Spraying BT

In a previous post I talked about spraying the bacteria BT (bacillus thuringiensis) onto brassica plants to deter the caterpillars that attack them (attacks usually come in the summer, which is why brassicas are usually grown in early spring and fall/winter to miss the caterpillar cycles). Daniel had asked about the mister I use to apply the BT, and which I have also used to apply foliar feeds (fertilizers) to other plants.

The mister is a Flowtron Bio-Mister. The liquid BT is diluted into the bottom container, then a powerful fan in the housing on the rear of the mister pulls the mix out of the container and atomizes it, creating a mist that clings to plant leaves.

There is a control on the front of the mister that increases or decreases the density of the mist:

Here are two short movies of the mister in action. The mist stream is strong -- you can see it shaking the plant leaves. When plants are this small there is obviously a lot of overspray and waste. The larger the brassicas get with their huge leaves, the more suitable as an application tool the Bio-Mister becomes. (The mist is more visible in the second video due to a darker background.)

As the water evaporates out of the droplets it leaves behind the BT which is what the caterpillars consume as they feed on the leaves. Spraying the underside of leaves as well as the tops is optimum, but when a caterpillar feeds on either side of a leaf (creating a hole in the leaf) it is eating the top-side and bottom-side of the leaf, consuming the BT regardless of which side of the leaf the BT is on. You can see the moisture collected on the leaves of this plant: