17 Aug 2016
Higher than normal aphid activity this winter in SE Australia
Reasons for high levels of activity
There has been a reported increase in the level of aphid activity this winter. Although the aphid in question looks like the lettuce aphid, Nasonovia ribisnigri, all the samples received have been identified as the Foxglove aphid (greenhouse-potato aphid), Aulacorthum solani.
The reason for the increase of Foxglove aphid in Australian lettuce fields this year is suspected to be the result of above average temperature during the winter months. Similar observations have been made overseas, eg. USA, where unseasonable warm weather led to a significant increase in Foxglove aphid activity.
The Foxglove aphid is a cool temperature aphid with an optimum temperature range of 10°C-25°C. Similar to the Nasonovia, this aphid species has a rapid population growth and infests the heart of lettuces, making it nearly impossible to eradicate with foliar aphicides applications once the lettuce hearted.
Foxglove aphid has one of the broadest host ranges recorded for any aphid, having been identified from samples taken from over 82 plant families (both monocot and dicot), including;
- crop species such as potatoes, lettuce, spinach, ornamentals, cucurbits, beans, celery, tomatoes, eggplants, capsicums
- common weed species such as shepherd’s purse, amaranth, nightshade, sowthistle, dandelion, pigweed and fat hen
Foxglove aphids have been implicated in the transmission of at least 45 plant viruses (eg. lettuce mosaic virus, cucumber mosaic virus).
Foxglove aphids have a toxic saliva, which is injected into the plant as it feeds. The toxin can lead to curled and twisted leaves, spots of dead leaf tissue, and can even cause early leaf-drop.
Identification & Control
There are some key characteristics that make the Foxglove aphid easy to differentiate from the Currant-Lettuce aphid. For more information and a guide to differentiating between the two aphid types we have created a leaflet that gives some clear pictures and instructions for identifying the Foxglove aphid, and some tips for controlling it.
Foxglove Aphid Information Leafet
- General information and identification tips for the Foxglove Aphid Pdf file 1.23 MB