Ask Mr. Smarty Plants

The Clara Curtis perennial chrysanthemum is, we trust, part of the 5% of your garden which is non-native. The genus Chrysanthemum is native to China and Japan, and the name of the mum you are asking about is Chrysanthem x rubellum 'Clara Curtis.'  The "x" indicates that it is a hybrid, which also removes it from native plant status, but we never did find out what the rubellum was, another species of chrysanthemum, we suppose. This article from Perennials.com will give you some information.

We are also assuming that the blue fall asters you are referring to are Symphyotrichum novae-angliae (New England aster), which, indeed, are native to North America and apparently grow in Texas, although they are not listed in our Native Plant Database as being native to Texas.

However, whatever help we can give you with ants and bugs eating your plants will surely apply to both. We extracted this comment from the University of California Integrated Pest Program article on Ants. 

"Inside buildings, household ants feed on sugars, syrups, honey, fruit juice, fats, and meat. Long trails of thousands of ants may lead from nests to food sources, causing considerable concern among building occupants. Outdoors they are attracted to honeydew, produced by soft scales, mealybugs, and aphids. This liquid excrement contains sugars, and other nutrients. Frequently outbreaks of scales and aphids occur when ants tend them for honeydew because the ants protect scales and aphids from their natural enemies."  

Ants are farmers, but they are not vegetarians. They won't eat your plants. There is a leaf cutter ant which carries off chunks of leaves, but we don't think that's what you're talking about. You might be interested in reading this previous Mr. Smarty Plants answer about leaf cutter ants in Texas. You will note from the article above that ants are a symptom of the presence of other bugs that ARE eating your plants. So, what you want to do is deal with those insects: scales, aphids and mealybugs. We will link you to articles on each so you can see what they look like and what suggestions the articles might have for their control.

First and foremost, forget the pesticide sprays. That's overkill, and what it will kill is the beneficials, the butterflies and pollinating bees, the ladybugs and wasps that are the enemies of the bugs that really do harm your plants. Those bugs that we mentioned as being harmful can all be controlled with a gentle spray of water when they are active on the plant. If you're really serious about it, add a little dishwashing liquid to the water in the spray. This will wash off the bugs, their honeydew and the ants that are farming same. Most of the bugs that are washed off cannot climb back up. This is about as low impact a pest solution as we know of.

From University of California Integrated Pest Management Aphids.

Learn 2 Grow All About Mealybugs

University of Missouri Extension Aphids, Scales and Mites on Home Garden and Landscape Plants. 

Pictures of Chrysanthemum x rubellum'Clara Curtis' from Google