o98 -TOVENAL OF THE DEPARTMENT OF AGRICULTURE. NoV., 1922. 



Cluster Bugs. — A few compkiints liave been received lately about 

 these evil smelling', grayish-coloured insects {Agonoscelis, spp.). They 

 usually attract attention because of their habit of clustering in 

 numbers of trees, where they seek shelter during the winter. When 

 warm weather comes they disperse to nearby veld plants to breed. 

 These insects are rarely troublesome, and it is mainly the numbers 

 in which they gather together that causes alarm. The time to destroy 

 them is while they are clustered on the trees. Brushing them into a 

 paraffin tin containing a little water and paraffin oil is the easiest way 

 to deal with them. 



Cotton Insects. — \\\ inleresting letter was received recently from 

 a correspondent living in the eastern Transvaal, relating his 

 experiences in controlling cotton insects. It was found that leaf- 

 hopper or jassid injury could be reduced to a minimum by practising 

 autumn or winter ploughing followed by a bare fallow until the crop 

 was planted the following spring. ITnploughed fields, overgrown with 

 weeds and old cotton plants, were observed to harbour the insect over 

 winter. Early planting on autumn or winter ploughed lands was 

 found to be beneficial in that it ensured a vigorous growth before 

 leaf-hopper attack eventuated. For cotton stainer control, a barrier 

 was ploughed around some fields, and a strip burned off around 

 others. The result was that these fields were practically free of 

 stainers, whereas neighbouring untreated fields were badly infested, 

 the conclusion being that infestation comes from the outside and 

 works inwards. 



These observations coincide with those of the Division, and it is 

 strongly recommended that the practices outlined be followed. Cotton 

 insect control must be accomplished by cultural methods, and this 

 piece of practical experience shows that it can be done. 



Wheat Louse or Aphis. — This pest of wheat and allied cereals 

 has been causing considerable trouble during September in Griqua- 

 land East and the northern and eastern parts of the Cape JProvince. 

 It is not a serious pest every year. Weather conditions that particu- 

 larly favour the insect, absence of parasites and enemies that 

 normally keep it in check, and adverse conditions for the growth of 

 the wheat crop, lead to outbreaks. An important point is to keep 

 the wheat in as healthy a condition as possible, especially during the 

 winter. As warm weather comes on the enemies of the louse and 

 conditions unfavourable to it usually increase, and control the pest 

 effectively. If the aphid attack is very severe in patches, it is advis- 

 able to burn these over, and if the whole field appears to be threatened 

 it should be fed off. Direct control measures such as spraying, are 

 impracticable. 



Refuse Tobacco as Insecticide. — Several inquiries have been 

 received recently as to how refuse tobacco can be used for insect 

 control. Tobacco, such as unmarketable leaves, stems, etc., can be 

 made into a decoction that is useful tor the control of sucking insects, 

 like plant lice. However, the strength of this liquor varies consider- 

 ably according to the tobacco used and the thoroughness of extrac- 

 tion. The usual formula is to chop up five pounds of tobacco and 

 allow it to soak in water for several days or to simmer over a fire 

 for about two hours. Such a decoction is diluted with water to make 

 ten gallons. 



