94 



THE AGRICULTURAL NEWS. 



March 18, 1911. 



FUNGUS NOTES. 



RECENT WORK WITH FUNGUS 



PARASITES OF SCALE 



INSECTS. 



In the Aiiricultural New» of September 11^, 190'j (Vol. 

 VIII, p. 299), a short account wa.s given of the fungi known 

 to be parasitic upon scale insects in the West Indies, and this 

 preliminary paper was followed by another in the Wvit Indian 

 Bulletin, Vol. A' I, p. I, where a detailed account of their 

 known distribution and hosts was given. It was also point- 

 ed out that for various reasons these fungi were likely to 

 prove a useful means of controlling scale insects, provided 

 that they were employed in the right way. Experiments 

 have been conducted recently with one of these, the shield 

 scale fungus ( Ceplialoiporium b-canii), in Barbados and (_!ren- 

 ada, which furnish .some interesting additional information; 

 while general ol)servations in (irenada have indicated the 

 advisability of paying careful attention to one or two matters 

 which will be mentioned below. 



(;renad.\. As is well known, many of the trees in this 

 island have been subject in recent years to bad attacks of 

 scale insects, attended by black blight fungus. These are 

 found on very many dift'erent trees, but are commonest on the 

 mango. The scale insects chiefly associated with the black 

 blight fungus, on whatever species of plants it occurs, are the 

 soft shield scales, members of the genus Coccus, which are 

 persistently attacked by the shield scale fungus. In conse- 

 quence of this, experiments were undertaken with a view to 

 extending as widely as pcssible the distribution of this 

 useful fungus thmughdut the island, as it was known 

 to occur there, l)ut appeared to be limited to the 

 Botanic Gardens and their neighbourhood, at the extreme 

 leeward end of the island. The Superintendent of Agri- 

 culture sent out packages of leaves bearing specimens of 

 soft shield scales attacked by the fungus, with the request 

 that they might be tied carefully into any big mango tree ou 

 the estate to which they were sent, provided that the tree 

 was badly infected with black blight. A request v.'as also 

 made that any results obtained as regards freeing the tree 

 from black blight and scale insects might be carefully noted. 

 In addition, experiments were conducted under the direction 

 of the Superintendent of Agriculture for the purpose of ex- 

 tending the di.sti'ibution of the fungus in the Botanic Gardens 

 themselves. As a result of these experiments, the fungus 

 has become definitely established at two localities in the 

 interior of the island, and its distribution in the Botanic 

 Gardens has been extended. The trees on which it has 

 spread successfully have been almost entirely freed from 

 scale insects and, in consequence, are not nearly so severely 

 affected with black blight. It was noted, moreover, that the 

 fungus had spread to a species of scale insect that it had 

 never been known to attack before, namely the mealy .shield 

 scale (Ptdvinarin pyriformix), which occurred on a cinnamon 

 tree in the gardens. 



Although the fungus mentioned cannot yet be said to 

 have attained anything approaching universal distribution in 

 the island, yet the ex|)eriments show tliat tliis much desired 

 result might be attained, by means of diligent and persist- 

 ent effort, in a rea.son.alily shnrt space of time, 



BARiJADo.s. In November 1910, the Superintendent of 

 Agriculture observed tlie shield scale fungus attacking the 

 black scale (Saissetia nii/ra) on some branches of Hibiscus, 

 and made use of this material to infect the green and mango 

 shield scales (Cocrus viridisi and C'ocms nMnriiferac) on guava 

 and mango plants at the Botanic Station at Dodd's Reform- 



atory. The results weie so satisfactory that similar experi- 

 ments were conducted at C^ueen's Park, and these were 

 also attended with success. In fact, in February, the Superin- 

 tendent of Agriculture reported that it was difficult to find 

 in the infected trees scales which were not attacked by the 

 fungus. 



Information as to the discovery made in Grenada that 

 the shield scale fungus could attack the mealy shield scale 

 was communicated by the Imperial Commissioner of Agricul- 

 ture to the local Department of Agriculture, Barbados. As 

 a result, examination was made in Februar}' of certain 

 trees at Dodd's Reformatory, of Java plum {Eugtnia 

 Jambolana) and rose apple {Eugenia Jamios), on which 

 this scale was known to be living, and it was found 

 that individual insects were attacked by the fungus in 

 that locality, also. In order to hasten the spread of the 

 para.site, the Superintendent of Agriculture caused certain 

 branches of the Barbados cherry {Malj>i<ihxa glabra), on 

 which the scale insects had been destroyed by it, to be tied 

 into the .Java plum and rose apple trees, with the result that 

 the spread of the fungus has gradually increased. 



These experiments afford most striking confirmation of 

 the results that might be ex|)ected in consequence of careful 

 and well directed applications, not only of the shield scale 

 fungus, but also of all the species known to destroy scale 

 insects in these islands, 



GENERAL CONSIDERATIONS. One of the most important 

 points requiring consideration when employing the.se fungi, 

 is that they have not yet become distributed throughout the 

 whole of several of the islands, Con.sequently, where this is 

 the case, if their spread is left entirely to natural means, it 

 may be many years before their benefit becomes at all evi- 

 dent, and in certain cases, their effect might never be so large 

 as to be of much practical service. Thus, in order to obtain 

 the best results as quickly as possible, every effort should be 

 made to increase their distribution artificially by means 

 similar to those indicated above. This effort, moreover, must 

 be sustained, the infection experiments being repeated until 

 they are definitely successful. 



In conducting these experiments, certain points should 

 be remembered. The trees chosen for infection should be 

 situated at the windward end of the district to be treated; 

 this applies especially to narrow valleys. The material should 

 be tied in at the top, and on the windward side of the trees; 

 while it is advisable also to cause the infected leaves to come 

 into fairly close contact with the under sides of the leaves to 

 be infected, as it is on the under .side of the leaf that the 

 majority of the .scale insects occur. 



Again, even when infection has been established, it is 

 possible that after an interval reinfection may become necess- 

 ary; for if all the scale insects are killed the fungus dies, so 

 that a new attack of insects will make it necessary to 

 introduce more fungus. 



Even when a given fungus has become well established 

 in an island, efforts to increase its prevalence by artificial 

 means will almost certainly be necessary, in order to ensure 

 that its spread keeps jiace with that of its hosts. This is 

 particularly the case in sea.sons unfavourable to the fungus, 

 which are bound to be of periodic occurrence. 



Although there is need of continuous ettbrt and of sus- 

 tained artificial encouragement in order to induce these fungi 

 to do the work required of them, yet there can be little 

 doubt of their economic usefulness. It may be added that 

 no such sustained effort has as yet been made, so that the 

 present condition of alfairs cannot be tAken as any criterion 

 of the possible effect of the.se para,sites in controlling the 

 scale insects of the West Indies, 



