Calag Archive

A new tagging and magnetic recapture system permits large-scale studies of the factors that apparently attract bees and regulate their distribution and foraging activities. These data may confirm or disprove many theories proposed from less detailed past research, and hopefully, lead to new concepts concerning pollination. The net result may be greater control over the foraging activities of honeybees and greater efficiency of utilization for pollination purposes and honey production.

Lettuce crops in the central coastal district of California may follow each other in rapid succession on the same land with only a short period between the harvest of one crop and planting of another. Some growers in this area use soil fumigation after a series of 5 to 6 lettuce crops to improve yields and quality. The effectiveness of such fumigation has been attributed to such factors as nutrient release and the control of unidentified pathogens but specific data has been lacking.

The petiole (leaf stalk) of a young fully expanded strawberry leaf indicates the nitrogen content of the strawberry plant when it is tested either by the “quick test” with diphenylamine reagent or by a laboratory analysis using either the phenoldisulfonic acid procedure or the new nitrate electrode method. In the quick test, if a drop of diphenylamine reagent placed on the cut surface of the petiole (cut at a slant) turns blue immediately, the strawberry plant is well supplied with nitrogen and fertilizing with nitrogen at that time is usually not warranted. If, however, the test is negative, as indicated either by a lack of blue color formation or by a browning of the cut surface, fertilizing with nitrogen is indicated·–provided, of course, that there is sufficient growing weather remaining for the crop to benefit from nitrogen fertilization.

AN improved version of the popular b wheat variety INIA 66 is now available to California growers. The new variety is INIA 66R–a high yielding selection from INIA 66.

Studies of the amount of outcrossing in alfalfa seed fields, as affected by flowering alfalfa, distance, and size of plots, at Davis in 1965 and 1966, indicated that field size probably contributed more toward minimizing contamination than the other factors. However, some evidence indicated that flowering alfalfa, and distance, also reduced the amount of outcrossing. These studies were made in Ranger alfalfa and a white-flowered type.

A field planting in Tulare county of Sevillano olives grafted on various rootstocks provided opportunity for observations on susceptibility to verticillium wilt. In this 16-year test period, trees growing on the Oblonga clonal rootstock remained free of symptoms while 20 to 100 percent of the trees grafted on other olive species and varieties were killed by verticillium. None of the trees with the highly susceptible Sevillano as the scion variety on the Oblonga root showed symptoms of verticillium wilt…suggesting that the pathogen is not transmitted through the graft. Several trials with two major strains of Verticillium albo-atrum taken from cotton and olives in Tulare county, using controlled inoculation techniques and greenhouse conditions at Davis, confirmed the resistance of Oblonga to verticillium wilt. Sevillano, Ascolano, and Mission develop to normal sized trees on Oblonga roots. However, in studies at Winters this rootstock exerted some dwarfing influence on Manzanillo. No evidence of graft incompatibility or a weak graft union has appeared in any of these combinations.