Fungous Diseases oe Colorado Crop Plants 
21 
Early blight may make its appearance in the early stages of 
the plant’s growth, either in the seed-bed or in the field. The outei' 
leaves are first attacked; grayish-green spots, roughly circular in 
outline and with slightly raised borders, appear. Later the spots 
become darker in color, an ashen-gray, and larger. In some cases 
several adjacent spots may run together. Finally the entire leaf 
withers and dies. When the spots become brownish, it is an in¬ 
dication that they are producing reproductive bodies, the spores. 
These are readily blown from plant to plant, and in this way the 
trouble is spread throughout the field. 
Late blight, in general appearance, resembles early blight (Plate 
V., Fig. 2). It may follow early blight in the same field and its effect 
upon the marketable value of the celery plant is similar. As compared 
with the early blight, the spots on the leaves are more irregular, and 
yellowish in color rather than ashen-gray. The spots later become 
covered with small, black fruiting bodies. Theise are readily seen 
with the hand lens. Late blight is found in the field until the plants 
are lifted and commonly continues its destructive work in storage. 
In fact, often the worst damage to the celery crop froiu late blight 
comes while the plants are in storage. 
Control .— (i) Do not set plants from the seed-bed that are the 
least spotted. 
(2) Dip leaves of all transplants in a weak solution of am- 
moniacal copper carbonate. 
(3) Keep the plants in as vigorous condition as possible from 
start to finish. This is important. 
(4) Remove and burn all diseased leaves, if practicable, as fast 
as they appear, so as tO' prevent further spread of the disease. 
(5) Remove and burn all celery debris from the celery plot in 
the fall; this debris may harbor the spores which will live over the 
winter to infect young plants the following spring. 
(6) Spray with ammoniacal copper carbonate, or 5-6-50 Bor¬ 
deaux mixture, first when the plants are in the seed-bed, following 
with treatments at two or three week intervals throughout the 
growing season. 
(7) In the case of late blight, dip only the leaves of lifted 
plants into ammoniacal copper carbonate before placing in storage. 
(8) Do not store plants that show any spotting. 
(9) The celery leaf spot disease may be spread by the use of 
affected seed. To render the seed safe, soak them three hours in 
formalin solution (t pint 40 per cent formalin in 70 gallons of 
water). Thoroughly dry seed before planting. 
