Got Caterpillars?

They Are Hungry Little Buggers

Cabbage White butterfly

Here in the upper East Tennessee region we had been experiencing some unseasonably warm weather for the month of November. The temperature stayed in the mid 70’s during the first few weeks and we continued to see many different insects in multiple stages of their life cycle here in our winter garden at the USARAI Farm Campus. One insect, or I could call it a persistent garden pest, that I had seen throughout the Brassica crops is the Cabbage White Butterfly. As I was sitting in the garden and writing I watched as this butterfly traveled back and forth from the cover crop and the raised beds.

Cabbage White Butterfly

To the untrained eye it’s an innocent butterfly but this one has many fooled. This butterfly enjoys feeding on Cole crops, specifically cabbage, broccoli, and cauliflower. It just so happens that the cole crops you have planted in your home gardens and the crops we have here at the farm campus are endless buffets for this butterfly.  The butterflies are in hog heaven throughout their life cycle.  They like to lay their eggs on the bottom side of the leaves and they can be easily missed. During the larva or caterpillar stage, they can be found eating on the outer leaves of the plant and working their way to the center of the cabbages or the stems of broccoli. Once the caterpillars emerge into the adult butterfly stage they will lay the next generation of eggs on the underside of the leaves and the cycle continues. I want to be sure to make the point that here in the garden we do not want to completely get rid of these insects because they are beneficial pollinators, but when you are planning to harvest the crops you want to produce a crop that is marketable or good for eating fresh at home.

Cabbage White Butterfly eggs on cabbage leaf

We have planted this seasons winter crop in three different growing settings. We have the same crops growing in a low tunnel, raised beds, and a high tunnel; we are calling it our garden experiment.  Each growing setting has its own unique challenges and we plan to use this crop to examine and understand what goes on in the tunnels with growing rates, pests, and other issues or interesting things that may arise. In this situation with the Cabbage White Butterfly I have compared the performance of the Cole crops we have growing in each setting; Blue Cabbage, Stone Head, broccoli, and Bok Choy.

Caterpillars on cabbage

At first the low tunnel crops were the only ones being chewed on and after a treatment of Diatomaceous Earth (DE) and close monitoring the plants recovered. In the high tunnel, we have thankfully had few pest issues and the crops are thriving.

High Tunnel cabbage without caterpillar damage

The raised beds are another story. This area is where I have seen a high concentration of the green caterpillars mostly on our cabbages. We treat these garden issues as naturally as possible. I initially started by picking the caterpillars off the plant and I would turn around and it seemed like there were five more in place of the ones I removed. The next day I came into the garden and started by picking off the caterpillars and then washing the cabbage plant so I could monitor if any new caterpillars were eating on the plant. A day or two went by and I had not seen any new signs of the caterpillars munching. It happened to be during the first short-lived cold snap of November. Once it warmed up again they were back at it, enjoying the buffet of brassicas.

Raised Bed cabbage affected by caterpillars

The next step of treatment was to mix up a spray bottle of soapy water and spray all over and under the plants. This method did not seem to faze the caterpillars at all and they continued, so I went back to the drawing board. We decided to split the treatments in the affected raised beds. Two beds of cabbage were treated with a spray bottle with a mix of neem oil and water, the other two boxes were treated with diatomaceous earth. A few cold days had gone by and I thought the cold would likely kill the caterpillars and I would not have to worry about them anymore. Boy, was I wrong and the battle continued. I saw signs of caterpillars on the outer leaves of the cabbages treated with both the DE and neem oil. When looking at the Cabbages that had been treated with neem oil, I saw less caterpillar activity. The neem oil seemed to be more effective in the treatment of the caterpillars. What I have learned from the battle with the caterpillars is that continuous treatment and monitoring is important if you want a crop that looks great and is marketable.

By Sarah Vogt, USARAAI Farm Campus Assistant