Ask Mr. Smarty Plants

It's nice somebody is getting some  rain, we sure aren't down here in Austin. But, you're correct, ants do seem to be driven to the surface by too much water in the soil, making their beds visible. However, we don't think the ants are the primary culprits for the damage to your spinach and Swiss chard. Ants are also farmers, but they are not fond of vegetables.

Let's begin by seeing what is really causing problems with your spinach and Swiss Chard. On the page from the University of California Integrated Pest Management Program How to Manage Pests-Spinach, you will see a list of predators on spinach. Do you see ants listed? No, but you  see  aphids. Ants are very fond of aphids, but not to eat. They will protect or fiercely defend aphids so they can harvest the "honeydew," exuded by the aphids. That honeydew is a major food source for the ants. On outdoor (and sometimes indoor) plants, ants protect and care for honeydew-producing insects such as aphids, soft scales, whiteflies, and mealybugs, increasing damage from these pests. The aphid is also a major pest of the Swiss chard, so the ant farmers will visit that, too.

What to do about it? Most vegetables are non-native to North America or so hybridized that they are unrecognizable genetically, and so we have no information on them in our Native Plant Database. If you eliminate the aphids, the ants will move on to somewhere else they can practice their honeydew farming.  Obviously, if you intend to eat the products from your garden, you will not want to apply any pesticides. We recommend a good hard spray of water onto the affected plants, which knocks aphids and their eggs off and they can't get back up. Since this year's vegetable crop is probably a lost cause, the next best thing you can do is try to keep the aphids from wintering over in your garden. See this aricle on Controlling Aphids in Your Garden.