110 |-;;"i;ii()!'r!:'; i;i.ii;ht oi" sl'(;ai;-c.\\"!;. 



Some jilanbers make a point of {giving special weefling to fields show- 

 ing signs of attack, while others say that such labour is wasted. 



If weeding is done dm-ing the flight of adults or while the insect is in 

 the nymph stage, little good can be expected, in fact the insects will be 

 left in the field and will feed on the canes in greater numbers than 

 before. If it is done at the time that the majority of insects ai'e in tlie 

 ei^g stage, good results should be obtained, but it ujust be emphasise 1 

 that these results will not be apparent until the next brood of frog- 

 hoppers two months, or, if the dry season intervenes, six or eiglit months 

 later. 



Weeding and trashing, when carried out in a field actually suffering 

 from blight, are liable to cause considerable damage by the number of 

 canes accidentally broken owing to their abnormal brittleness near the 

 growing point. 



Weeding is probably of less importance than trashing and no 

 immediate results can be obtained from either. 



Burning. — The question of burning the trash on cane fields before or 

 after cutting has been the subject of ]imch contr(jversy. It has 

 important effects both on the animal life in the cane field and the 

 physical condition of the soil. 



Considering first the effect on the froghopper there i.-- no doubt that 

 •a number of eggs will be destroyed, limited however hy several factors : — 

 (1) The eggs are chiefly near the ground where the trash is uioister and 

 less likely to be destroyed (2) Burning is often carried on at night to 

 prevent too severe scorching and this means that still more eggs will 

 tscape. (3) The eggs in the soil %viil probably escape. 



On the other hand many egg parasites will be destroy ed in addition 

 to the lizards, toads, spiders and other parasites and hyper-parasites 

 shown in Fig. 



The field evidence to decide whether the good or the harm done is the 

 greater is contradictory. Some fields have been burned regularly and 

 still have not suffered severely from blight. Mr. C. Connell of Esperanza 

 Estate reported in 1912 that fields Inirnt had suffered less than fields 

 not burnt. 



On the other hand I found in 1919 the blight definitely worse in a 

 corner of a field that had been accidentally burnt at Harmony Hall than 

 on the rest of the field that was not burnt. Mr. Halliday at' Picton in 

 1912 reports that the fields w-here the trash was burnt were the worst 

 attacked fields on the Estate. 



It is possible that the immediate effect depends largely on the 

 original proportion of the froghopjjers and their enemies. 



Burning during the wet season will have still less effect in the 

 destruction of the eggs, and nymphs have been seen making fresh froth 

 masses on the surface of the ground within twenty-four hours of the 

 burning of a field. 



In addition there is evidence that the burning of trash has, in Porto 

 Rico and Louisiana at least, a distinctly bad effect on the prevalence of 

 the small moth-borer of sugar-cane, probably by the destruction of its 

 parasites (see Wolcott, Annual Piept. Porto Rico, Insular Expt. Station 

 J917-1918 p. 43 ; and Loftin and Holloway, U.S. Department of Agricul- 

 ture Bulletin 746 p. 5.5). The latter authors give figures indicating 67 

 per cent, infestation of small moth-borers in a field previously burnt as 

 compared with 1.5'5 per cent, in an unburnt field. In view of the 

 presence of the small moth-borer in Trinidad this effect must not be 

 forgotten. 



