Greenhouse Update - June 22, 2006
Leanne Pundt, Extension Educator, University of Connecticut
The warmer, summer temperatures have lead to increases in insect and mite populations, especially in enclosed greenhouses without rollup sides that to help moderate temperatures.
Two-spotted spider mite damage may first begin as a faint discoloration or yellowing on the leaves that resembles a nutrient deficiency. (See photo.) If you assume this is the case, and then apply additional fertilizer, the resultant lush growth may actually encourage two-spotted spider mite development. If you see what looks like nutrient deficiency, take a quick look on the underside of the leaves for the various stages of the two-spotted mites (eggs, larvae, nymphs or adults) as well as their empty, whitish egg cases. A 10 to 20x hand lens may be helpful to see the mites or their eggs.
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Spider mite feeding
damage on dahlia |
Look for mites and their damage in hot, dry areas of the greenhouse and on their favorite hosts such as dahlia, numerous herbs, thunbergia, roses, brugmansia, New England Aster, as well as many others. As temperatures increase, spider development increases so that they can complete a generation in as little as 7 to 14 days at 86oF. If quick knockdown is needed, Floramite, Pylon or Avid may be some options for management. Repeated applications may be needed, especially if the miticides you select are not effective against the egg stage. Follow-up evaluations are needed to see if the spider mites have been killed, for mite populations develop resistant to miticides very quickly. For example, mite populations in nearby Long Island have developed resistance to Avid. You will also want to check to see if repeated applications are needed after the mite eggs have hatched.
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Mite feeding on
thungergia. |
Thrips populations have been increasing with the warmer temperatures. Look for thrips feeding deep within the blossoms or on the foliage of susceptible plants such as dahlia, verbena, superpetunia, herbs, zinnia etc. Repeated applications are often needed to reduce populations. Depending upon the temperatures, two to three applications are 5-day intervals may be needed.
Hibiscus Sawflies have been feeding upon hibiscus, especially Hibiscus moscheutos or Rose mallow in outdoor gardens and in container production. Larvae are yellowish-green with a dark head and are less than 3/8 of an inch long when mature. They also have 6 pairs of short fleshy prolegs on their underside.
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Hibiscus sawflies and
their feeding damage. |
The thick-waisted adults, relatives of bees and wasps, lay their eggs in the edges of leaves. Early instar larvae feed on the underside of leaves, so are easily overlooked. Older larvae feed on both the upper and lower leaves, leaving just the leaf veins, resulting in a lacy appearance. (See photo.) Multiple generations may occur in the Northeast.
Conserve, Azatin or Ornazin, Orthene, M-Pede or Insecticidal Soap are some of the materials labeled for use against sawflies on ornamentals. Consult and follow insecticide labels for registered uses. Some materials are labeled for greenhouse use only, some for outdoor nursery use. To avoid any potential phytotoxicity problems, spot test first before widespread use.
If you would like to receive an email notice when new greenhouse updates are posted on the website, please email me at: leanne.pundt@uconn.edu . This will be an undisclosed list, and your email address will remain private.
| New England Greenhouse Update now online. University Extension Specialists in New England, in conjunction with USDA's Northeast Sustainable Agriculture Research and Education, contribute information to this new website. Timely updates are provided for commercial growers of greenhouse crops and flowers in Massachusetts, Connecticut and Rhode Island. You can use this additional resource for more information about current observations and recommendations on environmentally safe production practices. |
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GREENHOUSE IPM COORDINATOR (commercial interests and growers) |
LEANNE PUNDT | 860-626-6240 |
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HOME GREENHOUSE
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Information on our site 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.
