You may not always get two birds with one stone, but going after two nut pests with one spraying could pay off for growers of almonds and pistachios.
That was among advice given recently at an area wide navel orangeworm and pest management update seminar for almonds and pistachios. The event was held at the International Agricenter in Tulare.
Speakers drew parallels for times when it’s best to spray for both the navel orangeworm and the peach twig borer. And they said newer “softer” insecticides may come into play for a May spraying for those pests because they are less injurious to beneficial insects. It’s those good insects that can prevent early mite outbreaks in almonds.
The speakers also emphasized a need for sanitation and removing mummies from the orchards. These King Tuts of the nut world are the perfect breeding ground for the navel orangeworm, considered the No. 1 pest in California almond orchards.
Leaving them in the orchard – especially if they’re clinging to the branches of trees – is asking for trouble, says Bob Beede, a University of California Cooperative Extension farm advisor for Kings County who moderated the discussion in Tulare.
If growers aren’t getting the mummies out of the orchard, Beede said, they would be mistaken to expect the strong results that are being obtained by Paramount Farming Co. with its mating disruption program.
“You need the sanitation part of it,” Beede said.
The program opened with Joel Siegel, an entomologist with the U.S. Department of Agriculture, Agricultural Research Service, at Parlier, talking about overwintering navel orangeworm pests that can cause problems during the harvest season — mummy-borne pests waiting to spring into action.
Siegel specifically looked at Butte and Padre almonds with an eye toward their susceptibility to orangeworm damage as differentiated from other varieties.
What he found – in a nutshell – is that the pest can emerge in the spring and attack more varieties. Forget the hardness of the nuts, he said. Some of the pests do just fine in the hulls, particularly in the Padre. And, he adds, “There’s no single generation, they always overlap. They’re a bank; the entire population does not come out at once.
“The Buttes appear to be more dangerous than the Padres in the ability to support populations and the emergence is prolonged.”
But he adds that Padre is an important source of overwintering populations.
Even just knocking mummies to the ground and mulching them lowers populations of the pest by nearly 77 percent, Siegel said.
“The take-home message here is to get them off the trees,” he said, adding that it’s best to knock them to the orchard floor before rains move in.
Siegel said it can be a mistake to concentrate on the Nonpareil variety, an almond leader, while ignoring hard nuts like the Padre that can harbor the pest.
Brad Higbee, research entomologist with Paramount Farming Co., warned of simply dropping mummies to the orchard floor “if there is not good moisture or a cover crop to enhance rotting.”
Higbee discussed ways to monitor for the navel orangeworm using devices that include egg traps and pheromone traps. He admits the science on that is still “touchy feely,” not yet formalized, but relying on “a gut feeling.”
For example, he said, it’s hard to correlate expected damage related to the number of eggs found.
A finding cited by Higbee and others is “the edge effect,” a likelihood of higher navel orangeworm pests in almond orchards neighboring pistachios, where the pest is more costly to remove, or next to almond orchards where good sanitation is not practiced. Higbee likes to use the derisive term “relaxed management” for those orchards where sanitation is lacking.
Higbee cited good results at keeping pest populations down by using insecticides as well as pheromone puffers for mating disruption
As for spraying, he said coverage with pesticides can be a problem if spray rigs speed through an orchard.
“About two miles an hour,” he replied when asked by Beede for an optimal speed.
Beede stood up, held up two fingers and said, “You heard that, two miles an hour.”
Beede emphasized that any treatment program is “all about insect numbers; it’s a numbers game — knowing what population you are dealing with.”
Among sprays found to be effective against the navel orangeworm are Brigade and Intrepid, but speakers stopped short of favoring any one chemical over another.
David Haviland, a UC farm adviser on entomology for Kern County, talked of threats posed by spider mites and changes in spraying protocols that are keeping more of the mites’ predators alive.
He said this year’s wetter weather may mean that growers could “get into June before a miticide is needed.”
Frank Zalom, with the UC Davis Entomology Department, said that prior to the 1960s, the peach twig borer was the top almond pest, and growers used broad spectrum sprays to cope with it. But those harsher sprays zapped spider mite predators.
Now, softer chemicals are being used.
The advent of mechanical harvesting of nuts meant that more nuts were left on trees to become mummies, he said. And in the 1960s, the navel orangeworm became the top pest.