347 



15 or 20 times the strength of cheaper aromatic oleoresins from plants 

 other than pyrethrum. The latter are distinctly less active, but their 

 advantage lies in their lower cost. The sulpho-aromatic insecticide is 

 eight times more active than pyrethrum-soap. It is hoped that other 

 workers will make chemical tests of the resistance of pyrethrum to 

 alkalis, and will also experiment with oleoresins other than those 

 obtained from pyrethrum. 



KuNKEL (L. O.). Insect Transmission of Yellow Stripe Disease. — 



Hawaiian Planters' Record, Honolulu, xxvi, no. 2, April 1922, 

 pp. 58-64, 1 fig. 



With a view to ascertaining by what means the yellow stripe or 

 mosaic disease is spread to healthy sugar-cane, experiments were 

 undertaken with Aphis sacchari, Zehnt. (cane aphis), Perkinsiella 

 saccharicida. Kirk, (cane leafliopper) , Peregrinus maidis, Ashm. (corn 

 leafhopper) and Aphis maidis. Fitch (corn aphis). The two former 

 do not carry the disease. Peregrinus maidis can carry the disease 

 from maize to maize, but does not appear to carry it from maize to 

 cane or from cane to cane. 



The results obtained by Brandes [R.A.E., A, viii, 370], that A. 

 maidis can carry the disease to cane, were confirmed. This Aphid 

 does not thrive on sugar-cane in Hawaii, and 1 1 days is the longest 

 period it can hve on the plants. It is not believed that it can invade 

 cane fields to such an extent as to be of importance in the spread of 

 the disease, unless other suitable food-plants are in or near them. 

 In 1921, mosaic disease spread rapidly amongst young cane plants, 

 and near the field some goose grass {Eleiisine indica) was found infested 

 with A. maidis, and some of the plants had the disease. This Aphid 

 is recorded in Java as a pest of sugar-cane. Its known food-plants 

 are maize, Sorghum, broom corn, barley, wood sorrel {Oxalis sp.), 

 foxtail {Setaria glanca), Panicum spp., knotweed {Polygonum penn- 

 sylvanicum), Eleusine indica, and the club rush {Scirpus maritimus). 

 In Hawaii, mosaic disease is known to occur on sugar-cane. Sorghum, 

 maize, Sudan grass, Andropogon sp. and Eleusine indica. 



All crops harbouring this Aphid and grasses subject to the disease 

 should be grown at a distance from sugar-cane fields, which should 

 be kept free from weeds and wild grasses. 



A bibliography of the mosaic diseases of plants that are carried 

 by insects is given. 



]\IuiR (F.) . Direct and Indirect Injury to Plants by Insects.— Hawaiian 

 Planters' Record, Honolulu, xxvi, no. 2, April 1922, pp. 65-66. 



The various ways in which insects can injure plants are described. 

 Mosaic disease is an example of damage done by foreign bodies that 

 are introduced into plants by insects. In Hawaii, this' disease is not 

 so serious as it is in Porto Rico, which may be due to the presence of 

 certain insects in the latter island that convey the disease directly 

 from unhealthy to healthy sugar-cane, whereas in Hawaii it is conveyed 

 by occasional visitors to the plants. 



In Trinidad, the damage done by the Cercopid leafliopper [Tomaspis 

 saccharina] is due to the adults feeding on the leaves, and causing 

 them to die. 



All insects should be kept out of the Island, except those already 

 demonstrated as being beneficial, as apparently harmless insects 



