by Katie Navarra
“Biological control programs use living organisms that are natural enemies of insects to control pests and diseases,” said Leanne Pundt, Extension Educator for University of Connecticut at the Litchfield County Extension Center.
“They do not act as quickly as pesticides, so cannot be used as a rescue treatment. Natural enemies are best used preventatively, early in the cropping cycle, when plants are small, pest numbers are low and pest damage has not yet occurred,” she added.
Biological controls also reduce worker exposure to pesticide and pesticide residues, limits spray damage, requires limited equipment for application and improves plant quality. Integrating biological controls also lengthens the lifespan of effective pesticides used in greenhouses by reducing opportunity for the development of resistance.
During the annual Bedding Plant/Nurseryman’s Education Day and Tradeshow held on March 9, Pundt shared strategies for culturally and biologically controlling pests common to herb and vegetable bedding plants.
Controlling common pests in these plant groups begins with proper growing conditions. Sanitation, water management and irrigation are considered cultural controls that can be used to manipulate the pest’s biological and physical environment making it more difficult for the pest to survive.
In herb bedding plants cultural controls also include well drained growing media that is aerated and maintained at drier levels than growing media for most other plants. Routine clear watering and proper spacing between each plant is also important to lowering pest populations.
For vegetable bedding, proper temperatures and recommended spacing increments are essential. “Keep vegetable bedding plants separate from ornamentals and provide a gradual hardening off period with gradual exposure to outdoor growing conditions and reduced watering,” she said.
In addition to sound greenhouse management practices, a pest management plan is necessary to manage insect populations common to herb and vegetable bedding plants. Yellow sticky cards placed throughout the greenhouse catch and allow for identification of pests and population density.
Proper identification of insects is critical. “Yellow sticky cards may also catch beneficial insects,” Pundt said. A hand lens or magnifying visor enlarges pests for easier identification. “If you’re unsure what pests are in your greenhouse ask a local extension agent for help,” she added, “resources are also available at www.ipm.uconn.edu .”
Getting started with biological controls
Using biological controls to manage pests takes commitment. It requires working with a supplier that will quickly and thoroughly answer any questions that arise. Using biocontrol requires gathering, tracking and reading a lot of information. But smartphone apps like the Pocket IPM: Greenhouse Scout, can assist with pest ID and biology, visual records of greenhouse pest populations and more.
Since it’s likely you’re growing more than herb and vegetable bedding plants, it’s important to be aware of the side effects traditional chemicals can have on biological controls. BASF maintains a database at http://betterplants.basf.us . A cell phone app is available from Biobest at www.biobest.be and Koppert Biological Systems (www.koppert.com) can also provide needed information.
Before diving in to biological controls learn the most common pests to herb and vegetable bedding plant crops and the beneficial insects that can naturally control those populations.
Common pests on edible crops
Chances are if you’ve grown herbs or vegetables before, you’re aware of the numerous pests that thrive on these bedding plants. An overview of the most common pests and their preferred habitats will prepare you for the biological controls that can be used to counteract them.
Fungus gnats are a common greenhouse pest that thrive in moist environments and have a broad host range. “Eliminate puddling around the greenhouse and keep the areas under benches dry,” Pundt suggested. Fungus gnats are attracted to young, open media and feed on young cuttings or plugs causing root injury or death. “Grow on the dry side if you can,” she suggested.
While shore flies don’t feed on plants, they carry disease and leave droppings on plant leaves. “It’s important to manage algae to control shore flies,” she said, “open up houses for better airflow to limit the growth of algae.”
Thrips are very small pests feed on plants ranging from eggplant and tomatoes to peppers and leafy greens. “They love tarragon. If you’re growing that herb watch out,” she warned. Thrips carry diseases like INSV and TSWV that affect fruit production. “There is no cure. Once a plant is affected by the virus it has to be thrown out,” she noted. A testing kit is available from suppliers. The kit tests plants and insects for disease. Weeds like chickweed have been found to be carriers of thrips and the viruses they spread. With few chemical options available to treat thrips, biologicals are the best option.
Cabbageworms, diamondback moths and the cross strip cabbageworms are all members of the caterpillar family attracted to fall transplants, specifically kale and cabbage. “Look for eggs and young caterpillars,” she said. Since these caterpillars tend to feed on the underside of the leaves, start scouting by lifting and inspecting the underside of first the outside, lowest or oldest leaves and moving toward the younger or center leaves or head, until all the leaves have been checked.
Herbs and sweet potato vines are the favorite host of Spider Mites, a difficult pest to control. “When the females overwinter they don’t give off cues to predators,” she said. Examine edge boards for clusters of spider mites, which are bright orange in color.
A wide range of Aphids are among the most destructive insects. Greenhouses raising herbs and vegetable bedding plants are likely to see Green Peach Aphids, Melon Aphids and Foxglvoe Aphids. These insects are likely to be found on the underside of leaves.
Biological controls for common pests will be discussed in an upcoming issue of Country Folks.