One day tomato plants look healthy, green and lush. The next, the leaves are gone and only stems remain. “What critter is attacking my tomato plants?” “How can something be eating the leaves – the plants are hanging high out of reach of critters?” “What are all these peppercorn-size pellets on the ground?” people want to know. It is no great mystery; except the insect responsible for the damage is so well camouflaged, it’s hard to see. However, once you spot this bright green 2-inch to 4-inch caterpillar, you will never 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.

Extra vigilance will help you control hornworms. They are easier to discover at dusk and dawn. Look carefully to find them on the leaves, pick them off and destroy them. They cut easily with shears. Bacillus thuringiensis is a bacterial disease you can purchase and apply. It will infect the hornworms and kill them. It is non-toxic to humans. Tilling or digging the soil after harvest will destroy the overwintering pupae to reduce next year’s infestation.

If you are interested in growing your own food, Cooperative Extension will be offering an 8-week series of classes starting September 20 through November 8, at the Carson City Extension office – 2621 Northgate, Suite 12; from 6:00 p.m. to 8:00 p.m. Learn what you need to know to prepare for next year’s growing season. The first class will cover site location, what to grow, how to plant and planting dates for three seasons. To get a complete list of classes or to register, please contact Teri Spraggins at spragginst@unce.unr.edu or 887-2252.

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