Caterpillar feeding on basil
Basil (Ocimum basilicum) is one of the basic aromatic plants that I maintain. Every summer I grow them in pots near the kitchen. This is the first year when I had to deal with some caterpillars which were trying to defoliate my basil at a high speed. I've never had "basil-eating caterpillars" in my garden before. Could it be that they have migrated from Tuscany? :)
Phytophagous insects are those that feed on plants. We see them all the time in our gardens on different plants. Different insects are attracted to different types of plants. For example, the tomato hornworm which is the larvae of the Five-Spotted Hawk moth (Manduca quinquemaculata) feeds on tomato leaves as their first choice.
How do they choose their host plant? The adult female insect chooses the host plant before they lay their eggs. The adult insects (moths and butterflies) are beneficial pollinators but their larval form is very destructive to plants. Although the adult does not have the same diet as the larvae, it knows what its offspring will want to eat. There are cues that they use to choose their host. The first one is visual cue - they choose green (plants) instead of brown (soil). Once they are on the right color location they start to inspect the other details such as the chemical properties of the plants that they have chosen. Only after they have made sure that the location is right that they begin to check out the other details of the host plant. The scent, palpability, and taste of the plant will be final test on whether the insect will decide to stay. Otherwise it will continue to look for another plant until the perfect one is found.
This is similar to house-hunting. First we choose the right location or city and then we look for the house that is affordable, with a big yard to garden, or a sparkling swimming pool. We view different houses until we make an offer only on the one that meets our requirements.
The voracious larvae that are on my basil plants did not choose to be there nor did they migrate from another yard because they liked the good smell of the herb. They were left there by their harmless parents (moth or butterfly) who made sure that their young will be fully supported.
Friends or Enemies? Well, a couple of days ago I wrote something about saving the pollinators. Now, I am talking about "future pollinators" eating my food. How then should we treat them - enemies or allies? No matter how I will answer this question it will always be wrong. The butterflies and moths are our partners in food production and they deserve to have food during the different stages of their life cycle. If we do not want them to feed on our own food then we need to make sure that they can find theirs somewhere. Therefore, diversify.