250 



The reduction of D. delauneyi to a position of minor importance 

 lias revealed the true status of other plant bugs injurious to cotton. 

 Of these, Nezara viridula (green bug) is abundant in St. Vincent and 

 probably throughout the West Indies. It has a \^"ide range of food- 

 plants, of which a list is given, and on many of which it breeds. It seems 

 likely that this species is able to subsist on almost any of the cultivated 

 vegetables in addition to many wild plants, but shows a decided 

 ^preference for Leguminosae. The jDosition of this bug with regard 

 to cotton is discussed [see follownng paper]. It is a dangerous practice 

 to grow a leguminous catch-crop followed by cotton, as this attracts 

 2V. viridula during the early part of the season and the bug is lilvely 

 to remain in the field throughout the cotton season. Maize might 

 however be used as a catch-crop. I'he seasonal abmidance of 

 N. viridula is apparently controlled by two factors, namely, the supply 

 of food and the efficiency of egg-parasites. It seems probable that 

 these two factors can be so regulated by artificial means as to assist 

 each other much more effectively than at present. But for the 

 various minute Hymenoj)tera that parasitise the egg-masses of 

 N. viridula, and are the only known enemies of this bug, the pest W' ould 

 be abundant in St. Vincent for about nine months in the year. 

 Apparently the bugs almost die out during the normal dry period from 

 March to May, but enough of them survive to start a new period of 

 abimdance about June, when they occur in sporadic outbursts in 

 areas differing from year to year. This would seem to be owing to 

 the uneven distribution of parasites. By September, the parasites 

 have increased sufficiently to be effective, while the food supply has 

 decreased. The pigeon-23ea crop then enables N. viridula to increase 

 again in some districts, only to decrease again as soon as this crop 

 is over. Eggs of N. viridula are usually laid in masses on the mider- 

 side of leaves or on the pods of leguminous plants, and give rise to 

 nymphs that undergo five moults before the adult stage is reached. 

 The various stages are described and are differentiated from those of 

 a similar bug, Edessa meditabmida. 



Control measures for N. viridula include clean cultivation in cotton 

 fields, and in particular the elimination of the weed, Polanisia viscosa, 

 on which the earlier stages of the bug breed, transferring later to 

 cotton, and returning as adults for oviposition on the weed. This 

 weed is sufficient to maintain N. viridula throughout the year. The 

 borders of cotton fields should be freed from miscellaneous weeds ; 

 a grass crop on the border is advisable. Leguminous crops should 

 not be intercropped with cotton, as the bugs not only attack the cotton, 

 but also infect the intercrops with the fungi of internal boll disease 

 and later carry this infection to the cotton bolls. Egg-parasites of 

 N. viridula should be encouraged ; it frequently occurs that in collec- 

 ting the eggs 100 per cent, of the parasitised ones are destroyed. 

 These can be distinguished by their darker colour. A certain number 

 ot the jDarasites can be liberated in the fields where leguminous crops 

 or cotton are grown, and if abimdant in any district, can be transferred 

 to other districts that need them. Individuals of TV. viridula should 

 be collected when possible and new infestations on pigeon peas from 

 December to February should be checked. 



Other cotton pests include Leptoglossus balteatus (leaf-footed tomato 

 bug), which is a general feeder found on tomatoes and bonavist beans. 



