Yellow or Brown Leaves With Webs suggests Spider Mite.
Spider mites turn leaves yellow or brown, giving them a parched appearance. The leaves may curl and become covered with fine webbing, especially on undersides, and fruit is deformed. Adult mites are reddish brown or pale tan and 1/150 to 1/50 inch long. They are more easily visible through a hand lens. Mites lay their eggs on leaves and buds or at the base of plants. You may control mites, which favor hot, dry locations, by spraying plants in early morning with a forceful jet of cold water. Repeat the water spray daily for three days. If that doesn't do the job, spray with insecticidal soap every three to five days for two weeks. Dormant oil spray will destroy many over wintering mites. Spray with 1 part flowable sulfur fungicide in 10 parts of "superior" type dormant oil before growth begins in spring.
For more information see file on Controlling Mites.
Spots on Leaves; Twig Dieback and Blackening indicates Fire blight.
Fire blight causes dark spots on or "shot holes" in leaves, death of flowers and twigs and girdling of main stems and branches. Infected twigs wilt from the tip and turn black. Cankers form on the bark, becoming sunken and cracked. Fruit shrivels and turns black. Sticky ooze may appear on any infected part. Fire blight is a bacterium which over winters on cankers and on large branches of apples and pears, and is spread from plant to plant by insects and splashing raindrops. To control this disease, prune all blighted plant parts 4 inches below visible cankers and burn them. Disinfest pruners in between cuts with a bleach or sodium hypochlorite solution. Also keep rapid growth in check by fertilizing only moderately and avoiding high-nitrogen applications. Dormant sprays of copper sulfate or Bordeaux mixture may offer some additional protection when used in combination with other control measures.
Foliage Burned due to Dogs.
Urination by dogs may discolor foliage and even kill branches. Spraying foliage with an anti transpirant gives some protection. Screen the plants or spray with an aerosol pet repellant. For more information see the file on Dogs and Cats
Bark of Stems and Roots Gnawed means Rodents.
Small rodents gnaw bark off main stem, causing injury that allows disease organisms to invade. Rake mulch away from plant bases during the winter; keep the area clear of weeds and grass; and wrap the base of the plant with a guard of 1/4-inch hardware cloth.
For more information see files on Dealing With Mice, Dealing With Rabbits and Dealing With Voles.