Monitoring insects and deciding if it pays to control them is rarely an easy job. Insects always have an element of unpredictability. Environmental risk and user risk of insecticides are also of prime importance and control of insect pests should never be cosmetic in this regard.
Insect traps and provincial maps can provide valuable insight into what severity can be expected.
Pests still require regular monitoring in order to gauge whether they may reach threshold levels at some point in the future.
Staying on Guard
Timing is very important with insects as each has a unique life cycle and habitat that requires a high level of understanding. No two years are ever the same and although weather cycles and growing degree days would suggest something definite, field scouting is always required in order to confirm the prediction.
Spray too early and you may have to spray again. Spray too late and you may not control them or only get revenge as the damage has already been done. Regular insect scouting is an essential IPM practice.