Navel Orangeworm is High This Season
Almond and pistachio growers
appear to be more on top of Navel Orangeworm control this season compared to
last year. “It’s human nature because all the people who got burned last year
are paying a lot more attention this year," said Joel Siegel, USDA ARS
entomologist based in Parlier, Calif.
Siegel said that in the areas
where he works, he is seeing the same type of population levels as he saw last
year. These areas are normally under very high NOW pressure--where
almonds, pistachios and figs are close together such as in Madera County--causing a perfect storm of pressure year after year.
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Joel Siegel is USDA ARS Research
Entomologist based in Parlier
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“I am also seeing growers with
traps showing very low levels of populations, so NOW is bouncing around quite a
bit this year,” Siegel said.
What causes a high pressure
year? Siegel suggests three things:
- Heat Unit Accumulation
- Overwintering Populations
- Nut Development Rate
This year, there were probably a lot of overwintering populations.
“However, if everyone is
harvesting two to three weeks earlier, growers may be able to dodge the
late pressure,” he said.
If pistachios prices continue to hold and growers are committed to that second shake
maybe deep into September, there could be a lot of NOW pressure. Pistachio
harvest this year may start as early as the last week of August, and the early
almond harvest may be starting this week.
Siegel said the Suttera
BioLure has been very helpful this year. “It is every bit as good as my virgin
female traps,” he said. “The advantage
of BioLure is that if you are running live females in a trap and there is a
spray operation, the moths would be killed, and those traps will not be attracting males. With BioLure, you will still be catching
males,” Siegel said.
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| Adult Navel Orangeworm |
This past spring, UC farm advisors and other researchers held an urgent meeting in
Visalia to warn growers of the assured high NOW pressure this year. Researchers
said that it would be very important for growers to apply a May spray to beat back the early NOW populations. “But the pressure is there, and I have
not seen a real drop this year,” Siegel said.
Siegel noted that during the
hot weather which occurred in late June and early July, male population numbers
dropped. “But when the heat broke around July 6, the capture rate tripled.
I had traps that were catching 30 per trap, and within three days, they were catching 149 per trap,”
he said. “Most of the males hunkered down for days during the heavy heat and once daytime temperatures dropped, their normal nighttime activity picked up,” Siegel said. "Interestingly, gravid females
were still laying eggs during the heatwave, and egg traps did not have the same
level of depression."