What are Beauveria and Metarhizium and how do I use them?

Beauveria bassiana and Metarhizium anisopliae are insect killing fungi. Their spores land on an insect, germinate, grow into the body and kill it, then sometimes you see a white or green fungal growth on the dead pest. In rough terms Beauveria is used more against soft bodied sucking pests like whitefly, aphids, mealybug, thrips and some caterpillars, while Metarhizium is widely used against soil grubs, white grub, termites and some beetles, often applied to the soil with FYM. They need moisture and cooler humid conditions to work, so spray in the evening, keep the canopy a bit humid, and do not expect quick knockdown, the insect takes several days to die. Apply at the label dose, repeat sprays, and do not tank mix with chemical fungicides which will kill these fungi too. They are slower and more weather dependent than chemicals, so they fit best as a preventive and early stage tool in humid weather, not as a rescue for a sudden heavy outbreak in dry heat. Confirm which fungus, strain and dose suit your pest with the local KVK.