The battle with the bugs continues. …
I am seeing damage on the lower leaves of purple dome asters. The leaves are getting a speckled yellow color, and if you look on the underside of the leaf, you will notice very small gray-colored spots that look like little bits of ash dust. Those are the critters causing the damage. The bug is called a psyllid, and they suck the sap out of the leaf, causing the discoloration and soon the death of the leaf.
The dry, hot weather we have had is perfect for this bug to multiply and do its damage. A Bonide brand product called Eight is my go-to for this pest. The active ingredient is permethrin and is a broad spectrum insecticide that is a good one for your arsenal. The bug is mostly on the underside of the leaf, so that is where the spray has to be applied to knock them out.
I also am seeing septora leaf spot on Goldstrum Rudbeckia (Black Eyed Susan). If left untreated, it will totally kill the foliage on the plant.
The fungus starts out as small irregular brown spots on the leaves that eventually kill the entire leaf. This loss of foliage doesn’t kill the plant, but it will definitely weaken it to the point of not surviving the winter. It also makes the plant look disgusting.
An application of Daconil will stop the spread but will not remove the spots from already damaged foliage.
Speaking of Daconil, I have just sprayed the lower leaves of my tomato plants with Daconil to prevent the blights that attack tomato foliage. Most blights start on the lower leaves and progress upward.
Our extreme humidity creates moisture on the leaves at sunset, and that leaf remains wet until the sun dries it off the next morning … perfect scenario for the fungus to attack and spread.
Prevention is much easier than a cure!