Tetranychus sinhai Baker (Acarina, Tetranychidae), a new pest was observed to infest barley, wheat, and rye crops in the Prairie Provinces of Canada. In barley, typical symptoms of the mite attack are manifested by a darkening of leaves, followed by yellowing and wilting from the bend of the leaf to its tip. The increase in number of mites per leaf was reflected by the showing of advanced symptoms on leaves. One hundred and sixty-five barley varieties from different parts of the world were examined for their reaction to T. sinhai infestation in the field. Of these 15 were found to be resistant, 47 moderately resistant, 88 moderately susceptible, and 15 susceptible. In general, the barley varieties grown in arid regions of the world appeared to be more resistant to T. sinhai infestation.
The most commonly grown barley varieties in Canada, Parkland, and Montcalm, were moderately susceptible. Only two North American varieties, Canadian Lake Shore–C.I. 2750, and Gem C.I. 7243 showed high resistance to T. sinhai infestation.