110 



THE AGRICULTURAL NEWS. 



Maech 25, 1916. 



PLANT DISEASES. 



SOME NEW ENTOMOGENOUS FUNGI 

 IN ST. VINCENT. 



ON A V\OOI>-H()RING GKUB. 



Kaily in 1915, !Mr. W. N. Sands, Agricultural Superin- 

 tendent, St. A'incent, forwarded for examination specimens 

 collected by him in the Botanic Garden^^, Kingstown, of 

 ■a fungus growing on the larvae of the beetle Cryptorhynchus 

 aorlicalis, Boh., boring the wood of Codiaeum mrier/atum, 

 the common 'croton'. 



The affected larvae are found in their tunnels in the 

 stems, retaining their form and colour, but converted into 

 Lard sclerotia. From them the stalk of the fruit body of the 

 fungus penetrates to the surface of the bark, and there 

 expands into a peltate disc; of a reddish brown colour, upon 

 the centre of which is borne a conical spine. These discs, 

 "when developed singly, measure, in the specimens to hand, up 

 to some 3 m.m. in diameter, but commonly .several run 

 together, in which case a more or less circular body is formed, 

 ■which may approach to a diameter of a centimetre, and bears 

 several of the above mentioned spines. Asci, of the form 

 usual in the genus Cordyceps, are produced at the base of 

 closely set, flask-shaped cavities opening on the upper surface 

 of the disc. Specimens of the fungus have been forwarded 

 to Kew for examination, and Miss E. M. Wakefield reports 

 that it appears to be a new species of Cordyceps, and will be 

 described as such. 



ON A SOIL GRUB. 



On January 1, 1916, the writer found, in the soil near 

 the roots of a cacao tree at Mount William estate, a grub 

 laving the larval characters of the species of Diaprepos and 

 Exophthalmus commf)n as root feeding weevils in these islands. 

 The grub Wius dead, but unshrunken and hard, and its form 

 ■Was perfectly preserved. The specimen was brought to 

 Barbados, and kept in the laboratory in a corked tube, and 

 after some weeks was observed to have devoloped a number 

 of erect brown threads, the fruit bodies of a fungus of the 

 ^enus Isaria. 



The fungus continues to develop, and at the time of 

 ■writing (March 2) about a dozen threads of various lengths 

 and thicknesses have appeared, the two longest and strongest 

 of which, arising from the anal end, are over 10 cm. in 

 length and about 5 m.m. in thickness. The growing tip 

 is white for some distance, and behind it, as it pro- 

 gresses, are developed lateral bristles 1-2 m.m. long, each 

 clothed with hairs bearing terminal conidia. 



ON THE C.VCAO THRIPS. 



Messrs. Sands and Harland, Agricultural Superintend- 

 «nt and Assistant Superintendent, respectively, have had 

 under observation for some months a fungus found by them 

 on Hdiothrips ru/troo'miK , Giard. infesting cacao leaves. 

 It has the appearance of being parasitic on this insect, 

 being found on larvae as well as adults, under circumstances 

 which suggest no other cau.se of death. It occurs as a 

 ■whitish mould on the body of the insect, attaching it lightly 

 to the leaf. The writer has as yet had the opportunity of 

 examining only a very small amount of material. In this 

 tliere seemed to be no differentiation of conidiospores, the 



conidia occurring in spherical groups scattered along the 

 tangled hyphae. during a recent visit to the somewhat 

 remote districts where it occurs, very little of the fungus 

 was found, but the writer is informed that it has been seen 

 to be so abundant as to justify its being regarded as a 

 considerable factor in reducing the numbers of the insect. 



ON SCALE INSECTS. 



During a visit paid to Queensbury estate in January of 

 this year the writer observed patches of a slaty grey fungus- 

 of the Corticiuni type extending over considerable areas on 

 the stems of pigeon pea, where they were heavily infested 

 with Aularaxpix yjeraia^o^ia, Targ. The fungus closely 

 resembles Septohaxidium pedicellatum. .Schwein.. common in 

 St. Lucia on colonies of the purple scale on citrus trees, and 

 will very possibly prove to be that species. Its occurrence 

 in St. Vincent is, so far as the writer is aware, not previously 

 recorded. 



The same remark applies to the fungus Ophionectria 

 coccicoh, E. and E., which was found on the same occassioa 

 in great abundance in one particular situation, growing on 

 scale insects infesting lime trees. The circumstances of its 

 occurrence under very sheltered conditions suggest that its 

 non-development in other districts, which has been the 

 subject of some regret, is due rather to insuflicient humidity 

 than to actual absence of the species. 



Another fungus found on the purple scale at Queensbury 

 appears to be quite new to these islands, so far as the records 

 of the Imperial Department go. It is a light clear pink 

 Aschersonia, forming groups of small, closely-set, rather 

 woolly, sessile stromata, mostlj- spherical or nearly so, but 

 in a few cases exposing a small open disc with a smooth 

 surface and of darker colour. 



It may be added that the red fungus, Sphaerosttlbe 

 coccophila, TuL, and the black fungus, Myrinngium Duriaei, 

 Mont., were also present in abundance with those above- 

 mentioned. 



W.N. 



THE CONNEXION BETWEEN CROP 



PRODUCTION AND BACTERIAL 



ACTIVITY. 



In his paper in' the Journal of A;iricultwal Renarch, 

 Vol. 5, No. 1 8, on the relation between certain bacterial activ- 

 ities in soils, and the crop producing power of these soils, 

 Mr. P. E. Browne, of the United States Department of 

 Agriculture, appears to have established that the connexion 

 between the two, that is to saj- between bacterial activities 

 and crop yields, is so clo.se as to make the examination of 

 a soil for bacterial change of great practical importance^ 

 It would appear that the tests of a soil in the laboratory 

 for ammonification, nitrification, and similar changes may 

 indicate accurately ttie crop producing power of the soil, or, 

 at least, the relative crop producing power of several soils. 



In one experiment with Indian corn it is shown that the 

 yields obtained are in close agreement with ammonification. 

 Thus in a plot which gave a yield of 50'25 bushels per acre the 

 ammonification was y5"33 m.gs., while in the plot which gave 

 74 bushels of corn per acre the ammonification was 

 72"79 m.gs. 



In conclusion It may be stated that these experiments 

 have shown that ammonification and crop production are very 

 closely related, and that the determinations of the anunoni- 

 fying power of soils made during the growing season may- 

 show their relative crop proflueing powers. 



