This has been “Caterpillar Week” in my backyard. Has it been in yours?
If you aren’t sure, look at all of your vegetables and grapevines. If you have holes in them, chances are you have caterpillars munching nearby. Other pests can cause similar problems at times, but for the most part, the chewed holes are from caterpillars.
The caveat is that caterpillars are the larvae of butterflies and moths. Given to their own devices, the caterpillars will reach adulthood and become pollinating butterflies. Then the process begins again as the butterfly lays eggs that hatch as larvae, etc. Life would be good if we jumped from egg to butterfly, wouldn’t it?
As a gardener, you have to decide if the damage is enough to cause crop loss or if they can be left alone to become butterflies or moths. If you have an infestation, your only choice is to destroy or relocate the caterpillars or count your crop as sacrificial food in a butterfly garden. We need butterflies and moths as pollinators but most of us want them not only to improve our environment but grow quality food in the process. Such a conundrum.
As organic gardeners, we struggle with this problem continually. For example, a “bird poop caterpillar” on your citrus leaf becomes the Giant Swallowtail Butterfly. Unless your tree is very young and small, the caterpillar won’t do much damage. It’s an easy choice to let the caterpillar become the butterfly in this case.
However, last Saturday, I noticed that many of my grape leaves were skeletonized – the leaf flesh was gone except for very thin veins within its tissue that held it together. It was clear that I was dealing with Skeletonizer Caterpillars. They can destroy a backyard vineyard in a matter of a couple of weeks, so you don’t have much choice but to get rid of them.
Before you run for the chemicals, remember that you will be picking these grapes, and unlike citrus, you will be eating the flesh that has grown from all of those chemicals. So your first line of defense is to pick them off. With this kind of caterpillar, it is easy. Their yellow color with black and blue stripes makes them stand out. They are small,
about ½-1-inch long and hide on the underside of the leaf. They will always congregate near the damage and usually on a leaf that is already compromised. As young caterpillars, they generally line up in a group, which makes them easy to remove. If quite a few reside on one leaf, I simply clip off the leaf carefully then place the leaf in water with a little dish soap added. If I find them individually, I pick them off and either squish them or drop them into the same solution. One warning: this caterpillar has small fibers that can irritate the skin, so use gloves. You will need to monitor your plants daily for about a week to make sure you got all of them.
If you just can’t stomach picking off caterpillars, you can spray the caterpillars directly with Neem Oil or use Bt (Bacillus thuringiensis), a natural bacterium that gets into the intestines of the caterpillars and kills them. Scientists have assured us that Bt doesn’t harm mammals or beneficial insects. I’m not sure what the difference is but all organic organizations approve of its use.
Spray on Bt every week for a few weeks then monitor. Unlike the Neem Oil that requires direct contact spray, the caterpillar can ingest the Bt if it is on the leaf. Spray the top and underside of each leaf. Both Neem Oil and Bt are organic sprays. However, you can’t get more organic than picking them off by hand.
I chose the picking method for three days. The first day was rather gross as I removed more than 200. On the second day, I found about 25 more. By the third day, I found three. I will continue to monitor for damage at least a few times a week.
So, I had no more breathed a sigh of relief than what to my wondering eyes did appear, but miniature holes in my broccoli so dear. (I have to stay out of Hallmark stores until after Thanksgiving. It has this effect on me.)
My heart sank. I had the dreaded cabbage worm in my garden. These bright green little caterpillars (not really worms) evolve into beautiful White Cabbage Butterflies. I had seen them flying around and admired them, but I didn’t know they were the egg-layers of these pests until I looked it up. Now my eyes narrow instead of widen as they fly by.
These caterpillars can decimate a small garden quickly. They are drawn to brassicas (cauliflower, Brussel sprouts, broccoli) and kale. They will eat all of the leaves and burrow into the fruit of the plant. Again, if you are an organic gardener, you have the caterpillar arsenal of choices: Neem Oil, Bt, or hand-picking. Insecticidal soap can also work if sprayed directly onto the caterpillars and eggs.
The caterpillars are bright green. If they form a loop as they crawl, they are cabbage loopers and come from a moth. Otherwise, they are cabbage worms and come from the butterfly. The results and treatments are the same.
They are very difficult to detect. During the heat of the day, they will often hide in the center of the plant, deep in the new tender leaves. Otherwise, you will find them on the underside of the leaves. They look like a leaf vein, especially when they are very small, until you look closer. A telltale sign that they are nearby is the presence of poop that looks like small black granules. The eggs are small, off-white balls and are generally laid on the top of the leaf. Remove or destroy these as well.
Because these are hard to detect, I am using two approaches. In the morning, I check the leaves for caterpillars and eggs and remove them manually. Just before dusk, I sprayed the plants top and bottom with Bt because the caterpillars will be most active at night and early morning. Application of Bt should be repeated weekly, not daily.
Next year, I think I will cover the raised beds with garden netting that keeps the butterflies and moths from the plants to prevent them from starting the process to begin with.
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