This week, I was reminded that nature is awesome and that, in many cases, sometimes you just cannot beat letting nature do its thing.
As I was out for a morning walk, I noticed a strange green shape, with some whitish protrusions. It was moving very slowly across the sidewalk. On closer examination, I noticed that it was decent-sized tomato hornworm. I noticed a second one a few feet later. Both hornworms had small white oval-shaped growths on their backs. One was almost entirely encased in these growths.
About half a block later, I saw another hornworm. This one was huge, close to 2-3 times as large as the other one. It was unencumbered by growths and it was moving really fast.
The growths are the cocoons of the larvae of braconid wasps. The caterpillars have been parasitized by the adult wasps, who lay their eggs inside the hornworm. The eggs hatch and grow within the living caterpillar, which becomes a sort of insect food truck. It was a vivid reminder that when left to its own devices, nature has its own back.
In the distant past, people would grow crops and plants without the assistance of commercially available pesticides. They relied on nature to sort out issues on its own, provided they gave fields and areas time to rest. They provided general cultural care of the plants, in the form of pruning, watering, and fertilizing. Pests would go through cycles, with years where they won, and years when the natural illness, predators and parasitoids caught up, ganging up on the pests and knocked them down.
Over time, people discovered pest controls by observing situations where a problem developed more slowly, or where some sort of secondary organism appeared to provide suppression. From there, they pinpointed various compounds and practices that suppressed diseases and pests more directly. These became modern fungicides and insecticides.
In recent years, there has been a resurgence of interest in biologically derived controls. Naturally occurring pathogens, predators and parasitoids have been selected to control very specific pests, with good effect, and almost no impact on the surrounding flora and fauna, including humans.
So, where do we sit today? We have lots of pesticide options, as well as an arsenal of biological controls, as well as cultural controls. In some cases, it is not economically feasible to apply a pesticide to control a pest, due to the size of the host, the nature of the product and pest, or the location of both. As a result, the recommendation is to look after the health of the plant and let natural illnesses or parasitoids/predators sort out the outbreaks over time. It is a good thing that nature has its own back, and it is always exciting to see it play out in nature.