Couplet 8

10/22/2010 1:32:57 AM

10 

 

8a.
Gray-brown weevil about 1/8 inch long. 



Insect may be:
8b.
Feeding damage that does not remove leaf entirely, scarring near edge of leaf, larva feeding inside leaf or pupa found in leaf.

Insect may be:


RICE WATER WEEVIL


RICE LEAFMINER





Photo by: Johnny Saichuk


Photos by: Johnny Saichuk



RICE WATER WEEVIL (RWW) adults are grayish-brown weevils (1/8 inch long). 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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                                                  For more information, please see the Rice section of the Insect Pest Management Guide on the LSU AgCenter's Management Guides webpage.

                                                  RICE LEAFMINER adults are metallic blue-green to gray flies with clear wings (1/4 inch long). They fly near the water and lay eggs on rice seedling leaves. Transparent or cream-colored larvae emerge in less than one week and feed between the layers of the rice leaf. Larvae become yellow to light green while feeding for one to two weeks before pupation. Adults emerge and live two to four months. The life cycle is completed in two weeks to one month.

                                                  Facts:

                                                  • Leafminers attack rice fields in early spring in the same vicinity year after year.
                                                  • Infestations usually occur where water is deepest on the upper side of levees.
                                                  • Leafminers are not usually a problem in shallow water.
                                                  • Leafminers are more severe in continuously flooded than in periodically flooded rice.
                                                  • Larvae tunnel between the leaf layers (mining the interior), attacking and killing leaves closest to the water before moving up the plant, killing additional leaves and possibly the entire seedling.

                                                  What you should look for:

                                                  • Walk through flooded rice fields and draw leaves between your thumb and forefinger.
                                                  • Bumps in leaves indicate leafminer larvae or pupae.

                                                  How you should manage rice leafminer:

                                                  • Maintain water depth at 4-6 inches.
                                                  • Lower the water level in fields so that rice leaves can stand up out of the water.
                                                  • Treat if plant numbers are reduced to less than 15 per square foot.










                                                   

                                                   



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