Vol. XVI. No. 400. 



THE AGRICULTURAL NEWS, 



267 



pest deposited in dry grass or cane-blades, or between dry 

 cane-blades and the earth. 



LEAF-FBEDBKS. 



The grass looper {Mods repanda) attacked the blades of 

 young ranes on several estates, and these outbreaks seem to 

 occur annually after the coming of the mid-year rains in 

 British Guiana. Outbreaks of this pest are experienced at 

 long intervals in some of the West Indian islands, but it is 

 generally considered lo be kept in check by its natural enemies 

 for long periods at a time In the?e islands this insect is 

 known as the Guinea grass moth fir the Guinea grass worm, 

 but the caterpillars are also very fond of Para grass, and 

 occasionally attack other trasses A good account of this 

 insect can be found in the A'irindtm-al News for June 5, 1915 

 (Vol. XIV, No. .342). 



The rice worm (Laphygnut jrvgiperda) also did a little 

 damage to canes in British Guiana in 1916. This insect is 

 known as the corn ear worm in the We.st Indies, and is called 

 the fall army worm in the I'nited States. 



.J.C.H. 



TRAPPING OF THE COTTON STAINER 



The following note has been furnislied to tiiis ( )ffice by 

 the Agricultural Superintendent, St. Vincent 



Experiments have recently been made with the trapping 

 and destruction of the cotton stainer {Dpsdercus delaunei/i. 

 Leth ), in the field in St. Vincent. 



During last year's campaign against the silk-cotton tree, 

 a noted food-plant of the pest, a small number of trees could 

 not be cut down or limbed, because they were growing in 

 situations where, if dealt witli, they would have destroyed 

 Taluable crops: the trees, however, were barked, but notwith- 

 standing this treatment three of them fruited before they 

 could be felled or cut back. In each ease a very large 

 number of cotton stainers was attracted to the trees from the 

 surrounding cotton districts .Mature insects and nymphs, 

 as well as egg-masses, were present when tht trees were 

 dealt with. 



The (|uestions to be solved were: (a) how could the 

 insects be prevented from scattering themselves about the 

 districts, and (b) how could they be trapped and destroyed. 



At the outset, heaps of silk- cotton pods were made under 

 the trees and three times daily the insects which collected 

 on them were killed with boiling water. As the pods became 

 exhausted cotton-seed meal was substituted. Although this 

 answered fairly well, on exposure it quickly lost its attractive- 

 ness to the cotton stainer.''. Cotton seed was next tried and 

 this proved a striking success. It was soon noticed that the 

 trap.", of whatever kind used, needed shading to obtain the 

 best results. If unshaded, the in.sects wandered away from 

 them in the hotter periods of the day. 



In previous experiments smne of the tra|is were sprayed 

 with strong kerosene emulsion. The cotton stainers on them 

 were readily killed: there was this drawback, however, that 

 the insecticide acted as a repellent, and fresh food material 

 had to be put down after each spraying. Boiling water 

 when readily available answered well, but in remote situa- 

 tions where the supervision of labourers was difficult, and 

 the weather continued wet, there was iiKv^ys a dnngei that 

 the work might Ue luetiectively carried out; with the result 

 that the traps might actually become dangerous breeding 

 places for the pest. 



It has now been found that the difBculties experienced 

 in the use of contact in.secticides or boiling water can be 

 largely overcoine by the use of the gasoline torch. Mr. Lewis 

 Punnent of Diamond estate, when assisting the Agricultural 

 Department in the trapping and destruction of cotton stainers 



which had attacked a silk-cotton tree in his district, thought 

 that a torch might be usefully employed for destroying the pest 

 on traps and in other situations where it might collect. He 

 made an experiment, the results of which were very satis- 

 factory. 



The writer witnessed a trial of the torch made in tht 

 early morning of .June 24 by Mr. Punnett, and the follow- 

 ing is a brief description of the torch and its use. 



The gasoline torch used was of American manufacture, 

 made to hold 1 quart of ga.soline. It had a horizontal 

 burner giving a long clear blue continuous jet of flame under 

 the pressure of the included force pump The torch was 

 easily carried in one hand, and the flame could be directed to 

 any recjuired point. The first cost of the instrument was 

 about $3-60. 



When heated and lighted the torch was taken to traps of 

 cotton seed placed under the .shade of cacao trees surrounding 

 a silk-cotton tree that had been destroyed when heavily 

 infested with the cotton stainer. Care was exercised that the 

 insects which had collected on th:' traps were not disturbed, 

 because once they were molested in any way they quickly 

 leave, and do not return for some hours. 



When the traps were approached they were seen to be 

 thicklj- covered with young insects. Few mature ones were 

 to be seen at this time. The torch was applied, and in 

 a lew minutes most of the insects were killed. Relativelj 

 few escaped, and many of these were destroyed in different 

 situations after the traps had been dealt with. The remains 

 of insects burnt the previous morning were seen, and it is 

 worthy of note here that the use of the torch does not 

 destroy the effectiveness or attracti\'eness of the cotton 

 seed or other bait of the traps, and the material can therefore 

 be used for several days in succession, if the weather is not 

 very wet. A sin^ll amount of moisture to soften cotton seed 

 used for traps appears to be necessary to obtain the best 

 results. It was found that the early morning was the best 

 time to visit the traps, because a far larger number of insects 

 are found then than at any other time. 



With a torch of the size described several large traps 

 and a very large number of cotton stainers can be dealt with 

 daily in a few hours. 



Taketi altogether, the gasoline torch method of destroy- 

 ing the cotton stainer on traps has proved expeditious, 

 efhcient, and inexpensive, and its adoption is strongly 

 recommended for the purpo.se indicated. 



Gaseous Pressure in Growth.— In an inter- 

 esting communication by Miss Ethel McLennan, B.Sc, 

 on the intiuencc of gaseous pressure on growth, con- 

 tained in the Proreediiigs of the Royal Society, Victoria, 

 2H N.S., P,2, 1916, it is stated that contrary to the suggestion 

 made in Shetfer's Physiology of Plants, namely 'a mere rise 

 of gaseous pressure it sufficiently great will produce a retar- 

 dation and ultiminate cessation of growth,' the effect of the 

 pressure made in the course of some experiments by 

 Miss, McLennan did not manifest itself immediately on the 

 wrowth, .so apparently the direct mechanical effect, if increasing 

 the gaseous pressure upuii turgor, is practically negligible as a 

 (actor which intiueuces growth. Generally in one day retar- 

 dation became noticeable, the amount of retardation being 

 dependent on the pressure; broadly speaking, the greater the 

 pressure the greater the retardation. It appears, too, that 

 this retardation is not permanent, for the plant accommodates 

 itself to tlie pressure, and the rate of growth is gradually 

 raised. Whether the retardation caused by increased gaseous 

 pressure is due to an increase in the partial pressure of the 

 dissolved oxygen or not has still to be determined. 



