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Stout insectsricecropphenology2011

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Stout presentation on Insect Infestations in Relation to Rice Crop Phenology. Advanced rice entomology training at rice research station in Crowley, La on March 2, 2011

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Stout insectsricecropphenology2011

  1. 1. Insect Infestations in Relation to Rice Crop Phenology Michael Stout Department of Entomology LSU AgCenter/LSU A&M
  2. 2. When do Rice Pests Attack? AND To What Extent can We Predict Attack? Insect Infestations in Relation to Rice Crop Phenology OR
  3. 3. Attack by a pest depends on several factors… <ul><li>Is the pest present, and at what levels? </li></ul><ul><li>--population dynamics and life history of pest </li></ul><ul><li>Are environmental conditions conducive to attack? </li></ul><ul><li>-- pests only attack under certain conditions </li></ul><ul><li>Is the plant susceptible to attack? </li></ul><ul><li>--pests specialize on certain plant parts </li></ul><ul><li>--suitability of plant parts change as plant develops </li></ul>
  4. 4. Attack by a pest depends on several factors… <ul><li>Is the pest present, and at what levels? </li></ul><ul><li>--population dynamics /life history of pest? </li></ul><ul><li>Are environmental conditions conducive to attack? </li></ul><ul><li>-- pests only attack under certain conditions </li></ul><ul><li>Is the plant susceptible to attack? </li></ul><ul><li>--pests specialize on certain plant parts </li></ul><ul><li>--suitability of plant parts change as plant develops </li></ul>
  5. 5. Attack by a pest depends on several factors… <ul><li>Is the pest present, and at what levels? </li></ul><ul><li> --population dynamics /life history of pest? </li></ul><ul><li>Are environmental conditions conducive to attack? </li></ul><ul><li>-- pests only attack under certain conditions </li></ul><ul><li>Is the plant susceptible to attack? </li></ul><ul><li>--pests specialize on certain plant parts </li></ul><ul><li>--suitability of plant parts change as plant develops </li></ul>
  6. 6. Attack by a pest depends on several factors… <ul><li>Is the pest present, and at what levels? </li></ul><ul><li> --population dynamics /life history of pest? </li></ul><ul><li>Are environmental conditions conducive to attack? </li></ul><ul><li>-- pests only attack under certain conditions </li></ul><ul><li>Is the plant susceptible to attack? </li></ul><ul><li>--pests specialize on certain plant parts </li></ul><ul><li>--suitability of plant parts changes as plant develops </li></ul>
  7. 7. If we had reliable answers to each of these questions, we could predict attack with reasonable certainty Unfortunately, we don’t have reliable answers for many pests Whether or not the pest is causing economic losses is a related, but separate issue
  8. 8. Let’s apply these principles to the best-studied rice pest in Louisiana, the rice water weevil… Adult overwintering Larval feeding Mating and oviposition Adult feeding
  9. 9. Attack by a pest depends on several factors… <ul><li>Is the pest present, and at what levels? </li></ul><ul><li> --population dynamics /life history of pest? </li></ul><ul><li>Are environmental conditions conducive to attack? </li></ul><ul><li>-- pests only attack under certain conditions </li></ul><ul><li>Is the plant susceptible to attack? </li></ul><ul><li>--pests specialize on certain plant parts </li></ul><ul><li>--suitability of plant parts changes as plant develops </li></ul>
  10. 10. Population dynamics of the rice water weevil over the growing season Emergence of the rice water weevil from overwintering does not begin until early April in most years, and may not be complete until late May… April May June % emergence from overwintering
  11. 11. Population dynamics of the rice water weevil over the growing season April May % emergence from overwintering … but less is known about population fluctuations during the season and return to overwintering June June July August Weevil population densities
  12. 12. Attack by a pest depends on several factors… <ul><li>Is the pest present, and at what levels? </li></ul><ul><li> --population dynamics /life history of pest? </li></ul><ul><li>Are environmental conditions conducive to attack? </li></ul><ul><li>-- pests only attack under certain conditions </li></ul><ul><li>Is the plant susceptible to attack? </li></ul><ul><li>--pests specialize on certain plant parts </li></ul><ul><li>--suitability of plant parts changes as plant develops </li></ul>
  13. 13. Oviposition (egg-laying) by rice water weevil is triggered by flooding… Treatment/Flood depth Eggs per plant 0 10 20 30 40 50 dry soil wet soil 1.3 cm 5.1 cm 10.2 cm c bc bc b a
  14. 14. Attack by a pest depends on several factors… <ul><li>Is the pest present, and at what levels? </li></ul><ul><li> --population dynamics /life history of pest? </li></ul><ul><li>Are environmental conditions conducive to attack? </li></ul><ul><li>-- pests only attack under certain conditions </li></ul><ul><li>Is the plant susceptible to attack? </li></ul><ul><li>--pests specialize on certain plant parts </li></ul><ul><li>--suitability of plant parts changes as plant develops </li></ul>
  15. 15. Suitability of rice for oviposition changes as rice grows and develops
  16. 18. What are the implications for rice water weevil management? <ul><li>Rice planted early can escape, to some degree, rice water weevil infestation because weevil populations have not fully emerged before rice passes through susceptible stages </li></ul><ul><li>Rice can be attacked by rice water weevils for most of its development, but is most susceptible during tillering </li></ul><ul><li>Early flooding (e.g., pinpoint flooding) of rice extends the window of time in which rice is vulnerable to infestation </li></ul><ul><li>Delayed flooding of rice can reduce the window of vulnerability </li></ul>
  17. 19. We lack basic information (on population dynamics, environmental effects, plant susceptibilty) for most other rice pests… So, we are less capable of predicting attack by these pests
  18. 20. Pests of young / early season rice <ul><li>Intolerant of flooding </li></ul><ul><li>Fall armyworm </li></ul><ul><li>Thrips </li></ul><ul><li>Aphids </li></ul><ul><li>Colaspis </li></ul><ul><li>Tolerant /dependent on flooding </li></ul><ul><li>Rice water weevil </li></ul><ul><li>Seed midges (feed on seeds, likes floods) </li></ul><ul><li>Rice leafminer (likes floods) </li></ul><ul><li>South American rice miner </li></ul>
  19. 21. Pests of mid to late season rice <ul><li>Stem borers </li></ul><ul><li>--population dynamics unknown, appears to require large stems, prefers reproductive stages </li></ul><ul><li>Rice stink bug </li></ul><ul><li>--feeds on developing grains, susceptibility changes as grains mature </li></ul><ul><li>Skippers, grasshoppers, other defoliators </li></ul>
  20. 22. Author <ul><li>Michael Stout </li></ul><ul><li>[email_address] </li></ul>

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