Caterpillar Insecticide for Roses

Roses are one of the most cultivated plants on earth. While there are a host of insects that may play havoc with a rose bush, they can usually be dealt with without recourse to harsh chemical insecticides. Caterpillars can prove to be a pest for roses as they often feed on the leaves and can bore into the buds or growing flowers. If caterpillars become a problem, applying an insecticide can help.

Types

The most effective natural insecticide for caterpillars is made from bacteria called Bacillus thuringiensis (Bt). Products containing Bt are affective on almost all types of caterpillar pests as the Bt becomes a poison in the stomach of the caterpillar. Bt can help to control problematic lawn grubs, green loopers, cabbage moth caterpillars, tent caterpillars and omnivorous loopers, among others. It can also help with tobacco budworms which like to burrow into the flower bud.

Application

Bt insecticides should be applied to rose bushes on the tops and undersides of leaves as well as buds. The insecticide solution should be sprayed onto plants every couple of days for a week, as the sun breaks down the Bt bacteria. This week-long series will help to break the breeding cycle of the caterpillars and reduce their numbers rapidly.

Effects

The Bt insecticide will take effect once it is ingested by a caterpillar, which will then take a number of days to die. Why Bt is favored in insecticides for roses is that it will not have any harmful effect on beneficial bugs like bees or lagybugs and it is not harmful for mammals, so it is a relatively safe insecticide for use in the garden, especially if children and animals frequent the area.

Timing

Because sunlight works on the Bt bacteria and breaks it down, it is best to apply the insecticide on rose bushes at evening time, so that it has the whole night to work before it is weakened by the sun. Repeated applications every couple of days may be necessary to fully eradicate the problem caterpillars.

Alternatives

Bt is the caterpillar insecticide with the least toxicity, however there are even more natural methods that can be used to help with caterpillars on the rose bush. These include using neem oil soap or hot pepper wax as a spray diluted in water. Rather than killing the caterpillars, these will make the rose plant unappetizing for them and they will go elsewhere for food.

References

• University of California: Roses: Insects and Mite Pests and Beneficials
• Yardener: Controlling Caterpillars Using Natural Insecticides