— t. ow Nh oe ~ 
| x 
| The first account of the disease was published by F. Lamson-Scribner 
| in October, 1886 (Bulletin of the Torrey Botanical Club, New York, 
| Vol. XIII, No. 10, pp. 181-183), at which time Professor Scribner was 
| : Chief of the Section of Vegetable Pathology of the Department of 
_ Agriculture. <A fuller account, with a colored plate, was published in 
_ the Annual Report of the Commissioner of Agriculture for 1886, pp. 120, 
| 121. <A disease undoubtedly the same was reported from Australia 
| on orange and lemon leaves by Henry Tyron.! 
The principal loss from scab occurs in Florida, where it often renders 
lemon groves so unprofitable that they are cut off and budded to other 
citrous fruits. In many cases a very large percentage of the fruit is 
_ rendered unsalable, sometimes one-third or even one-half being unfit 
_ for market. It also causes some injury to sour orange trees (before 
they are budded) when grown for nursery stock. 
Scab, or a disease closely allied to it, occurs on very young fruit of 
the lime (Citrus limetta), and in some localities is often so severe as to 
entirely destroy the crop. For example, a grove in tropical Florida, 
capable of yielding 500 boxes of fruit annually, when attacked by this 
disease produced for several years only a few hundred fruits, and the 
majority of these fell off while still very young. In Louisiana it is said 
to have attacked Satsuma oranges; in Japan it causes considerable 
damage to orange groves situated on low, moist land; in Australia it 
is reported as causing orange and lemon trees to lose their leaves and 
to yield poor crops, badly affected trees often not setting a single fruit. 
Probably the annual loss from scab in the United States is not far from 
| $50,000, most of the damage being done to the lemon in Florida. 
| Symptoms.—The leaves and fruit of trees affected with this disease 
Show small, wart-like excrescences (Pls. V, VI). ‘These exerescences 
are of various sizes, the diameter ranging from 4 mm. to 1 cm. (one-fif- 
tieth to two-fifths of an inch), but usually being from 1 to5mm. They 
sometimes run together and cover a large portion of the leaf or fruit. 
In case the fruit is attacked while still very young the tissues below the 
wart grow morerapidly than normally. This causes the fruit to become 
} covered with bumps, of irregular pyramidal shape. ‘These grow propor- 
tionally with the fruit and on the mature fruit may sometimes be 1 to 
2 em. across and project out nearly the same distance. At first the 
i} warts look like small semi-translucent pimples, of a slightly lighter 
/§ shade of green than the surrounding healthy tissue. Ina few days, if 
the weather be favorable, the warts become prominent, assume a con- 
Spicuously light green color, and look watery. After this they become 
covered with a delicate fungus, which is at first gray, then dusky, and 
|} atlast black. Finally the infected tissue covering the tips of the warts 
j is cut off from the healthy tissue below by a formation of cork, and ulti- 
-§} mately the cork formation becomes so abundant as to give a dingy white 
_# color to the old warts. The appearance and development of the warts 
1 Report on Insect and Fungous Pests, No. 1, Queensland, 1889, pp. 144, 145. 
