Colorado Plant Diseases 
3:3 
tlie Aviiiter months or it may be due to late spring frosts. Injury 
occurring during the Avinter months is sometimes spoken of as Avinter 
injury. 
All parts of the trees may be affected. TAvigs, portions of large 
branches and roots are often killed by severe cold during the Avinter 
months. Late spring frosts usually injure leaves, fruit, buds, and 
blossoms. Affected leaves crimp and curl and ‘‘frost blisters” are 
often formed. Young fruits may be entirely killed or may be only 
slightly injured giving rise to the peculiar russeting or “frost band.” 
To preA^ent frost injury do not irrigate or cultivate late in the fall. 
AIIoav the trees to thoroughly mature before cold Aveather. Do not 
apply nitrogenous fertilizers except in early spring. 
Spray Injury (19), (20) — Apple leaves and fruit are sometimes 
injured by improperly applying sprays or by applying sprays im- 
properly prepared. Injured fruits shoAV characteristic russet 
blotches. Leaf injury is in the form of irregular scattered light broAvn 
spots. If the spray is very strong holes may be burned into the 
leaves. 
To avoid spray injury: (1) FoIIoav carefully directions for the 
preparation of a spray mixture. Do not get it too strong. (2) Use 
pure chemicals. (3) Use a good nozzle and apply spray under high 
pressure in order to obtain a fine mist. (4) Be sure that the spray is 
thoroughly mixed. 
NEGLECTED ORCHARDS 
Throughout Colorado there are many orchards Avhich are suffer- 
ing from the lack of attention. No orchard can be expected to yield 
profit Avithout a reasonable amount of care. Many orchards have 
never had a spray applied. Improper cultural practices, careless 
pruning and general neglect all go to produce the most favorable 
conditions for the groAAdh and deA^elopment of all fungus and insect 
diseases. 
After large sums of money have been spent in establishing an 
orchard it is poor business not to give it proper care and make it 
yield its maximum production. Many orchards in Colorado that are 
not noAv paying interest on the investment could be made profitable 
by a little intelligent orchard management including judical use of 
sprays. 
APRICOT 
Black Knot (PloAvrightia morbosa) (21) — see Plum. BroAvn Rot 
(Sclerotinia cinerea) (22), (23) — see Peach. Fruit Spot (Coryneum 
beyerinckii) (24), (25) — see Peach. Scab ( Cladosporium carpophi- 
