Katy, yes very true... Often times the damage is already done.
I grow lettuce for market. On the self sits the organic pesticide Azamax, which I rarely use.. Why, because I find once I see any sign of an infestation it is already too late, the and the crop quality will suffer worse if I intervene. A early harvest is usually the best route to go.
I believe the best pesticide ever "invented" is mother nature and bio-diversity, once I recreate the natural conditions a given plant needs for optimum health while nurturing bio-diversity and the soil food web, plants can fend for them selves quite well..
My need to intervene only signifies my failure to maintain the proper natural conditions for a given plant.
ON