154 



THE AGRICULTUKAL NEWS. 



May 15, 1909. 



INSECT NOTES. 



The Use of the Bengal Bean in Lime 

 Cultivations. 



The Bengal bean {2faraii(i prurievH, var.) which 

 has ofDeii been referred to in the publications of the 

 Imperial Department of Agriculture on account of its 

 value as a green dressing, is closely related to the 

 velvet bean and the weed known as 'cow itch,' which 

 are perhaps known to some of the reader.s of the Agri- 

 cultural News, who are not familiar with the Bengal 

 bean. It is a strong, vigorous-growing species, capable 

 of making a dense covering on the land and even over 



Fii;. 20. Lime Trees Covkkeh by Bex(;al Be 

 otlier plants. The accompanying illustration (Fig. 20) 

 shows a field of limes in Montscrrat thoroughly covered 

 over by Bengal beans. 



The Bengal bean was at first used at Montserrat purely 

 as a green dressing on aixoufit of the large amount of organic 

 matter which it returns to the land, and becau.sc of its ability, 

 in common with other leguihinous plants, to gather atmo.s- 

 phenc nitrogen. It was discovered by chance that certain trees, 

 wliich had been in a dying ^fate for some time past as the 

 result of attack by scale insects, showed themselves much 

 improved in general vigoiu' and freedom from scales after the 

 Bengal bean plants liad climbed over tlieni and covered their 

 brandies for a year or two. Since then, extended trials have 

 been made with Bengal beans, and it is re[)orted that good 

 results ahvaj's follow, and^that the results are better the 

 more completely flie beans, cover in all the trees. The 

 practice ijr Montserrat is to plant four or five beans around 

 each tree at the lime of the jfirst rains in May or June, and 

 to allow them to grow until the beans are ripe in the follow- 

 ing March or April. The stems of the beans are then cut- 



l^^dnear the ground, and any portion of the vines that 

 hSagi free from tiie tfees is cut oil', but the mass of vines on 

 top of the tree is ;iot disturbed. No attempt is made to 

 remove it. 



Up to the present time thjs has been tried only on limes 

 that were badly %fested with scales before the beans 

 were planted, and ifTias been found that many of the scales — 

 perhaps most of them — were dead when the beails were 

 cutlassed, hi addition to this, it has been observed that the 

 limes have made particularly vigorous growth immediately 

 after the beans have been ciula.ssed. It often happens that 

 none of the lime shtrots show above the mat of bean vines 

 at the time they are cut, but within a few weeks strong 

 vigorous shoots, ti or o feet long, may be seen, which 

 have penetrated tlie "dead bean vines. So far as observa- 

 tion goes, this giowth is healthy, and the improvement ia 

 the trees is fairly [lermanent. One field which received this 

 treatment some seven years ago, and has had no spraying or 

 other treatment of similar kind since, is remarkably healthy 

 and free from scales.. One drawback to this method is that 

 the covered-in limes give a short yield for that year. 



Although it is known what results follow when Bengal 

 beans areallowed to climb upon lime tree.s, the e-vact reason why 

 these results come about is not known. It 

 seem.s likely that the covering of beans main- 

 tains a more mi:>ist condition beneath it, and 

 in this way encourages the growth of those 

 fungi which attack and kill scale insects. 

 It is likely also that the conditions under 

 this canopy of bean foliage are favourable 

 to the insect parasites of scale.s, and enables 

 these to multiply more rapidly than when 

 the trees are e.xijosed to the strong winds 

 which, during a large part of the year, 

 Mow across the island of Montserrat. 



Fungus [)arasites and insect parasites 



<if the .scales, or in other words, the natural 



crieniies of the scale insects, are present 



;uid are encouraged b\ . the covering 



of Bengal beans. It would seem, however, 



that there nuist also be some other agency 



in operation favourable to the lime trees, 



lor the killing off C'f the scales could hardly 



itceount for the remarkable vigour of the 



new growth of the lime.s, which follows 



ijumediately after the cutlassing of the 



ANs. beans. Possibly the rest, or partial rest, 



that the trees have had, while covered, would account in 



some measure for this vigour. 



Sugar in Porto Rico. It is reported that the sugar 

 crop for 1909 in I'ortd Rico is estimated at from 205,000 to 

 255,000 tons, which indicates that very great advances have 

 been made in the output during the past seven or eight years. 

 The probable limit of sugar pr"ihu;tion in the island is 

 generally placed ait about oOO.OOO tons. It is assumed, 

 however, that the latter figure will be reached less by increas- 

 ing the area novv;;iplanted with siigjir-cane than by the 

 introduction of improvements in machinery and existing 

 plants. An a.ssociation of sugiir growers, with an Kxperiment 

 Station is to be tbrmeil, and pre|)aratory work on an 

 extensive system of' irrigation, involving several thousiind 

 acres of land, has been started. There are now three central 

 factories in Porto "Kico whidi use twelve roller mills, and 

 another is in cwrse'of erection. . 



