caterpillar poop (frass)
Seeing signs that caterpillars (I lazily call them worms) are eating up your vegetable plant?
Before going to the ‘spray to kill’ route, let’s think through a few other options first.
Did you know hornworms glow (iridescent) when a black light is shined on them? It may feel a little strange to work in your garden at night, but a few trips with a special flashlight might be enough to resolve the problem.
Beneficial wasps – tiny little wasps that kill caterpillars? That is really a thing! Keep in mind these little guys are the first to be killed if insecticides are sprayed nearby.
Attract birds – have a small birdhouse and perches near your garden gives birds a place to hang out and watch for food. Birds love fat caterpillars.
Sacrificial crops – if you have the space plant some plants just for the caterpillars to enjoy.
If you decide to use a pesticide, one of the most environmentally friendly ones is BT, Bacillius thuringiensis. This is a spray that causes a caterpillar’s digestive system to shut down when eaten. It only affects caterpillars, so it is considered safe to use since it doesn’t harm other critters. A few things to keep in mind with this product:
- Timing is important – the caterpillars must be actively eating the part of the plant you can get spray on to.
- BT washes off easily – if it rains after you spray it, it is gone
- BT breaks down in the sunlight. So it is only effective for a few days.
- It takes a few days for the caterpillars to die after they eat BT.
- Read and follow the instructions on the label
