Entomologist studies apple snails in rice-growing areas

apple snail egg mass on ricejpg Stored grain weevils on ricejpg

LEFT: A mass of apple snail eggs on a rice plant. The snails have not been a pest of rice in Louisiana yet, but they can cause problems for crawfish farmers. RIGHT: Rice weevils feed on rice grains.

LSU AgCenter entomologists are working to defend rice crops from insects both before and after harvest.

The apple snail that is spreading to more rice-growing areas and building to high populations in some areas does not appear to be an economic pest of rice for Louisiana, according to Blake Wilson, LSU AgCenter entomologist.

However, the invasive species is a problem for young rice in Asia and Spain.

“In the greenhouse studies, we weren’t able to get the snails to eat seedlings,” Wilson said. “I’m hesitant to say that they don’t pose any threat.”

Wilson said he has received reports from Texas that the snails burrow into levees.

He said monitoring of drill-seeded and water-seeded rice didn’t reveal any damage to rice by the snails.

“We didn’t see any stand losses,” Wilson said.

He said the snail is a pest for crawfish farmers because it can clog traps and reduce vegetation used for forage.

The use of copper sulfate has shown to be effective at 2 parts per million, but he is conducting work to see if a reduced rate can remain effective. Copper sulfate is harmful to crawfish, he said. On-going research is investigating chemical controls that are compatible with crawfish production.

Graduate student Julian Lucero is monitoring fields to determine how rapidly the snail is expanding its range in Louisiana, and he will look for factors that may be related to the mollusk’s expansion.

Protecting a crop in storage after harvest and before milling has been the focus of work by Wilson and Qian Sun, LSU AgCenter entomologists.

Wilson said the use of precision temperature controls in grain bins has proven to be effective at preventing damaging insect populations from developing in stored grain. He said the systems’ abilities to maintain low temperatures and humidity repress insect reproduction.

The main pests of stored rice are the rice weevil, the lesser grain borer and the Angoumois grain moth.

He said work is being done to learn if chemical controls are more effective when they are applied to a grain bin when it is empty or directly on stored rice.

“We’re testing all the different options alone, as well as in combination,” Wilson said.

He said simulated grain bins are being used for the testing.

Six products are registered for use on stored grain, he said, but their effectiveness on rice has not been thoroughly tested.

Wilson also said testing is being done to find out if insect pests have a rice variety preference and to examine sampling protocols, which can be used to assess the need for fumigation.

12/19/2019 9:22:56 PM
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