Reducing Pest Pressure, Page 5
|Hanging a sticky sphere coated with a fruit-like odor to attract apple maggot flies helps apple growers determine when pests are present in significant numbers, allowing them to target insect controls rather than spraying the typical three times a season. |
Photo by Ron Prokapy.
Enhance Beneficial Organisms
'Farmscaping' - a term coined by Robert Bugg of the University of California - describes a comprehensive approach to nurturing populations of beneficials. It examines and redesigns the whole farm landscape, rearranging fields, hedgerows, conservation buffers and other farm features to favor the beneficial organisms that protect crops.
Beneficial predatory and parasitic organisms generally do not flourish in fields with only one plant species. They need overwintering sites and different types of microenvironments - such as shady, moist places - where they can find protection from their own natural enemies. Besides the pests on which they prey, beneficials often need additional sources of food. Parasitic wasps and predacious hoverflies, for example, depend on a daily supply of honeydew, nectar and pollen for energy and reproduction. Alternative food sources are critical to the development of slow-reproducing predators.
To improve habitat for beneficials, consider:
sowing cover crops between rows of cash crops,
maintaining 'beneficial insectary plantings' at field edges,
providing permanent refuge strips - 'or beetle banks' - for ground beetles, an important group of soil-dwelling generalist predators,
harboring natural predators, parasitoids and wildlife in perennial grasses, forbs, shrubs and trees on field edges or in strips,
through conservation tillage, preserving soil structure and complex food webs for ground beetles and other beneficials, and
supplying root disease-suppressing microbes with life-sustaining organic matter by means of cover crops, animal manures and composts.
'An intelligent addition to the diversity of habitat on the farm allows a lot of different kinds of predators and parasites to work on the side of the farmer,' says Kim Stoner, assistant entomologist at the Connecticut Agricultural Experiment Station in New Haven. 'It makes sense to go for a spectrum of flowering plants over the course of the year.'
In western Texas, pecan grower Kyle Brookshier uses one key strategy to limit dispersal of stink bugs. He plants black-eyed peas between or around all 1,300 acres of his nut trees. Drawn to the peas, the stink bugs now leave his pecans virtually alone. Rather than the 1213 percent damage they used to cause in his nut crop, Brookshier now sees less than 1 percent.
'We have almost ceased to get damage from stink bug,' he says. 'I think it should be a standard cultural practice in pecan orchards.'
Brookshier plants the peas two to four rows wide at two-week intervals between late June and late July. That way, his trap crop is always lush when the stink bugs are active. An added bonus of this inexpensive pest control strategy: The black-eyed peas are a hit at family meals.
Only as a Last Resort, Use Targeted Attacks
Even in ecologically based pest management systems, farmers may need to use pest control tactics, including pesticides. Managing weeds without tillage or herbicides, for example, is not consistently reliable. Because unwanted populations of annual and perennial vegetation can build very rapidly, herbicides remain an important tool, especially in no-till systems.
Judicious selection and limited use of herbicides that are low in toxicity and short in environmental persistence - combined with minimum-till and cover crop management - will help create habitat for beneficial organisms and develop healthy soils.
Sometimes key insect and disease pests - often introduced from another part of the world - can damage crops significantly. Ecologically based controls may not be available for these recently imported species. In this situation, reacting with the least disruptive, most specific chemical may be the farmer's best option.
Use reactive interventions only after clear decision-making. As you assess, consider the following:
properly identifying the pest and possible beneficial species present,
assessing the pest population and its threat to the crop, and
selecting the appropriate tactic - a chemical, biocontrol organism or other intervention - based on full knowledge of the range of measures available and their effectiveness, cost and side effects.
Options for pesticides and biorationals. To kill pests, disrupt their life cycles or deny their access to crops, farmers have an assortment of conventional and biorational materials at their disposal. Conventional chemicals include synthetic, broad-spectrum pesticides that often leave in their wake unwanted side effects - harming other species or polluting the environment.
Biorationals are more specifically toxic to or disruptive of target pests. Naturally derived or synthesized, they include growth regulators, microbial toxins, anti-feeding agents, pest-smothering oils, and disruption pheromones that confuse insects and reduce their reproductive success.
'They're an improvement and - if used properly - there should be an economic gain to the grower,' says Ed Rajotte, integrated pest management coordinator at Penn State University. For now, he says, many biorationals are more expensive and more difficult to use.
Rajotte's emphasis today: helping farmers substitute the many 'little hammers' of management information for the 'big hammer' of broad-spectrum pesticides.
If the agricultural research and extension community applies 'a concerted effort' over the next decade, Magdoff believes ecologically based pest management systems could be widely adopted.
'A lot of people have parts of this ecologically based pest management system working very well for them right now,' says Magdoff.
Beware the temptations of the 'big hammer,' says Fred Kirschenmann, an organic grain farmer in North Dakota. Like everyone, he points out, farmers want to see immediate results. Quick satisfaction from a big hammer strategy often gives way to disappointment over the long term.
'Develop the attitude that every time a big hammer' strategy is used, it represents a failure in the system,' Kirschenmann says. 'You should always assess what went wrong and what strategies to follow up with to put the many little hammers' back in place.'