Protection of Rice from
Invertebrate Pests - 84
 
 

Home.gif (3162 bytes)

Next.gif (3180 bytes)

Back.gif (3162 bytes)

 

The Rice Research Board has supported research on invertebrate pest control throughout the last 16 years. The Department of Entomology at UC Davis has had the responsibility for these studies. The objectives are to determine the amount of injury to rice from various invertebrate pests and to reduce these losses without damaging the environment. To accomplish these objectives, it is necessary to determine the physical and biological factors that allow the buildup and movement of invertebrate pest populations in rice fields.

Figure 15. Adult rice water weevils feed on rice leaves but cause little damage.

There are at least seven invertebrate pest species or groups that can, and frequently do, cause economic loss to rice. These are the rice water weevil, two species of armyworms, rice leafminer, aster leafhopper, red crayfish, three species of seed midges, and the tadpole shrimp. Another pest which does not injure rice but concerns growers and those who live in rice-growing areas is mosquitos. Aside from being a public nuisance, certain species of mosquitos create public health problems as vectors for malaria and encephalitis.

The relationships between pest population levels and plant injury and/or yield have been established. In California, the most serious invertebrate pest problems occur in the first month to six weeks after planting. Therefore, the period of most intensive activity in managing invertebrate pests is from seed sowing to stand establishment.

Field sampling procedures also have been developed to determine when control is needed for rice water weevil, armyworm, rice leafminer, and tadpole shrimp.

Figure 16. Water weevil larvae feed on roots, causing root pruning, reduced tillering, stunted growth, and delayed maturity.

Weevil resistant rice

A cooperative program with the plant breeders at the Rice Experiment Station is developing lines of rice that are more tolerant to the rice water weevil. In tests using comparable weevil populations, the tolerant rice lines are showing a 10 to 20 percent loss in yield compared with 50 to 70 percent losses by susceptible commercial varieties.

Large numbers of tadpole shrimp can reduce stands of young submerged seedlings by their feeding and digging activities. Parathion (ethyl) has been used for control, but shrimp in San Joaquin County are exhibiting resistance to this treatment. Copper sulfate is very effective for shrimp control.

Pest knowledge helps control

Biological information has been developed on the life histories of the major invertebrate pests as well as on many invertebrates that are beneficial because they prey on some that injure rice. These life history studies provide information on the presence, distribution, host plant relationships, relative importance and duration in rice fields. This information, used to develop environmentally and economically sound management practices, has resulted in:

  • water management guidelines for control of seed midges and the rice leafminer;
  • timing seeding and flooding to reduce injury from tadpole shrimp and seed midges;
  • limiting chemical treatment for rice water weevil control to the areas adjacent to the levees and field margins; and
  • understanding the relationship between broadleaf weed control and the buildup of the aster leafhopper.

 

Home.gif (3162 bytes)Next.gif (3180 bytes)Back.gif (3162 bytes)