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THE AGRICULTUKAL NEWS. 



September 8, 1917. 



INSECT NOTES. 



SOME INSECT PESTS IN JAMAICA. 



The Annual Report of the Government Entomologist of 

 Jamaica, Mr. A H. Ritchie, has recently been received. 

 This deals with the more important insects occurring in 

 Jamaica during the year ended March 31,1917, and forms 

 part of the Annual Report of the Jamaica Department of 

 Agriculture for the above period. For the most part, only 

 those insects which are likely to be of interest to readers in 

 these islands will be referred to under their host plants in 

 the following notes. 



suoAE-CAXE. The West Indian sugar-cane leafhopper 

 (Stenocranus mccharivorus [Delphax saccharivora]) has been 

 the most important pest of this crop during the past year. 

 A parasitic fungus (Fusarium sp.) was instrumental in check 

 ing this leafhopper to a considerable extent during the rainy 

 season of 1916. This disease is apparently not fatal to the 

 insect until the adult stage is reached, as the young stages 

 are never found dead from the attack, whereas the adult 

 hoppers are killed by the fungus, and usually remain attached 

 to the cane leaves. During the dry months from December 

 to March this fungus ceased to be of any value except where 

 the standing canes were thick enough to maintain the humid- 

 ity necessary for its development. Consequently the leaf- 

 hoppers were practically unchecked, and the young plant 

 canes soon became infested with young hoppers, followed by 

 the 'sooty mould' fungus or 'black blight', which is not 

 parasitic. An attack of this descri|>tior on the young canes 

 reduces the number of canes per stool, and with unfavourable 

 weather, leads to the ultimate failure of the plants. 



Three other natural enemies of this leafhopper are 

 recorded: (1) a species of Chry.sopa, or 'lace-wing', (2) a pre- 

 daceous bug {Zelus r-uhidus), and (3) the larvae of a Syrphid 

 fly. Various ants were observed carrying oflF the young 

 hoppers, especially when any of these were blown ofl" the 

 plants by high winds. The ants, however, were also seen 

 carrying off the beneficial Syrphid larvae, and the predaceous 

 bug Zelus seems to show a similar lack of discrimination 

 between beneficial and injurious in.sects. Of all the above 

 natural enemies the parasitic fungus seems to be the most 

 efficient when weather conditions are moist enough to favour 

 its development. The introduction into Jamaica of more 

 natural enemies of the sugar-cane leafhopper is being 

 considered. 



This same species of leafhopper or 'cane fly' is 

 occasionally a pest in other West Indian islands, but it is 

 usually controlled by natural enemies, chiefly a species of 

 Chrysopa. The red ladybird beetle (Cycloneda sanguinea) 

 has also been observed on cane plants infested with the 

 hoppers. 



coco-NUTS. The glossy star scale {Vinsonia slellifera) 

 occurred on one estate in such unusual numbers on young 

 bearing coco-nuts as to be injurious. This scale is found on 

 many plants in the West Indie.s, but it is rarely abundant. 



Strateffvs titanus is the common coco-nut beetle in 

 Jamaica, but is not a serious pest, only occasionally injuring 

 the cabbage, especially of younger palms. The beetles are 



usually dug out by hand-, or a strong carbolic solution is 

 poured into the burrow. 



As a remedy for palm stems attacked by the pin-hole 

 hoKx [XyUborus sp.), an emulsion of carbolineum is recom- 

 mended. Such tree.s, if left untreated, succumb to the attack 

 in from eighteen months to two years. 



The brown weevil {Metamasius sericeus) is only found 

 on diseased or wounded coco-nut trees, and is not regarded as 

 a primary pest. It also breeds in felled banana stems 

 unless these are cut up and spread out to dry. This beetle, 

 it may be remembered, is the same as the sugar-cane weevil 

 borer in other islands, and was formerly called Sphenophcn-us 

 sericeus. It is generally considered to be a secondary pest, 

 and is usually found only attacking cane that has been 

 previously injured by the moth borer, etc., or that is diseased 

 in any way. 



ciTEUs. The spiny white fly {Aleurocanthus ivoqlumi) 

 since its discovery in Jamaica in 1913 has been spreading 

 throughout the citrus-growing districts, and is now considered 

 to be the most serious pest on this crop. When once 

 this white fly has gained entry into a grove it has been 

 observed to spread very rapidly, and its effect on the 

 trees very soon becomes evident. In connexion with the 

 control of this pest, experiments are being made with a 

 variety of ant {Vremastogasln- brevispinosa, Mayr, sub-sp. 

 tumulijera, Forel, var. tumulicula, Forel). Mr. Ritchie states 

 that a citrus grove on one estate 'had ceased to bear as 

 a result of the excessive injury of the fly, and growth 

 was completely arrested. With the establishment of the 

 anr, the trees are perfectly clean and have returned to bear- 

 ing. Trees minus a nest or where a nest has failed may 

 readily be recognized— intensely black, foliage shrivelled 

 and dry, new growth absent, crop nil.' The exact behaviour 

 of this ant towards the scale insects and aphids occurring on 

 citrus has not been determined, but other members of the 

 ant group are known to protect and even to colonize 

 scale insects and aphids, both of which are often injurious 

 to many plants. It may be of interest to note that a closely 

 related sub-species of the above ant is generally distributed 

 in Barbados, and ia often found on plants atUcked by scale 

 insects, mealy-bugs, or aphids. Both this ant and another 

 related species in Grenada have been found by Ballou to 

 damage trees directly by getting into pruning cuts or wounds 

 in the bark and preventing the cuts and wounds from healing 

 over. These ants are known locally as acrobat ants from 

 their habit of walking along with the abdomen, or hinder 

 part of the body, turned up. The Barbados acrobat is 

 Cremasloga^ter brevispiiiosa, Mayr., sub-sp. minutior, Forel. 



The natural insect enemies of Aleurocanthus in Jamaica, 

 include the ladybird beetle (Lwscymnus diversipes) and 

 a species of Chrysopa. An attempt will be made to 

 introduce another ladybird beetle (Belphastus catalinae) 

 from California. Parasitic fungi also occur on the spiny 

 white fly, but are unable to control it. An oil emulsion 

 spray is being useil ;igatnst this pest with great success. 

 Owing to the scarcity and high prices of the potash whale- 

 oil soaps, it has been found necessary to use hard soaps 

 instead. The following formula, mixed in the usual way, has 

 given good results: Hard soap. 2 ft.; diamond paraffin oil, 

 2 gallons; soft water, 1 gallon. For the spray use 1 part oif 

 this solution to 60 gallons of water. 



Mr. Ritchie ha.s found Aleurocanthus woglumi on two 

 new host plants, both introduced into Jamaica from the East 

 some years ago. The.se are the Mahwa tree {Bassia latifolia) 

 and the Wampie (Clausenia wampi). 



Among other citrus insects is a new species of green 

 weevil which injures citrus leaves. This has been described 



