Disease:
Septoria leaf spot was diagnosed last week on Renaissance Reflection® paper birch and 'Bloodgood' London planetree. Disease stricken trees have leaves with small brown spots and larger necrotic areas surrounded by lighter green and yellowing tissue. The affected leaves generally drop, reducing the photosynthetic capacity of the tree and detracting from its appearance. Septoria is a concern on young trees with few leaves and on PNP and above ground container trees that will be sold during the growing season. To the extent it is practical, rake and destroy fallen leaves. Chlorothalonil and mancozeb can be used to control septoria.

Source: Sinclair, Lyon, and Johnson. Diseases of Trees and Shrubs. Cornell University Press.

Insect:
Bagworms
Bagworms have been observed on crabapples, honeylocusts, and maples recently. According to Purdue University thresholds bagworms that will be handpicked should be controlled when 1 bag per tree is present and those that will be sprayed should be controlled when 10 bags are present. As of today bagworms in West Kentucky were almost 3/4 inch in size. Bagworms that are larger than 1/2 inch are no longer easily controlled by Bt, leaving conventional insecticides as the only option. Applications should be made soon as Ohio State University entomologists report caterpillars have the ability to skip the final instar stage and pupate when exposed to insecticides.

Planted Too Deep
With warmer days and less rainfall, cherries and dogwoods that were planted too deep have begun to dry up. Some of these plants never leafed out, others leafed out sporatically during the spring and then dried up. Upon inspection of the root system, there was no root system! Plants that do not tolerate wet soil conditions also do not tolerate being planted too deep. The dogwood on the far right was budded much higher on the stem making it particularly easy to plant it too deep. Be sure to communicate with employees to set plants at the root flare, not at the graft union.

There are a few things to consider when summer pruning. First, look closely at the plant's response to dormant pruning. How many nodes broke behind the heading cut? This is an indication of how hard they need to be headed now to encourage branching without cutting back too hard. Also, notice how vigorous each cultivar is. Red maple, honeylocust, cherry, and redbud will grow alot in the remaining season, especially with proper fertilization and continued rainfall. Without summer pruning these plants, those long branches can easily continue growing without developing any secondary branches. The result is a poorly branched tree with a very thin canopy. Always consider the planned harvest date when pruning.