This damage is due to the Pigweed Flea Beetle (and we see a couple of them in the photos), which looks superficially similar to the Striped Cucumber Beetle, but which is a different species that prefers members of the amaranth family (to which callaloo belongs). As with other leaf-chewing insects, there are a couple approaches you can try (one of which will have to wait until next year at this point):

• use a low-toxicity insecticide to discourage their feeding (as long as the product is labeled for use on edible plants), like kaolin clay (which coats the leaves and irritates their mouthparts) or spinosad; there are strains of B.t. (Bacillus thuringiensis) that specifically affect beetles, though we don't know if they are widely available as sprays for vegetable plants
• cover the plants with insect mesh netting immediately after planting so pests can't access the plants; this is best for plants like callaloo that don't need pollinators to visit the flowers for fruit production (unlike, for comparison, cucumbers, where a cover would need to be removed once they flower)

As they are now, they leaves are still edible, albeit perhaps unappealing. Other suppression or prevention tips for flea beetles as a group are included in our Flea Beetles on Vegetables page. (The focus of that page is another, smaller species of flea beetle that is a very common eggplant pest, but its tips apply to other species as well.)

Miri