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Field trials conducted the last two years show that dust or spray preparations using spores of the microbial insecticide, Bacillus thuringiensis, resulted in control of grape leaf folder equivalent to that obtained with carbaryl (Sevin), the current standard chemical employed against this pest.

Beneficial insect populations are often reduced by insecticides applied for control of specific pest species. The seven insecticides evaluated in this progress report were found to affect adversely the populations of six of the common predators in cotton fields. Populations of some beneficial insects (though severely reduced) recovered rapidly in plots treated with organophosphate materials that have short residual properties—but failed to recover rapidly in plots treated with long-residual materials.

Water-base paints appear capable of preventing sunburn for one season when used properly. Exterior water-base paints last longer than interior, but also may cause more tree injury. Therefore, the interior water-base paints appear to give the greatest margin of safety of any of the commercial paints tested.

The six-man labor carrier designed and tested by the University of California demonstrates a basic concept that can be adapted to the needs of individual growers and produced at a low cost per man—offering a useful tool to aid in attracting and keeping labor for thinning and weeding.

Celery is the vegetable crop with the highest total nutrient removal and also gives large returns on the investment in fertilizer. A direct-seeded crop in the central-coastal district of California requires approximately six months to mature. Only 2% of the growth and subsequent nutrient removal occurs during the first half of the growth period, while more than 42% of the nutrients were removed during the last month of growth. Good crops of celery grown in this area remove an average of 280 Ib of nitrogen (N), 72 Ib of phosphorus (P), and 635 Ib potassium (K) per acre.

Animal and poultry manures are often evaluated on the basis of their nitrogen content. Field experiments in the Antelope Valley on producing alfalfa fields have shown that poultry, steer, and dairy manure are also good sources of phosphorus. In this study, yield comparisons were made between treble superphosphate and manures when applied in amounts to provide the same rates of phosphorus as conventionally used on alfalfa.

Gibberellic acid is registered and recommended in California for certain uses (particularly in delaying rind and fruit maturity) on navel oranges and lemons. Favorable responses have also been obtained on limes and mandarins, but our present knowledge is insufficient to warrant registration or recommendation for use on these fruits. So far, we do not know how to take advantage of the delayed softening and aging of Valencia orange and grapefruit rind tissue without obtaining considerable regreening. The influence of GA₃ on retention of young fruit has potential value, but no practical method has yet been devised to avoid phytotoxic responses.

Recent tests point out the danger of phytotoxicity to young grapevines when planted in contact with freshly treated grape stakes.