especially troublesome for pistachio growers.
“It’s a major threat to the pistachio industry,” he says. “We monitor it throughout the season.”
Usually, if Gilli mealybug was a problem the previous year, growers spray for it during the early weeks of June and monitor it to make sure the population remains under control. “But, if you’ve never had them, your orchards have been clean, and you start seeing low levels of activity for the first time in July or August, you’re probably OK without spraying this mealybug as long as you monitor it,” Thomas says.
In selecting pesticides for late-season treatment of Gilli mealybug, he adds, keep in mind packers are becoming concerned about the Maximum Residue Limit (MRL) of some California-registered products.