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Open Access Publications from the University of California

Volume 55, Issue 5, 2001


BIOS and conventional almond orchard management compared

Conventional almond growers in Merced and Stanislaus counties who use organophosphate, carb-amate and pyrethroid insecticides were compared with participants in the Biologically Integrated Orchard Systems (BIOS) program, who do not use these broad-spectrum insecticides. The results demonstrated consistent but not significantly lower infestation by navel orangeworm and peach twig borer for growers who used broad-spectrum sprays. Infestation by ants resulted in the most consistent difference between the two management practices, with significantly less damage when broad-spectrum sprays were used. The differences in overall pest damage were relatively minor, but the variation was greatest among those not using broad-spectrum sprays. Winter survival of the navel orangeworm parasitoid, Goniozus legneri, and parasitism by this beneficial insect were low in all orchards, sprayed or unsprayed. Winter removal of unharvested almonds to fewer than two per tree reduced navel orangeworm infestations in both treatments. Although many of the almond growers not using organo-phosphate, carbamate or pyrethroid sprays had less damage than some who used these materials, the greater range of damage experienced by these growers may explain why more almond growers prefer to use them annually to combat insect pests.

Armored scale insecticide resistance challenges San Joaquin Valley citrus growers

Organophosphate and carbamate insecticides have been used to treat citrus pest problems for more than 40 years. From 1990 to 1998, we documented California red scale and yellow scale resistance to these insecticides. Armored scale resistance is found on an estimated 40% of 163,000 acres of citrus in the San Joaquin Valley. Citrus growers have responded by either increasing their use of natural enemies, especially the parasitoid wasp Aphytis melinus, or by applying newly registered insect growth regulator or neonicotinoid insecticides. While the California red scale problem is, for the moment, greatly reduced, outbreaks of cottony cushion scale are occurring because the new insecticides are highly toxic to the predatory vedalia beetle.

Managing manure and conserving predators helps control flies in caged-layer poultry systems

As the rural-urban interface expands, controlling flies has become increasingly important on California poultry farms. Manure management is a critical component of keeping fly populations in check. Recent research demonstrates that the dry pad left behind after manure cleanouts in cagedlayer poultry systems aids manure drying because of the elevation and improved airflow. Most mites and beetles that prey on fly eggs and larvae are removed in a cleanout, although predator populations require longer than flies to recover. Leaving undisturbed manure (with a larger number of predators) adjacent to recently removed manure did not improve fly control significantly in open-sided layer houses, but might be more important in fully enclosed houses.

Host-specific strain of Stemphylium causes leaf spot disease of California spinach

The California spinach industry has grown dramatically over the past few decades; it now supplies well over 100,000 tons of various high-quality products to consumers. But a new foliar disease. Stemphylium leaf spot, can reduce spinach quality. After identifying this disease, we determined that the pathogen may also be a new, distinct strain of the fungus that is specific to spinach. Inoculation experiments demonstrated that numerous spinach lines are susceptible, including new downy mildew-resistant cultivars. Diagnosing this disease can be difficult because its symptoms often resemble damage from agrochemicals. Growers and pest control advisors should become familiar with the symptoms of the various foliar spinach diseases that occur in California because consumers of this crop tolerate only a small level of leaf spots and defects.

Rust disease continues to threaten California garlic crop

In 1998, following the very wet EI Niño weather event, a devastating outbreak of rust disease severely damaged the garlic crop in California. The disease also occurred in 1999 and 2000, indicating that rust may have developed into an annual problem. We identified the pathogen as Puccinia allii. In our study, it infected allium crops such as garlic, onion and chives, but not leek, elephant garlic or shallot. Currently registered materials did not control the disease, but tebuconazole (Folicur) and azoxystrobin (Quadris) provided good protection against garlic rust. Based on our work, a Section 18 emergency exomption for tebuconazole was approved by state pesticide regulators. We tested 34 UC and industry garlic varieties and found that none were completely resistant to garlic rust.

Interpersonal communication tops concerns of farm supervisors

I interviewed 42 farm supervisors in the northern San Joaquin Valley, in order to explore how they became supervisors and how they feel about the work and deal with employee discipline. This study revealed that supervisors generally feel little need for additional training before they take on supervisory responsibilities. Like their farmworker counterparts, supervisors feel good about their jobs, rating them an average of 4.5 on a scale where 5 means the job is fantastic and 1 is terrible. When asked to identify the most challenging and rewarding aspects of their positions, farm supervisors overwhelmingly mentioned their relations with people. Those in upper management were more likely to have fired an employee than first-line supervisors, yet employee discipline was an important aspect of supervisors' work.

One-pass tillage equipment outstrips conventional tillage method

For this study, we compared a new one-pass tillage implement called the Incorpramaster with a conventional tillage practice of stubble disking and land planing. Our randomized block experiment on the UC Davis campus evaluated the equipment's energy and time savings. We found that the one-pass tillage equipment (OPTE) outperformed conventional land preparation methods in fuel consumption and speed. Fuel savings ranged from 19% to 81% with a mean savings of 50%. Time savings ranged from 67% to 83% with mean of 72%. The mean soil particle size created by the one-pass tillage implement was comparable to that produced by conventional tillage methods.