Dr. David E. Bayer (shown) uses the UCD rice research facility for some of his extensive rice weed control research. Dr. Don Seaman of UCD is stationed at the Rice Station at Biggs, where he, too, has an extensive weed control research program underway.

To obtain the maximum control of smallflowered umbrellaplant, MCPA must be applied before the small buds form at the base of the main stem. Once these buds have developed, the control decreases rapidly. This may mean the water level should be lowered to expose maximum weed foliage.

Bentazon (BasagranŽ) provides optimum control when applied to smallflowered umbrellaplant during the seedling stages if good coverage of the plants can be obtained. This requires draining the fields to expose the plants. The addition of nonphytotoxic oil frequently enhances the activity of bentazon, especially under adverse environmental conditions or when the plants are older and better developed.

Water management is critical when molinate (OrdramŽ) is applied in a water-run treatment. For optimum results, the fields should be level and flooded rapidly. Once the molinate has been applied, the water level should be maintained. Draining of the field or loss of water for any reason will decrease barnyardgrass control. Five new formulations of molinate were evaluated at UCD to determine if the period of barnyardgrass control could be lengthened.

"To obtain maximum control of smallflowered umbrellaplant, MCPA must be applied before the small buds form at the base of the main stem."

A new formulation of bifenox and two formulations of acifluorfen showed promise for sedge and broadleaf weed control in rice, and the experimental herbicides H-8254, RH-5730 and RH-8817 also showed promise for control of watergrass and other weeds in rice. Further evaluation of MBR-18337 showed that its activity was similar to propanil except that it also may be used effectively before flooding. Silvex was a better MCPA alternative than bentazon, and it was most effective for control of ducksalad. Triclopyr was nearly as effective as silvex.

The new long-grain rice variety L-201 was injured rather severely by post-flood applications of granular OrdramŽ at five pounds active ingredient per acre or higher and by granular BoleroŽ at four pounds active ingredient per acre or higher. This indicates that growers of L-201 probably should not use the high rates of granular OrdramŽ now permitted by its California Special Local Need label, and that granular BoleroŽ, when registered, probably cannot be used for watergrass control in L-201.

However, studies indicate that DrepamonŽ should control watergrass without injury to L-201 as soon as this new herbicide becomes registered for use in California rice. The Chevron Chemical Company, manufacturer of BoleroŽ, has applied for full label registration for sprangletop grass control on a maximum of 50,000 acres of California rice in 1980. Industry problems with securing registration of promising pesticides is still slowing progress in implementing use of these chemicals.

Water-run applications of OrdramŽ were adversely affected by prior rainfall, high spots in the field and discontinuous flooding. Where the water-run applications were followed by continuous flooding, OrdramŽ and BoleroŽ gave about the same control of the early form of watergrass, but both failed to give satisfactory control of late watergrass at three or five pounds active ingredient per acre in densely infested fields.

Among fields that were drained and flush-irrigated after initial flooding and treatment, water-run OrdramŽ gave very little control of watergrass and no control of sprangletop, ducksalad or waterhyssop. Under similar water management conditions, water-run BoleroŽ gave excellent control of sprangletop, ducksalad and waterhyssop, but it failed to control watergrass.