Ron, I long ago removed our 'inherited' old quince tree. I tried making quince jam, but it seems like the recipe called for one part quince - four parts sugar!
I'm no expert on quince trees, but I do remember that ragged dead-look it had; yet it produced all-too-well. Ours too was leaning slightly, but had a very hunched over appearance, with limbs touching the ground.
All I can suggest is the old: scrape-the-bark-and-see-if-it's-green-underneath test!
But, after some additional research online, I found an interesting description of one of its few diseases: "Fleck." Granted, the site refers to "New South Wales," and the second description of Fleck is from the American east coast... Maybe its also found the Pacific Northwest? Other than these two descriptions of "Fabraea maculata," aka: Fleck; I'm probably little help.
But here's Fleck
: [from] http://www.agric.nsw.gov.au/reader/deci ... .htm#Pests
"The only disease of consequence is Fleck (Fabraea maculata), which occurs throughout New South Wales. Its effects can be serious. In coastal and tableland areas, fleck may defoliate quince trees if uncontrolled from January onwards. With severe infections, no marketable fruit develops.
Leaf infection may occur soon after leaf buds burst. The spots are very small, slightly raised and purple with a small central white dot. Spots may remain circular, or they may enlarge and change colour to dark brown, then ashy grey or reddish-brown. They join together to form large irregular areas which may cover most of the leaf surface. By this stage, leaf stalks can be fatally affected and the leaves fall.
Dark brown spots develop on the skin of the fruit, which enlarge and become black and slightly sunken. With heavy infections, spots may join to form large, irregular areas, which cause fruit to be misshapen and often cracked. The disease may also cause fruit to fall prematurely.
Shoots develop inconspicuous lesions, which can enable the disease to carry over between seasons.
Fleck can be controlled in home garden trees by raking and burning all fallen leaves in autumn. Prune regularly, and heavily enough to remove all dead and spent wood. The best way to overcome problems with fleck is to either choose moderately resistant varieties for humid climates, or use fungicides
And: Fabraea Leaf Spot:
Fabraea leaf spot, also known as leaf blight and black spot, is caused by the fungus Fabraea maculata. This disease usually appears late in the growing season but can occasionally develop in late May and early June. Fabraea leaf spot attacks leaves, fruit, and twigs of pear. Symptoms first appear as brown to black spots on the leaves. Heavily infected leaves often yellow and drop prematurely. Severe defoliation can substantially reduce tree vigor and yield, especially if trees are defoliated several years in a row. Lesions on fruit appear similar to those on leaves but become slightly sunken as fruit expand. Severely infected fruit may also crack. Once established in a tree or planting, this disease is difficult to control since significant amounts of fungal inoculum overwinter on infected leaves. Spores of the fungus are easily spread by splashing rain and wind in the spring.
Effective control includes a good sanitation program. Since overwintering infected leaves are a major source of spores in the spring, removal of all fallen leaves during the dormant season significantly reduces the chances for new infection. In addition, properly selected and timed fungicide sprays are important for disease control
Good luck, Viron.