Calag Archive

California almond growers commonly use organophosphate pesticides, which can be disruptive to biological control. Sprays during the spring and summer kill beneficial arthropods, including parasitic and predatory insects and spiders. In addition, pesticides have been detected by Cal EPA in winter fog and in runoff water flowing into the rivers of the San Joaquin Valley, which may lead to further restrictions in pesticide use. However, some almond growers are able to grow nuts with low insect damage without using toxic insecticide sprays. This article reports the results of a 6-year study, begun in 1988, of three almond orchards in Merced County to identify grower practices that permit reduced pesticide use.

Agronomic and economic benefits of diversification have been well documented, but social benefits are less well known. Two recent California studies show that diversity of crops and farm enterprises creates year-round or extended season employment for farmworkers. Additional strategies for doing so are paced work, selective mechanization, new technologies, break-even crops and coordinating work with other farmers or local industries. Workers employed on a year-round basis or for a longer season have higher incomes, more employer-paid benefits and can provide a better standard of living for their families than their seasonal counterparts. Farmers have found many benefits from a year-round or extended employment system. Some of these are increased worker availability, increased productivity and dependability, less need for worker training and increased personal satisfaction.

Some farmers resist increasing incentive pay levels when compensating seasonal crew workers. They have hypothesized that workers have a certain earnings goal for each day and that once this goal is achieved, workers will go home. This study conducted in the San Joaquin Valley shows that crew workers generally do not have such an earnings goal. When piece-rate paid crew workers do leave work early, it is more likely because they are overly hot or tired or that wages are low.

Yields from five irrigation regimes that each applied 16 acre-inches/acre were evaluated during a simulated drought year and for the subsequent two seasons under full irrigation. Drought-year production was mildly reduced by regimes that produced smaller kernels. Much greater losses occurred in the season immediately following the drought due to reduced nut load. Applying a limited allotment of water early in the drought season proved less effective in limiting subsequent production losses than irrigating at a lower rate but for a longer period of the drought season. Avoiding severe water stress during flower bud development (August and September) is critical for subsequent bloom and fruit set.

Yields and fruit quality of French prune trees in Tulare and Yuba counties were not improved by controlling late-season prune rust with mancozeb or sulfur over a 3-year period. Accelerated postharvest leaf loss induced by disease did not appear to cause a decline in yields in the following year. In a comparison of mancozeb 80W and sulfur 92W for control of prune rust, mancozeb provided superior control.

The California Grapevine Certification Program has been based on two assumptions about leafroll disease in grapevines: that the disease does not spread significantly in the field in California and that the viruses that cause the disease are evenly distributed in infected vines. Careful testing of the Foundation Plant Materials Service vineyards at Davis using a new ELISA test suggests that these assumptions are not true. Changes in the California Grapevine Certification Program are underway as a result of this new information.

A population of the Formosan subterranean termite, Coptotermes formosanus Shiraki, was discovered in La Mesa, San Diego County, in February 1992. This is the first instance of a non-native termite species being introduced and established in California. Due to the extremely destructive nature of this termite, a study was initiated to attempt to eradicate or control it using an insect growth regulator (hexaflumuron). Preliminary results suggest the product suppresses the population, but evaluation of this control is continuing. In the meantime, removal of excess wood reduces the food sources available to the termites and may help limit the growth and expansion of the colony.

Phoracantha semipunctata F., a cerambycid beetle introduced into California within the last 10 years, is killing large numbers of eucalyptus trees throughout much of the state. Risk of tree mortality can be reduced through managing tree stress, selection of more resistant tree species and disposal of infested wood. A biological control program to reduce beetle populations through the introduction of egg and larval parasites is currently being implemented. The combination of appropriate tree management and biological control holds promise for protecting these valuable ornamental tree species.

The eucalyptus snout beetle is a defoliator with tremendous potential to damage urban and commercial forest plantings of eucalyptus. It has just recently been detected in California, but experience gained from other parts of the world gives us advance knowledge of its life history and host preferences. As with other recently introduced eucalyptus pests, use of host resistance and biological control appear to be the most appropriate management options.