Calag Archive

Extensive research by U.C. entomologists, in both greenhouse and field test plots, on the relation of insects to the cause or spread of pear decline disease indicates that the pear psylla, Psylla pyricola Foerster, is the key to the problem.

Field scale tests with young pear trees last year at Davis provided further evidence that the pear psylla (Psylla pyricola Foerster) plays a central role in the pear decline disease.

Abandoned orchards studied during the 1962 season showed substantial variation in their ability to support heavy populations of the pear psylla. There were indications that trees abandoned for several years may have arrived at a point where biological control factors will control the densities of this pest. The removal of single trees or of entire orchards that had been in this neglected state for several years is, therefore, of questionable value. However, in those orchards left unsprayed for only one or two years, psylla populations did reach high densities. Under these high summer population levels, several psylla adults were captured on traps placed considerable distances from the orchard. This greatly increases the danger from abandoned orchards in the adequate control of this pest in commercial plantings.

Oil sprays show promise for pear psylla control, but the addition of pyrethrins offers little advantage.

Use of double-pane, clear plastic panels with prismatic lower surfaces to direct sunlight downward from the roof, and patterned for diffusion of light from side panels, allowed 93% more sunlight for plant growth than the glass block design used previously in phytotron tests at Davis.

Purple vetch produces greater rice yields when turned under 4 to 6 inches than when placed at shallower depths. Shortening the time interval between turning under the vetch and flooding and sowing the rice, also increases yields—when conditions are favorable to nitrification during the preflooding period. When properly incorporated, vetch green manure is equal to mineral sources of ammonium nitrogen in increasing rice yields.

Field trials in Lassen County demonstrated that granulated heptachlor was more effective against the alfalfa weevil than comparable dosages of heptachlor used as a spray. Applications in the dormant season, or as growth begins in the spring, are believed to kill the adult weevils before eggs are laid.

Seed yields are highest when 50% of the panicles are mature in orchardgrass and 11% mature in hardinggrass.