531 



was found to be effective against T. yothersi, but for controlling leaf- 

 hoppers and leaf thrips as well, liquid lime-sulpliur solution with 

 Black-leaf 40 proved the more effective and the cheaper treatment. 



Brandes (E. W.). Mosaic Disease of Corn. — Jl. Agric. Research, 

 Washington, D.C., xix, no. 10, 16th August 1920, ])]). 517-521, 

 2 plates. 



It has been proved experimentally that mosaic disease of maize may 

 be transmitted by Aphis maidis, but under natural cond'tions this is 

 probably not the only means of dissemination \R.A.E., A, viii, 370]. 

 The virus of the disease is identical with that of sugar-cane and sorghum 

 mosaic. Its existence on perennial grasses may explain its appearance 

 on maize in the spring. The only effective method of eliminating the 

 disease is to destroy all plants affected by it. 



Parks (T. H.). Wheat-Sowing Dates to avoid Hessian Fly. — Mthly. 

 Bull. Ohio Agric. Expt. Sta., Woosfer, v, no. 9, September 1920, 

 pp. 243-246. 



Ohio has just experienced one of the worst outbreaks of Hessian fly 

 [Mayetiola destructor]. The spring brood in 1920 killed or damaged 

 an average of 44 per cent, of aU wheat straw in the State. The northern 

 counties suffered most, apparently because wheat became infested 

 there during the autumn of 1919, even when sown a w^ek later than 

 dates that are usually fly-free. By 15th July 1920, 31 per cent, of all 

 puparia were parasitised. Parasites usually control a serious outbreak 

 eventually, but not soon enough to prevent severe damage for two or 

 three years. The present outbreak will call for united effort on the 

 part of the growers to prevent early sowing of w^heat this autumn. A 

 map is given showing safe dates to sow wheat in different parts of 

 Ohio. They are somewhat later in northern Ohio than those previously 

 recommended, for the reason indicated above, but are consistent ^\^th 

 maxmium yields. 



Wheat joint- worm [Harmolita tritici] was not present in serious 

 numbers, except on the western edge of the State. It had been 

 becoming steadily less numerous for the past three years, and no 

 trouble is expected from it in 1921. 



NowELL (W.) & Williams (C. B.). Sugar-Cane Blight in Trinidad : 

 A Summary of Conclusions. — Bull. Dept. Agric. Trinidad & 

 Tobago, Port-of-Spain, xix, part 1, 1920, pp. 8-10. 



As a result of investigations made during 1919 it was found that 

 iroghoppers [Tomaspis saccharina] can produce a definite form of 

 bhght on sugar-cane without other insect or fungus agencies. The 

 condition thus produced is different in character from that caused by 

 any form of root disease, and is apparently mainly the result of injury 

 to the leaves. The chief damage is caused by the presence of large 

 numbers of insects where the local conditions of a field especially 

 favour it. In certain cases the infested patches are sharply defined 

 from the rest of the field. A merely backward or stunted condition 



1727) b2 



