Hello, I have a large Valencia Orange citrus tree which I grow in my greenhouse. The tree is putting on size, flowering and fruiting, somewhat, but I am concerned because most of the somewhat older leaves quickly seem to yellow, curl and drop off. New growth seems healthy. A friend suggested it might be spider mites, but I could see no direct evidence of them. I attach three pictures of the leaves. Any guidance as to what the problem is, and a suggested solution would be very gratefully received. Thank you in advance Peter
Black stippling can indicate the presence of Thrip. http://www.ozanimals.com/Insect/Thrip/Thripidae family/.html
