Depending on the severity of the caterpillar impact there are several options. Always first try to use preventive measures to avoid caterpillar problems:
- Plant companion plants!
- Avoid dry stress and mulch beds in dry conditions.
- Avoid underfeeding of plants.
- Regularly, every second week and after strong rain apply worm-juice or seaweed solution (should look like a thin tea, 1/2 a watering can per bed) as a tonic for the plants.
- Build nets around the crops we know to be vulnerable: tomato, chili, cabbage family. The mesh size of the net needs to be fine enough to physically block the parent animal, a moth or butterfly, from reaching the plant.
Dealing with caterpillars:
- Collect the caterpillars you can find and manually destroy them.
- Remove infested plant material. You can put it into the compost, the caterpillar will not survive composting.
- In cases of serious infestations or under tight netting apply a spray containing bacterial spores (bacillus thuringiensis). These bacteria do not affect humans, but they will make the caterpillars ill and die. The spray should be used only focally to avoid to put too much pressure on other insects.
The recipe uses a commercial product called Dipel, we add in some soap to make it more spray-able:
Thoroughly mix in the 5 litre spray-can
1/2 sachet of Dipel powder
1 dash of liquid soap
5 liters of water
Important notes on using the spray
- this spray is not toxic to humans
- make sure you mix and dissolve the ingredients in the spray-can
- spray top- and downside of the leaves and all of the rest of the plant, it’s important to cover everything
- never spray in bright sunlight because this will burn the leaves and cause more damage than it helps. Spray in the late afternoon
- don’t spray too late in the day. The leaves need to dry off before nightfall, otherwise you are inviting in spores fungi by offering a humid night environment. Spray in the late afternoon
- spraying needs to be done consistently, once per week and after every serious rainfall until the caterpillar problem is in control
- make a note in the garden log book about what you applied and where, so following gardeners know where to pick up the work
- always rinse the spray-can and its hose. It’s hard to fix it, if it gets clogged up