Greenhouse Update - April 3, 2006
Leanne Pundt, Extension Educator, University of Connecticut
Aphids – continue to appear on their favorite hosts such as pansies, ipomoea, calibrachoa, gerbera daisy etc. Rely on plant inspections to detect aphids. Yellow sticky cards will only detect winged aphids – which may be migrating over from an infestation either inside or outside the greenhouse.
Avoid high nitrogen fertilizer that promotes lush growth that is favorable to aphids. The neonictonioids (Tristar, Flagship (spray), Safari (drench), or Marathon) or Endeavor has been working well for many growers. If only a few plants are infested, a forceful jet of water helps clean up infestations.
Two-spotted spider mites – isolated hot spots of mites are appearing on incoming plants, plants held over from last year, or on young plants propagated from stock plants that were held over. I’ve seen mites on scalevola, Brugmansia, thunbergia, New Guinea impatiens, and mandevilla when visiting growers. Keep a close eye on hanging baskets – especially hangers placed in hot, dry areas of your greenhouse. A 16 to 20x hand lens may be needed to see the small eggs and nymphs. Many different miticides are available including those with translaminar activity such as Avid, Judo (do not use on geraniums, ivy and impatiens), TetraSan and Pylon. There are also many different contact miticides including Floramite, Ultra fine oil, or Synergy Super Fine Spray Oil Emulsion, Akari, Sanmite (to name a few) that may also work well provided you can obtain good coverage to the underside of the leaves.
Thrips – the warmer temperatures and increasing number of plants are in flower has resulted in more thrips being detected on ivy geraniums, brugsmania, alcea, ipomoea, and verbena to name a few.
Do not rely on chemical controls alone. Cultural methods to reduce thrips include – rigorous weed control, removing flowers from plants (if practible), and tossing out heavily infested plants. Some insecticides to suppress thrips include: Botanigard, Ornazin, Pedestal, and Enstar. Save Conserve until you really need it – when plants are in flower, and populations are high. Long rotations of 2 to 3 weeks are preferred over shorter rotations (if the label permits it).
Bittercress – is now flowering. Rogue out bittercress now before it sets seed. Bittercress seed can be expelled up to 9 feet from the plant! Seeds germinate in cool, moist soils. This weed is a favorite of aphids (some growers nickname it the “aphid weed”). There are no pre-emergence weeds registered for us in enclosed structures such as greenhouses because of the potential for severe crop injury.
Liverworts -thrive in conditions of high fertility, moisture and high humidity and require moister conditions than mosses. Inspect incoming plants for signs of liverworts and isolate infected plants.
Avoid overwatering crops and water according to plant need. Use of coarse textured mulch helps reduce surface moisture levels. Topdressing slow release fertilizers contribute to increased fertility levels on the media surface and to the growth of liverworts. Proper plant spacing helps to reduce humidity levels. Liverworts lack true roots, so allowing the media to dry between watering, helps reduce their vigor.
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Previous 2006 UConn IPM Greenhouse Updates
|March 27, 2006|
|March 20, 2006|
|March 3, 2006|
|February 25, 2006|
|February 17, 2006|
|January 31, 2006|
|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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