The volume of flame, however, is increased by inert gas, and there is a proportionate diminution of the heating effect. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 Various. Nitrogen by itself is an inert gas, colorless and uninflammable. Scientific American Supplement No. 819 Various.
Tomato Spotted Wilt Virus. The tomato spotted wilt virus (TSWV) causes dark brown, purple or black spots on leaves. The spots can spread to the stems, causing cankers and streaks. The foliage begins to wilt once the disease spreads, and the leaves become stiff.
Like Septorialeaf spot, early blight is common in Iowa tomatoplantings, and the two diseases may attack the sameplants. Premature loss of lower leaves is the most obvioussymptom of the disease (Figure 3). Brown to black spots, 1 â 4 to 1 â 2 inch in diameter with dark edges, appear on lowerleaves (Figure 4).