Couplet 19

10/24/2010 8:47:07 PM

10

19a.
Spiracles visible, black-brown head capsule.


Insect may be:

19b.
C-shaped larva with visible spines, golden-brown head capsule.

Insect may be:


RICE WATER
WEEVIL LARVA


COLASPIS LARVA




Photo by: Natalie Hummel

Photo by: Natalie Hummel


RICE WATER WEEVIL (RWW)
Adults leave overwintering sites, invade rice fields and begin feeding on the leaves of rice plants. Females deposit eggs in the leaf sheath at or below the waterline. White larvae emerge from eggs in              about one week and develop through four instars while feeding on the roots of rice plants. Larvae pupate in cocoons that are covered with a compact layer of mud and are attached to rice roots. The life cycle from egg to adult takes about one month.

Facts:

  • Application of the permanent flood triggers females to lay eggs in rice leaf sheaths.
  • Economic damage caused by larval root pruning reduces the number of tillers produced by the damaged plant.
What should you look for:
  • Elongate feeding scars caused by adult feeding.
  • Infested stands may be thin in appearance and contain yellow plants.

How you can manage rice water weevils:

  • Avoid late planting of rice.
  • Delay the application of permanent flood.
  • Apply a pesticide to control rice water    weevils at the correct time. Adults must be controlled before egg-laying occurs. Sample larvae by taking core samples








Rice Water Weevils

How to Scout for Rice Water Weevils Video



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There are two species of COLASPIS
that can be found in Louisiana rice: Colaspis brunnae and Colaspis louisianae. This pest can be found damaging fields of dry-seeded rice in a soybean-rice rotation. Colaspis will complete a single generation in soybeans and lespedeza. The larvae of colaspis will overwinter in the soil. When rice, or another crop, is planted into a field that is infested with colaspis larvae, the larvae will begin to feed on the roots of the plant. Feeding on fine root hair may result in plant death. The larvae will then pupate and emerge as adults. Adults are oval in shape and about 1/4 inch in length. They are a light golden color with white/gold stripes down their back and long antennae. Adults will not lay eggs on rice, but will most likely travel to a near soybean field. It is common to ind a clumped distribution of larvae in the soil and patches of stand loss.

What you should look for:

  • To scout this pest, located plants that are stunted, dying and surrounded by declining plants. The plants will often appear withering or drying.
  • Dig around the base of the plants, carefully peeling back the soil and looking for white grubs with brown heads, being slightly larger than RWW larvae. Pupae or adults may also be found in the soil.

How you can manage colaspis:

  • There are no specific pesticides to control colaspis in louisiana rice.
  • Only recommendation is to apply permanent flood as soon as possible.
  • These insects are not aquatic so they cannot survive a permanent flood.




Colaspis in rice

How to Scout for Colaspis in Rice Video




For more information, please see the Rice section of the Insect Pest Management Guide on the LSU AgCenter's Management Guides webpage.

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