Remember squigs, both Ken and I are a relative handful of miles from California's Central Valley, damn near the home of factory/conventional agriculture. The world expo is held down in Bakersfield... or is it Fresno? I can't remember, but every time we head down 99 we drive past the center.
I don't fully understand the mechanisms of resistance, nor do I fully understand how that might expand. Thus my extreme caution here. Plus, the
Spinosad is just no good for my pollinators, of which I've got a qualified metric buttload.
Resistance is actually pretty easy to talk about, so I will.
Basically what you're looking at is the following:
1. Chemical/process kills most of a species in an area--say 99.9% of them.
2. The only surviving members in that area are, thus, naturally resistant.
3. Competition for reproduction is, thus, reduced.
4. If the resistance can be passed genetically, either by one parent (bacteria/insects), or two (insects)--then the next generation will have some members (if not all) which are naturally resistant.
5. The resistant population is initially small, however, continued application of only this one chemical/process can cause this same process to repeat--reducing competition for reproduction among that group over and over again. Eventually you end up with a fully resistant population.
A few notes:
1. If only one parent is needed to pass the resistant mutation, resistance develops more quickly (as with bacteria).
2. If only one chemical/process is used--development of resistance is more common.
3. If application rates for the chemical are not high enough, resistance is more likely (as some in the population may be only *slightly* resistant, but this still selects for greater resistance than none)--in this case resistance can take many generations to develop.
4. This is why it is important that if you need antibiotics you FINISH THE ENTIRE PRESCRIPTION. The doses of antibiotics given is usually way overkill, and there is a reason for that (see #3). Even if you fight back the infection to the point where it can't get a foothold in your body, by not eradicating it you may be passing a semi (if not fully) resistant bacteria to someone else. Bacteria are a worst case scenario because they reproduce asexually (copy themselves), so it's a mixture of #1, #2, and #3 that has brought wonderful things like MRSA to us.
If you want to avoid this happening in your garden here are some things to do:
1. Use more than one thing to kill the bug you're after. If a portion of the group is resistant to one thing, it probably will not be to the other and vice versa.
2. Rotate what you're using each crop cycle (or within a given cycle depending upon the life cycle of the pest you'r'e after)
What I want you to realize, Sea, is that by removing Bti from your rotation you are actually increasing the liklihood that the buggers will become resistant to something else that you are using. Diversity is the key when dealing with pests.
You don't want to overuse Bti, but you should absolutely use it. It will reduce the incidence of resistance with the other products/methods you're using.
