DISEASES OF PLANTS. 55 



A peculiar disease, known as " sancocliado " in Porto Rico, was observed in 

 tobacco seed beds of CVijinas. This disease spreads from a center in ring-like 

 progression. The circle of dead, bleached seedlings increasing continuously is 

 cheeked only by removing the soil to some depth and treating the spot with diluted 

 formaldehyde (1 spoonful to 30 gal. of water). A microscopical examination 

 revealed no mycelium, but numerous active nematodes were found, which are 

 thought to cause the disease. 



The tobacco flea beetle and the chauga are considered the worst enemies of 

 tobacco in Porto Rico. The majority of the insect pests, including the cutworm, 

 are avoided by growing the tobacco under cheese-cloth. 



Peach leaf curl, I. B. P. Evans {Transvaal Agr. Jour., 6 (1908), No. 22, 

 IH). 259, 260, pis. 2). — The author descril)es the peach leaf curl caused by 

 Ej-oascus (U'forinaus, giving particular attention to its occurrence on nectarines 

 and apricots. When the fungus attacks the fruit of the nectarine it becomes 

 covered with wart-like growths, while apricots are arrested in their develop- 

 ment so that they never attain more than half the normal size. 



For the prevention of this disease the author recommends thorough spray- 

 ing with Bordeaux mixtui'e. 



Notes on the black knot of plum, J. B. Dandeno {Ri)t. Mich. Acad. Sci., 

 9 (1901), pp. l-'i, 15, pg. 1). — The author reports on successful attempts in ob- 

 taining the ascospores from the black knot of plums. Upon careful examina- 

 tion it was found that the perithecia are not produced for about 3 years after 

 infection. After the perithecia are produced the asci are quickly disseminated, 

 and the old knots remain on the twigs. In order to collect material showing 

 the asci and ascospores the third year's growth of the plum knots must be 

 secured. 



From inoculation experiments with conidia formed by the fungus, it seems that 

 they are not very active as infecting agents. Only a small proportion of infec- 

 tion with ascospores succeeded in producing the disease, which seemed to indi- 

 cate that artificial inoculation is not readily accomplished. 



Gooseberry black knot {Jour. Bd. Agr. [London], IJ, (1908), No. 11, pp. 680, 

 6S1, figs. //). — A descrii)tion is given of a disease of gooseberries and red and 

 black currants that is due to the fungus Plowrightia ribesia. 



The fungus is a wound parasite, and it seems probable that ai>hids and scale 

 insects enable it to gain entrance into the living tissues of the plant. The first 

 indication of disease is the wilting and yellowing of the leaves, which fall quite 

 early in the season. As a rule a branch is not killed outright in the first season 

 of the attack, but during the second year the leaf buds remain In half-opened 

 condition and the branch dies, owing to the presence of the fungus mycelium in 

 tlie water conducting vessels. There is no external evidence t)f the fungus until 

 the brj'.uches are dead or nearly so, when the fruiting bodies burst through the 

 bark, forming elongated or grouped blackish warts. 



It is believed that spraying will have little or no effect in controlling this 

 disease, and it is recommended that on its l>rst appearance all branches whose 

 foliage is wilting should be removed and burned. 



A combined treatment for the prevention of the powdery and downy mil- 

 dew of grapes, 1). Donon {Jour. Agr. Prat., n. scr., 15 {1908), No. 5, pp. I.'f6- 

 l-'i8). — A description is given of a fungicide that is said to consist of a copper 

 and sulphur mixture to which formaldehyde is added. This fungicide is claimetl 

 to be very efficient in the control of various grape diseases, including the poW' 

 dery mildew, and its use does away with the necessity of sulphuring the vines. 

 The fungicide is prepared for the trade in a concentrated form, and is said to 

 be of easy application and less expensive than a liquid spray for the prevention of 

 black rot, etc., with a separate application of sulphur for the powdery mildew, 



53818— No. 1—08 5 



