They attribute the drop to lack of pesticides because according to the researcher the drops coincided with changes in policy, drops were also seen in other coun

They attribute the drop to lack of pesticides because according to the researcher the drops coincided with changes in policy, drops were also seen in other countries that banned pesticides, and simular situations were seen when access to common forms of suicide were restricted in other countries also saw a drop in rates (i.e. gun restrictions led to fewer suicides). It's hard to run controlled trials at a macro scale so it's unlikely that the effect was only pesticides but it sounds like historically these sorts of interventions do work.