James Quinn
Horticulture Extension Specialist

David Trinklein
Division of Plant Sciences

Raymond A. Cloyd
Ornamental Entomology/Integrated Pest Management
Kansas State University

For more than 30 years the U.S. Department of Agriculture has promoted integrated pest management (IPM) as a way of dealing with arthropod (insect and mite) pests in greenhouses and herbaceous nurseries. IPM strategies include the use of cultural, biological and physical (or mechanical) methods as well as pesticides to manage pests. IPM relies on routine inspection, scouting and monitoring of arthropod populations followed by the use of insecticides or miticides only when pest populations are capable of causing plant damage. If the use of these pesticides is warranted, then it is important to choose those products that are less harmful to the environment and to beneficial insects and mites (Figure 1).

This publication is designed to assist greenhouse and nursery managers in selecting the appropriate pesticides to control or regulate the multitude of arthropod pests encountered in greenhouses and nurseries. The primary arthropod pests encountered in greenhouses and herbaceous nurseries in both Missouri and Kansas are aphids, thrips, fungus gnats, shore flies, spider mites, mealybugs, plant bugs, whiteflies, leafhoppers, leafminers, leaf-feeding beetles and caterpillars.

Figure 1
Ladybird beetles, known for their appetite for aphids, occur naturally in Missouri but also can be introduced as biocontrol agents in greenhouses and nurseries.
 

Alternative or "reduced-risk" pesticides

Use of pesticides has changed dramatically since 1985. Before that time, pesticides in three chemical classes — organophosphates, carbamates and chlorinated hydrocarbons — were relied upon to manage plant-feeding insects and mites. Use of materials in these older chemical classes was reduced somewhat with the availability of products in a fourth chemical class, pyrethroids. Since 1985, the Environmental Protection Agency (EPA) has reevaluated the registration of older pesticides and has encouraged the development of alternative pesticides that reduce risk to human health, toxicity to nontarget organisms, and the potential for groundwater contamination. These materials are preferred for use in greenhouses and herbaceous nurseries because they are

• Less persistent (shorter residual activity) in the environment
• Less directly harmful to natural enemies, including parasitoids and predators
• Effective in controlling arthropod pests at reduced application rates when compared with other pesticides

In 1993, the EPA defined alternative or “reduced-risk” pesticides as those that present less risk to human health and the environment than conventional alternatives. Although EPA does not permit manufacturers to use the term “reduced-risk” on product labels, the term is commonly used in promotional and marketing materials. In addition to chemical pesticides, some reduced-risk pesticides contain microorganisms. Examples include spinosad (Conserve), abamectin (Avid), Bacillus thuringienisis spp. kurstaki (Dipel), and Bacillus thuringiensis spp. israelensis (Gnatrol). Pesticides derived from plants, often called botanicals or plant-derived essential oils, are also available for use in greenhouses and herbaceous nurseries. Examples are the clarified hydrophobic extract from neem seed (Triact) and the product GC-Mite, which contains cottonseed, clove and garlic oil.

Tables 1 and 3 list pesticides registered for use in greenhouses and herbaceous nurseries. Table 2 lists those specifically designated for use in organic cropping systems. More information on the Conventional Reduced Risk Pesticide Program is available online at https://www.epa.gov/pesticide-registration/conventional-reduced-risk-pesticide-program.

New pesticides are generally registered more rapidly for use on ornamental plants than on food crops because they are not edible and do not require extensive food safety testing. However, registration for greenhouse-grown vegetables is usually delayed or may not occur. This may be confusing especially with regard to vegetable bedding plants. Several of the pesticides listed in Table 1 may be used on vegetable bedding plants. However, it is critical to read the label to obtain this information. Higher infestation levels of arthropod pests are more tolerable in vegetable production systems than in ornamental crops because plants such as tomatoes and cucumbers are primarily grown for fruit production, and may even be saleable if the plants exhibit damage from insect or mite pest feeding. Overall, it is important to read the product label before applying any pesticide to make sure that the insect or mite pests as well as the treatment site are designated.
 

Biological control

Biological control agents, or natural enemies such as parasitoids and predators, can be purchased from commercial suppliers or distributors and released into greenhouses. This practice is referred to as augmentative biological control, for which there are two control strategies: inoculation and inundation. Inoculation consists of releasing small numbers of natural enemies early in the growing season or cropping cycle so that a population of natural enemies will establish and reproduce in the greenhouse, providing long-term control. Inundation is the introduction of much larger numbers of natural enemies into a greenhouse to provide control in the short term. Additional releases may be required during the growing season or cropping cycle to keep arthropod pest populations at low levels.

Consult biological control suppliers and distributors for additional information on the use of natural enemies in greenhouses and herbaceous nurseries. Biological control programs tend to be more effective when crops are grown for extended periods (e.g., cut flowers and vegetables) and when environmental conditions (e.g., temperature and relative humidity) are constant. Preventive releases of natural enemies are more efficient and easier in a monoculture (e.g., single crop) cropping system when there is only one arthropod pest than in a polyculture (e.g., multiple crops) cropping systems where there may be more than three different arthropod pests. For example, in the production of spring bedding plants, various insect pests may be present simultaneously, including aphids, thrips, whiteflies and fungus gnats.

The greenhouse environment does not contain the abundance and diversity of natural enemies found in outdoor settings or nurseries. This is mainly because of the extensive use of pesticides and because natural enemies typically do not migrate into greenhouses. The survival of natural enemies in a greenhouse is influenced by the abundance and types of prey that are present. However, certain parasitoids and predators sometimes occur naturally in greenhouses. For example, parasitoids in the genus Aphidius, which prey upon many different types of aphids, can inadvertently enter greenhouses through doors, vents or sidewalls. Adult females lay eggs into aphids, and these eggs hatch into larvae that consume the internal organs of the aphids, leaving only their hardened, brown exteriors, or “aphid mummies” (Figure 2). Eventually, a new adult parasitoid creates an exit hole and emerges from the dead aphid. Minute pirate bugs, Orius spp., are predatory anthocorid bugs that feed on thrips. These black and white bugs may also enter greenhouses through openings, particularly when weeds and field crops start desiccating.

Natural enemies that may be present in outdoor nurseries include ladybird beetles, green lacewings, ground beetles, soldier beetles, assassin/ambush bugs, damsel bugs, hover (syrphid) flies, tachinid flies, predatory mites and spiders.
 

Figure 2
The Aphidius wasp, left, stings the aphid and lays an egg in the aphid's body, which mummifies, right, as the egg develops.

Marion Herbert, Alberta Research Station, Vegreville, photo
 

Table 1
Pesticides (insecticides and miticides) registered for use on ornamental plants or greenhouse-grown vegetables. (Always read the label to determine if a pesticide can be used in a particular facility and on a specific crop.)

Note
Numbers and letters in brackets [xx] indicate the IRAC (Insecticide Resistance Action Committee) mode of action designation found on the label.

Table 2
Pesticides (insecticides and miticides) registered for use in organic production systems (ornamental plants, vegetables and herbs).

Common name or active ingredient (Trade name)	Class	Mode of action	Reentry interval	Labeled pests
azadirachtin (Azatrol/Neemix)	Botanical (insect growth regulator)	Ecdysone antagonist [18B]	4/12 hours	aphids, fungus gnat larvae, thrips, whiteflies, caterpillars
Bacillus thuringiensis spp. israelensis (Gnatrol)	Microbial	Midgut membrane disruptor [11A1]	4 hours	fungus gnat larvae
Bacillus thuringiensis spp. kurstaki (Dipel)	Microbial	Midgut membrane disruptor [11B2]	4 hours	caterpillars
clarified hydrophobic extract of neem oil (Triact)	Botanical	Suffocation or membrane disruptor	12 hours	aphids, whiteflies, spider mites, scales
horticultural oils: petroleum oils (PureSpray Green), plant-based oils (GC-Mite/Golden Pest Spray Oil), fish-based oils (Organocide)	Refined petroleum distillate and botanical	Suffocation or membrane disruptor (some products have multiple modes of action; refer to label).	4 hours	aphids, mealybugs, scales, spider mites, whiteflies
kaolin clay (Surround)	Protectant	Multiple modes of action (refer to label)	4 hours	caterpillars, beetles, tarnished plant bug, stink bug, thrips
potassium salts of fatty acids (insecticidal soap/M-Pede)	Insecticidal soap	Desiccation or membrane disruptor	12 hours	aphids, caterpillars, fungus gnat adults, leafhoppers, mealybugs, scales, spider mites, whiteflies
pyrethrin (Pyganic)	Botanical	Sodium channel blocker [3]	12 hours	aphids, caterpillars, beetles, mealybugs, thrips, whiteflies
spinosad (Entrust)	Spinosyn	Nicotinic acetylcholine receptor agonist and GABA chloride channel activator [5]	4 hours	caterpillars, thrips, leafminers

Note
Numbers and letters in brackets [xx] indicate the IRAC (Insecticide Resistance Action Committee) mode of action designation found on the label.

More information about the National Organic Program, online at http://usda.gov/wps/portal/!ut/_s.7_0_A/7_0_1OB?navid=ORGANIC_CERTIFICATIO&navtype=RT&parentnav=AGRICULTURE

Biological control suppliers

Sources of biological control agents are listed in the publication Suppliers of Beneficial Organisms in North America by Charles Hunter, which is available from the California Environmental Protection Agency (CEPA) online at http://cdpr.ca.gov/docs/pestmgt/ipminov/bensuppl.htm or from reputable suppliers.

Be sure to consult your biological control supplier to determine the availability and shipping requirements for the natural enemy species you are interested in.

• Green Spot
  93 Priest Road
  Nottingham, N.H. 03290-6204
  603-942-8925
  greenmethods.com
  info@greenmethods.com
• IPM Laboratories
  P.O. Box 300
  Locke, N.Y. 13092-0300
  315-497-2063
  ipmlabs.com
  ipminfo@Ipmlabs.com
• Koppert Inc.
  Romulus, Mich.
  734-641-3763
  info@koppertline.com
• Syngenta Bioline
  Oxnard, Calif.
  805-986-8255
  info@syngentabioline.com
• BioBest Biological Systems
  biobest.be
  info@biobest.ca

Table 3
Common greenhouse and nursery pests and pesticides registered for their control. (Always read the label to determine if a pesticide can be used in a particular facility and on a specific crop.)

Further information

• Albajes, R., M. L. Gullino, J. C. van Lenteren, and Y. Elad (eds.). 1999. Integrated pest and disease management in greenhouse crops. Kluwer Academic Publishers, Netherlands.
• Bennett, K. C (ed.). 2009. Pest management guide for the production and maintenance of herbaceous perennials. Cornell University, Cooperative Extension, Ithaca, N.Y.
• Cloyd, R. A. 2007. Plant protection: Managing greenhouse insect and mite pests. Ball Publishing, Batavia, Ill.
• Dreistadt, S. H. 2001. Integrated pest management for floriculture and nurseries. University of California, Statewide Integrated Pest Management Project, Division of Agriculture and Natural Resources, Publication 3402. Oakland, Calif.
• Gill, S., R. A. Cloyd, J. R. Baker, D. L. Clement, and E. Dutky. 2006. Pests and diseases of herbaceous perennials: The biological approach. Ball Publishing, Batavia, Ill.
• Gill, S., and J. Sanderson. 1998. Ball identification guide to greenhouse pests and beneficials. Ball Publishing, Batavia, Ill.
• Heinz, K. M., R. G. Van Driesche, and M. P. Parrella (eds.). 2004. Biocontrol in protected culture. Ball Publishing, Batavia, Ill.
• Helyer, N., K. Brown, and N. D. Cattlin. 2003. A color handbook of biological control in plant protection. Timber Press, Portland, Ore.
• Hofer, S. E., and D. H. Headrick. 2001. The bug cards: Greenhouse beneficials. Ball Publishing, Batavia, Ill.
• Krischik, V., and J. Davidson (eds.). 2004. IPM (integrated pest management) of Midwest landscapes. Cooperative Project of NCR-193, North Central Committee on Landscape IPM, Minnesota Agricultural Experiment Station SB-07645.
• Lindquist, R. K., and R. A. Cloyd. 2005. Identification of insects and related pests of horticultural plants. Ohio Floriculture Association Services, Inc., Columbus, Ohio.
• Rice Mahr, S. E., R. A. Cloyd, D. L. Mahr, and C. S. Sadof. 2001. Biological control of insects and other pests of greenhouse crops. North Central Regional Publication 581. Cooperative Extension of the University of Wisconsin, Madison, Wis.
• Thomas, C. 2005. Greenhouse IPM with an emphasis on biocontrols. Publication AGRS-96. Pennsylvania Integrated Pest Management Program, Pennsylvania Department of Agriculture, Pennsylvania State University, University Park, Pa.