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THE AGRICULTURAL NEWS. 



iiAY 9, 1914. 



FUNGUS NOTES. 



CONTROL OF DAMPING OFF DISEASE. 



The following summary of investigations by Mr. 

 James .Johnson, of the University of Wisconsin, is taken 

 from Research Bulletin No. 31, of that institution. 



Damping off of seedlings in plant beds in Wisconsin is 

 commonly caused by one of two fungi, P;/thiiij/i deharyammi 

 or Rhizoctonia. 



These fungi are capable of attacking a large variety of 

 different plants, as well as of living upon the dead organic 

 matter of the soil, and are hence extremely persistent when 

 once present in the soil. 



The disease is fa scoured particularly by certain weather 

 conditions such as excessive moisture and high temperatures, 

 and very little can be done to check the disease when such 

 conditions prevail. Therefore this necessitates the adoption 

 of methods which kill the fungi in order to prevent the 

 disease. 



The preventive methods are of such a nature that they 

 must be applied before the sowing of the seed, since the 

 methods used to kill the fungi would also kill the seed. 



A number of chemical agents have been tested as fungi- 

 cides against damping off, but of these, formalin alone has 

 proven of any value under conditions favourable to 

 damping off. 



Treatment of the soil with formalin at strengths of one 

 part formalin to 100 parts of water and lesser strengths, as 

 frequently recommended, does not kill the fungus. Although 

 it may hold the disease in check for some time, it will allow 

 it to develop later if weather conditions permit. The value 

 of formalin at these strengths is therefore dependent, in 

 a large measure, upon the time of the appearance of weather 

 conditions favourable for damping off. 



Treating the soil with 1-50 formalin at the rate of 2 

 quarts per square foot of soil, will kill the fungi which cause 

 damping off, and will hence effectively prevent damping oft' 

 under the most favourable weather conditions for fungus 

 growth. Formalin soil treatment is also somewhat beneficial 

 in stimulating the plant growth and in killing some weed 

 seeds. The chief objections are the cost of the formalin, the 

 time required for it to act, and the time required for the 

 soil to dry out. 



Sterilization of the soil by heat has proven the most 

 satisfactory method of preventing damping oft' from all stand- 

 points, excepting that under certain conditions it may be 

 more expensive than the formalin treatment. Steam sterili- 

 zation Viy the 'inverted pan' method is especially recom- 

 mended where a steam traction engine is on the farm or can 

 be obtained in the neighbourhood. 



Aside from preventing damping off, there are several 

 beneficial secondary effects of soil sterilization by heat. 

 These are principally the killing of all weed seeds and insect 

 pe.sts of the soil, and greatly increased size and vigour of 

 plants grown on such soil. 



As a cultural control of damping off', growers should 

 avoid infected, poorly drained soils and thick sowing of seed. 



The only means of checking the disease after it has 

 occurred in the plant beds is to remove the covers in order 

 to reduce the temperature and the moisture of the soil and 

 of the air immediately above the plants. 



FUNGOID DISEASES IN BARBADOS, 



1912-13. 



The following notes form a brief review of that portion 

 of the Annual Report of the Barbados (Local) Department 

 of Agriculture for the year ended March 31, 1913. The 

 investigations were carried out by Mr. William Xowell, 

 Assistant Superintendent of the Local Department, and the 

 information contained below has been taken from the report 

 of that officer. 



SUGAE-CANE DiSEASi.s, The fungus, Marasmius sacc/iari, 

 which causes root disease, was abundant and injurious during 

 the period under review, while Colletotriclium falcatiim, the 

 fungus which plays the most important part in causing rind 

 disease was observed in onlj- a few instances. The root 

 disease fungus is universally present, but being a weak 

 parasite does not cause much injury as long as the canes 

 are in a vigorous condition of growth. The effect of the 

 severe drought of 1912 was to weaken the canes and, as 

 a result, root disease was much in evidence, causing serious 

 injury. With the advent of the rains many stools, appar- 

 ently dying from root disease, sent out fresh shoots and 

 produced healthy canes. 



It is pointed out that planters should exercise greater 

 care in the selection of the cane cuttings for planting, with 

 special reference to the use of the strongest and healthiest 

 plants, free from the presence of the fungus. 



EvERGEEEN TEEES (Ficus nitido). Many of these 

 beautiful shade trees have died in Barbados, the dead 

 trees often showing signs of the presence of the 

 black crustaceous fructifications of the fungus Eutypa 

 eruinpens. The extent of the parasitism of this fungus is 

 not dehnitelj known, but it seems to be in some degree 

 responsible for the death of the tree. It is recommended 

 that dying branches should be cut off close and smooth at 

 their bases so as not to leave any stubs or projections, and 

 painted to prevent the cut surface from rotting until the 

 new growth has time to cover it. Bad trimming, hacking 

 of branches and tearing of bark are responsible for much 

 injury to trees in Barbados. 



A fungus, probably a Coiiiut/iecium sp., has been found 

 on limes, producing a silvery scurf on the surface of the 

 unripe fruits. It is suggested that spraying with Bordeaux 

 mixture would be useful in controlling it. 



EOSEs. These have been attacked by a fungus, Actino- 

 neiiia rosae, Lib., probably the same as Dicocctun (Marssonia) 

 rosea, Bon., which causes the leaves to turn yellow and fall. 

 Spraying with Bordeaux mixture soon after the young leaves 

 have unfolded, and at intervals during active growth is 

 recommended as treatment. The picking oft' of infested leaves 

 and clearing away fallen ones is likely to give results ia- 

 checking the spread of the disease. 



EOSE MILDEW {Spkaevotkera pauuosa) is of frequent 

 occurrence. Dusting with a mixture of flowers of sulphur 

 and dry slaked lime is recommended as the treatment. 



VINE DISEA.SE. The mildew {JJnrimda spiralis, B. it C.) 

 has caused trouble resulting in a brown spotting of the leaves 

 and a general sickly appearance of the plant. The fungus may 

 easily be recognized as a whitish mealy deposit on the leaves, 

 stems and fruit. It may be controlled, or at least checked^ 

 by dusting with sulphur and lime. This should be done in 

 dry weather, preferably in the early morning when the plants 

 are moist with dew, which will enable the dust to adhere to 

 the plant better than if it is applied when the surface is 

 quite dry. 



