The dozen or more attendees at Penn State Extension’s New Organic Vegetable Producers class — the second class in an ongoing series of five spring and four fall classes offered in the Lehigh Valley — were playing games. In this case, it was a game of “Insect Jeopardy,” designed to insure that they will know if crops are in jeopardy from insect attacks, what to do to prevent pest problems, and how to treat them.
Each class in this series covers a different aspect of organic farming. Classes are offered “a la carte,” and walk-ins are welcomed, both at the in-class and the on-farm workshops.
Tianna Dupont, Sustainable Agricultural Educator, who leads the classes, was determined that these new and aspiring farmers would have the basics of organic pest control within their grasps by the end of the evening.
“Just by looking at the damage, we can figure out what we have,” Dupont said, as the contestants pondered the Jeopardy clues.
Scouting for pests and correctly identifying them, as well as identifying plant damage and correlating it to the correct insect culprits, are a main priority for organic growers. Before any control methods can be implemented, farmers first need to know exactly what they are battling.
Knowing where, when and how to scout properly greatly increases the chances of catching a pest or disease issue before it’s too late. Scouting all parts of the plant — leaves, stems, fruits — and scouting field edges as well as interior rows, observing several plants in each selected area, is important. Ultimately, a dozen or so locations in the crop field should be examined, moving in a random “W” pattern. Visual observation using a hand-held magnifying glass is key to scouting.
Another tool is the sweep net. With this, the net is swung in a full 180 degree arc from side to side, one stroke per step, as the farmer walks the field. The net should be swung low for short plants, and kept just below the top of the crop for taller ones.
Traps are used to attract pests, monitoring their maturity stage and population levels. In pheromone traps, female hormones attract and kill males, limiting reproduction of the existing pest population. Pitfall traps are sunk into the ground, capturing insects as they move in along the soil, and killing them via a solution such as soapy water, both reducing the pest population and monitoring pest levels.
If insects or eggs are not observed, or if there is some concern about proper identification, plant damage gives another important clue to the culprit, Dupont said. Common types of damage include: stippling/speckling; defoliation; leaf mining; tunneling; frass (insect excrement); and plant distortion.
Dupont emphasized that knowing the life cycles and habitat of the common insect pests is imperative to understanding how best to control them. Farmers can utilize a variety of cultural controls to combat pests by making the environment unfriendly.
Many insects over-winter in crops residue. Squash bugs, for example, find winter habitat in their adult form. They like to live in heavy mulch, and will ultimately emerge and lay eggs. Nymphs feed on the crop, causing the plant to wilt. While scouting for the eggs masses is effective, preventing the adults from overwintering is a primary control method.
“If you can’t till it in, at least chop it,” Dupont said of crop residues.
Rotating crops annually, so the emerging insects have to travel to find their preferred crop, is another control method. Potato beetles overwinter as adults, then walk to the crops to lay eggs. They only feed on solanaceous crops, so if the crop is no longer there, they will die. If they do succeed in laying their eggs, however, the larvae will quickly become adults, and these second generation adults can fly up to 1/2 mile seeking food.
Crop rotation alone won’t work. Leaf hoppers come in on air currents from the south. Therefore, the timing of their appearance varies from year to year. The damage they cause is easily confused with late blight. Curling, stunting and burnt looking leaf edges are some signs of these “flying dandruff” pests.
Planting resistant varieties is one way to beat pests. Row covers might help at certain times, excluding the pest from the crop. With the Brassica flea beetle, there is a mid-summer period where the pests are not active. Brassica family crops planted during this window of time won’t be as stressed by the pest.
Soil temperatures of about 55 degrees indicate that pests will be emerging, Dupont said. Knowing this, along with a basic understanding of pest life cycles and habits, can go a long way to preventing problems, or controlling problems before they reach the threshold of economic impact.
“If you are going to have a problem, you really have to start managing it early on,” Dupont said, specifically referring to harlequin bugs, but applicable to controlling pests in general, particularly in organic systems.
Harlequin bugs are finding refuge in Brassica crops, such as tillage radish, grown in fields over the winter. The popularity of winter Brassicas, with many farmers “trying to grow Brassicas all year long,” is another concern. With no host-free periods, these bugs readily multiply.
One method of control is to aggregate the bugs in a trap crop. Planting a trap crop well away from the cash crop can keep the crop bug-free, while also making it easy to eliminate the pest via a backpack vacuum.
“It takes advantage of aggregation,” Dupont said of the contraption. Special high-powered suction vacuums are needed, which are available on the commercial market, or can be crafted from leaf blowers.
Providing crops with a healthy soil and enough water, so they do not become stressed, is a first line of defense against pests. Increasing plant vigor helps to fend off diseases that pests can vector. Succession planting, so that a new crop is available throughout the season, can help alleviate economic concerns of pest damage.
Providing beneficial and predatory insect habitat is another means of decreasing pest pressure. Flowers provide nectar and pollen for beneficial insect food sources, attracting them whether or not the pest is around, and making them available when pests do attack. Undisturbed strips of grass can increase ground predator levels.
In some cases, handpicking insects is just as effective as organic sprays, and “can be economically effective even compared to an organic spray,” Dupont said. But for some pests, “most of our organic farms are spraying.”
Proper use of sprays, and proper spraying technique, is imperative. Organic crop protectants need to be started early, at a lower insect threshold, than conventional sprays. Complete coverage is necessary. Water may need to be buffered for pH level. Nozzles and equipment need to be calibrated properly.
Certain sprays are best for certain pests, and will be ineffectual against others, or during certain life cycle stages. Thus the importance of knowing the pest’s characteristics is the basis for all organic pest control techniques.
“Know your insecticides before using them,” Dupont cautioned. Resistance can develop quickly, and “we don’t want to lose the effectiveness of the product.”