Natural Enemies of Aphids

Insect Pathogens

Insects are attacked by many different microorganisms that cause disease, often ending in death. Under some conditions, disease can infect a high percentage of the population very rapidly, resulting in significant levels of control. In particular, fungi called entomopathogenic fungi are key mortality factors keeping insects and mites from reaching damaging levels.

With aphids, there are quite a few fungal pathogens that can cause high levels of mortality, especially during warm, humid periods. Recent work in Minnesota found high levels of diseased aphids on soybean, especially late in the growing season at a time of the year when aphids leave soybean and migrate to buckthorn to begin the sexual phase of the aphid’s life cycle.

Aphids infected by fungi will have varying degrees of "fuzzy" fungal mycelial growth emerging from the dead bodies. This mycelium produces spores which are released into the environment and infect additional insects.

Foliar fungicides applied to soybean are detrimental to this group of natural enemies and unnecessary fungicide applications should be avoided to preserve these beneficial fungi.

Paecilomyces lilacinus, a fungal pathogen that infects aphids Photo credit: Bill Stoneman

An aphid covered with mycelium of Paecilomyces lilacinus Photo credit: Bill Stoneman