Greenhouse Update - July 15, 2005
Leanne Pundt, Extension Educator, University of Connecticut
Due to the hot, humid weather, populations of thrips, mites and other pests remain high. Leaf spot diseases, powdery mildew, and downy mildew are occurring on various herbaceous perennials.
Two spotted spider mite damage can go undetected on waxy-leaved plants such as elephant ear and banana until outbreaks occur. Mites may be active on the underside of the leaves, but you don't see their damage until high populations develop. Due to the water repellant nature of the leaves, it may be helpful to apply a spreader-sticker to your sprays to help improve coverage. (Read the pesticide label carefully to make sure that there are no precautions against adding spreader stickers to the particular miticide you select). See previous updates for more information.
Thrips Damage on Garden Mums -- Look for distortion and scarring on the leaves. (See photo). Some varieties may be more susceptible than others. Tap foliage over a sheet of white paper to look for the adult thrips and larvae.
Premature Budding on Garden Mums
Garden mums are very reproductive and will set buds during short days. But, as growers know, garden mums can also set bud under long days. Anything that checks a cutting's growth may push the mums into bud. To prevent garden mum cuttings from becoming prematurely budded, keep them actively growing. Provide optimum moisture and fertility levels. In Connecticut, cool nights often occur in June. With several cool nights in a row, garden mums can initiate many buds prematurely. Pinch off these buds, and supply adequate moisture and fertilizer to keep plants growing.
Unusual Insect on Rudbeckia
The Home and Garden Center at UConn received samples of Rudbeckia (Black-eyed Susan) with leaf spots resembling a disease. However, the leaves were infested with a scale-like insect which was the nymphal stage of a bizarre type of psyllid (Bactericera antennata).
The nymphs feed by inserting their needle-like mouthparts into lower surfaces of the leaf and sucking plant fluids. In response to their feeding, a shallow but distinct depression develops on lower leaf surface. Purplish- to- black spots about ½ to 1 inch in diameter developed. The veins may also turn purple over much of the lower leaf surface. (See photo).
The mature nymphs are about 1/8 inch long, flattened and very colorful with a light green abdomen, red-orange head and thorax, and white wing pads. The eyes are large and the nymph is completely fringed in white hairs (See photo). The adult is very small and has two pairs of transparent wings and red eyes. The body is mostly black (See photo).
 Psyllid nymph (Bactericera antennata) Photo by Robert Durgy, Horticultural Diagnostician, University of Connecticut. Click for a larger image. |
 Psyllid damage (Bactericera antennata) on Rudbeckia Photo by Robert Durgy, Horticultural Diagnostician, University of Connecticut. Click for a larger image. |
 Psyllid adult (Bactericera antennata) Photo by Robert Durgy, Horticultural Diagnostician, University of Connecticut. Click for a larger image. |
This insect has been reported in Michigan, Ohio and New York (Long Island) in previous seasons. For more information see: http://www.ipm.msu.edu/CAT02_land/L07-12-02.htm#9
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.
| Topics posted July 2005 |
| July 1--Slugs |
| July 5 -- Daylily Rust |
| July 15 -- Anthracnose on Sedum |
| July 15 -- Angular Leaf Spot on Zinnia |
| GREENHOUSE IPM COORDINATOR (commercial interests and growers) |
LEANNE PUNDT | 860-626-6240 |
| . | . | . |
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HOME GREENHOUSE QUESTIONS |
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