Good question about repellants. Indeed, if food were the limiting factor, repellants would be much more effective. But in agricultural lands, crops constitute a superabundant source of potential food. In these landscapes, invertebrates like some insects or snails do not seem to be mainly limited by the amount of available food –instead, access to quality feed appears to be a matter of greater importance.
Therefore, deterring insects typically move off on to a new crop, where they do not necessarily compete for food, and their populations can thrive. So it is unclear whether repellants will actually reduce populations of target invertebrates. That is why repellents are only used occasionally in crops. They work better as a part of a strategy that incorporates other forms of population control.
I’m really impressed by all these writeups!
But wouldn’t this reduce the total insect population if food were the limiting factor?
Thanks!
Good question about repellants. Indeed, if food were the limiting factor, repellants would be much more effective. But in agricultural lands, crops constitute a superabundant source of potential food. In these landscapes, invertebrates like some insects or snails do not seem to be mainly limited by the amount of available food –instead, access to quality feed appears to be a matter of greater importance.
Therefore, deterring insects typically move off on to a new crop, where they do not necessarily compete for food, and their populations can thrive. So it is unclear whether repellants will actually reduce populations of target invertebrates. That is why repellents are only used occasionally in crops. They work better as a part of a strategy that incorporates other forms of population control.