408 



Natural control is exercised to some extent by a number of factors. 

 Experiments in Porto Rico indicate that tliis borer is adversely affected 

 by rainfall [see this Review, Ser. A, iv, p. 115 etc.], but in Louisiana 

 this does not seem to be the case ; a series of graphs illustrates the 

 absence of relation between rainfall and infestation in that State. 

 Flooding the cane-fields apparently reduces the numbers considerably, 

 but in the following year the borers occur as abundantly as ever. 

 Irrigation seems to have no effect upon infestation. A fungous 

 disease has been observed to infest the larvae, but its occurrence 

 under natural conditions is very rare. 



Parasites and predaceous enemies of the borer include a Chalcid, 

 Trichogramma minutum, Riley, which is well known as an important 

 factor in control in Louisiana and Texas. A similar parasite, Ufens 

 niger, Ashm., was found in Texas in 1912, but has not been observed 

 since. Microgaster sp. and another Braconid have been reared from 

 the larvae of other species of Diatraea. A Telephorid beetle, Chaulio- 

 gnathus marginatus, ¥., has been recorded as feeding on the larvae, 

 and is occasionally found in considerable numbers in sugar-cane fields 

 in Louisiana. Earwigs and the Argentine ant {Iridomyrmex humilis, 

 Mayr) are predators, but cannot be considered of any importance. 

 The natural enemies of D. saccharalis in foreign countries are reviewed. 



The methods of diposing of cane trash left in the fields after the crop 

 has been gathered are dealt with. These include burning with oil, 

 the efiicacy of which, as compared with ploughing imder, has been 

 much discussed [see this Review, Ser. A, ii, p. 279 & iv, p. 114]. Cutting 

 out the dead hearts of infested plants and burning them in the spring, 

 when the larvae are still within them^ is theoretically a sound practice, 

 and where labour is abundant and cheap, has proved successful. 

 This practice should be carried out three times early in the growing 

 season. Arsenical poisons on the cane plants are of no value, probably 

 because the poison does not enter the central whorl where the young 

 larvae are feeding. Experiments with honey and other baits and also 

 with light-traps were tried without success. 



Seed should be planted in autumn, if possible, and kept as deeply 

 covered as is practicable. Very deep planting is not advocated, but 

 as the moths can emerge from cane under |--inch of either clay soil 

 or sand (though larger numbers emerge from sand), a good covering 

 of soil should be maintained and replaced if washed away by rain. 

 Canes for planting in uninfested areas should be obtained free from 

 borers if possible, otherwise they should be soaked for at least an hour 

 in nicotine sulphate or Bordeaux mixture, which prevents the eggs 

 from hatching. 



The ploughing in of the stubble and rubbish left in the fields after 

 gathering the crop is described. Experiments over a number of 

 years tend to show that burning is unnecessary, but that the trash 

 should be lightly covered with soU in the autumn and ploughed under 

 in the spring ; in this way very valuable fertilising matter is 

 added to the soil and its mechanical condition greatly improved. The 

 authors are of opinion that burning or not burning trash will be found 

 to be a matter for the judgment of the plantation manager, in Louisiana 

 as well as in other countries. The introduction of parasites of the 

 moth borer from Cuba and other tropical countries is recommended 

 [see also this Review, Ser. A, vii, p. 279]. 



