Entomologist finding newly registered insecticides less toxic to crawfish

Entomology graduate student Bryce Blackman counts stink bugs in a sweep net at the LSU AgCenter’s Rice Research Station. Farmers reported few stink bug problems in this year’s rice crops, although high numbers of the insects were found in some fields at midseason.

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LSU AgCenter entomologist Dr. Mike Stout says testing of insecticides is showing newly registered insecticides are far less toxic to crawfish than pyrethroids

"There’s no question that Dermacor, CruiserMax and Nipsit are safer for crawfish," Stout said. "I would be less concerned if these insecticides drifted onto a crawfish pond than if pyrethroids did."

The researcher cautioned, however, that rice farmers who also use their fields for crawfish production should closely follow the label restrictions. Stout said today’s insecticides are considerably safer for invertebrates such as crawfish.

"We’ve come a long ways in 15 years in terms of the insecticides we now have available," he said. "Farmers now have a huge choice compared to what they had 20 years ago."

On the other hand, Stout said insecticide makers are not putting truly new chemicals on the market these days. Even "new" products are just slight variations of pyrethroids and neonicotinoids, he said.

Stout said he is still trying to determine the effects of a recent decision by the U.S. Environmental Protection Agency regarding neonicotinoids and assertions that the chemicals affect pollinating insects. "I think where it’s going to affect growers the most is in the application of neonicotinoids at or near flowering," he said.

The product most affected by that would be Tenchu, used in late season against stink bugs, he said.

The scientist said testing of neonicotinoids used as a seed treatment on rice plants showed little or no traces of the chemical 45 days after planting. That test was conducted on the roots and shoots of 40 samples of rice plants, Stout said.

"That tells me neonicotinoids are probably not present in plants at flowering," he said.

Stout is conducting work to find out if agronomic practices can reduce insect pressure. For example, he will be working with Dr. Dustin Harrell, an LSU AgCenter agronomist, on a project to see if fertilizer can compensate for plant damage inflicted by rice water weevils.

He said hybrids also will be tested to see if they are affected less by weevils than conventional varieties.

In addition, Stout is continuing work to see if water management and planting dates affect weevils’ effects on rice, and he is working with LSU AgCenter rice breeder Dr. Steve Linscombe to develop rice lines with more resistance to weevils.

(This article was published in the 2014 Louisiana Rice Research Board Annual Report.)

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2/4/2014 10:41:28 PM
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