Aphids

April 12, 2017

Foxglove aphids have been reported on Ipomoea ‘Marguerite’ and other aphids on ornamental grasses, many perennials, dahlias, zonal geraniums and tomato bedding plants. Watch for aphids including the foxglove, green peach aphids and melon aphids. Foxglove aphids tend to feed first on the underside of the lowermost leaves and then migrate to the flowers. Because foxglove aphids reproduce faster at 50˚ to 60˚ F than at 77˚ F, they are more of a problem if your crops are grown cool. Foxglove aphids also tend to drop off of the plant and cause more leaf distortion than the other types of aphids. Green peach aphids blend in and you will often see signs of aphid activity (white shed skins, curled growth) before seeing the actual aphids. Green peach aphids are typically located on the terminal growth. Aphids often first appear on isolated weeds, so be sure to check those, too.  Rely on plant inspection, not sticky cards, which will only detect the winged aphids. If you see winged aphids on sticky cards, you already have a hot spot of activity somewhere in the greenhouse.

Biological Control: Using biological controls against aphids (especially the foxglove aphids) has been challenging for growers.  Growers uncertain about the aphid species, have been using mixes of different natural enemies. Growers often begin with a mixture of wasps, Aphidius colemani (for green peach and cotton aphid) and Aphidius ervi (for the larger potato and foxglove aphids) as preventative, or when numbers are low. The parasitic wasp, Aphelinus abdominalis has also been used for potato and foxglove aphids.

The predatory midge, Aphidoletes aphidimyza, can be used as clean up, now that the days are longer.  Lacewings can also be used to clean up aphids in hot spots. Some growers use lacewing larvae that are shipped in rice hulls that are ready to hatch or they use adult lacewings.

Chemical Control: 

  • Aria (flonicamid - Group 9C), Contact and systemic activity, selective feeding blocker. (Not for viola or pansy). Aphids quickly stop feeding.
  • Endeavor (ornamentals), Fulfill (edibles)  (pymetrozine –Group 9B), Translaminar activity, selective feeding blocker.  When aphids feed on treated plants, the aphids stop feeding within hours after treatment and eventually starve to death. However, the aphids will continue to be present for 2 – 3 days after ingesting the material. 
  • Mainspring (cyantranilprole- Group 28), Translaminar and systemic activity. Apply as a preventative drench on aphid prone ornamentals. Aphids stop feeding and become paralyzed after ingestion.
  • Rycar (pyrifluquinazon – Group 9B), Contact and translaminar activity. Aphids quickly stop feeding.

Important - Follow label cautions regarding plant safety.
The Rutgers IR-4 Program has a summary of what has been working based upon research reports across the country.  According to this report, Aria, Endeavor, Mainspring (used preventively) and Rycar all exhibited good to excellent control and are non-neonicotinoids.

Resources

2015 IR-4 Ornamental Horticulture Program Aphid Efficacy (Scroll down to pgs 66 - 69 for a summary by active ingredient).

Slide show: Tips on Scouting Vegetable Bedding Plants (with photos of different species of aphids), UConn Extension

Leanne Pundt, UConn Extension and Tina Smith, UMass Extension