Plant Sanitation. 



430 



[November, 1911. 



Red-headed Fungus. — This most com- 

 monly appears as a small, conical, or 

 club-shaped outgrowth from the scale 

 attacked ; it is usually inclined at an 

 obtuse angle to the surface of the scale, 

 and is from to £ inch or J to 3 milli- 

 metres in length. The end of each out- 

 growth is bright-red in colour and some- 

 what horny in consistency. This is 

 supported on a delicate, pinkish, velvety 

 base. As many as five or six of these 

 outgrowths, or sporodochia, may arise 

 from a single scale. They are borne on 

 an interwoven mass of the fungal 

 hyphse, known as a stroma, which fills 

 the space once occupied by the body of 

 the dead scale insect. Another form of 

 fructification may also be produced by 

 the fungus. This consists of more or less 

 spherical, smooth, bright-red perithecia, 

 which are usually borne in groups of 

 four or five on the same stroma as the 

 other fruiting form. It must be re- 

 membered that the hyphse of this fungus 

 are colourlesss and fine, and that, con- 

 sequently, when the fungus is not pro- 

 ducing either of the forms of fructific- 

 ation described above, it is very hard to 

 see, and may be present in large quan- 

 tities and doing most effective work, 

 although entirely invisible to the naked 

 eye. Practically the only indication of 

 its presence in this stage, visible with- 

 out a microscope, is the large number 

 of dead scale insects to be found on the 

 host plant. 



White-headed Fungus,— This also has 

 two forms of fructification, both pro- 

 duced, as in the case of the red-headed 

 fungus, on a stroma occupying the body 

 cavity, and also frequently covering the 

 body of the scale insect. The stroma is 

 white or cream-coloured, and gives rise 

 to a small, brown, cylindrical outgrowth 

 about | millimetre long. When this 

 becomes mature, it turns white at the 

 top, owing to the formation of a more 

 or less conical head of white spores. 

 The second stage consists of numerous, 

 more or less spherical, smooth perithecia, 

 of a coffee colour, which occur in groups 

 on the stroma. Owing to the scattering 

 of the conidia over the stroma, the 

 fungus frequently appears white or grey 

 in colour. 



Black Fungus — This appears as irre- 

 gular, smooth, coal-black lumps on stems 

 and branches of trees infected with 

 scale insects ; it rarely occurs on the 

 ieaves. The major portion of the black 

 stroma is of a brittle nature, somewhat 

 like charcoal, and the stroma, as a 

 whole, is of a definite appearance. 

 These characters serve to distinguish it 

 from black blight to which, however, it 



bears in reality but little resemblance. 

 This fungus also consists of fine, nearly 

 colourless hyphse in its early vegetative 

 stages, and probably kills many more 

 scales than those on which its stroma 

 actually appears. While useful on the 

 stems and branches, this fungus is more 

 disfiguring than the scales themselves 

 when it occurs on the fruit. No 

 instance of its occurrence there is, how- 

 ever, recorded at present in these is- 

 lands, though it has been known to 

 occur on fruit in Cuba. 



Shield Scale Fungus — This differs 

 very considerably in appearance from 

 any of the other three, its characters 

 being more those of a mould. In the 

 early stages it kills the insects without 

 any outward appearance of its presence 

 such as would be visible to the naked 

 eye. But when the scale is dead a white 

 or slightly buff coloured fringe, often 

 of a rather waxy appearance, grows out 

 from beneath it over the surface of the 

 leaf. The scale itself often becomes 

 brown in colour and of a papery consis- 

 tency, that is, if it is one of the soft 

 shield scales. At an even later stage 

 the whole surface of the scale insect 

 becomes covered with a slightly buff- 

 coloured coating of the fungus hyphse, 

 and this often has a very powdery 

 surface owing to the presence of very 

 numerous heads of spores. The appear- 

 ance is most characteristic, and when 

 once seen cannot easily be mistaken. 



Effectiveness of the Fungi. 



In treating of the red-headed fungus 

 on the San Jose scale in Florida, Pro- 

 fessor Rolfs remarks that the ordinary 

 observer would overlook it altogether. 

 This would hardly happen in the West 

 Indies in places where the fungus is 

 really active, and producing numerous 

 fructifications, as the result is to give a 

 quite definite pink appearance to the 

 parts affected, even when they are 

 viewed from a short distance. The 

 above effect has been seen by the author 

 on lime tree stems iu Dominica ; it is also 

 mentioned by the Imperial Commis- 

 sioner of Agriculture as having been 

 even more noticeable in the case of a 

 specimen of Castilloa elastica at the 

 Agricultural School, St. Lucia, on which 

 numerous parasitized scales occurred. 

 These instances serve as an illustration 

 of the effectiveness of this parasite 

 under favourable conditions. Iu dealing 

 with this point in his paper on ' Fungi 

 Parasitic upon Aleyrodes Citri,' Pro- 

 fessor Fawcett of the Florida State 

 Experiment Station remarks : — 



"The effective work of this fungus 

 (the red-headed fungus), and of two 



