black pecan aphid injury and gibberellic acid

Comparing two trays of slides, the top shows a series of photos of a leaf with almost no yellow spots or chlorotic injury. And the bottom row shows a leaf with increasingly worse injury.

Chlorotic feeding injury elicited by the
black pecan aphid seven days after a newborn
aphid was placed on a pecan leaf disc that (A) had been treated with gibberellic acid (GA3) or (B) was not treated, i.e., the untreated control. (Photo by Ted Cottrell)