Hornworm caterpillar eating a tomato plant. (Photo: AdobeStock)
One day, tomato plants look healthy, green and lush. The next, the leaves are gone and only stems remain. There might be peppercorn-size pellets on the ground. The insect responsible for the damage is well camouflaged and difficult to see.
However, once you spot this bright, green 2-inch to 4-inch caterpillar, you will not forget it. It’s a hornworm and those pellets are fecal droppings.
The hornworm is one of the largest caterpillars in the west. Its parent is called a sphinx moth, hawk moth or hummingbird moth. These large moths resemble a hummingbird in flight as they feed from deep-throated flowers, such as honeysuckle. They are most active in late afternoon and at dusk and may occasionally be seen at porch lights. They are strong fliers and can travel long distances.
The female lays smooth, round, pale green eggs singly on the upper surfaces of leaves. The caterpillars hatch and then feed for a month or so on the leaves. They then migrate from the plant to the soil where they pupate. The “horn” at the hind end of the larval or caterpillar stage is actually a flexible spine.
Vigilance will help you control hornworms. They are most easily discovered at dusk and dawn. Look carefully to find them on the leaves, pick them off and destroy them. They cut easily with scissors or pruning shears.
Bacillus thuringiensis is a bacterial disease organism you can purchase and apply. It will infect the hornworms and kill them. It is non-toxic to humans and animals. Tilling or digging the soil after harvest will destroy the overwintering pupae to reduce next year’s infestation.
I’m also seeing tiny “bugs” that leave a red stain when I squish them. While these clover mites, a relative of spiders, are common and annoying, they do not bite humans or animals. They do not transmit diseases and do not feed on household furnishing or foods. They are a temporary nuisance. They appear suddenly and then are gone.
Clover mites thrive on clover and lawns. They also eat dandelion, strawberry, iris and other plants. To prevent mites from getting into the house, begin by modifying their habitat. Remove all grass and weeds from 18 inches to 24 inches around your home, especially on the south, southwest and east sides. Cover this area with pea gravel or mulch. The mites can be sprayed with insecticidal soaps or washed off with soapy water from surfaces outdoors.
To get rid of clover mites indoors, vacuum them up and dispose of the vacuumings thoroughly. Or, wipe them up with a soapy rag or sponge. Be careful not to crush them to prevent staining surfaces. Avoid using insecticides indoors particularly on kitchen counters.
Isn’t nature wonderful!
JoAnne Skelly is Associate Professor & Extension Educator Emerita at the University of Nevada Cooperative Extension. Email skellyj@unr.edu.
