In other words, if we run the risk of population collapse within ten years, and population collapse will lead to crop failure and mass starvation & death, but rigorous studies on cause will take fifteen years to complete... do we wait for them to finish?
For example, corn is wind pollinated and wheat, soy, rice and potatoes are self pollinating.
Having reduced access to things like almonds and apples is gonna suck, but even with 0 insects it's still going to be reduced access, as hand pollination is quite a fast process.
More importantly I wonder what unforeseen unintended consequences will arise from disassembling food chains, after we've lost those species, and it's too late.
Insect deaths are acutely reported in the last decade.
Insect population may be down overall, but not down with crop pests.
Insecticides may require a certain density of use to be effective; that is, there may be a non-linear dose/response curve such that it's not really meaningful to reduce the current levels.
The goal is to maximize income. Reduced insecticide use, even with the relatively low corresponding insect populations, might still reduce the yield and/or quality and therefore profit. Think of how the oceans are overfished, but while there's a good reason that everyone should greatly reduce their catch, there's no good reason for any one fishing crew to do that on their own.
I am not aware of any scientific publication showing a causal link. Let's be a little careful about this. By increasing crop yields and reducing deaths from insect borne diseases, insecticides have greatly reduced human suffering over the past century.
It's possible that insecticides are the cause, and if so, something has to be done, but such decisions need to be based on facts, on science, NOT on superstition and storytelling.