OSU suggests later application to control thrips
ONTARIO, Ore. — If onion growers could push applications of Movento back a little later in the season, they might have more success controlling thrips, Oregon State University research is showing.
Onion thrips are the biggest pest problem for bulb onion growers in Idaho and Eastern Oregon. Besides causing feeding damage, which results in smaller onions, the insects can transmit the iris yellow spot virus, which can devastate onion fields.
According to OSU researchers in Ontario, an aggressive spraying program to keep thrips populations down is the only effective way for onion growers to control the insect.
OSU Cropping Systems Extension Agent Stuart Reitz said Movento is one of the most effective pesticides in controlling immature populations of onion thrips and recommendations have been for growers to start their spray program off with Movento and apply it early in the season because it takes awhile for it to absorb into the plant and become effective.
But if growers in this area apply the pesticide too early, its residual effect is gone by late June or early July, right as thrips populations in the area are starting to soar, he added.
Pushing use of Movento back a little later in the season can result in better control when thrips numbers are exploding, Reitz said.
“If you can push using that to a little later in the season, I think you can get a bigger bang for your investment,” he said. “If you use another material early in the season to hold those low populations in check and put the Movento out a little bit later, I think it will ultimately pay off.”
OSU researchers in Malheur County have been conducting field trials supported by the Idaho-Eastern Oregon Onion Committee to try to find the best way for onion growers to manage thrips.
Nyssa farmer Bruce Corn said the various onion-related trials there have greatly benefited the area’s onion industry over the years and growers have high hopes the thrips trial will help them manage thrips with as little spraying as possible.
“It sounds very reasonable,” he said of Reitz’ Movento recommendation. “We really depend on them and look to them to figure out the best way to do things.”
Because of the roller-coaster weather in the valley this year — it’s gone from hot early to cooler, than hot again and cooler — populations of thrips, which like hot, dry weather, have been spotty, Reitz said.
“Thrips pressure has come up and gone down and come up and gone down,” he said.
Growers have had decent success this year in controlling thrips but they’ve had to spend money to do that, said Nyssa grower Paul Skeen.
According to Skeen, it costs a grower about $50 per acre on average each time they spray for thrips.
“We feel like we’re keeping them under control this year,” he said. “Of course, we’ve already sprayed five times and we still have a ways to go.”