331 



THE AGRICULTURAL NEWS. 



Octobee 9, 1915. 



PLANT DISEASES. 



THE EFFECTS OF EXPOSURE ON 

 LIME TREES. 



The question of the influence dt wind on lime trees has 

 1m i reci ntlj 'ed con id i ion 03 a repoi I 



of the M 'it- 1 Imperial Departmenl on conditions 



in Montserral From various considerations it is suggested 

 thai ;m increase of \ igour \v< is a resull 



would enable the trees to resist the 

 ,| pool grubs, scale insects, and certain weaklj parasitic 

 n fungi which at present give trouble in that 

 island. 



As a contribution to the dis' ' immissioner oi 



Agriculture invited an expression of views on this subject 

 from the principal agricultural officers in Dominica and 

 Lucia, these being the islands in which lime cultivation 

 has received most attention. The communications received 

 are given below, and it will be seen that the res peri 



ence in the two islands are in verj close accord. 



Mr. Joseph Jones, Curator of the Dominica Botanic 

 ( ■ u-dens, writes: '! Senerally it may be stated that 95 per cent. 

 of the lime cultivation in Dominica lies snugly in sheltered 



iys or under the protection oi windbreaks. Mistakes may 

 be made by planters, particularly young men from England 

 who are engaged in learning planting: but when it is 

 perceived that thi subjeqjl to persistent winds, and 



that windbelts cannot be established, or if established, would 

 in. 1 adequately protect the lime trees, as in the ease of rising 



Hid, then attempts to establish linn fields under si 

 conditions are al loned. 



'I have in my mind's eye a picture of a large field of 

 limes "ii a Windward estate. The lower part of the field is 

 protected by windbelts, the results in crop beinggood. The 

 upper part of the field is exposed to the trade wind. Here 

 the trees are stunted, with the usual dead tops, and the 

 crop obtained due.- not pay the cost "I weeding the Held. 



'Lime trees can and do stand a considerable amount ol 

 wind provided their are periods of comparative calm between 

 when young growth can be made and hardened. It 

 is the persistent deadly trade wind which blows for 

 months on end that is to be feared. This stunts the plants 

 from tin start and portions of the small branches dry 



up, but the tires do not die. They strugg] , and 



with alleviating conditions, such as windbreaks, may ulti- 

 mate ed, but do no1 beconie first rate cultivations. 

 I do not 11 v lime trees, young or old, being actually 

 killed by the effect of the wind. Possibly this is due in 

 1 guava and other bush springing up quickly in 



doned fields and affording some protection. 



'There have been cases in which young planters, 



oi the effect of the wind on lime cultivation, have 



iidered windbreaks unnecessary and caused them to be cut 



down. In each case the results have been .disastrous. The 



only means of again improving the<cultivation and making it 



profitable is bj the long | iss of establishing new 



windbelts. 



•In I linica experienced plantersand all the peasants 



l.i w that the chief enemy to cultivation is persistent wind. 



This knowledge has beco ingrai I owing to long 



. ion with cacao cultivation. The importance of 



thoroughly understanding tin effect of wind on cultivation 



rated as follows: Suppose that two island 



with similar climatic conditions and I 



phical features were about to embark on lime cultivation. 



Suppose that in one island I n tin- -tapir ci 



in the other, cacao. Thei doubt in mj mind that the 



cacao pi. niter- wamld build up tut lime industry 



while the cane planters were blunderii , because cne 



community (cacao growers) had been compelled to study the 

 effect of the wind on cultivation and would act on the 

 knowledge gained, and the other 1. rowers) had no 



pan . d to trouble abot I it. and consequently would 



little "i no thought in the initial stage to this important 

 fact ir in lime gi • •■ ing 



'Although lime trees can stand much more wind than 

 cacao, there is no dourjl that this cultivation must receive 

 lerable measure of protection if good results are to be 

 obtained. 1 



Mr. Archibald Brooks, Agricultural Superintendent 

 St. Lucia, writes: 'If the plants are sel outina field exposed to 

 strong winds the plants do not make good growth in the early 

 stage-. They form smaller leaves, often only halfthe size 



ol those previously formed in the nurserj beds. The si ts 



are stunted and often possess more spines than leaves. Tin- 

 plant seldom it ever dies from the wind, but lingers until 

 killed by pests or di 



'Sometimes young limes are planted in such situations 



that they an ly exposed to strong winds at certain seasons 



of the year (about March and April); in such instances the 



plants make good growth during the rainy season, and are 



partly -tripped of theif leaves during the months mentioned. 

 This sometimes accounts" for lime plants being found in 



a lingering slate when eight 01' ten years old. 



'Again limes are often planted where thej have sufficient 



protection dining the first few years, but later their tops 



extend beyond this protection and at once become stunted. 



'I doubt very much if there is any authentic case on 

 rei ord where any lime tree has been directly killed by wind. 



•Wind is undoubtedly one of the greatest evils with 

 which we have to deal in lime cultivation, and I believe it 

 will be found that the condition of much of the diseased and 



unprofitable lii cultivation now existing is indirectly caused 



by insufficient protection. 



'Limes should be protected from wind in exactly the 

 same way as cacao, not with the object of maintaining 

 a heavj humid atmosphere such as cacao re< pi ires, but one 

 sufficiently humid to prevenl the young -hoot- and leaves 

 from becoming wind-hardened. 



'Whether the lime tree is originally planted in ail 

 exposed position or whether it extends until it becomes 



exposed does not affect the case. From the time of its 

 exposure to wind its progress is stopped audit becomes 



unprofitable and unhealty until the conditions are improved.' 

 The actual physiological effects which wind, or. it would 



lie better to say, exposure produces in the plant organ- have as 

 yet received little attention. Reduction in size and increase in 

 thickness of the leaves is well known to occur in many pla 

 as a reaction to condition- which tend to induce increased 

 transpiration, or where the SUpplj of water is for any reason 

 inadequate. The effect of this reduction on the economy of 



the plant has not. -., far a- the writer i- aware, been closely 



investigated, but it land- in familiar association with reduced 



or even stunted growth. No doubt it is some degree of this 

 condition which Mr. Brooks refers to as 'wind hardened'. It 



is evident that for economic efficiency thi lime tree requ 



to he grown under i trcumstances in which it is free to develop 



the softer and more generous type oi foliage. The fai 

 controlling this ability i- atmospheric humidity, which in 

 exposed situations is liable to bi dispersed by the freely 

 moving air. Hence the need for wind breaks. 



Tin- writer has little doubt that another factor is of 

 iderable importance, nol jo i tch in the typical districts 



