All Issues

Decline in production and in size of fruit is an increasing problem in southern California's citrus groves. Package plot experiments, under way for some time, have not solved that problem, but they have provided promising leads. This report is concerned with one phase of the project—the effect of various treatments on production, fruit size, and the physical properties of the soil within the plots. Treatments were made in: navel orange groves at Redlands, Highlands, and Riverside; Valencia orange groves at Olive and Santa Paula; and a lemon grove at Ventura. Two replications of four tree plots were used in the groves at Redlands, Highlands, and Olive; four replications of four tree plots were used at Ventura and Santa Paula; and five replications of two tree plots were used at Riverside.

Whether Troyer citrange rootstock can be used successfully in old citrus soils, or in soils contaminated by microorganisms that attack citrus roots, and whether it is profitable to pretreat planting sites to disinfest them of root-destroying fungi were objectives of experiments in southern California.

The distinctive color of redwood is due—in part, at least—to the nature of its extractive components. The excellent durability of redwood heartwood also is attributed to the fungicidal properties of its extractives. However, one of the problems associated with the manufacture of redwood lumber is the chemical seasoning stain resulting from the chemical nature of some of the extractives.

Experiments indicate that photoperiod, or daylength, is of great importance in the heading of rice plants and that maturity of rice varieties can be classified in the field by their sensitivity to above-optimum daylength. Early varieties such as Colusa are less sensitive and will head in the field under the longer days of midsummer, while Caloro, a midseason variety, is more sensitive and heads in the field later in the summer after the photoperiod has shortened considerably. A very late variety such as Texas Patna 49 is highly sensitive to photoperiod and does not head until the days have become much shorter in the fall.

Plants propagated vegetatively, rather than by true seed, frequently carry diseases in the vegetative parts. One of the diseases of garlic, the stem and bulb nematode, is carried in the cloves and has become widely established

Nitrogen is a necessary element in the production of fruit but there is considerable confusion as to the most economical amounts to use and the most satisfactory timing of the applications.

Flies in mushroom houses act as carriers of various mushroom diseases. In addition, fly larvae break down the compost of the mushroom producing beds, in which the flies breed, and feed on the mushroom mycelia. In southern California, where mushrooms are grown throughout the year, the problem of fly reinfestation from the outside is always present. Phorid and sciarid flies are the most numerous, attracted by the odor of the beds immediately after spawning. Infestations are heaviest after wet weather or following irrigation of adjacent areas. Control is necessary both for protection of the mushrooms and from the standpoint of sanitation. Flies must be kept out of the producing houses and nearby dwellings. One large mushroom farm has developed a successful fly-control program.