Government of New Brunswick

Plant Stage of Growth 
Growers with a recurrent aphid problem may apply a systemic insecticide. It can control aphids for secen weeks or longer, sometimes eliminating the need for further control. Aphid populations normally increase slowly during this period and therefore should not require any control. Aphids may start multiplying rapidly during warm days. Examine potatoes frequently. No sprays should be considered until a sudden and rapid increase in aphid numbers is observed. Tablestock potato fields should be treated if 50% or more of plants are infested. This should prevent any risk of yield losses and should reduce the number of winged forms capable of spreading virus diseases in nearby seed fields. The seed fields should be treated if 10% or more of the plants are infested with green peach and buckthorn aphids. Topkill as early as tuber maturity allows. The earlier the better for aphid control. This will limit virus spread by aphids. Usually it is not necessary to use an insecticide within eight days of topkilling.
Colorado Potato Beetle
Avoid planting potatoes in a field that had unusually large numbers of adults at the end of the previous season or has been in potatoes for three years or more. Otherwise, apply a systemic insecticide. When poresent, adult beetles are scattered on a few plants or along field edges. It is sufficient to spot spray with foliar insecticides. Monitor the abundance of larvae and consider applying an insecticide if there are an average of two larvae per plant in 12m of row examined on different parts of the field. One spray against the large larvae (3rd - 4th instars) before they start going down to the ground to pupate may be sufficient. If unusually large numbers of adult beetles are present, an insecticide could help reduce next year's spring problem.
White Grub and Wireworm
Avoid planting potatoes on land that has been in sod for two years or more to prevent a white grub problem, before the third season after breaking the sod for wireworm. If potatoes are to be planted on sod land the year after June beetles are abundant, apply an effective systemic insecticide. If two or more wireworms per shovel of soil are found, broadcast and harrow a systemic insecticide into the upper 15cm of soil or hand it at planting.      
Flea Beetle
  Should not require treatment. The plants usually compensate for the damage with their rapid growth. Specific sprays are normally not required against the second peak of beetles except for large numbers of beetles on very susceptible varieties. Beetles are usually below threshold or their numbers are reduced by sprays against other pests.  
European Corn Borer
    Monitor pan traps baited with the Z-type (Iowa strain) pheromone for adult males. Begin sampling plants for egg masses when adults are detected. If sprays are warranted, apply to control newly hatched larvae before they enter the stem. High number or larvae will reduce yield through wind damage, water stress and invasions from pathogens
Tarnished Plant Bug
    Monitor for abundance of pests and apply sprays if large numbers are present.  
General Comments
  This is the plant stage that can tolerate the most leaf injury. Damage to the plants at the pre-bloom and bloom stages can have pronounced effect on yield.