186 



THE AGRICULTURAL NEWS. 



Juke 12, 1909. 



INSECT NOTES. 



Scale Insects and Fungi. 



Limes and other citrus fnuts in the West Indies 

 :u e persistently attacked by scale insects : and at times, 

 :uid in certain localities, the citrus white tly also 

 uppears. 



While it is true tliat on certain estates the trees are 

 sprayed and other remedial measures carried out, it is also 

 true, <in many estates, tliat no efforts are made by the manage- 

 ment for the control of scale insects. Vet these insects occur 

 year after year without becoming sutticiently abundant to kill 

 "the trees. The reason for this is, that the natural enemies of 

 the scales keep them in check. Knowing this, it remains for 

 us to consider which are the most useful of the natural 

 enemies of the scales, and what are the most favourable 

 conditions for the best development of these natural enemies. 



The natural enemies of scale insects are of two general 

 kinds : parasitic insects, and parasitic fungi. While .some of 

 the insect parasites of scales in the West Indies are known, 

 no method has yet been devised by means of which an exten- 

 .sive use can be made of them in a practical way. AVith the 

 fungoid parasites, hoWever, it is somewhat different. Our 

 knowledge concerning the West Indian forms is at present 

 .somewhat scanty, but a systematic study of the cpiestion is 

 now in progress. A useful amount of work has been done in 

 other countries, and, thaidvs to the efforts of the officials of the 

 Experiment Station in Florida, the lines are known along 

 which experiments may be tried with a likelihood of success. 



It is generally recognized that fungi as a rule require 

 moisture for their dcvelo|)ment, and this is true of the fungi 

 j)arasitic on scales. When limes are covered with Bengal 

 beans (aee Af/ricii/funi/ A'cirx, Vol. VIII, p. I.')-!), the air 

 contained under the canopy of bean vines is kept moist. 

 This would be of tlic greatest importance in the growth of 

 fungi in dry localities where, under the ordinary conditions, 

 they would not be able to make rapid develo]imerit, and 

 it appears highly probable that the usefulness of the covering 

 of liengal beans is largely dependent on this fact. 



In Florida several fungi are known as i>ara.Mtes of tlu' 

 .scale a;id white tl}-, and they arc being used in a practical 

 way. in tlic \Ve.*t Indies there are probably (juite as many, 

 but they are not all known. Investigations in ihis direction 

 jtre however in progress. 



The reddieaded fungus (Sphin/xtl//ic ntci-o/i/u/n) which 

 attacks the purple scale {Mi/lihi.yiix ritvicolit) and the orange 

 snow scale (C/iioiinxj/ia citri), and a grayish fungus which 

 was also attacking .scales on limes, were leported from 

 |)(.nunica in H)o:l (see .\<jrlctilliinil Xciix, Vol U, p. 23-_'). 

 'I'liese ami other simil.ir species of fungi are known to occur 

 ill several i.sland.s, and exist [lerhaps in all. In addition, it 

 is likely that there are scver.d fungous parasites not yet 

 lecngnized, which attack scale insects, and which will ipiickly 

 become known .so .soon as the attention ot the planter 

 is directed to tliis kind of useful orgaiusni. 



The red-headed fungus is abuiufint in Dominic.i, ;ii\d it 

 pinl.alily occurs in tin' other i>lanils i.l the West Indies, nmre 

 or less in proportion to the conditions of moisture under 

 which the trees grow. 



This fungus attacks the purple or mussel scale princi- 

 pally, and the orange snow- scale slightly. It can often be 

 seen growing on and among the scales on the trunk and. 

 limbs of the trees, although it is frequentlj- present and 

 aceompli.shing a considerable amount of good when it cannot 

 be seen. 



When seen, however, it appears in the form of irregular 

 pustules, reddish \\\ colour and ranging from very small 

 points up to the size of a pin's head. They are not 

 difficult to distinguish. A small reddi.sh mite is of frequent 

 occurrence among these scales, and may be mistaken for the 

 fungus ; but by careful observation one ma}- quickly learn to 

 distinguish the one from the other. 



The green shield .scale {Lernniunt ririih), the brown 

 shield scale (Lcramutii hetnUpht'iirum), and similar scales 

 are often attacked by a whitish fungus, which nray be 

 detected by the fact that these scales often leave a whitish 

 nnirk on leaf or bark when they are removed. This whitish 

 appearance is often due to the presence of a fungus, which is 

 parasitic on the .scale. 



When it is desired to locate the [larasitic fungi on scale 

 insects, one should first visit localities where the scales have 

 been abundant for some time without having become destruc- 

 tive, or where serious outbreaks of scales have checked their 

 rapid development without apparent cau.se, and have subsided. 

 The probability is that the natural enemies of the scales 

 have been at work in these places and that they can be 

 found there. It is desiiable to locate these places as sources 

 from which these beneficial parasites can be obtained for 

 study or experiment. 



It is ))foposed in the next number of the Agri- 

 citlt II r<il A'l'irs to suggest ways in which the value of 

 these natural eiieiuies may be tried on a practical scale. 



SUBSTITUTE FOR LIGNUM VITAE. 



The Km: Ihdli'lin (No. 8, 190!)) suniinarizes an 

 aecoiinr. which appeared in a late number of the 

 Iiiiliiiii Fiirr^trr lA a substitute for the Lignum vitae 

 (Gini iiini III I iffiri Dill/') of the West Indies. 'I'he new 

 wood is called ' ManC'^v.o' (Xantliusti'ui m Vcnlurin- 

 iihinii^). and IS found in considerable abundance in 

 north-eastern Maiidanao, Philippine Islatids. 



The wood is .said to be so heavy and hard that it is most 

 ditiii-ult to cut, and the splitting of a log is almost impo.ssible. 

 Accoifling to Mr. Dunlap of the IJnreau of Forestiy for the 

 l'liili[i[)ino Islands, itigrows along steep slopes near beache.s, 

 where it can be shipped b}' w-ater transportation, and as it i.s 

 only reiiuired for use in short lengtlis, the work can all bfr 

 done in the forests. The wood of the ' Mancono ' tree, even 

 in the tropics, is practically indestructible, and is not attacked 

 liy white ants. Many of the Filipinos of the Southern 

 Islands use the logs for posts and ground timbers 



The heaitwond of the tree is uniformly reddish-black, 

 but after a number (if years of .seasoning it tiu'ns a black 

 walnut enlniir. Like all Philippine woods, it takes a fine 

 piilish. 



The wood is of such density that it sinks in water, so- 

 lliat till' lugs have to be rafted between native boats to keep- 

 them on the .surtace of the water when being taken to the 

 steamer. 



This wood has been used as a substitute for I.igiuim 

 vitae at the I'nited. .States Naval Station, Cavite, I'hilippine 

 Islands, ami has been pronounced a succc.ss after a year's 

 trial, h has also been satisfactorily tested in the shipyard 

 of the llureau of Navigation, Manila. 



