November, 1911.] 



437 



Plant Sanitation. 



scale (Chonaspis citii), and the red 

 scale (Aspidiotus sp.), though the star 

 scale (Vinsonia stellijera) was un- 

 affected. Experiments in transferring 

 the fungus from tree to tree were 

 successful whenever the weather was 

 wet, and the author now has hopes, nit 

 only of keeping his trees alive, but of 

 getting them into a good condition for 

 cropping. 



On the other hand, under exceptional 

 circumstances, such as a serious epidemic 

 of scale insects in a dry season, it is 

 probable that the judicious use of in- 

 secticides such as whale-oil soap com- 

 pound, kerosene emulsiou. or rosin 

 compound would prove of the utmost 

 value. Not only would such spraying 

 mixtures prevent the immediate in- 

 fliction of excessive damage on the 

 trees, but they would as already pointed 

 out, enable the natural enemies to regain 

 their position in a shorter time. Dr. 

 Berger in a short article ' Citrus Scales 

 and Whitefly ' contained in the Florida 

 Agriculturist for March, 1910, supports 

 this view, but insists on the avoidance 

 for this purpose of any insecticides 

 containing sulphur or possessing any 

 fungicidal ingredients. 



When considering this point it 

 must, however, be borne in mind 

 that, in addition to the four 

 species of fungi, there are also several 

 species of insects which live on scale 

 insects. Among these is a small 

 hymenopterous species which lives as 

 an internal parasite on the purple scale 

 (Mytilaspis citricola). Such delicate 

 insects, and especially that just referred 

 to would almost certainly be destroyed 

 by insecticides, and the proportion of 

 them thus killed would be even greater 

 than that of their hosts. Thus it would 

 probably be found after employing 

 insecticides, that parasitism by these 

 insects would not be as common as 

 before. Asa result of these arguments 

 it will be evident that, even in serious 

 cases, insecticides should only be used 

 as a last resource, once it has been 

 determined that the natural means of 



control is that most suited to ordinary 

 conditions. 



Summary. 



(1) Four species of fungoid parasites 



occur on scale insects in the 

 Lesser Antilles, namely : Cepha- 

 losperium lecanii, Myriangium 

 Duricei, Ophionectria coccicola, 

 Sphcerostilbe coccophila. 



(2) These may artificially spread 



either by the spore-spraying 

 method, or the tying-in method. 



(3) The fungi are most effective in 



the islands of Dominica and 

 Montserrat upon the scale insects 

 attacking limes, but are also of 

 general importance in all the 

 islands. 



(4) The use of Bengal beans as a cover 



to trees, more especially lime 

 trees, serves to protect them 

 from attacks of scale insects, 

 probably by encouraging the 

 natural enemies. 



(5) The factors which affect the use- 



fulness of these fungi are 

 temperature, wind and moisture ; 

 of these the last two are the 

 most important locally. 



(6) The natural means of controlling 



scale insects is that most suited 

 to circumstances here, both 

 owing to the general conditions 

 and tc the much smaller expense 

 involved. Under the exceptional 

 circumstances of an epidemic, 

 the use of non-fungicidal sprays 

 may be found advisable. 

 In conclusion, the thanks of the 

 Department and of the writer are due 

 to Professor H. S. Pawcett, m.a., of 

 the Florida State Experiment Station, 

 for much valuable assistance and inform- 

 ation ; to Dr. H. T. Fernald, Ph.D., of 

 the Agricultural Experimental Station, 

 Massachusetts, Mr. J. H. Hart, f.l.s., of 

 Trinidad, and Mr. R. H. Compton, b.a., 

 of Gonville and Caius College, Cam- 

 bridge, for assistance in obtaining 

 publications, and in other ways. 



