California Agriculture, January-February 1998
Volume 52, Number 1
Enlisting nature: Bats pack punch in pest control
peer-reviewed research articles
Bats feed on crop pests in Sacramento Valley
by Rachael Freeman Long , Tiffanie Simpson , Tzung-Su Ding , Steve Heydon , Wilbur Reil
Food habits of Mexican free-tailed bats and Yuma myotis bats were examined in the Sacramento Valley. Analyses of guano samples indicated that Mexican free-tailed and Yuma myotis bats fed on moths, water boatmen, beetles, flies, midges, mosquitoes and plant bugs. The diet of Yuma myotis bats tended to be diverse early in the season, but more uniform later on when they ate more moths. In contrast, Mexican free-tailed bats primarily fed on midges, flies and mosquitoes early in the season, then became more generalized feeders later on. These data demonstrate that bats are beneficial as they feed on insects that can be pests of agriculture.
Media campaigns promote driver safety for farmworkers
by James I. Grieshop , Myriam Grajales-Hall , Lupe Ortiz
During the peak harvest season from April to October, hundreds of thousands of San Joaquin Valley farmworkers commute from field to field and farm to farm, sometimes two or three times a day. Motor vehicle crashes — the largest documented cause of injuries and fatalities to farm workers — increase dramatically at this time. To educate farm-worker families about motor vehicle safety, we designed a program called ¡Maneje Seguro! (Drive Safely!). Its centerpiece was a game, La Loteria del Manejo Seguro, based on a bingo-like game popular in Mexico (known simply as La Loteria). We disseminated safe-driving information by featuring the game in weekly bilingual newspapers and Spanish radio and TV station. Assessments suggest that media campaigns had favorable impact on farmworker knowledge, awareness and, to some degree, driving behavior.
New crop coefficients estimate water use of vegetables, row crops
by Stephen R. Grattan , Wilbur Bowers , Allen Dong , Richard L. Snyder , John J. Carroll , William George
To estimate the water use of vegetable and row crops, crop coefficients were developed using portable Bowen ratio instruments that were constructed and tested against lysimeters. These instruments measured evapotranspiration (ET) in fields of vegetable and row crops at various developmental stages. The crop coefficient was calculated at different percentages of ground cover using a direct ratio between the ET of the crop and that of a reference grass, which was calculated using meteorological data calculated from local CIMIS weather stations. The crop coefficients for most of the crops increased as the percentage of ground cover increased.
Earlier irrigation cutoff for sugarbeets conserves water
by Stephen R. Kaffka , Gary R. Peterson , Don Kirby
In the Tulelake region near the Oregon border, sugarbeets are grown on organic soil reclaimed from a shallow lake. Groundwater is present continuously through-out the season at depths of approximately 4 feet in most fields. Typically, beets planted in April and May are irrigated until mid-September and harvested in October. However, environmental restrictions may reduce farm water supplies in the future. To determine whether sugarbeets can be grown with less irrigation water, five irrigation cutoff treatments were applied to replicated large plots at approximately 2-week intervals starting in mid-july in 1995 and 1996. Results from these trials suggest that farmers can save 4 to 6 inches of irrigation water by cutting off irrigation to sugarbeet crops 6 to 7 weeks before harvest under these soil and climate conditions.
Water turbulence disrupts accuracy of some flow meters
by Blaine R. Hanson , Larry J. Schwankl
Flow meters were tested under a variety of conditions to determine potential errors in flow rate measurements due to excessive turbulence in the water. Results showed that propeller meters, the Hall meter and the Collins meter were not particularly sensitive to turbulence caused by elbows, while paddle-wheel meters and velocity gauges were sensitive to turbulence. Relatively large errors occurred for all meters under turbulence caused by a partially closed butterfly valve. Inserting six straightening vanes greatly reduced the error caused by partially closed valves.
Parasitoid wasp controls blue gum psyllid
by Donald L. Dahlsten , David L. Rowney , William A. Copper , Richard L. Tassan , William E. Chaney , Karen L. Robb , Steven Tjosvold , Mary Bianchi , Priscilla Lane
The blue gum psyllid was first discovered in North America in Monterey County in January 1991. Since then it has quickly spread throughout the California coastal area and has became a major pest on Eucalyptus palverulenta in commercial foliage plantations. Large amounts of pesticides have been used to control the psyllid in these plantations. A primary parasitoid wasp, Psyllaephagus pilosus Noyes (Hymenoptera: Encyrtidae), was found in Australia and New Zealand and released at eight sites in California in spring/summer 1993. As a result, psyllid populations declined somewhat at most sites in 1993, and in 1994 psyllids were no longer a problem. The parasitoid has spread rapidly to other coastal areas.
Biological control of the blue gum psyllid proves economically beneficial
by Donald L. Dahlsten , Evan P. Hansen , Robert L. Zuparko , Richard B. Norgaard
In 1992 a parasitoid native to Australia was introduced into California in a biological control program directed against the blue gum psyllid from Australia. Interviews with baby blue gum eucalyptus growers indicate that this program has had a benefit-cost ratio ranging from at least 9:1 to 24:1, based solely on the reduction of insecticide treatments. Additional economic benefits, including greater foliage yield, possible reduced environmental and health effects, and avoided pesticide resistance, were not calculated, but would further increase this ratio.
editorial, news, letters & science briefs
Times and programs change, but Division carries on tradition of public service
by W.R. Gomes
“City Bugs” website turns teens into taxonomists
by Jill Goetz
UC trains welfare recipients
Science Briefs: Bison disease still threatens cattle
Bats can pack a punch in pest control