Answer: There are several possible contributing causes to your phlox problem. First, your plants would prefer to have morning sun and some afternoon shade. The blazing hot afternoon sun is enough to cause them to wilt temporarily, as their "plumbing" just can't keep up with the transpiration of water out of the leaves. Make sure and keep them adequately moist. Consider a new location to transplant them into this fall.
Phox is susceptible to nematodes. These pests damage and stress the plant by decreasing the effectiveness of the root system. Above ground symptoms appear as stunted, drought stressed plants. There is not a cure for nematodes. You can purchase nematode free planting stock and locate it in another area in hopes that it is a nematode-free location.
Regarding the leaf feeding pest...
It could be a beetle or a catapillar. If your can't find the culprit by closely inspecting plants during the day, try going out with a flashlight at night as some pests are primarily nocturnal. Turn over a few leaves as some pests hide under the leaf.
If the pest is a catapillar, you can use a product containing B.t. to control it without harming your bees or other beneficial insects.
Good luck with your flowers!
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