Manage flexibly and responsively

On the rare occasions that leafhoppers or thrips exceed economic thresholds in his clients' vineyards, Berkowitz recommends insecticides. "We try to use systems that control pests without chemicals, but sometimes you're just stuck."

That's often the case with Pierces disease, whose damage can force frequent replanting. Berkowitz says insecticide treatment for the blue-green sharpshooter during the first hot spells can regulate this vectors early movement into vineyards. Another approach showing "some merit" is riparian vegetation management: replacing host plants with non-hosts. This reduces the sharpshooter's populations while broadening diversity. "Today we try to manage the vector, but someday we hope to be able to control the disease itself," he says.

California vintners seed mixtures of Blando brome grass, Zorro fescue and crimson and rose clovers to prevent erosion, regulate vine growth and attract beneficial insects.

Over the years, Berkowitz has learned not to include 'Berber' orchard grass or annual ryegrass in cover crop mixtures because they're simply too competitive with grapevines. He has also observed that using sulfur to organically control powdery mildew kills predaceous beneficial mites faster than its kills prey mites.

"You think you're doing a good thing by dusting with sulfur, but at the end of the season you wind up with these mite problems." In vineyards where this has occurred, Berkowitz advises producers to substitute non-sulfur controls like biofungicides after early-spring treatments with sulfur. He has watched that strategy "really help" in repeatedly mite-infested vineyards.

"It's a systems approach," says Berkowitz. "That's what makes sustainable agriculture interesting to me: everything is connected."

Bob Nichols, USDA NRCS

Bob Nichols, USDA NRCS

Conservation filter strips can include flowering plants to attract beneficials and provide quality habitat for many species of wildlife.

In Norway's apple orchards, the abundance of apple fruit moth pests depends largely on the amount of berries produced by the European mountain ash (Sorbus aucuparia), a wild shrub. Because only one apple fruit moth larva can develop inside each berry, the number of these pests is directly limited by the number of berries. Thus, when European mountain ash fails to bear, apple fruit moth populations fail as well. Unfortunately, that also spells death for a naturally occurring parasite of the apple fruit moth, the braconid parasitoid wasp (Microgaster politus). Entomologists have advised Norwegian orchardists to plant a cultivated Sorbus (ash) for its regular and abundant crops. By sustaining both apple fruit moths and Microgaster, this practice allows the natural enemies to hold the moths at levels Sorbus can support. The result: the moths don't abandon Sorbus for orchards.

Manage plants surrounding fields to manage specific pests. One practice, called perimeter trap cropping, works best when plants like snap beans or cowpeas are grown to attract stink bugs and Mexican bean beetles away from soybeans. In perimeter trap cropping, plants that are especially attractive to target pests are planted around a cash crop, encircling it completely without gaps.

REDUCE MOWING T"ree fruit growers seeking alternatives to

- broad-spectrum pesticides are looking to

FREQUENCYTO

manage insect pests using a more environ-INCREASE mentally friendly approach. In Washington

BENEFICIALS state pear orchards, SARE-funded research has found that mowing once a month rather than two or three times a month creates alluring habitats for beneficial insects.

An ARS researcher partly funded by SARE ran trials at three orchards and varied mowing frequency (weekly, monthly and just once a season). With less frequent mowing, the natural enemies moved into the ground cover in greater numbers, likely attracted to the pollen and nectar newly available from flowering plants as well as more abundant prey, such as aphids and thrips. Researcher Dave Horton found more lacewing larvae, spiders, ladybug beetles, damsel bugs, parasitoids and minute pirate bugs. "If you mow a lot, you won't have much in the way of natural enemies on the ground," Horton said. "By reducing the frequency to once a month, you see a dramatic increase in natural enemies moving into the ground cover without a big increase in pests that feed on fruit."

Questions remain whether the predators migrate from the ground cover into the pear trees to attack orchard pests, although evidence supports that some predators, especially spiders, appeared in higher numbers in pear trees in the less frequently mowed plots, good news for pear growers.

One of Horton's farmer collaborators, who received a SARE farmer/rancher grant to study similar ways to manage orchard pests, is convinced that minimal mowing provides control. "I'm practicing this, and I've never had to spray for mites," said George Ing of Hood River, Ore., who has a 16-year-old orchard. "Other orchards that are conventionally treated have more pests. I'm convinced it helped." At the behest of area growers, who provided a research grant through their pear and apple association, Horton will test how seeding cover crops such as white clover between tree rows affects populations of both pests and pest predators.

USDA ARS researcher Dave Horton found that less frequent mowing in orchards attracts more beneficial insects to prey on pear psylla, leaf miners and other serious pests.

USDA ARS

USDA ARS

Field boundary plants that harbor beneficials can go to seed, contaminating field edges with weeds. Mow or plow down these plants before seeds are mature or maintain field margins at a small distance from the field edges to prevent weed problems in your cash crop.

Perimeter trap cropping can sharply reduce pesticide applications by attracting pests away from the cash crop. By limiting pesticide use in field borders or eliminating it entirely, you can preserve the beneficials in the main crop. Extension vegetable educators at the University of Connecticut report that up to 92 percent of pepper maggot infestation occurs on trap crops of unsprayed hot cherry peppers, effectively protecting the sweet bell peppers inside. Applying pesticide to the trap crop during the flight of the adult pepper maggot fly reduces infestations in the unsprayed bell peppers by 98 to 100 percent. Connecticut commercial growers with low to moderate pepper maggot populations have confirmed the method's success on fields as small as one-quarter acre and as large as 20 acres.

In Florida, researchers with the USDA-ARS found that a collard trap crop barrier around commercial cabbage fields prevented diamondback moth larvae from exceeding action thresholds and acted as a refuge planting to build parasite numbers; cabbage growers who used perimeter trap cropping reduced their insecticide applications by 56 percent. In Ontario, Canada, researchers also found that planting 'Southern Giant' mustard around fields of cabbage, cauliflower and broccoli protected them from flea beetles.

Alternately, flowering plants such as Phacelia or buckwheat can be grown in field margins to increase populations of syrphid flies and reduce aphid populations in adjacent vegetable crops. This method is most effective for pests of intermediate mobility. Consider plants that support beneficial insects and can be harvested to generate revenue.

T. Jude Boucher, Univ. of Conn.

T. Jude Boucher, Univ. of Conn.

Planting squash as a "trap" crop draws pests like cucumber beetles away from cash crops, reducing insecticide use and improving yields.

Create corridors for natural enemies. You can provide natural enemies with highways of habitat by sowing diverse flowering plants into strips every 165 to 330 feet (50-100 m) across the field. Beneficials can use these corridors to circulate and disperse into field centers.

European studies have confirmed that this practice increases the diversity and abundance of natural enemies. When sugar beet fields were drilled with corridors of tansy leaf

(Phacelia tanacetifolia) every 20 to 30 Sowing diverse flowering rows, destruction of bean aphids by plants, such as tansy leaf syrphids intensified. Similarly, strips and buckwheat mto strips that cut of buckwheat and tansy leaf in Swiss ^ffi1? ^ 16S, to 3?°_fet cabbage fields increased populations of a small parasitic wasp that attacks the cabbage aphid. Because of its long summer flowering period, tansy leaf has also been used as a pollen source to boost syrphid populations in cereal fields.

For more extended effects, plant corridors with longer-flowering shrubs. In northern California, researchers connected a riparian forest with the center of a large monoculture vineyard using a vegetational corridor of 60 plant species. This corridor, which included many woody and herbaceous

Miguel Altieri, Univ. of Calif.

(50-100 m) can provide natural enemies with highways of habitat.

Miguel Altieri, Univ. of Calif.

A corridor of Alyssum acts as a highway of habitat drawing beneficial insects into this large field of lettuce.

CAUTION!T

The plants you choose must provide food resources early in the season so that populations of beneficials can build before pests colonize fields. Also, make sure these plants don't harbor viruses or other diseases or high densities of insect pests.

perennials, bloomed throughout the growing season, furnishing natural enemies with a constant supply of alternative foods and breaking their strict dependence on grape-eating pests. A complex of predators entered the vineyard sooner, circulating continuously and thoroughly through the vines. The subsequent food-chain interactions enriched populations of natural enemies and curbed numbers of leafhoppers and thrips. These impacts were measured on vines as far as 100 to 150 feet (30-45 m) from the corridor.

BEETLE BANKS

boost beneficials

Jack Kelly Clark, Univ of Calif

Jack Kelly Clark, Univ of Calif

Predaceous ground beetles feed mainly on caterpillars and other insect larvae.

Some grass species can be important for natural enemies. For example, they can provide temperature-moderating overwintering habitats for predaceous ground beetles. In England, researchers established "beetle banks" by sowing earth ridges with orchard grass at the centers of cereal fields. Recreating the qualities of field boundaries that favor high densities of overwintering predators, these banks particularly boosted populations of two ground beetles (Demetrias atricapillus and Tachyporus hyp-norum), important cereal aphid predators. A 1994 study found that the natural enemies the beetle banks harbored were so cost-effective in preventing cereal aphid outbreaks that pesticide savings outweighed the labor and seed costs required to establish them. The ridges in this study were 1.3 feet high, 5 feet wide and 950 feet long (0.4 m x 1.5 m x 290 m).

For more information, see"Habitat management to conserve natural enemies of arthropod pests in agriculture" (Resources, p. 104).

When choosing flowering plants to attract beneficial insects, note the size and shape of the blossoms. For most beneficials, including parasitic wasps, the most helpful blossoms are small and relatively open. Plants from the aster, carrot and buckwheat families are especially useful.

Rob Myers, Jefferson Institute

Rob Myers, Jefferson Institute

Buckwheat

(Fagopyrum esculentum)

Select the most appropriate plants. Beneficial insects are attracted to specific plants, so if you are trying to manage a specific pest, choose flowering plants that will attract the right beneficial insect(s). The size and shape of the blossoms dictate which insects will be able to access the flowers' pollen and nectar. For most beneficials, including parasitic wasps, the most helpful blossoms are small and relatively open. Plants from the aster, carrot and buckwheat families are especially useful (Table 1).

Timing is as important to natural enemies as blossom size and shape, so also note when the flower produces pollen and nectar. Many beneficial insects are active only as adults and only for discrete periods during the growing season: They need pollen and nectar during those active times, particularly in the early season when prey is scarce. One of the easiest ways you can help is to provide mixtures of plants with relatively long, overlapping bloom times. Examples of flowering plant mixes might include species from the daisy or sunflower family (Compositae) and from the carrot family (Umbelliferae).

Information about which plants are the most useful sources of pollen, nectar, habitat and other critical needs is far from complete. Clearly, many plants encourage natural enemies, but scientists have much more to learn about which plants are associated with which beneficials and how and when to make desirable plants available to key predators and parasitoids. Because

Buckwheat

(Fagopyrum esculentum)

Peggy Greb, USDA ARS

Peggy Greb, USDA ARS

A cover crop of mustard can be disked into soil as "green manure to act as a natural fumigant for weeds and diseases.

surrounding crops with perimeter fools pests

Nelson Cecarelli of Northford, Conn., who often lost an entire season's cucumber crop to — voracious cucumber beetles, planted squash around his field perimeter, sprayed minimally, and harvested a bounty of cukes in 2003 and 2004. Cecarelli was one of about 30 farmers in New England to adopt a perimeter trap cropping strategy recommended by a University of Connecticut researcher who, with a SARE grant, tested the theory over two seasons - with terrific results. The system, popular among growers, encircles a vulnerable vegetable with a crop that can attract and better withstand pest pressure, reducing the need for pesticides.

"What you're seeking in a trap crop is something that gets up and out of the ground fast with lots of foliage and won't be over-run easily when beetles come into the field," said T. Jude Boucher, Extension Educator and project leader, who recommends a thick-skinned squash called Blue Hubbard. "If we can stop beetles during the seedling stage, we can eliminate most of the damage."

In 2004, nine New England growers, including Randy Blackmer (below), increased yields of cucumbers and summer squash by 18 percent and reduced insecticide use by 96 percent, earning an extra $11,000 each, on average, Boucher said. The research compared a dozen farms using perimeter trap cropping to farms that used the typical regimen of four sprays per year.

Growers planting perimeters applauded the time savings in pest scouting and pesticide spraying, and the improved economics thanks to lower input costs and higher, better-quality yields.

Despite pessimism that the Blue Hubbard squash wouldn't appeal to customers, most participating farmers found that Blue Hubbard resisted beetle damage and sold at their markets. In postproject surveys, farmers said the system not only saved money, but also that planting a perimeter was simpler than applying multiple full-field insecticide sprays.

"We're trying to get away from the 'silver bullet' mentality that you can put on a pesticide and it'll stop your problem," Boucher said. "We're changing the pest populations' dynamics in the field."

Randy Blackmer examines pumpkins planted as a trap crop to draw cucumber beetles away from squash on his Connecticut farm.

T. Jude Boucher, Univ. of Conn.

T. Jude Boucher, Univ. of Conn.

Edward McCain, USDA ARS

Sunflowers in California vineyards draw the leafhopper egg wasp, a parasite of the grape leafhopper.

beneficial interactions are site-specific, geographic location and overall farm management are critical variables. In lieu of universal recommendations, which are impossible to make, you can discover many answers for yourself by investigating the usefulness of alternative flowering plants on your farm. Also consider tapping into informational networks, such as Extension, NRCS and nonprofit organizations. Other farmers make great information sources, too (Resources, p. 104).

Use weeds to attract beneficials. Sometimes, the best flowering plant to attract beneficials is a weed, but this practice complicates management. Although some weeds support insect pests, harbor plant diseases or compete with the cash crop, others supply essential resources to many beneficial insects and contribute to the biodiversity of agroecosystems.

In the last 20 years, researchers have found that outbreaks of certain pests are less likely in weed-diversified cropping systems than in weed-free fields. In some cases, this is because weeds camouflage crops from colonizing pests, making the crops

When using weeds in your biological control program, first define your pest management strategy precisely, then investigate the economic thresholds that weeds should not exceed.

TABLE 1

Flowering Plants That Attract Natural Enemies

PHOTO

COMMON NAME GENUS AND SPECIES LOCATION

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