PLANT DISEASES 



315 



Rhizoctonia Stem rot (Corticium vagum 

 var. Solam). Rot take3 place at or just 

 below the surface of the soil and causes the 

 plant to suddenly wilt. Observe the same 

 precautions as controlling of Fusarium stem 

 rot. Do not set plants too deep. 



Rust {Uromyces Caryophyllinus) . 

 Appears first as a small elongated blister like 

 structure which later ruptures and exposes 

 deep brown powdery masses. Present on 

 both the stems and leaves. Avoid an excess 

 of moisture in the greenhouse and spray 

 with blue vitriol, 1 pound to 20 gallons of 

 water. 



CELERY 



Early blight (Cercospora Apii). Spots 

 appear first as pale yellow areas, irregular 

 and somewhat angular in outline. Later 

 they turn brown and finally the center 

 becomes an ashen gray._ May destroy the 

 entire plant. Spray with Bordeaux mix- 

 ture (5-5-50). Beginning when the plants 

 are first set, make about 6 applications 

 during the season. 



CHERRY 



Late blight (Septoria Petroselini va r 

 Apii). Affects flowers, which turn brown 

 and wither, and fruit, which at first is 

 rotted; then small, light brown pustules 

 are produced on its surface. Finally the 

 fruit becomes a hard, wrinkled mummy, 

 which either hangs on the tree or falls to 

 the ground. Spray with lime-sulfur (1-50) 

 or dust with 90 parts of sulfur to 10 parts of 

 arsenate of lead, first when the blossoms 

 show white but before they open, later 

 when the calyx is being shed, and finally 

 about 2 to 3 weeks before fruit begins 

 to ripen. 



Leaf curl (Exoascus Cerasi). The leaves 

 become crinkled and turn reddish in color. 

 On their lower sxirface appears a whitish 

 coating. They fall premateurly. The dis- 

 eased leaves appear only on abnormal out- 

 growths from affected twigs called witches' 

 brooms. Prune out the diseased twigs. 



Leaf spot or Shot hole (Coccomyces 

 hiemalis) . Spots appear on the leaves which 

 at first mere discolorations, soon become 

 dark red or purple in color; finally the 

 center drops out leaving a "shothole," or 

 the leaf turns yellow and falls. Plow under 

 eld leaves and spray with lime-sulfur (1-40) 

 or Bordeaux mixture (5-5-50); or dust with 

 sulfur 90 parts and arsenate of lead 10 parts. 

 Make first application when calyx ia shed- 

 ding; repeat 10 days later and again after 

 picking. Do not use Bordeaux on sweet 

 cherries. 



Powdery mildew (Podosphaera Oxya- 

 canthae) . Leaves and twigs of young shoots 

 are covered with patches of white mildew 

 which spreads finally over the whole leaf or 

 twig. Small black spherical bodies develop 

 on the surface of this mildew. Dust with 

 sulfur or spray with lime-sulfur (1 to 50). 



CRANBERRY 



Gall (Synchytrium Vaccinit). Small, 

 reddish galls are formed on the young stems, 

 leaves, and sometimes, on the flowers and 

 fruit. They are in color. Burn the bog 

 over in the Autumn and keep it dry during 

 Winter. 



Hypertrophy (Exobasidium Oxycocci). 

 The buds in the leaf axils grow out into 

 shoots which bear swollen, enlarged leaves 

 of a pinkish color. No remedy ia known. 



Scald (Guignardia Vaccinii). Appears 

 on berries, first as watery areas which en- 

 large and soften the whole berry which 

 turns brown; several spots may develop 

 on one berry. Finally the affected berries 

 become scalded in appearance. Sometimes 

 black dots appear on them. Spray with 

 Bordeaux mixture (5-5-50) to which a resin 

 fish oil sticker is added. 



CUCUMBER, MELON AND SQUASH 

 Anthracnose (Coletotrichum Lagena- 

 rium) causes circular brownish spots on 

 leaves and elongated light brown spots on 

 stems. The spots on the fruits are sunken 

 and have small pinkish gelatinous masses 

 on their surfaces. Spray frequently with 

 Bordeaux mixture (5-5-50). 



Downy Mildew (Peronoplasmopara 

 cubensis). At first small yellowish angular 

 spots are produced oa the leaves. These 

 enlarge and may involve the entire leaf 

 which finally dies. In moist weather a 

 white downy growth may be seen on the 

 under side of the leaf. Spray the vines every 

 10 days with Bordeaux mixture (5-5-50). 



Wilt (Bacillus tracheiphilus). Causes a 

 wilting of a leaf and finally of the entire 

 vine, which dies. Keep vines free of bugs 

 and striped beetles which spread the bac- 

 teria. Pull and bum diseased vines. 



CURRANT 

 Leaf spot (Mycosphaerdla Grossulariae) . 

 Appears as small brown spots on the upper 

 and lower sides of the leaf. As these spots, 

 which often run together, enlarge, the 

 centers become whitish and small black 

 pimples arise on their surfaces. Leaves 

 turn yellow and fall prematurely. Spray 

 with lime-sulfur (1-50) or dust with a mix- 

 ture of ground sulfur 90 parts and powdered 

 lead arsenate 10 parts, as follows: When 

 the first leaves appear and every two weeks 

 following. 



Anthracnose (Pseudopeziza Ribis). Ap- 

 pears as numerous small brown circular 

 spots on the upper aurface of the leaves, and 

 also on the berries. When severe the leaves 

 turn yellow and fall. On the leaf stems 

 stnall, slightly sunken spots may be seen. 

 Spray with Bordeaux mixture (5-5-50) or 

 lime-sulfur (1-40) first, when the leaves 

 are unfolding and subsequently at intervals 

 of from 10 days to two weeks. Spray more 

 frequently in moist weather. 



