A tiny grub — often small as a pinhead — is busy denuding large chunks of central Arkansas rice fields. Its name, grape colaspis, is as unthreatening as its size. But looks are deceiving. There is no sure-fire way to control the lespedeza worm and it has taken advantage.
“Look here,” says Gus Lorenz, pointing to what looks like a wriggling rice grain on the end of his pocketknife. It has taken him only seconds of prodding the soil to find the pest. “This little thing is the cause of all this.”
Lorenz, Arkansas Extension entomologist, sweeps his arm towards the mangy rice field behind him. At least a third of the field looks to be suffering or is completely without a stand. Entire rows of rice are missing and the field is typical of many in the state.
That becomes obvious as an early June tour — also in Lorenz’s pickup truck: Chuck Wilson, Arkansas Extension rice specialist; Hank Chaney, Prairie County Extension agent; and Ford Baldwin, consultant and Delta Farm Press contributor — easily locates grape colaspis-ravaged fields.
So far, the biggest problem with the pest has been in the state’s prairie counties — Arkansas, Prairie, Lonoke, Woodruff, Monroe and Poinsett.
As Lorenz navigates back roads and turn-rows, the groups’ cell phones beep constantly. Grape colaspis may be a problem, but so is a sudden dearth of Clearfield rice herbicides. Baldwin is especially busy working several phones, talking folks off ledges.
The grape colaspis infestations didn’t sneak up on the specialists.
When this season began, Arkansas had a Section 18 in place for Dermacor, a product proven to work well on rice water weevils. The hope was it would also control grape colaspis.
Lorenz and colleagues pushed for it, “because we’ve been seeing this situation with grape colaspis building. It hasn’t worked like we’d hoped.”
“We’ve been pretty desperate for a solution since we lost Icon,” says Wilson, referring to a very effective grape colaspis control. “We had that for several years. Then, they found it was killing crawfish in Louisiana. The EPA had concerns about it, but the company pulled it voluntarily.”
Icon was taken off the market in 2002, but existing stocks were allowed to run out. It’s been unavailable for about three years.
Asked if there’s any chance Icon might make a return, Wilson says the product is “unfortunately dead and it isn’t coming back.”
When Dermacor looked so good on rice water weevils and did well in trials, “we felt it would have good activity on grape colaspis, as well,” says Lorenz. “That’s why we went after the Section 18 — although it’s only for about 20,000 acres, because they ran out of product. Regardless, we were able to put the Dermacor on large areas.
“I have little doubt that one of the reasons it hasn’t done well is the overwhelming population of grape colaspis. This is one of the worst infestations we’ve seen in a long time. That put Dermacor straight into the fire.”
As the pickup rumbles along, it isn’t hard to pick out rice fields with normal growth mixed with large, bald spots. Some flooded fields look to contain large ponds with no vegetation.
What typically happens with grape colaspis, says Chaney, is shortly after emergence a farmer begins noticing his stand is thinning. The standard recommendation for this problem, since there’s no chemical control that’s really effective, “is to put out 100 pounds of ammonium sulfate and flush it in. They keep trying to flush it to stimulate some root growth.”
Lorenz concurs. “You can see this field has had the fertilizer and been flushed a couple of times. This is the kind of field where, in 6 inches of drill, we’ll dig up as many as 12 larvae.”
What’s the pest’s threshold number? “Really, there’s never been a hard, fast threshold number. That’s part of the problem and why we need more research. Work done several years ago suggests a threshold of about one per square foot. So, we’re getting 10 to 12 on 6 inches of drill — that tells you this is serious.”
The men began getting calls about grape colaspis in early May. “We dug some larvae up and said, ‘Yeah, there’s damage but it looks like it’s holding up,’” says Lorenz. “But it kept getting worse. Grape colaspis is deceptive like that. You think it’ll cause only minor damage — but it keeps getting worse. Then, it gets so late in the season, options are limited to almost nothing.”
The pest can actually be tracked down rice and bean rows. Even in a rice field, “you can tell where (last season’s) bean rows were because the larvae travel up and down that drill from the original clutch of eggs,” says Lorenz. “That’s why you’ll find all the plants dead in a row — that’s one way you know it’s grape colaspis and not salt injury or Roundup drift, or whatever.”
Time is also a factor in studying the pest. To gain needed data, researchers must be on their toes because, depending on environmental conditions, grape colaspis are in the damaging larval stage for only three or four weeks.
The problem in researching and finding answers for grape colaspis is real. Lorenz has research plots all over the state. He’s trying to do small-plot work — including seed treatments to replace Icon — to combat the pest.
But it is elusive and nomadic. “It’s so frustrating, you wouldn’t believe,” says Lorenz. “Inevitably, if the plots are put here next year, they should’ve been in the next field. If we put the plots in this hard-hit corner, next season they’ll be on the neighbor’s farm.
“We just can’t hit the right spot. They move around too much to do small plot work. There’s seemingly no rhyme or reason for why they end up here one year and down the road the next.”
A lack of pests renders 250-square-foot plots pointless. Lorenz needs larger acreage to study — maybe 5 or 10 acres. But he knows producers are justifiably shy about providing it.
Larger-scale research could get expensive because some crop destruction may be necessary. “It’s hard to ask someone to give up 5 acres, or whatever, of their crop,” says Wilson. “But that’s what it’s going to take.”
“We need people to understand how this pest is different and what’s required in researching it,” says Lorenz, who insists he isn’t pushing for any additional research funds. “We’ll make it work with the funds we’ve got. The main thing is just getting the right to study this larger scale. We need two or three years of that to find answers.
“Small-plot work just won’t cut it. I’ve worked two years with six locations and have yet to get grape colaspis to hit the plots.
“And it’s not feasible to get a Section 18 for everything that comes down the pipe. There are products available that I think could provide control. But we can’t study them because they aren’t labeled on these crops. An additional problem with researching rice pests is, because it’s a flooded environment, the EPA has all kinds of rules.”
Baldwin says too often EPA views Arkansas’ gummy rice land the same as looser Midwest soils. “They don’t understand you’re less likely to contaminate groundwater in a flooded culture in an Arkansas rice field than you are, say, using the same product in a Midwest cornfield. The reason you can grow rice so well here is there’s an impermeable hardpan under these fields. Very little can get through it.”
At this point, all there is to deal with grape colaspis is an insecticide seed treatment “or Mustang Max, a pyrethroid that’s only about 50 percent effective,” says Wilson. At such a late date, “it’s iffy … whether that would be worth the money.”
A farmer who has had trouble with grape colaspis in the past should increase seeding rates to better overcome damage. The problem with that approach is the stand loss is never uniform. That means there are areas of the field where the stand is too thick or thin, no matter how much seed is put out.
“Once the problem reaches this level, we recommend flushing and fertilizing,” says Wilson, echoing Chaney. “That never hurts and can help. But it’s not a sure thing and fertilizing and flushing are no longer an automatic thing. Both are just too expensive to do nonchalantly.”
A farmer putting out 100 pounds of DAP — at $1,000 per ton — “is looking at $50 per acre. A flush using diesel at $4-plus is also expensive.”
And flooding doesn’t kill the pest. “Hopefully, it’ll float them up and out of the soil zone. What we’re aiming for is to get the rice moving so it’ll outgrow the problem.”
Wilson scans the field, shaking his head. “Let me tell you, this field looks much worse than it did two weeks ago. And it looked bad enough then.”
There are fields all over Prairie County that look the same, says Chaney. “You can drive down Highway 11 between Stuttgart and Hazen and check the rice. It isn’t hard to find that same ragged look.”
What kind of yield loss is this field facing? “Heck, 30 percent, if we’re lucky,” says Chaney. “And this isn’t even the worst one. What’s interesting is the farmer told me he has never had a problem in this particular field before.”
Many believe Arkansas’ number one rice pest is the rice water weevil. But Lorenz says it’s actually grape colaspis.
“We may have bad stinkbug or rice water weevil years — and early indications are we’ll have a bad one this year — but grape colaspis is consistently the worst.”
Lorenz, in a field awaiting a flush, bends over and pulls up a sprig of rice that has caught his attention. “Look at that! This scarring is from rice water weevil. That’s where Dermacor-treated fields will do well. But we can’t get to the rice water weevils if grape colaspis is so bad.”
Here’s another issue: the rice water weevil keys on thin stands. “It loves thin stands — the thinner the better. So they’re already attracted to the areas where grape colaspis have done the thinning work. That means the farmer will be hit with a one-two punch.”
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