Dormant oil spraying for aphids

Posted by gardensoul on February - 14 - 2013

Green Peach AphidWhen do I spray with dormant horticulture oil? The first rule is spray only if you know there is a problem. I grew cabbage for a two years, but was plagued with so many aphids I stopped growing cabbage.  I think I’ll try again this year because I sprayed my peach tree this February.

Are aphids a problem in your garden?  There are many types of aphids and they are generally host specific.  The aphids that over-winter on a primary host and then feast on secondary hosts can be controlled with winter spray of dormant oil.  Here is a partial list.

Note:  Spray the Primary Host with horticultural oil now to prevent summer aphid infestation on the Secondary Host.



Scientific Name Common Name Primary Host Secondary Host
Aphis fabae Bean aphid Euonymus, viburnum Bean, beet, cucumber, carrot, lettuce, etc.
Aphis nasturtii Buckhorn aphid Buckhorn (Rhamnus spp.) Potato, cuburbits, thistle, many garden flowers
Cavariella aegopodii Carrot-willow aphid Willow Carrot, parsley, dill, coriander
Eriosoma lanigerum Woolly apple aphid Elm Apple, crabapple, mountain-ash, hawthorn
Macrosiphum euphorbiae Potato aphid Rose Potato, tomato, many other garden plants
Myzus persicae Green peach aphid Peach, plum, apricot Pepper, cabbage, potato, spinach, many other vegetables and garden plants
Nasonovia ribisnigri Lettuce aphid Currant, gooseberry Lettuce, chicory, radicchio
Pemphigus bursarius Lettuce root aphid Poplar Roots of lettuce, endive, chicory, dandelion, sowthistle, some other weeds

How do I spray with dormant horticultural oil?

  • Buy horticultural oil.   I prefer oil with the ORMI (Organic Materials Review Institute) seal.  
  • Read the instructions carefully!
  • Cover the plant completely with the spray

Horticultural oil use in winter is very safe and effective.

Do you have a persistent aphid problem not covered in this post?  Leave a comment with your question and I’ll research a solution.