This week, based on greenhouse scouting, aphids were observed on Fuchsia (particularly on the variety ‘Dark Eyes’) and on Calibrachoa.
The most common aphids in greenhouses are green peach and melon aphids. Foxglove aphids are also very common and they especially thrive in cool conditions (50-60⁰ F). They are most likely to be a problem in spring production. Aphids have a wide host range.
Scout and monitor crops regularly. Look for wingless aphids on young tender growth, white cast skins, shiny honeydew and dark sooty mold. Also, use yellow sticky cards to monitor for winged aphids. Aphids feed by inserting their stylet-like sucking mouthparts into the phloem to remove the sap. Plants infested with high aphid populations can become stunted, with curling and twisted young leaves.
Several biological control approaches are available for control of aphids in the greenhouse. For effective control, biological control agents are best released preventively before aphids become a problem. It is important to correctly identify the aphids because the biocontrol agent should be matched to the specific aphids in the greenhouse. For example, Aphidius colemani is best used to control small aphids such as green peach and melon aphids. For larger aphids such as foxglove and potato aphids, Aphidius ervi is the most effective. Contact your supplier for more information on matching the aphids in your greenhouse to the appropriate biological control.
Aphids can be difficult to control with insecticides, and insecticide resistance has been reported, especially with green peach aphids. With that said, there are several insecticides labeled for the control of aphids. Consult the latest edition of the New England Greenhouse Floriculture Guide. Systemic insecticides are more effective because aphids ingest large amounts of sap. For contact insecticides, thorough coverage of the underside of leaves is needed to achieve good control. Be sure to rotate between different insecticide classes (modes-of-action) to prevent resistance build up.
Dan Gilrein, Cornell Extension: Time to think of about aphids again
Sarah Jandricic and John Sanderson, Cornell: Early season pest threat
Tina Smith, UMass Extension: Aphids on Greenhouse crops
UMass Extension: Aphids photos
Geoffrey Njue, UMass Extension with contribution from Jim Mussoni