DISEASES OF CULTIVATED PLANTS 371 
Leaf-spot or Frog-eye. There is a common leaf-spot disease of apple trees in 
which the dead spots show the presence of pycnidia. This troubleis really due 
to the black-rot fungus (Sphacropsis malorum Pk.) but at times another fungus, 
{Coniothyrium pirini Sacc.), comes in afterwards. In the later season the 
second type develops in concentric areas to which the common name of ‘‘Frog. 
Eye’’ has been given. Yet other forms of leaf-spot due to spray injuries also 
occur, but are easily distinguishable from the two first named. It has been 
shown that control of the black-rot fungus keeps the leaf-spot in hand, but early 
treatments should be made. 
Mold. A blue mold is very commonly associated with soft rot of apples in 
storage. The fungus (Penicillium glaucum Lk.) is a very common one and may 
be regarded as associated with the presence of decay or bruising, not as a first 
cause of rot. 
Mildew. The powdery mildew (Sphaerotheca mali (Duby) Burr.) often occurs 
upon nursery growths of the apple and occaionally upon rather thrifty growing 
young trees. The dense felt-like covering of the fungus is usually very apparent 
and the spreading of the fungus upon the foliage is sometimes noticeable. Spray- 
ing with fungicides usually keeps the trouble in check. 
Rust. The bright orange growths of this rust fungus (Gymnosporangium 
macropus Lk., etc., I) are occasionally found on cultivated apple leaves as well 
as on leaves of wild thorn apples, especially where these are within reach ofthe 
cedar trees which bear the cedar apples. In 1909 the rust attacked apple fruits 
in Ohio and Nebraska. These so-called cedar apples are no more than the 
development of the rust fungus from which the spores are spread to the apple, 
Crataegus, etc. A remedy in indicated by this statement, viz., get rid of cedar 
trees. 7 : 
Root-Rot. Serious root-rot troubles have been reported to us from Missouri, 
Arkansas and Oklahoma where orchard plantings have been made quite soon 
following the clearing of scrub oak, etc. Similar cases have been studied in 
Ohio where plantings were made soon after the removal of the timber, especially 
of oaks. One is usually able to identfy the rhizomorphs of the root-rot fungus, 
(Agaricus melleus L.. (Armillaria mellia) and the characters by the occurrence 
upon orchard trees and also the original growth is usually quite clear. Any 
inadequacy of drainage is very serious in connection with root-rot. (See root-rot 
of peach, etc.). More recently Von Schrenck has identified another fungus 
(Thelephora galactinia Fe.) with a form of root-rot which shows no superficial 
symptoms until after the tree is dead; it then shows the orange, leathery sheets. 
Scab. Apple scab fungus ( Venturia inegualis Aderh, Fusicladium deudriti. 
cum (Wallr.) Fuckl.) is a common source of large losses in Ohio apple 
orchards. It attacks first the leaves and afterwards the young fruit, causing it 
to drop. Aside from injuring the salability of the crop obtained and reducing 
the vigor of the tree by reason of its attacks on the foliage, scab may prevent a 
crop altogether because of this dropping of the young apples. The Ohio Station 
was in the van of progress in studying this disease, and the work has been 
steadily followed (Bulletin Vol. IV, No. 9, (1891) B. 79, (1897) B. 111, (1899). 
Full details may be found in the various bulletins given. Apple scab develops 
when moisture is abundant during the early months of she season, and low 
temperatures are usually prevalent at such times. The dropping of apples often 
attributed to lack of pollination seems more often to be ascribed to the work of 
scab. All varieties are attacked by scab but some suffer more than others. 
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