Protection from Invertebrate Pests-82
 

 

 

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Project Leader and Principal UC Investigators

A.A. Grigarick, Department of Entomology, UC Davis

 

Objectives of this project are to determine the physical and biological factors that allow pest populations to build up and cause economic injury to rice and to find effective pest control measures that are not environmentally detrimental.

Rice Leafminer

The first leaf to emerge through water was found to be the most susceptible to leafminer injury in greenhouse studies. The mining significantly reduced seedling top and root weight. Larvae mining on more than one leaf reduced plant growth more than an equal number of larvae on a single leaf. Prone leaves were more susceptible than upright leaves. Some plants were killed when larvae moved to and fed on the sheath.

Aster Leafhopper

Natural infestation of the aster leafhopper reduced grain yields 11.6 and 12.2 percent during a two-year study, primarily by reducing the number of panicles per plant. Infestations both years peaked in July. Late applications of MCPA (52 and 58 days) resulted in the movement of leafhoppers from weeds to rice in plots with thin stands of rice. This did not occur following early applications (38 days) which probably prevented a leafhopper buildup on weeds.

Tadpole Shrimp

Tadpole shrimp were controlled in San Joaquin county by applications of copper sulfate crystals and Strike®, a chelated copper sulfate recommended for algae control. These two materials resulted in 100 percent shrimp mortality in 5 1/2 hours at 5 and 10 pounds active ingredient per acre laboratory tests.

Resistance of the tadpole shrimp to parathion was strongly suspected in San Joaquin County near Escalon. Shrimp were collected from Colusa, Butte, and San Joaquin counties and tested in the laboratory for resistance to parathion. The most susceptible shrimp were from Colusa County, and the least susceptible (more resistant) ones were from San Joaquin County. Butte County shrimp showed intermediate levels of susceptibility. These tests demonstrated that apparent resistance of shrimp to parathion is not uniform throughout . rice growing areas.

Rice Water Weevil Control

A field survey for distribution of the rice water weevil in San Joaquin Valley showed the presence of weevils as far south as Modesto. Adult feeding was observed near Merced, and suspected feeding scars were observed near South Dos Palos, but no activity was found below that area.

Insect growth regulators diflubenzuron and Bay Sir 8514 sprayed on rice for water weevil control in flooded paddies resulted in 25 and 33 percent more yield than untreated paddies. One application at one week after emergence was just as effective as two applications a week apart. The most effective rate was 6 ounces active ingredient per acre. Laboratory tests with these materials showed them to be most effective when applied 1) to rice foliage with adults present and 2) in water containing rice stems with eggs.

Two new carbamates, Oncol® and Union Carbide 54229 compared favorably with carbofuran for rice water weevil control when used as preplant granule treatments in field and laboratory tests. Application rate was 1 pound active ingredient per acre of these new materials. Standard formulations of carbofuran (0.5 and 1.0 lb ai/acre) were effective but slow release granules of carbofuran were ineffective.

Selection of rice lines for tolerance to the water weevil looks very promising. The susceptible variety M9 showed a 57 percent yield reduction from exposure to the weevils when compared with chemically treated plots. Nine lines selected for greatest tolerance averaged only 7.4 percent reduction in yield from water weevil. Reason for tolerance of selected lines has not been determined.

 

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