Fungous diseases of plants . stimate the average losses from thesefungi, and this is particularly true on account of the fact that thescab fungi are more or less superficial in their effects. In severecases the fruit is wholly unmarketable, but in too many casesscabby fruit is regularly put upon the market and the reducedprices which it brings are not estimated. During seasons favor-able for the fungus, probably one year in two, the losses in manysections of the country amount to a reduction in price or totaldestruction of from 25 to 50 per cent of the entire crop. 266 FUNGOUS DISEASES OF PLAN
Fungous diseases of plants . stimate the average losses from thesefungi, and this is particularly true on account of the fact that thescab fungi are more or less superficial in their effects. In severecases the fruit is wholly unmarketable, but in too many casesscabby fruit is regularly put upon the market and the reducedprices which it brings are not estimated. During seasons favor-able for the fungus, probably one year in two, the losses in manysections of the country amount to a reduction in price or totaldestruction of from 25 to 50 per cent of the entire crop. 266 FUNGOUS DISEASES OF PLANTS The relation of host and fungus. These fungi commonlyaffect fruit and leaves, but they may also be found upon leafstalks, flowers, and twigs. Upon the leaves (Fig. ii8) in eachcase the spots are more abundant, as a rule, upon the lowersurface. Where the fungus is made evident by an olivaceous,velvety, superficial growth, or when the disease is very abundant,both surfaces of the leaf may be covered and considerable curling. Vie. ii8. AiiLK Scab on Leaves: Different Types of Infection may result. Upon the fruit there are at first small, circular, oli-vaceous spots, especially upon the pear, but as a rule the appear-ance changes as the fungus spreads, the epidermis is killed, andthe familiar scabby spots are produced. At times practically thewhole fruit may show indications of the fungous growth, and ageneral puckering of the tissues may result in an abnormal formof the fruit. Some varieties of pear may develop cracks orfissures extending halfway to the core. Fig. ii6 shows a severeattack of scab on Flemish Beauty. ASCOMYCETES 267 There are probably no varieties of the pear or apple whichare entirely free from scab. Nevertheless, there is a great dif-ference in susceptibility. In New York, Flemish Beauty, vSum-mer Doyenne, Duchess, Clairgeau, Sheldon, Seckel, Anjou, andLawrence have been reported as more generally affected thanLe Conte, Kieffer, and Bartlett. In California the
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