Tag Archives: Weeds

Mark Van Horn, director of the student farm at the University of California, is nearly lost as he walks through a yellow cloud of wild sunflowers around the edge of a field of tomatoes and sweet corn. Research here on wild sunflowers, he says, shows they are home to lady beetles and parasitic wasps, which are good bugs that kill bad bugs. “The sunflowers help us provide a bed-and-breakfast for beneficial insects and keep them going year round,” he said. “And native sunflowers are a lot better at it than domestic. There’s a lot more insect biodiversity in wild sunflowers.” While conventional farmers have a quiver full of chemical arrows to battle the invasion of weeds and pests, the organic farmer has a tougher row to hoe. There simply aren’t organic bug sprays that can match the power of synthetic chemicals and almost nothing in the way of organic herbicides. Instead, there’s a growing understanding among organic farmers of ways to harness natural systems as part of what is called integrated pest management. And there’s a small burst of new research into organic farming techniques as a result of the 2008 farm bill, which finances a range of agricultural programs at a total of $307 billion. For years such research was financed at $3 million a year, and though the funds are still minuscule compared with conventional agricultural research, it’s now $20 million annually for the next few years, and may increase further. Instead of five to seven research grants per year, there are now two dozen. “You aren’t considered a kook anymore if you do this kind of research, as you were in the 1980s,” said Fred Kirschenmann, an organic farmer and a distinguished fellow at the Leopold Center for Sustainable Agriculture in Iowa. Research on organic agricultural ecosystems in the last few years has made some key findings and refined techniques organic growers use. A paper published in Nature this year confirmed what organic farmers have long suspected — that conventional farming can make the pest problem worse. David Crowder, an entomologist at Washington State University and an author of the paper, says that if there are more varieties of plants around the field, and no broad-spectrum pesticides, as in organic farming, it promotes balance among insect species, rather than letting one species dominate. “There are more natural enemies and they do a lot better job in organic fields controlling pests,” Dr. Crowder said. Natural enemies are key to the organic approach. Eric Brennan is the lone full-time organic researcher for the Agriculture Department, and he works in the Salinas Valley, the so-called salad bowl of America, where some 80 percent of the country gets its salad greens. One of the most difficult pests is the lettuce aphid. The treatment of choice for commercial organic lettuce is to plant an ornamental flower called alyssum among lettuce beds, taking up 5 to 10 percent of the total field. Hoverflies live in the alyssum and need a source of aphids to feed their young, so they lay their eggs in the lettuce. When they hatch, the larvae start preying on the aphids. “If you were an aphid on a head of lettuce, a hoverfly larva would be a nightmare,” said Dr. Brennan. “They are voracious eaters of aphids. One larva per plant will control the aphids.” Dr. Brennan is studying the most effective configuration of lettuce and alyssum beds. Some organic strawberry farmers use “trap crops” to lure insects away from their cash crop. Lygus bugs cause the berries to deform. But the bugs like alfalfa better than strawberries, so some farmers plant one bed of alfalfa for every 50 rows of berries. As the lygus bugs crowd into the green growth, a giant tractor-mounted vacuum cleaner comes by and sucks them up. Other farmers simply suck the bugs off the strawberry plants. cont. added by: JanforGore