PART IV. ‘73 in abundance depending on certain factors as to weather, soil, ete. The only possible exception is the Sudan boll worm, which has not yet been reported from parts of the Cape Province where cotton is grown. A wider survey of our cotton areas is necessary before any definite statements can be made. There is evidence that cultivation, rotations, and size of field has some effect on the occurrence of the major cotton pests; but so many exceptions have arisen, that I have no statement to make until the matter is more thoroughly studied. Experiments along these lines will be conducted next season.’ (f) APHIDES AND JASSIDS.{ The questions raised by the Empire Cotton Growing Corporation were left in abeyance more or less for the consideration of this combined session, as far as the matter of formulating replies thereto is concerned. For the information of this meeting I beg to submit the following observations : — 1. Mr. Haines (contributed): (a) Natural enemies are numerous in South Africa, as everywhere, on Aphides, and special mention need not be made of them. No study of the natural enemies of the jassid has been made. (b) The question of plant selection for resistance will be dealt with by Mr. Parnell, but I might add that long ago we noticed that certain cotton plants resisted the jassid, especially those with hairy leaves and stems. We also noticed that the growing plant was more resistant than the matured plant; and also, that there is a definite relationship between jassid attack and rainfall, i.e., prolonged periods of wet weather, which seem to hasten jassid attacks. Jassid occurs, so far as we know, all over the cotton areas, but it has never given serious trouble in the higher altitudes of these areas, and has only under certain conditions become pestiferous in certain parts of our low-veld. (¢) Nicotine dust kills the jassid if applied strong enough, but the effect is only transient, as the plants very soon become infested again. Calcium cyanide dust gave very unsatisfactory results. Bordeaux mixture, as a dust and a spray, was the only substance that gave results at all lasting, but it is doubtful if it would pay to use it. It is certainly not advisable to recommend spraying or dusting as a satisfactory control measure for jassid, as it seems certain that jassidresistant strains of cotton will be found. (d) We have no direct evidence that cultivation makes any difference as to jassid outbreaks vn cotton, except that well-drained cotton fields seem to delay the attacks somewhat. In general, it seems to hold true that h:althy, well-grown cotton plants withstand jassid attack longer than those plants which are poorly and slowly grown. 2. Mr. Hargreaves stated that in Uganda the Aphides was perhaps the most serious pest on Cotton; certainly the accumulated effect appeared to be greater than that of any other insect. 3. Mr. Ritchie suggested that the control of Aphides and Jassids by fungi might be further investigated; a fungus was the most potent controlling factor of Aphis in Tanganyika, and he instanced the success of a fungus as the controlling factor of West Indian Cane I See also pages 180 and 181. I