202 



THE AGKICULTURAL NEWS, 



June 17, 1916. 



INSECT NOTES, 



NATIVE FOOD PLANTS AND FEEDINa 



HABITS OF THE COTTON STAINER IN 



ST. VINCENT. 



The following notes bave been prepared and forwarded 

 to this Office for publication by Mr. W. N. Sands, F.L.S,, 

 Agriculturiil Superintendent, St. Vincent: — 



The cotton stainer (Dysdercus delaunei/i, Letli.) is 

 a .serious pest of Sea Island cotton in St. Vincent, and res- 

 ponsible for much loss of crop each season. It has been 

 recently shown by Noweli* that besides damaging lint and 

 seed in the process of feeding, the cotton stainer enables the 

 fungus causing the internal boll disease to enter the boll and 

 destroy ■ its contents, either in part or whole, under certain 

 conditions which are not yet fully worked out. It is the 

 fact, however, that internal boll disease following the attacks 

 of cottoo stainers has assumed quite alarming proportions in 

 St. Vincent during the past three seasons of unfavourable 

 weather. Under tiieso circum,stances it was considered very 

 desirable, in the interest of the local industry, that the feeding 

 habits of the insect and its native food plants should be 

 .studied, in order that additional measures for its control, 

 other than by hand-collecting in the cotton fields might, 

 if possible, he devised. 



In St. Vincent all cotton plants have to be pulled up 

 and burnt by April 30 in each year. As the crop is usually 

 over by February, most of the old cotton plants are ]iulled 

 up by the end of that month. Planting of the new crop is 

 started in May, if the rains have come in by that time. 



There was no difficulty, therefore, in respect to culti- 

 vated or wild cottons, and it was not on these that the cotton 

 stainer was able to subsist throughout the year. 



An account will now be given of the investigations made 

 during the past four months, February to May inclusive, in 

 districts where Sea Island cotton was grown on an extensive 

 scale. 



The weather was showery throughout the period and 

 there were no dry spells. In the Leeward and Windward 

 districts where the work was performed, it was with difficulty 

 that the cotton st;alks could be burnt, but they were all 

 uprooted by the end of February. The cotton stainers which 

 were present in large numbers in the fields then migrated to 

 trees, bushes and herbaceous plants near-by. In these places 

 it was observed that many of the insects collected together 

 in colonies under the leaves of plants and ri'mained quiescent 

 for several days, whilst others foraged abroad and eked out a 

 precarious existence. 



They were seen at this time feeding on : — 



Flowers of the Mango (Mawpfera indica). 

 ,, ,, Eupatwi-um odorcUuru. 

 ,, ,, ISlack Sage ('-oj(iif/, cylindvastachya). 

 ,, ,, Horse Uadish tree (Moringa pteri/gosjjermu). 



Fruit of Okro (Ilibwusesculenlus). 

 ,, ,, Maiilen's I'.lush (Mon/ivi-dica Charantia). 



Secretions of Scale Insects. 



They were also ob.served on certain otiier wiUl plants in 

 small numbers, but the larger number were seen on those 

 given above. The food supplied by these flowers, fruit and 

 insects seemed to serve only as a makeshift to .sust.ain life 

 or complete maturity; the insect did not appear to be able 



*A(irhvU>'V(d Neirs. Vol. XV, No. 3ri4. 



to breed upon it, for neither young ones nor mature insects 

 in coilu were observed. 



In Trinidad and Tobago, the Wild Ochro {Mahickm 

 capitiila) and Sida glomerata are given as food plants of 

 another cotton stainer, D. Iioirm-di, and its variety, minor, 

 but the.se plants do not commonly occur here. 



Attention was then directed to the two malvaceous 

 food plants other than cotton, namely, the Silk-Cotton 

 {Kriodendion nnfracluosum, D.C.) and the 'John Bull' 

 (Thes/ e.na populriea, Corr.). The .story of the relation of 

 these to the cotton stainer is of much interest and impor- 

 tance, i 



THE .siLK-roTTON TREK {Eriodendfon anfractuosum). 



This large tree was found chiefly in the Leeward district 

 on lands near to the coast, but a few trees occur in the 

 Windward district. At the beginning of February this tree 

 was almost bare of leaves and < mly on a few trees were leaves to 

 be .seen. Xo stainers were pr&sent. By the end of February most 

 of the trees were in full Bower and still no stainers were 

 observed, but when the young bolls commenced to swell, then 

 the insect appeared, and in a very short time swarms of 

 mature insects in flight, both male and female, were seen ' 

 approaching the trees from all directions and settling on the 

 bolls. In many instances the bolls were almost covered by 

 them. Just before this happened a certain 'liveliness' was 

 noticed among the stainers on other trees and plants, and 

 they very quickly left these for the silk-cotton trees. 



After feeding for some time on the silk-cotton boils, 

 the stainers starting mating. Voung bugs were first seen 

 at the beginning of April, and before any sound bolls were 

 ripe. They were seen both on the ground and on the trees 

 feeding on cracked or damaged bolls, and later on seed 

 distributed over the ground. They did not appear to be 

 able to feed through the thick wail of the unopened fruit in 

 the same way as the mature in&ects. 



On the groundjhey were attracted to, or hunted out of, 

 silk-cotton seed over a considerable area. To give an instance 

 some silk-cotton bolls were cut up in an office quite 50 yards 

 away from a fruiting silk-cotton tree which had been recently 

 destroyed, and pieces of the bolls were thrown into 

 a waste paper basket. Within three days a large number 

 of young stainers, less than half-grow-n and unable to fly, 

 found out the pieces and started feeding on them. It 

 was no uncommon sight to see scattered about the ground, 

 often long distances from trees, bright red balls made up of 

 young stainers conij)letely covering and feeding on single 

 silk-cotton seeds. 



It was towards the end of April that the bolls on the 

 trees opened and the seed, suiTOunded by its floss, was distri- 

 buted far and wide by the wind. At the end of May there 

 were still large numbers of sUiiners to be seen hunting 

 about for the seed, so that already they have been able to 

 tide over a period of three months by means of the silk-cotton 

 trees. In two months' time there will be food again for them 

 in the cotton fields 



A large number 'of bolls picked both from attacked and 

 unattacked trees were examined in order to ascertain whether 

 there was evidence of internal boll disease. As with culti- 

 vated cotton, there is no e.xternal evidence that a boll has 

 been attacked by the insect. Internally there are prolifera- 

 tions of the carpels, disorganized seed, and stained lint. In 

 certain cases the state of seed and lint appeared to indicate 

 the jiresence of a definite rot. In specimens forwarded to 

 the Mycologist of the Imperial Department of Agriculture at 

 a later date, the fungus causing internal boll disease of 

 cultivated cotton was not discovered: it is possible, however 

 that the silk-cotton bolls may subsequently be found to be 



