I16 THE PEARS OF NEW YORK 
reddish-brown circular spots on the upper surface of the leaves, but the 
fungus penetrates through to the lower surface as the disease progresses. 
Eventually the color changes to dark brown, and later a coal-black, raised 
spot appears in the center. The spots sometimes run together. Young 
leaves shrivel under the attacks of the fungus; while old ones, if badly 
diseased, turn yellow and drop prematurely. Twigs and leaf-stalks are 
frequently girdled, and the lesions are more elongated. The spots are 
similar on the fruits to those on the leaves. The fungus spends the winter 
in fallen leaves. In the spring the spores are discharged from the fruiting 
organs of the fungi and are carried to the tender leaf or twig of the pear or 
quince. The parasite begins growth at once and in about a month a new 
crop of spores develop. This fungus grows on various other pome-fruits 
which complicates remedial measures. The treatment recommended for 
leaf-spot should control leaf-blight. 
As are all tree-fruits in New York, the pear is attacked by crown-gall 
(Bacterium tumefaciens Smith & Townsend). This disease, however, is 
seldom a serious menace to orchard trees this far north, but the vigor 
of nursery stock is sapped when the galls girdle the tap-root or the stem 
at the collar. Moreover, trees affected by crown-gall are barred in most 
states by inspection laws so that nurserymen can ill afford to produce 
gall-infected trees. It is a wise precaution not to plant badly diseased 
trees. The galls are tumor-like structures on the roots of the plant, or 
often at the juncture of root and stem. They vary from the size of a pea 
to that of a large egg, forming at maturity rough, knotty, dark-colored 
masses. Another form of the disease appears as a dense tangle of hair- 
like roots arising from callous-like galls. This form passes under the name 
“hairy root.” Neither preventive nor cure is known. Orchard or nursery 
should not be planted on ground known to have been infected as the disease 
is highly contagious. The brambles, especially raspberries, are common 
carriers of crown-gall, and none of the brambles should be planted as inter- 
crops in pear-orchards. 
Brown-blotch (Leptothyrium pomi (Mont. & Fr.) Sace. var.) is another 
fungus which is sometimes troublesome. The fungus causes reddish blotches 
on the fruit which coalesce into rusty-brown patches often covering the 
whole surface of the pear. Here, again, the Kieffer suffers most although 
fruits of other varieties are often disfigured by the blotch. The disease is 
most common on heavy soils and in densely shaded trees. Pruning to let 
