The low chemical activity of the inert gases is due to the fact that their outermost, or valence, electron shell is complete, containing two electrons in the case of helium and eight in the remaining cases.
Often only one side of a plant is affected at first, but symptoms eventually spread. Tomato Leaf SpotâSeptoria lycopersici Fruit is not affected, although sunscald can be a problem due to foliage loss. Numerous brown spots on leaves, each about 1/16 inch in diameter. They do not have a yellow halo and they do have black specks in the center. First symptoms are usually on lower leaves after the first fruit sets.
New growth of tomato plants infected with TSWV often appears pale or bronzed. Since the mid 90âs, tomato spotted wilt virus (TSWV) has become one of the most serious diseases of tomatoes in our area. Infections of TSWV in our region usually first appear in May and peak in June.