The major issues with pears in Wisconsin are fireblight and plum curculio. Fireblight is caused by bacteria. This disease primarily shows up in spring with cankers on the tree or rapidly wilting and dying branches (affected leaves wilt and turn black in 24 hours). Any forms of wilting and dying branches or cankers on older wood need to be pruned out as soon as they are found. Sterilize pruners or saw blades between cuts with a bleach solution (1 part bleach & 9 parts water) to prevent the spread of the bacteria.
Plum curculios are native snout weevil that attacks young pear fruits in June and attempt to lay eggs in the fruit. While usually unsuccessful, the affected fruit will develop with a dimple on the skin but the flesh underneath will stay hard and gritty even when the fruit ripens. Best controlled by spraying an insecticide from petal fall-mid June in S.E. WI.