New Insect Growth Regulator for Whitefly Available

PyriGro is a new microencapsulated insect growth regulator now available to greenhouse growers. It is labeled for use on bedding plants (impatiens, marigolds, petunias, geraniums, garden mums, verbena, New Guinea impatiens, and dahlia); cut flowers (roses, chrysanthemums, snapdragons and orchids); flowering hanging baskets (fuchsia and lantana); and foliage plants (dracaena, ficus and philodendron). The active ingredient in PyriGro is pyriproxyfen which is a juvenile hormone mimic. This insect growth regulator affects the insects hormonal balance suppressing the development of eggs, metamorphosis, and adult formation. PyriGro has long residual control and is especially effective on young whitefly nymphs and eggs. It is effective against both silverleaf and greenhouse whiteflies.

Adult emergence is inhibited when the immature crawlers (nymphs) are exposed to this insecticide. The immature whitefly nymphs are not able to complete their development and emerge as adults. Little or no direct adult kill should be expected after a treatment with PyriGro. However, you may tank mix pyriproxyfen with an approved adulticide.

Pyriproxfen has strong translaminar activity which means that when the upper surfaces of leaves are treated, the chemical will affect the immature whiteflies found on the underside of leaves. (Growers are familiar with the miticide abamectin (Avid) that also has strong translaminar activity).

Silverleaf whitefly is also a serious problem on cotton. In Arizona, researchers investigated the impact of two insect growth regulators, buprofezin (still to be given a trade name by Scotts) and pyriproxyfen on the activity of whitefly natural enemies. When both of these insect growth regulators were used, populations of natural enemies were conserved, compared to when conventional insecticides were applied. Researchers have also found that pyriproxyfen is compatible with the parasitoids used in biological control programs for whitefly on poinsettia. PyriGro has a relatively low mammalian toxicity and a reentry interval of 12 hours. It can be a part of your rotation scheme against whitefly that includes insecticides with different modes of action. To optimize resistance management programs, the label states that applications should be made no more than two times per cropping cycle or per six month period. In 1996, resistance to pyriproxyfen was documented in sweet potato populations in cotton in Israel.

Editors note: Pyriproxyfen is also the active ingredient in a product by Valent to be called "Distance" that has not yet been registered in Connecticut at the time of publication

More information on greenhouse whiteflies:

  • Greenhouse whitefly pictures
  • Managing Whiteflies in the Greenhouse

    • By Leanne Pundt, Extension Educator, Commercial Horticulture, University of Connecticut

    Originally published in Connecticut Greenhouse Newsletter. September/October 1998, Issue 206

    References.

    DeCock, A.; I. Ishaaya, M. Van De Veire and D. Degheele. 1995. Response of buprofezin-susceptible and resistant strains of Trialeurodes vaporiorum (Homoptera: Aleyrodidae) to pyriproxyfen and diafenthiuron. Journal of Economic Entomology 88(4):763-767.

    Ishaaya, I; A. DeCock and D. Degheele. 1994. Pyriproxyfen, a potent suppressor of egg hatch and adult formation of the greenhouse whitefly (Homoptera: Aleyrodidae). Journal of Economic Entomology 87(5)1185-1189.

    Naranjo, S. and J. Hagler. 1997. Bemisia growth regulators: conservation of Natural Enemies? Agricultural Research Service. Tektran. USDA Report No. 0000081107. 1 pp.

    Sanderson, J.P. 1998.Weapons against whitefly. GrowerTalks. Sept. 1998. 94-96.

    Whitmire MicroGen. 1998. PyriGro Microencapsulated Insect Growth Regulator Supplemental Label. Whitmire MicroGenResearchLaboratories, Inc.St. Louis, MO.63122.

    This information was developed for conditions in the Northeast. Use in other geographical areas may be inappropriate.

    The information in this material is for educational purposes. The recommendations contained are based on the best available knowledge at the time of printing. Any reference to commercial products, trade or brand names is for information only, and no endorsement or approval is intended. The Cooperative Extension system does not guarantee or warrant the standard of any product referenced or imply approval of the product to the exclusion of others which also may be available.All agrochemicals/pesticides listed are registered for suggested uses in accordance with federal and Connecticut state laws and regulations as of the date of printing. If the information does not agree with current labeling, follow the label instructions. The label is the law.Warning! Agrochemicals/pesticides are dangerous. Read and follow all instructions and safety precautions on labels. Carefully handle and store agrochemicals/pesticides in originally labeled containers immediately in a safe manner and place. Contact the Connecticut Department of Environmental Protection for current regulations.The user of this information assumes all risks for personal injury or property damage.Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Kirklyn M. Kerr, Director, Cooperative Extension System, The University of Connecticut, Storrs. The Connecticut Cooperative Extension System offers its programs to persons regardless of race, color, national origin, sex, age or disability and is an equal opportunity employer.

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