PRODUCTION PESTS

Recommendations already developed for the major pests of rice provide acceptable control, are economically rewarding, and meet California Fish and Game standards as causing minimum disruption of wildlife. The most recent research results led to registration of carbofuran and Bux for control of rice water weevil.

Information has been developed comparing alternative strategies against water weevil: preventive preflood treatment vs postflood treatment of an established infestation. Studies continue on levels of pests that are economically tolerable.

PLANT RESISTANCE

No resistance to water weevil has been found in 5,000 lines of rice plants examined. Hope of such control would thus have to await some future rice line.

WEEVIL LIFE CYCLE

As the major insect pest in California rice, the rice water weevil is being studied intensively for the weakest link in its life cycle. So far, its food habits, flight patterns, and general life cycle have led to selective placement of insecticides adjacent to levees in most fields. Such treatment of only about 20% of the area gives adequate control at low cost.

INSECT SURVEYS

Spread of the rice water weevil is followed constantly to alert growers to threats to new areas. The rice seed midge is also surveyed as to distribution of damage. Survey techniques for this pest are being investigated.

RESIDUE INFLUENCE ON INVERTEBRATE PESTS

Populations of aquatic organisms did not differ significantly as a result of burning or cultivation practices.

Efficiency of soil treatment with Bux and carbofuran in controlling rice water weevil could not be related to burning or incorporation of residues.

Adult water weevils were not reduced significantly by burning the grass clumps that are their over-wintering sites.

Eggs of tadpole shrimp survived in rice fields treated with weed burners.(RP3)