94 



THE AORICULTURAL NEWS. 



March 15, 1913. 



FUNGUS NOTES. 



A ROOT DISEASE OF PASPALUM 



DILATATUM. 

 In the Report on the Botanic Station, Montscrrat, for 

 1910-11, 1'. 15, appears a "short note on the introduction of 

 this host plant which runs as follows: 'This C'alifornian grass, 

 which has been grown with remarkable results in serai tropi- 

 cal countries, was intro<luced in July 1910 Seedlings were 

 raised and an experimental plot formed. The growth, so far, 

 has been more .satisfactory than that of the Pennisetum, 

 (Indian Fodder grass also recently introduced into Montserrat) 

 but it is yet too early to say if it will ultimately prove to be 

 a useful acquisition.' 



The grass did fairly well at first, but was subsequently 

 attacked by a root disease, which at the present time, has 

 destroyed it. A recent examination of the diseased clumps, 

 revealed the presence in them of a white mycelium which 

 attacked the roots and sheathing leaf-bases in a manner 

 strongly reminiscent of the effect produced by Marannius 

 sacchari on the sugar cane. The leaf bases were cemented 

 together in the way so familiar to cane planters by a waxy 

 white mycelium easily visible on the outside nf the base of 

 each shoot, whilst numbers of the roots were dead and dry. 

 The fungus appeared to grow right through the compact leaf- 

 sheaths, and may even have penetrated the growing point. 

 In any case the ultimate result was that the whole shoot 

 dried up. In each clump either all or the majority of the 

 shoots were dead. On breaking up the clumps the fruc- 

 tifications of two or three rather small agarics were found, 

 attached to the decaying leaves near the moist centre 

 of the clump. One of these was a very small JIarasmius 

 with a delicate white cap and thin black wiry stalk; 

 another, which was apparently a species of Crepidotus, had 

 a resupinate thin pileus, attached to the substratum excentri- 

 cally, and from this excentric point the gills radiated. The 

 pileus averaged about 2 mm. in diameter, was often 

 kidney-shaped, and in some cases provided with a very short 

 stalk which bent over from the substratum to the point from 

 which the gills radiated. The outside of the cap was white 

 and the inside and gills pink. 



It was not possible to determine if any of the fructifica- 

 tions observed belonged to the mycelium causing the damage. 

 The grass has been taken up and destroyed, as it is unlikely 

 to prove of much economic importance in Montserrat when 

 liable to a disease of this nature. 



almost always water-soaked. When the spots reach a size of 

 about 5 to 6 mm. in diameter, the central portion dries 

 out and becomes grey brown in colour. This drying con- 

 tinues indefinitely as the margin of the diseased area 

 advances into the healthy tissue, so that eventually large 

 patches are formed consisting of grey brown dry tissues 

 bordered by a somewhat indefinite water-soaked margin 

 about 2 mm. wide. Several of the spots may occur 

 on one leaf, and may run into one another and form very 

 large dead patches: in some cases this results in the death of 

 the tip and the major portion of either side of the leaf, and 

 nothing but a narrow green strip of healthy tissue is left 

 along the mid-rib. No fungus fructifications were observed 

 on any of the dried patches. 



A small portion of one of these young light green spots was 

 cut out with a scalpel and rinsed in corrosive sublimate solu- 

 tion 1 part in 1 000 of water, then in sterilized tap water, and 

 finally crushed in a drop of sterile tap water with a sterilized 

 glass rod. After half an hour, two plates of nutrient agar 

 were poured by the dilution method from this drop. In both 

 plates a mixed growth consisting only of bacteria resulted, 

 but there predominated certain small circular white colonies, 

 with a smooth surface and a very definite margin, consisting 

 of short straight rod-shaped bacteria. The occurrence of 

 these colonies taken in connexion with the absence of fungi in 

 the plates and of their fructifications on the spots, as well as 

 with the appearance of the spots themselves, suggest a bacterial 

 origin for this disease. Unfortunately, time did not allow of 

 the carrying out of any further work to ci infirm this con- 

 jecture. 



The disease could probably be controlled by the use of 

 Bordeaux mixture. It is not of much importance, but is of 

 interest as being one of the few diseases observed on the 

 genus Eucalyptus in the West Indies. 



Citrus Scab. — A description is given of this disease, 

 due to Cladospui-itim citri, in the Hiperiment Station Record, 

 Vol. XXVII, No. 7. The fungus has been i.solated from 

 sour orange leaves and cultivated, and infection experiments 

 have been made demonstrating that it is the cause of the 

 trouble described. 



The organism seems particularly injurious to sour orange 

 and lemon sprouts, and the author recommends the des- 

 truction of these, together with spraying with amnioniacal 

 copper carbonate or Bordeaux mixture. The copper car- 

 bonate solution is preferred since it usually does not cause 

 an increase of scale insects as sometimes follows the use of 

 Bordeaux mixture. 



A LEAF SPOT OF EUCALYPTUS 

 PULVERULENTA. 



A young tree of this species growing in the Botanic 

 Cardens, Montserrat, .showed on its leaves the presence of 

 numerous spots, which at the time of the examination were 

 particularly noticeable on the leaves attached to the lower 

 Ijranches, and on the older leaves of the upper branches; 

 whilst on a young shoot arising on the side of, and above, the 

 infected portions, the foliage was quite healthy. The general 

 appearance ratlier suggested that the infection wa.s rain-borne. 



The spots themselves are first visible as irregular areas 

 1 to 3 mm. in diameter of a colour rather paler than the 

 general green of the rest of the leaf. As they increase in 

 size they become slightly brownish in colour or may present 

 a water-soaked appearance near the centre of the upper surface 

 of the leaf, whilst on the under surface the same part is 



Cotton anthracnose is a widespread and destructive 

 disease in South Carolina. The disease is caused by 

 a fungus {G/omerella Gossypii) which grows as a parasite in 

 the parts of the plant and destroys the tissues. The fungus 

 which causes the disease grows into the seeds before they are 

 mature and remains alive there until the seeds are planted. 

 When such disd&Sed seeds are planted in less than three 

 years from the time of maturity they [)roduce diseased 

 plants. Diseased seed is tbe most important factor in the 

 spread of the disease. By careful selection, seeds which are 

 free from anthracnose can be secured from a field where the 

 disease is present. The fungus which causes anthracnose 

 does not remain alive in the field for more than one year. 

 Crop rotation and seed selection will control cotton anthrac- 

 nose. (From the Bulletin of tlu ll)orean of At/ricultural 

 Iiitdliijence and of Plant Diseases, for December 1912.) 



