Calag Archive

Linuron applications at 1 lb per acre severely injured only one of the nine ground cover species tested in this study (C. edule). Amino triazole at 1 lb per acre was applied to all species, except Ajuga repens or Delasperma alba, without severe injury. Injury from MCPP was less severe than 2,4-D in most instances and would appear to be safer in these tests at herbicidal rates. However, injury was apparent from MCPP on Ajuga repens, although 2,4-D amine did not appear to cause injury in this test. Bromoxynil appeared to have contact effects only (as indicated by early leaf burning) on Carpobrotus edule, Delasperma alba, Hypericum calycinum, and Vinca minor; however, regrowth was normal.

Replicated field trials conducted in Colusa and Glenn Counties demonstrated that poor growth and production of grain sorghum (milo) the first year after rice may be improved by phosphorus banded near the seed. Treble super phosphate, 11-48-0, 8-24-0, and 10-50-0, improved seedling growth and grain yields when placed with or below seed. After four or more years of continuous rice, P banded near sorghum seed provided economic returns and striking seedling growth responses. Sorghum trials after only two years of rice showed fewer seedling growth differences and variable yield responses to banded P. Soil analysis using critical levels developed on soils with no rice history could not be used to successfully predict yield responses to banded P after rice. Further studies are necessary to answer such questions as: (1) Why are some soils P deficient after rice? (2) How can we predict situations where banded P is effective? (3) What are the optimum rates of P for highest economic returns?

Pulling alternate trees and pruning to increase the amount of sunlight available to each tree failed to increase per-acre yield or grower returns over a four-year period in a red grapefruit grove near Coachella. The grove was planted in 1956 on fertile soil at a spacing of 13.5 × 24 ft with the expectation that alternate trees would be thinned out when the grove began to be crowded. The grower originally planned to inter-plant trees on rough lemon alternated with trees on Cleopatra mandarin. The trees on rough lemon were expected to give high early production and to be eliminated at thinning time, allowing the Cleopatra mandarin trees to remain for the permanent orchard. By 1967 when the plot work was undertaken, no trees had been pulled, and the grove was overcrowded and too shady.

Ancymidol was found to be effective in retarding growth of many plant species and cultivars. It was effective on woody and herbaceous species. It appears that this new chemical has a wide latitude of safety on most plants. However, some objectionable effects were observed—which may be partly the result of the high dosages used for this series of experiments. Ancymidol is not registered for use at this time, and is not recommended by the University of California.

Leaf-feeding mites are one of the most J severe pest problems for growers of deciduous fruits and nuts in California. The mites primarily responsible for these problems include the European red mite, Panonychus ulmi (Koch), the two-spotted mite, Tetranychus urticae Koch, and the Pacific mite, T. pacificus McGregor. Control of these and other species of mite pests has depended upon the use of pesticides that may be harmful to non-target species of insects and mites, and may also lose their efficacy against target species because of a build-up of resistance. In an attempt to find those materials that are effective against the target species, and the least harmful to non-target species, new chemicals are continually being evaluated for their effect on both pest and beneficial species of mites and insects. This report presents the results of field trials of new, but as yet unregistered, pesticides that were evaluated as miticides on the European red mite and Pacific mite during 1971.