Thursday, March 6, 2008

Greenhouse - Watch for Aphids

Aphids can explode in the greenhouse and can catch you off-guard. The following is an article on the subject.

Aphids can occur on many greenhouse crops including some of their favorites: million belles, fuchsia, heliotrope, mandevilla, sweet pototo vine, portulaca, ivy geraniums, pansies and many other ornamental crops. It seems like aphids can feed upon almost every greenhouse crop produced. They also feed on many different herbaceous perennials including Alcea, Dianthus, Heuchera, Hibiscus, Monarda, Primula, Saliva, Veronica etc. As greenhouses become more crowded, tender plant growth becomes lush, and plants are beginning to flower, growers report that aphid populations seem to “explode” overnight. Aphids often remain undetected on weeds below greenhouse benches, or hitchhike a ride into the greenhouse on over wintered perennials from a cold frame, or other incoming plant material. By the time you see, winged aphids on the yellow sticky cards, you may already have a serious infestation. Heavy nitrogen fertilization can also promote aphid infestations.

So, rely on regular plant inspection to detect aphids. Look for distorted plant growth (especially when foxglove aphids feed), shiny honeydew and sooty mold. The presence of ants may also alert you to a potential aphid infestation. Aphids, like most other insects and mites, tend to occur in localized “hot spots”. The whitish shed skins (as aphids molt and grow, they shed their exoskeleton, much like a snake shedding its skin) can also alert you to the present of aphids. These shed skins are not whiteflies nor a white type of aphid, but an indication that you need to look on the underside of the leaves for the presence of aphids. In many locations, I am seeing the winged aphids, which are signs of a serious aphid infestation. Most of the aphids found in greenhouses have a wide host range, but they may have certain favored hosts.

Modified from an article in the New England Greenhouse Update. Go to

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