Sanet Post, Joel B. Gruver
Plant Resistance to Herbivory
June 25, 1997

Joel Gruver wrote:

"Hello to all...

A general school of thought amongst "sustainable" growers is that plants that are under significant stress are more often the recipient of herbivory than less stressed plants. I have observed that the scientific literature substantiates this theory to some extent.

My question for the group is... what is the ecological logic behind pests consuming weak plants preferentially to strong plants ? and what are the specific mechanisms by which herbivores discriminate between stressed and less stressed plants ?

In animal ecology it seems very logical that predators have an easier time catching and killing weak/young/injured prey...

How well does this analogy hold true for plants ? Do strong/less stressed plants tend to have more active defense mechanisms than weaker/stressed plants ?

...but some stressed plants have elevated levels of alkaloids and other anti-feedant compounds...

Any insights or recommended reading on this subject ?

On another subject:
I have read about the insecticidal compounds in Assimina triloba (Pawpaw) foliage... What is the current status of research on these bioactive compounds and can anyone provide any recommendations for how one would prepare pawpaw leaf extract for pest control use ?

Joel Gruver
U of MD, Agronomy