November 25, 2021
Recently KBFA was asked about biocontrol options for aphid management. We asked Linda Gilkeson, KBFA’s expert advisor for pest management. Here is a summary about what she had to say about controlling aphids.
As a better alternative to ladybugs, you would be much better off releasing the native aphid predator, the aphid midge, Aphidoletes aphidimyza , when there is an outbreak of aphids. These are readily available from Applied BioNomics https://www.appliedbio-nomics.com/ These tiny predators have many advantages over lady beetles outdoors: they don’t fly away when released, they are specific to aphids, unlike ladybeetles which will eat other insects as well (including aphid midge larvae), they are native and will remain on the farm to build up local populations. Along with many other aphid predators, this midge is undoubtedly also present on the farm unless insecticides have been used. It occurs all around the globe at this latitude and is very hardy. Releasing them in the spring is a good strategy, however, to enhance their numbers and get a head start on aphid control. Also, see the attached file for conditions that cause aphids to thrive—particularly drought stress.
The approach to controlling aphids outdoors is most successful if it also includes attracting, feeding and protecting the many, many other native aphid predators (there are many species of hover flies, lacewings, parasitic wasps, native lady beetles, etc.) See the attached files for more info on these. Build up a good local population of these species by not using any pesticides (not even soap sprays, which kill beneficials) and by providing nectar plants to attract them and feed them. The adult stages of these insects all need pollen and nectar as it is the larval stage that eat aphids. Sweet alyssum works great to attract many of these species as do other plants with tiny, nectar-rich blossoms, such as dill, cilantro, herbs, brassica family plants. The big, showy flowers that humans like for bouquets are generally not useful for beneficial insects. Such flowers may not have nectar or they may have been bred not to have pollen (e.g., cutting sunflowers). Or the flowers are too big for these tiny insects or the petals are colours the insects don’t recognize or mutations that cause the double flowers prevent insects from reaching nectar. So it is well worth enriching a flower farm with some beds or borders with plantings of pollen and nectar-rich flowers just for the aphid predators.
Aphid Fact Sheets by Linda Gilkeson: