Gary Pitt Farms, an 800-acre table grape operation near Fresno, Calif., is demonstrating alternative practices to manage vine mealybug and other vineyard pests this season as part of a sustainable agriculture project sponsored by the University of California.
Following a biologically integrated farming systems (BIFS) approach, the two-year project, funded with $200,000 from the U.S. Environmental Protection Agency, is comparing reduced-risk materials and methods with spraying of organophosphates, carbamates, and carcinogens under fire from regulatory agencies.
Many of the targeted high-risk, conventional materials contribute to air and water pollution with their volatile organic compounds or through leaching and run-off.
A major goal is to replace those conventional chemicals with less disruptive materials and methods, all without compromising the high cosmetic quality standards demanded of the table grape industry.
The project leader, Walt Bentley, UC IPM entomologist at Parlier, said it is “designed to help table grape growers address critical pest issues as they transition from use of several high-risk, biologically disruptive materials to more environmentally sound pest-management practices.”
Those practices include an increased reliance on monitoring and uses of research-based action thresholds, along with alternative biological and cultural controls, such as vineyard floor and canopy management. Key pests involved are mealybugs, lepidopterous insects, mites, powdery mildew and weeds.
Findings from research begun early this year on the Pitts vineyards outside Del Rey, Calif., and six other table-grape operations between Fresno, Calif., and Arvin, Calif., Bentley said, will provide experience and baselines on a regional basis. Demonstrations at the various sites are on 20-acre plots, split between standard and BIFS treatments.
Grower cooperators were selected because of their innovative approach to solving pest management problems and problems with a particular pest.
“It's notable,” he said, “that some of these growers have already adopted programs we are investigating. Our main focus, so far, has been on alternatives for vine mealybug and a biological antagonist for powdery mildew.”
For example, Bentley said, the Pitt ranch has begun trial treatments with the neonicotinoid Admire (imidacloprid) and the insect growth regulator Applaud via drip lines to control vine mealybug.
Another dimension is evaluation of methods for new products such as Chateau to reduce use of preemergence herbicides. New materials may aid control of weeds such as mare's tail, which has begun to show resistance to Roundup.
In discussing how growers can move toward BIFS principles, Bentley said he does not believe costs across the board will be significantly different, although some conventional materials such as preemergence herbicides may be easier to apply than reduced-risk products.
“We are concerned that there needs to be something new to counter the resistance becoming more prevalent in mare's tail. For insects I believe growers can benefit from having a group of three or four insect growth regulators to help reduce the need for miticides, since they are softer on predatory mites.”
Biological products to control powdery mildew, however, cost more than the age-old sulfur, he added.
He pointed out that BIFS practices can be adopted more readily to grapes for wine or raisins. “But when you are shipping table grapes to Japan or Australia, it is much more important to have a cosmetically appealing product, and it will be tough for those growers to change. With organophosphates, carbamates, or pyrethroids it is pretty easy to clean up an insect problem in a hurry.”
Nevertheless, Bentley contends the softer, more environmentally friendly products can do the job, provided they are keyed with close monitoring for pests so applications are made at the optimum time for the greatest effect.
“This project will help farmers use lower-risk pesticides that target specific pests without wiping out beneficial insects or their habitats. Close monitoring will help growers determine the exact dates that insects are most vulnerable to pesticides, which prevents unnecessary pesticide applications.
“New academic programs at UC campuses at Riverside and Davis are designed to put people in the field to do just that. And the state universities will also need to produce PCAs who are well-trained in monitoring.”
Pitt Farms manager Clint Young recently hosted a briefing on their pest management programs for a tour of advisory group members of a California Department of Pesticide Regulation program monitoring air for pesticides at a group of Parlier elementary schools.
Young said his main concern in pest management is the safety of the 100 to 500 workers in the vineyards at various times of year. Cultural practices vary for each of the nine varieties of table grapes grown.
“So we have to take care of the vines properly while we are observing the proper re-entry period for workers after a spray,” he said.
The chief pest is powdery mildew, and once the disease threatens in March the main treatment is sulfur applied at 14-day intervals through the remainder of the season. They make treatments in the evening or early morning to avoid drift.
Mites are the second greatest pest and among their efforts is keeping roads oiled to reduce dust which attracts the mites. They have also adopted minimum tillage to reduce dust from tractor traffic in the field. They are using softer materials to preserve predatory mites.
For mildew and mites, they are rotating materials to discourage resistance developing in either pest.
Young and neighboring growers are very concerned that vine mealybug, a new vineyard pest that destroys foliage and fruit, will become their No. 1 pest. It is particularly difficult to control because it hides in bark and roots, protected from sprays, and can be carried by birds. The growers are in close touch and share word of any new infestations.
“We will find it one place, and later it shows up in another place across a 200-acre block,” he said. In addition to their treatments through drip irrigation, they are practicing field sanitation to avoid transmitting the pest on equipment or fallen leaves.
Harold McClarty, a partner in the Pitt operation, said consumer demand for “picture perfect” table grapes puts considerable pressure on growers to control pests and ensure their product is free of even the most minor blemishes. Retailers, he added, demand color rather than taste and even require a certain size of berries.