Aphids on Dahlias - Ask Extension
Hi - I start my dahlia tubers early in my basement (February/March). This year I noticed that I have an aphid infestation. I have no idea where they c...
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Aphids on Dahlias #791017
Asked May 16, 2022, 11:18 AM EDT
Hi - I start my dahlia tubers early in my basement (February/March). This year I noticed that I have an aphid infestation. I have no idea where they came from. Could it be from the potting mix? I used all new in the bag mix. There were no other plants in the basement. I'm just sick over it. How will I ever get rid of them? Any suggestions on treatment and any idea how the got the aphids to begin with?
Thank you for your help!
Julie Amman
Oakland County Michigan
Expert Response
Hello Julie,
I'm not sure how the aphids ended up on your dahlias. Aphid larvae overwinter in the soil. If the tubers had soil on them when they were stored, I suppose that might have produced an aphid infestation. Also, if organic matter, such as shredded leaves, was used to store the tubers, the aphid larvae may have been present. Aphids could enter the home on the shoes or clothes of the gardener or even by the wind, but it's highly unlikely they were in the potting mix you used.
The following information is from the University of Wisconsin Extension:
Cultural:
Keeping your garden free of weeds can help to reduce potential aphid hosts. Weeds such as sowthistle and mustard can support large colonies of aphids. Excessive nitrogen can favor aphid reproduction; therefore plants should be grown with
appropriate soil fertility levels. Application of less soluble forms of nitrogen, in small portions throughout the season is less likely to promote aphid infestations.
Physical:
Aphids can be physically knocked off of plants with a strong spray of water from a garden hose.
In addition, this will also help wash off any honeydew or sooty mold that may be present.
https://milwaukee.extension.wisc.edu/files/2016/11/Aphids-in-home-gardens.pdf
The following information is from the University of Minnesota Extension. It also gives some valuable information about the use of pesticides:
In most cases, aphids cause little to no damage to plants and can be ignored. If aphids are causing problems, and it is necessary to treat them, you may want to consider using insecticides.
Low risk pesticides:
Several insecticides are low risk to people, beneficial insecticides and the environment. Neem (azadirachtin) is a plant based pesticide that discourages aphid feeding. Insects are not killed quickly, but it makes them stop feeding and they slowly die. Insecticidal soap, horticultural oil and pyrethrins can be effective at controlling aphids.
I apologize for the lateness of this reply, but please contact us again if you have any other questions or need further explanation.
I'm not sure how the aphids ended up on your dahlias. Aphid larvae overwinter in the soil. If the tubers had soil on them when they were stored, I suppose that might have produced an aphid infestation. Also, if organic matter, such as shredded leaves, was used to store the tubers, the aphid larvae may have been present. Aphids could enter the home on the shoes or clothes of the gardener or even by the wind, but it's highly unlikely they were in the potting mix you used.
The following information is from the University of Wisconsin Extension:
Cultural:
Keeping your garden free of weeds can help to reduce potential aphid hosts. Weeds such as sowthistle and mustard can support large colonies of aphids. Excessive nitrogen can favor aphid reproduction; therefore plants should be grown with
appropriate soil fertility levels. Application of less soluble forms of nitrogen, in small portions throughout the season is less likely to promote aphid infestations.
Physical:
Aphids can be physically knocked off of plants with a strong spray of water from a garden hose.
In addition, this will also help wash off any honeydew or sooty mold that may be present.
https://milwaukee.extension.wisc.edu/files/2016/11/Aphids-in-home-gardens.pdf
The following information is from the University of Minnesota Extension. It also gives some valuable information about the use of pesticides:
In most cases, aphids cause little to no damage to plants and can be ignored. If aphids are causing problems, and it is necessary to treat them, you may want to consider using insecticides.
Low risk pesticides:
Several insecticides are low risk to people, beneficial insecticides and the environment. Neem (azadirachtin) is a plant based pesticide that discourages aphid feeding. Insects are not killed quickly, but it makes them stop feeding and they slowly die. Insecticidal soap, horticultural oil and pyrethrins can be effective at controlling aphids.
- Remember to spray the underside of leaves as well as the top.
- These materials will only kill aphids that they come in contact with. Repeat applications may be needed.
I apologize for the lateness of this reply, but please contact us again if you have any other questions or need further explanation.
