In greenhouse production, upper leaf interveinal chlorosis (yellowing) occurs quite often. While these symptoms may be unsightly, they are easily remedied. Initial symptoms appear as a light green to yellow coloration of the new upper leaves, progress to a more pronounced interveinal chlorosis , and finally, in severe cases, total yellowing and bleaching (whitening) of the foliage with stark green veins.
One readily observes the signs of interveinal chlorosis, but the underlying cause of the disorder requires additional investigation to diagnosis and correct the problem. There are a number of abiotic and biotic factors that can result in interveinal chlorosis of the upper foliage.