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The Basics of Biologicals
| Dr. Raymond A. Cloyd
>> Published Date: 3/26/2014
It’s important to understand that biological control is a regulatory process. Biological control agents or natural enemies won’t eradicate an insect or mite pest population; the success of natural enemies is based on maintaining insect or mite pest numbers at levels low enough to minimize plant damage. One of the primary reasons why growers are interested in implementing a biological control program is due to pesticide (e.g., insecticide and miticide) resistance, in which the level of efficacy of a given pesticide against insect and/or mite pest populations is less than what was obtained previously. Since spring greenhouse crops, in general, are relatively small, this provides an opportunity to use biological control to regulate populations of the primary insect and mite pests encountered in the greenhouse.

Packets of Amblyseius swirski—predatory mites that feed on several types of prey. 

The advantages of implementing a biological control program are:
1 | Fewer worker and customer exposure risks
2 | Fewer rules and regulations
3 | No phytotoxicity issues (crop safety)
4 | No issues associated with pesticide resistance
5 | Minimal equipment required for application
6 | Minimal cleanup required after application
7 | Specificity (in general)

However, there are some potential disadvantages or issues associated with implementing a biological control program, such as:
1 | Inconsistent regulation
2 | Inconsistent availability of natural enemies
3 | Specificity (problem when dealing with multiple insect and mite pests)
4 | Cost of the product (including shipping)
5 | Short shelf life
6 | Quality-control issues affiliated with natural enemies

When using biological control, it’s important to:
1 | Know the availability of biological control agents or natural enemies from suppliers or distributors
2 | Understand the biology, life cycle and behavior of insect and mite pests within spring greenhouse cropping systems (plant material)
3 | Scout crops regularly and order biological control agents early
4 | Conduct yearly follow-up assessments to determine successes and failures

The first item that needs to be considered before attempting biological control is the establishment of a reliable scouting program. Furthermore, in order to be successful in implementing a biological control program, it’s essential to:
1 | Determine and correctly identify all primary insect and mite pests (e.g., aphids, thrips, whiteflies and fungus gnats)
2 | Identify available natural enemies for specific insect and mite pests
3 | Establish relationships with “reliable” suppliers/distributors of biological control agents
4 | Minimize pesticide residues
5 | Start with a “clean” greenhouse by removing weeds and plant debris from both inside and outside the greenhouse
6 | Order biological control agents early (at least two weeks prior to release)
7 | Assess the quality of natural enemies (make sure they’re alive)
8 | Release natural enemies immediately upon arrival
9 | Apply natural enemies in the early morning or early evening
10 | Introduce or release natural enemies before insect and/or mite pest populations are “high” or reach outbreak proportions
11 | Apply natural enemies at the recommended release rates
12 | Evaluate the performance of natural enemies throughout the growing season

Natural enemies can be placed into two distinct categories: specialist or generalist. Specialist natural enemies feed on only one insect or mite host (prey) or particular life stage (egg, larva or adult) of the host. Generalist natural enemies feed on a variety of insect or mite hosts (prey) and also tend to feed on different life stages (egg, larva, nymph and/or adult) of a particular host. The primary natural enemies that are commercially available for use on spring crops are parasitoids, predators and entomopathogenic (beneficial) nematodes.

The characteristics of parasitoids include:
1 | Kills host living off of the plant
2 | Free-living in the adult stage with the immature either inside (endoparasitoid) or outside (ectoparasitoid) of the host
3 | Kills host slowly, but may reduce host fitness and reproduction
4 | Kills one host with a single host needed to develop to an adult; however, an individual female may be capable of laying more than 100 eggs
5 | Specific with regards to insect species and particular life stage attacked

The characteristics of predators are:

1 | Kills more than one host
2 | All stages are free-living
3 | Kills or consumes prey quickly
4 | In general, both the immature and adult are predacious
5 | Eats a diversity of host-prey types, although this depends on the specific predator

Entomopathogenic or beneficial nematodes are microscopic roundworms that usually enter the larval stage of insects through natural openings such as the mouth, anus or breathing pores (spiracles). Once inside the larva, the beneficial nematode releases a bacterium that attacks the mid-gut by producing protein-destroying enzymes that results in septicemia within 24 to 48 hours. Since beneficial nematodes require moisture for survival, they’re primarily used against fungus gnat larvae residing in the growing medium.

In conclusion, in order to be successful when using biological control, it’s essential to understand the basics and continually evaluate the effectiveness of biological control programs. If you have any questions regarding the use of biological control, contact your extension office or statewide entomologist. GT

Dr. Raymond A. Cloyd is Professor and Extension Specialist in Horticultural Entomology/Integrated Pest Management in the Department of Entomology at Kansas State University in Manhattan, Kansas. He can be reached at (785) 532-4750 or rcloyd@ksu.edu.

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