Entomopathogens
Fungi, bacteria, nematodes and viruses that infect insects in nature. Their effects can be seen with the naked eye: cadavers covered with white mycelium or green spores, orange clubs, hanging caterpillars… Here are the ten main ones, each with a freely licensed photo.
Soil fungus found worldwide. Its spores germinate on the insect's cuticle and pass through it; after death the body becomes covered with a powdery white felt, like icing sugar, which releases new spores.
Soil fungus that also lives near roots. It mainly infects soil-dwelling larvae (white grubs) and locusts: the hardened cadaver is covered first with white mycelium, then with an olive-green powder of spores.
Fungus of temperate woods and meadows that develops inside buried moth caterpillars and pupae. In autumn, one or more bright orange clubs, 2 to 8 cm tall, grow from the mummified pupa and rise above the soil.
Tropical-forest fungus that infects carpenter ants. The infected ant climbs into the vegetation, clamps its mandibles onto a leaf vein or stem and dies; a stalk then grows from the back of its head and scatters spores over the colony.
Soil bacterium that produces protein crystals as it forms its spores. Each subspecies acts on one group of insects (caterpillars, mosquito larvae, beetle larvae) that ingest them: they stop feeding within hours, and the dead caterpillar turns black and soft.
Fungus that infects flies. Late in the day the infected fly climbs to a high point (plant, window), spreads its wings and dies; the swollen abdomen shows white bands from which the fungus shoots its spores around.
Common fungus in woodland litter and soil, on moth caterpillars and pupae. Small branched white stalks covered with a mealy powder of spores grow from the dead insect.
Fungal genus that now includes the former Lecanicillium (formerly Verticillium lecanii). They need high humidity; on aphids, whiteflies or scale insects they form a halo of white mycelium, and some species cover whole moths with small white spikes.
Microscopic soil worms that enter insect larvae and release an associated bacterium inside them. The larva dies within one or two days and changes colour: brick red with Heterorhabditis, ochre or brown with Steinernema; thousands of new nematodes then leave it for the soil.
Insect-specific viruses, mostly of caterpillars, each affecting only a few species. The infected caterpillar climbs to the top of the plant, hangs head down and dies; its skin becomes fragile and releases a liquid full of virus particles.
Trichoderma, often mentioned alongside them, is not an entomopathogen: it is a soil fungus that colonises roots and other fungi (see its ingredient sheet).
Descriptive page. In the EU, some strains (Beauveria, Metarhizium, Bt, Lecanicillium, baculoviruses…) are plant-protection active substances: they may only be used as commercial products authorised in the country, never multiplied at home for that purpose. No homemade recipe is offered here.