Three years ago, Chuck Wilson started noticing rice stinkbug numbers reaching treatment threshold levels in southeast Arkansas. Wilson, the Arkansas Extension rice specialist, has since seen both stinkbug numbers and problems related to the pest steadily increase. Last year, stinkbugs — rice, green and brown — reached “incredible” numbers. Wilson says things aren't shaping up well this growing season.
“Over the last couple of decades, stinkbugs were considered a minor pest. We'd spray a few fields — mostly fields without really good grass control — but we never reached levels of crisis. Many farmers weren't even looking for them. That's all changed,” says Wilson.
The rice crop is later in south Louisiana than it is in the rest of the Delta. Rice stinkbug worries in are almost past for the year in south Louisiana where pressure from rice stinkbugs was not nearly as great as it was in the past several years.
A few rice fields in south Louisiana have been harvested. “We're hearing some encouraging yields and some disappointments,” says John Saichuk, Louisiana Extension rice specialist. “I don't have enough reports to get a good overall feel yet, but we don't think the crop will be anything special — it likely will be decent. It's certainly not going to be a record-setter like we had the last two years.
“For years the Louisiana Extension Service has stressed the importance of keeping these pests out of your crop. I believe the rice stinkbug is the most underrated pest we have in rice. I think the same is true of the Southern green stinkbug in soybeans. The damage from both pests isn't immediately apparent, as is the case of a foliage-feeding worm. It sneaks up on you,” says Saichuk.
Mississippi rice is just at the beginning of heading and farmers are seeing stinkbugs around the edges of fields. “They haven't moved into the rice yet, but they will and farmers need to watch out,” says Joe Street, Mississippi Extension rice specialist.
There's another reason to pay close attention to stinkbugs this year: millers are watching.
“I've spoken with marketers and industry folks about quality issues. They're all concerned about what stinkbugs have done in Delta rice fields the last couple of years. They've voiced displeasure with how stinkbugs are affecting quality. Uncle Ben representatives have made it very clear how much stinkbugs are on their minds,” says Street.
The evidence that rice stinkbugs adversely affect the Delta crop has hit home for a couple of years. That's translated to much more spraying in Mississippi.
“Last year, Mississippi growers did a pretty good job of controlling the pest. I recommend growers use a residual insecticide like Karate or Fury as their first application. Then, they can use a non-residual like methyl parathion if the field needs a second shot. So far, this year's crop looks pretty good. It's grassy in spots, but overall it should do well,” says Street.
Millers have estimated that losses last year from stinkbugs in the rice crop alone was in the neighborhood of $30 million. That equates to about $18 per acre.
“That's significant for both farmers and millers. Last year, millers docked some farmers, but I'm hearing that they're going to be very strict this year and that dockages could be really high if quality rice doesn't come in,” says Wilson.
The rice stinkbug is a fairly simple insect to monitor.
“Use a standard 15-inch diameter sweep net. We have a sliding threshold that begins at 30 per 100 sweeps and ends up at 100 per 100 sweeps. We start sweeping when rice begins flowering and continue until the field is drained about two weeks prior to harvest,” says Boris Castro, Louisiana Extension rice entomologist.
How many stinkbugs a field will tolerate depends on how mature the rice is. Normally, a person will take a 10-sweep sample, move and make another 10 sweeps and then figure threshold based on 100 sweeps.
“I like a 25-sweep sample — especially if I'm on the edge of a threshold and numbers are borderline,” says Saichuk.
Wilson has gotten reports and seen himself that the number of rice stinkbugs is high in Arkansas. “I suspect we're going to have to spray a bunch of fields. I've already seen them in rice fields that haven't headed. They're coming, so get ready.
“Last year, using a sweep net at 10 sweeps, it wasn't uncommon to find 40 or 50 stinkbugs. That's way above threshold levels.”
Wilson says farmers should begin scouting at 50 percent to 75 percent heading and continue for the next four weeks. During pollination, stinkbugs can feed on the grains and interfere with fertilization and damage yields. As the grain matures and gets into milk stage, the stinkbugs cause pecky rice that millers don't like.
“One of the first things to do to control rice stinkbugs is get a clean field. Most growers seem to have accomplished that, so the first step has been taken. Another thing we recommend is to keep the borders of fields mowed year-round. Right now, rice is beginning to head. If they start mowing now, it'll just force the bugs into the rice,” says Wilson.
All specialists caution that stinkbugs are very mobile. They fly in and out of fields with ease. Just because a field is free of the pest today doesn't mean it will be tomorrow.
Castro says the ideal time to scout for stinkbugs is early in the morning or late evening. “They're like humans in this regard: when the sun gets hot, they want to travel to cooler shade. They move into the canopy and make it more difficult to get an accurate scouting read.
“You also want to treat fields when the bugs will be atop the plants rather than deep into the canopy. So spray at the same times you should be scouting. Use a lot of water when spraying. Five- to 10-gallon spray volume is best for coverage.”
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