When counts drop to 1 or 2 moths per week, the insecticide spray that should be in place about 240 DD later is not so critical. If it goes on a day or two late because other jobs need to be done, it's still unlikely that significant damage will show up. And in such circumstances an alternate-middle spray program is likely to work fine. Dogwood borers are caterpillars that grow up to be clearwing moths. They tunnel beneath the bark of trees, and in young trees are active especially in the burrknot.
Pheromone traps are available to monitor flights and guide in timing sprays.
However, with the dramatic change in the weather, I think that particular threat is no longer a concern. I had received a report from Arkansas that levels of common rust were reaching fairly high levels even on field corn. Common rust does not overwinter in Illinois, but is carried up from the south on air currents, and usually arrives here in late June or early July. The cool wet weather we were having was ideal for rust development, and I thought that we might see some major problems with rust on sweet corn. Infection typically takes place in the whorl, where humidity levels remain high most of the time.