There are many  species of wasps that live in the area.  The United States only has two (one recent and Not in DE) - the European hornet and the Asia murder hornet (Not in DE).  Insects can be identified by sending them into plant diagnostic clinic if they are of concern (https://www.udel.edu/academics/colleges/canr/cooperative-extension/sustainable-production/plant-diagnostic-clinic/)

Bald-faced hornets (not technically a hornet), cicada killers, mud daubers, ground nesting bees, paper wasps and yellow jackets are common wasps found in our area.  I am unaware of any guaranteed way of discouraging them from nesting in an area other than eliminating areas they prefer (empty cavities - European hornets, yellow jackets for example) or careful removal of nests as you notice their construction earlier in the year.  

 Wasps begin shifting their feeding focus in the late summer to early fall.  I suspect people on picnics have already started noticing this phenomenon.  They usually begin to focus on consuming sugars or more sweet related foods in August.  Worker production slows down as we move later into the year (August); consequently, the proteins are needed less often but maintenance requires the more sugary based foods.  Wasp populations crash as temperatures become cool to cold the further into fall we proceed until only next year's queens are searching for overwintering locations.

Thank you for the response.  We have observed the presence of hornets swarming our porch at night.  In our research, we have read that European hornets are the only nocturnal hornets however your reply indicates that they are not present in Delaware.  Am I correct in that understanding?  I can try to capture a specimen but they seem to be erratic in their flight pattern and never seem to land still for more than a second.   

The European hornet is in DE, but the Asian murder hornet is not.  Treatments for European hornets are rarely effective unless you are able to find the nest.

I do not, there should be any number of pest control companies that should be able to assist.  The European hornet is attracted to lights at night, so just because they are there at night does not necessarily mean you have a nest at your porch.