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Controlling Aphids by Paul Pilon

April 27, 2010

There are numerous types of aphids that feed on a wide range of commercially grown annuals, perennials, and woody ornamentals. The most common aphid species that feed on greenhouse and nursery crops are the chrysanthemum aphid (Macrosiphoniella sanborni), green peach aphid (Myzus persicae), foxglove aphid (Aulacorthum solani), melon or cotton aphid (Aphis gossypii), and potato aphid (Marcosiphum euphorbiae). There are several other aphid species that may be observed feeding on ornamental crops on occasion.

Aphids cause crop injury such as stunting and deformities, vector viruses including Cucumber mosaic virus (CMV), dasheen mosaic virus (DsMV), and tobacco ringspot virus (TRSV), and reduce a plant’s quality and marketability. Aphids have piercing-sucking mouthparts they use to remove plant fluids from within the plant. These slow moving insects are gregarious and quickly form large colonies on plant stems.

Generally, the biology and methods of controlling aphids is similar for all species. They have small soft, pear-shaped bodies, measuring 1 to 3 millimeters in length. Most aphids are wingless; however, winged aphids may be observed on occasion. Most species can be identified by the two tubes projecting from their abdomen called cornicles, which resemble small tailpipes. They are the only insects that have these tubes on their abdomens. The color and size of the aphids vary with species, environmental conditions, and the host plant. Common colorations include green, brown, black, purplish, red, or pink.

Aphids are usually all females that give live birth to young nymphs. Each female is capable of producing 50 to 200 nymphs in her lifespan of about one month. The nymphs become mature within 7 to 10 days and begin giving birth to their own offspring. The ability to mature and have offspring so quickly is one reason aphids are problematic for growers. Unlike other insects, aphids remain active and capable of reproducing at cool temperatures (less than 50º F), which potentially causes problems on cool season and overwintered crops.

Since they are able to produce a new generation each week, their population increases very quickly, therefore growers should scout their crops at least once per week to find localized aphid infestations. Aphids are usually observed in large numbers on young succulent stems of flowering or non-flowering plants, but are commonly present on nearly every above ground plant part. One signal that aphids are present is the presence of small white skins left behind during the molting or growth process. These skins are sometimes easier to see than the live aphids themselves. The presence of honeydew (a digestive by-product which contains sugars) often occurs when the populations are high.

Aphid populations can be can be controlled biologically by releasing predatory ladybird beetles (Adalia bipunctata), lacewing larvae (Chrysoperla carnea), or midges (Aphidoletes aphidimyza) into the production area. Parasitic wasps (Aphelinus abdominalis, Aphidius colemani, Aphidius ervi, or Aphidius matricariae) are also commonly released into production facilities to control aphid populations biologically. The entomopathogenic fungus Beauveria bassiana is effective at controlling aphids without taking out the populations of natural enemies. Other biological control options include products containing azadirachtin, horticultural oil, insecticidal soap, or neem oil.

There are numerous insecticides labeled for controlling aphids. Several insecticides (acephate, acetamiprid, imidacloprid, pymetrozine, and thiamethoxam) have systemic or translaminar activity and can be used to provide control over various durations of time. Others insecticides (abamectin, bifenthrin, cyfluthrin, fenpropathrin, and pyrethrins) provide ‘knock down’ control and do not offer much residual control.

To effectively control aphid infestations, it is best to scout crops regularly to detect them and implement control strategies before the populations are high. Once aphids become established and spread deep within the plant canopy, they are increasingly difficult to deal with. Most growers resort to using chemicals as the most effective and quickest method of reducing, or eliminating existing aphid populations on their ornamentals.

Paul Pilon
Perennial Solutions Consulting
paul@perennial-solutions.com

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