Tomato plants might unravel the riddle of the sphinx moths

Q: A couple of evenings ago, we were sitting on the back porch with well-deserved glasses of iced tea. We were looking at the neighbor’s desert willow tree and saw hummingbirds flitting all around. It was so near dark that I wondered if in fact they were hummingbirds we were seeing. It seemed odd to have them flying that late. Then I remembered you teaching about big moths that fly around, and wondered if what we thought were hummingbirds could be the big moths you’ve spoken of in the past. What do you think? — C.M., Albuquerque

A: The moths you speak of, I’ve always known them as sphinx moths, could very well be the critter you noticed at dusk that evening.

The tomato hornworm moth is really large and easily mistaken for hummingbirds at a distance. If they are hornworm moths, with their 5-inch wingspan, and you grow tomatoes in a garden, now is the time to be on the lookout for the green hornworm caterpillar. It only takes a few of these voracious eaters to strip a tomato plant, leaving behind leafless stems. So tomato growers, be on guard.

During the evening hours, head out to the gardens and closely inspect your tomato plants for any of these destructive creatures. During the daylight hours they hang out, not moving around much, clinging to the stems and branches of the tomato plants perfectly disguised and matching the green of the plants near perfectly. It’s during the late evening and nighttime hours that they are active.

You can invest in a fluorescent flashlight to assist you while looking for the hornworm caterpillar, they will actually glow a different color than the plant. It’s pretty gross, but you can pluck the hornworm and chuck them into an old coffee can filled a quarter of the way with water and several drops of dish soap to hasten their demise.

Get used to watching the gardens at that dusk hour to monitor for any large, hummingbird-sized winged creatures flitting about. Actually, the moth is beautiful in its own right, it’s just the hornworm in caterpillar form that does all the damage. The only insecticidal spray I will recommend is one containing Bacillus thuringiensis kurstaki, BTK for short. Just know that this insecticide has a very short effective window, and degrades rapidly in sunlight, so multiple sprays in those evening hours, so the insecticide is “fresh,” would be required to gain the upper hand if you are going to rely on spraying alone.

Going out caterpillar hunting with your flashlight will be the most effective way to protect your tomatoes from the hornworm.

Now if it was hummingbirds you noticed around the desert willow, and you have feeders, it’s really time to step up the cleaning and refilling of those feeders. With the temperatures so dreadfully hot, the nectar you make has a tendency to sour, so to speak. Offering fresh sugar-water for your hummingbirds, more often during this heat, will be a very good thing to do for your hummingbirds.

Happy Diggin’ In watching the hummingbirds and being on guard for tomato hornworms!

Tracey Fitzgibbon is a certified nurseryman. Send garden-related questions to Digging In, Albuquerque Journal, 7777 Jefferson St. NE, Albuquerque, N.M. 87109, or to features@abqjournal.com.