398 



THE AGRICULTURAL NEWS. 



Dec'embeii C, 191; 



FUNGUS NOTES. 



MYCOLOGICAL INVESTIGATIONS IN 



FLORIDA. 



The Annual Report for the year 1 9 1 2, of the University 

 of Florida Agricultural Experiment Station is to hand, and 

 contains as usual matter of interest to tropical agriculturists, 

 especially with regard to the artificial control of insects by 

 fungoid parasites, and the pathology of Citrus trees. 



ENTO^tOGENOUS? FUNGI. 



One looks forward to this report for information 

 as to the progress of the campaign against the Citrus 

 white fly {Alturodes citri) carried on by spraying with 

 the spores of A&chersonia aleyrodis, Aeijerita wehheri, 

 ifirroccra sp. and Vfrtifilliuni /leterocladum. This and 

 the similar campaign against the froghopper in Trinidad 

 by means of Metarrlir.iuin anisoplioe are being watched 

 with very great interest by plant pathologists, as serious 

 attempts to demonstraie the possibility of the arti 

 ficial spread of insect destroying fungi to a practical extent. 

 Previous attempts, where they have not completely failed, 

 have at least been indecisive, and the writer knows of no 

 case where a method of this nature has passed into accepted 

 practice. Usually the attempts have been discontinued 

 when the first enthusiasm of the persons conducting the 

 experiments has been dissipated. With the larger supply of 

 material rendered readily available \>y improved mycological 

 technique, there is howecer room for hope of a practical out- 

 come, though the intimate dependence of the fungi for 

 •uccessful development on weather conditions will probably 

 limit the use of such methods of control to specially situated 

 localities or specially favourable seasons. 



In Florida, according to the report before uf, the highly 

 favourable results hitberto announced are being well main- 

 tained. For example, in a specified I. itrus grove sprayed with 

 fungi in 1909, at which time the white Hy was said to have 

 been very prevalent, so complete was the parasitism 

 still prevailing that it required a five minute search to find 

 a single live larva, although no further application since the 

 original one had been made. The spraying of the spores ha.s 

 become an established commercial pursuit, and one of the 

 operators thus employed reported in September 191 l,that with 

 two, three, or four helper.s he had sprayed altogether 94,129 

 trees, belonging to 108 different owners, since March 1911, 

 while two other men associated with him sprayed from 

 2.5-30,000. Besides this spraying he had shipped 218,800 

 leaves bearing the different fungi to 10-5 growers. Another 

 man following the same business in 1911 sprayed 39,444 

 trees: 3,330 of these he re.sprayed, and 935 were sprayed 

 a third time. 



Only passing allusion is made in the report to the con- 

 trol of scale insects by fungi, but there is an observation that 

 certain trees sprayed with Bordeaux mixture showed such an 

 immense increase in scale insects, due to the destruction of 

 the parasitic fungi, that they were nearly killed. 



PATHOLOGY OK CITRUS FRUITS. 



The most interesting information in this connexion con- 

 cerns the long standing and much discussed problem of the 

 origin of raelanose, which information is contained partly in 

 the sectional report of the Plant Pathologist and continued 

 in the subsequent Bulletin 111 by B. F. Floyd and 

 M. K. Stevens. 



Melanose was first discovered in Florida in 1892, and 

 has since been reported from Australia, Algeria, Jamaica, 

 and Porto Rico. It has been observed on nearly all varieties 

 of Citrus plants, none having been found to be particularly 

 immune. It affects leaves, stems and fruits while they are 

 young and succulent, producing markings which consist of 

 raised areas of brown gum filled cells, forming dots, lines, 

 curves, rings and irregularly shaped .spot.s. The markings are 

 often arranged in vertical streaks (tear streaking) following 

 the track of water dripping from an overhanging dead twig. 

 To the touch, the roughness suggests the feel of sand paper — 

 a fact which is of some value in distinguishing this from 

 other forms of injury of a similar nature. Xo fungus or 

 bacterial organism was found in connexion with the spots 

 which could be considered as producing the disease. 



The organism ultimately established as the cause works 

 in a highly novel way. The observation which gave the 

 clue to the solution of the problem was that the markings 

 were regularly associated with dead twigs overhanging the 

 afl^ected organs. It was found that water in which such dead 

 twigs had been soaked would produce the characteristic 

 markings on young growths upon which it was allowed to 

 drip, provided that the latter were kept for a short time in 

 a humid atmosphere. Such water when thoroughly filtered 

 failed to produce this effect, thus excluding soluble toxins as 

 the cause. The twigs were infested by various saprophytes, 

 amongst which the fungus P/i'uno/isis citri, Fawcetf, regu- 

 larly occurred. Finally, spores from pure cultures of this 

 organism when suspended in water were ffiund to be capable 

 of causing the characteristic appearance of melanose. The 

 fungus is but weakly parasitic and appears to undergo no 

 further development after the marks have been produced. 



The same fungus has been established as the cause of 

 stem end rot of Citrus fruits, usually gaining access where 

 scale insects have weakened the fruit by developing in great 

 numbers about the calyx. 



The incidence of these two diseases is thus shown to 

 be dependent upon the presence of dead twigs or branches, 

 and it is upon the removal of such that their control depends. 



VEGETABLE OILS. 



OIL PALM FOR THE WEST INDIES. 



Some mention has been made lately with I'eference 

 to the possibility of growing the oil palm of .Southern 

 Nigeiia on plantation lines in British Guiana and in 

 British Honduras. The same question has apparently 

 been brought up in the Federated Malay States for in 

 the Agricultural Bulli'tin (September 1918), F.M.8., 

 the whole question of production is dealt with in some 

 detail. The following extract dealing with the cul- 

 tivation of the oil palm is taken from the paper 

 referred to: — 



The oil palm is propagated from seed, only seed from 

 eight to tenyear-old trees and upwards should be used for 

 planting purposes as those from young trees are extremely 

 small and in all probability would not give as good results 

 as seed from mature trees. 



The nursery beds should be raised, made of fairly rich 

 humus soil and near a watercourse if possible to ensure the 

 proper humidity of the soil. The seed should be jilanted 

 about 18 inches apart each way at a depth of from 1 to IJ 



