40*2 INSECTICIDES, FUNGICIDES, AND WEED KILLERS, 



Rot — White, Pailb, Livid. Coniv- 

 thyrium J)ijilo,/i,'l/a.—Thh fuugiis is a 

 parasite of the grape, which may in certain 

 cases <lo tonsil ieniMe ihmiage, as occurred in 

 1,SS6 in I^i Ven.lee, in 1887 in Le Gard, and 

 in L'lleraiilt in Upper Italy and Switzer- 

 land. The ('(riiidtfii/riiaii do not attack the 

 grapes in the same way as the (UUgnardw. 

 Whilst the latter attacks isolated grapes in 

 an irregular manner leaving tlie stalk un- 

 altered, the former invades the stalk of the 

 grape shoot and the sheatli of the grapes. 

 The latter change colour, become livid brown, 

 and soften, and then wither, turning an 

 earthy colour. On the skin of the dead 

 grapes there form small globular conceptacles 

 which give them a shagreen appearance. 

 Often it Is the peduncle alone which is dis- 

 organized which causes the almost ripe gi-apes 

 to fall. Tlie mycelium develops in the par- 

 enchyma of the grape stalks attacked and 

 spreads thence into the skin of the grapes 

 ■where it forms, when that is withered, 

 picynides like black rot. These picynides 

 are up to now the only organs of reproduc- 

 tion known ; their spores appear to preserve 

 their germinative faculty all the winter and 

 even up to the following summer, and can 

 thus transmit the disease from one year to 

 another. These spores do not appear to at- 

 tack the leaves, as the disease is unknown on 

 the grapes. Generally the germination tube 

 of the spores penetrates into the stalks of 

 the grapes by wounds prod wed by large 

 hail-stones or by insects. This fungus ap- 

 pears to be more particularly a wound 

 parasite which thus renders it especially 

 dangerous alter violent storms or an inva- 

 sion of cochylis. 



Rust, Linear or Common. Puccinia 

 graminis. — This rust attacks wheat, barley, 

 oats, a host of common grasses, such as 

 meadow grass, couch grass, dactyla, agrostis, 

 cauche?, flouve?, foxtails, brizes?, fleoles?, 

 festuca, etc. It is the most dangerous rust of 

 cereals. It particularly attacks the leaves, 

 their sheaths, and the stalks (straw). The 

 uredo form appears at the end of the month 

 of June. They are elongated pustules which 

 let an orange-coloured juiwdcr escape. At 

 the latter end of the season these spores 

 form black pustules, puccinia, the black rust 

 of farmers, in which the teleutospores are 

 <leveloped. These spores ennt in the follow- 

 ing spring a proiuycelium of which the spor- 

 idia only g.-rminatc On the barberry, they 

 produce UTidiiun, the si)()rcs of which infect 

 cereals and produce the uredo form. 



Rdst of Bekt. Unmii/res Betes. — This 

 rust is autoic, which means that the whole 

 cycle of its evohition is gone through on the 

 ,same plant. All the forms of fructification 

 may therefore be formed on the beet. It 

 attacks the beet in summer, and may, when 

 it assumes a great development, damage the 

 leaves, and cause a perceptible decrease in 

 crop. The uredospores form small, very 

 numerous ovoid or round pustules, which 

 pierce the epidermis and let a yellowish- 

 brown powder escape. 



Rust of Cereals. Puccinia.—At least 

 three different species of rust are to be seen 

 on grain crops. They are uredina; which 

 are termed heteroic because during their 

 cycle of evolution they must live on nurse 

 plants of different orders. Uredina; of this 

 genus have, therefore, multiple methoiis of 

 fructification which generally succeed each 

 other hi the course of the year in a fixed 

 order. In the early spring the sperniagones 

 and the fficidium appear ; in the course of 

 summer the uredo ; finally in autuiini the 

 teleutospores. The uredo or red rust form 

 is the form of dissemination of the fungus 

 during the germination of the cereal, the 

 black rust or puccinia assures the trans- 

 mission of the disease from year to year. 

 The mycelium of these fungi grows ex- 

 clusively in the interior of the organs of the 

 plant attacked. The spores are generally 

 formed under the epidermis of the nurse 

 plant through rupture of which it is spread 

 outside. The mycelium is most often local- 

 ized and only occupies a limited point of the 

 tissues which it destroys. The orange spots 

 seen on plants each correspond to a special 

 hotbed of infection. At these spots the 

 mycelium forms felted masses which destroy 

 the living tissues. The spores which form 

 under the epidermis become detached as 

 soon as ripe, and may germinate immedi- 

 ately if they fall in a drop of water in warm 

 weather. The germinating tube, crawling 

 on the surface of a leaf, for example, pene- 

 trates into a stomata and extends into the 

 tissue, reproducing in eight days an analogous 

 spot to that from which it escaped. A rust 

 spot on a cereal may thus contaminate the 

 whole field in a few weeks. At the back- 

 end of the season orange rust is no longer 

 formed, but black rust or puccinia, a pustule 

 of a black colour. The spores formed in the 

 puccinia differ from the uredospores in the 

 fact that they do not become detached on 

 ripening from the end of their support and 

 do not germinate until after several months' 

 rest in the following spring. These spores 

 are termed teleutospores. The teleutospores 

 do not prcxluce a germinative tube capable 

 of penetrating by a stomata into the nurse 

 plant and of developing there. The teleuto- 

 spores give rise to a promycelium, the 

 growth of which is limited and on which 

 spores form the sporidia. As they develop 

 they may pierce the epidermis of the nurse 

 plant which is always a difterent species. 

 The mycelium has a form of fructification 

 which differs from that of the uredos and 

 the puccinia ; the pustules appear in the 

 spring and are of two sorts, the a?cidium, 

 forming on the lower surface of the leaves, 

 and the spermagones, forming on the upper 

 surface of the leaves. These two forms spring 

 from the same mycelium ; spores are formed 

 in these two receptacles. The spores formed 

 in the recidium are capable of reproducing 

 the rust disease on a new support which is 

 always a cereal. Those formed in the sper- 

 magones are called spermatia. Their role is 

 not yet finally established. 



