Recently I got an e-mail communication from a Hopkins County resident related to her tomatoes. The digital pictures showed tomato fruit damage similar to hookworm damage. Gardner and Goodwin (Texas Master Gardener’s) wrote related to hookworms as follow: Hookworms are chewing insects (Manduca sexta Linnaeus), with complete metamorphous (egg, larva, pupa, adult stages) affecting tomato, tobacco, eggplant, pepper, potato, datura and some weeds. Occurrence from late April through August, over the spring growing season, tobacco hornworms can also be a problem in fall grown tomatoes. Female moths deposit greenish-yellow eggs individually on the undersides of host plant leaves. Eggs hatch in about 7 days (depending on temperatures and other conditions). CATERPILLAR STAGE: 3 – 4″ long when full size. The caterpillars are pale green with 7 straight oblique white lines laterally. White lines are edged with black on upper edge. Caterpillars develop through five stages (instars) for 3 – 4 weeks until they pupate 3 – 4″ deep in the soil. One of the last abdominal segments has a red colored horn-shaped structure — gives this insect its name. PUPAL STAGE: Winter is spent as a pupa in the soil. Pupa is about 2″ long, dark brown in color and spindle-shaped, with the encased mouthparts prominent and separated from the body, appearing like a handle. Unless the pupa overwinters, adults can emerge in about 3 weeks, producing two generations per year. Description / Symptoms: The caterpillar stage is the damaging stage. Caterpillars feed on the leaves and stems of the tomato plant. Caterpillars leave dark green or black droppings. CULTURAL CONTROL: Hand picking is an effective control in small gardens. Plants will continue to grow and produce under light to moderate infestations. BIOLOGICAL CONTROL: This insect is parasitized by various insects including a small braconid wasp. Larvae of braconid wasp will kill the hornworms when they emerge from their cocoons. Leave parasitized caterpillars alone as the newly emerged braconid wasp adults will seek out other hornworms to parasitize. The bacterium Bacillus thuringiensis (commonly known as Bt) is effective as a spray if it is used against young larvae. CHEMICAL CONTROL: Several insecticides provide effective control of tomato hornworms. Follow product label instructions.
Coming Up: The Hopkins County Tomato Festival will be held at the Sulphur Springs market at the square Saturday July 5th, 2014 from 4:00 to 6:00 PM. 3 tomato fruits make an entry. Entries can be made on pearl, cherry and large red. Two classes: Junior and Open. Entries to the Hopkins County tomato festival are free. Awards will be given to first, second and third contestants in each category. For more information in this or any other agricultural topic call the Hopkins County Extension Office at 903-885-3443 or email me at [email protected].
Mario Villarino DVM, Ph.D.
Hopkins County Extension Agent for Ag and NR
1200B Houston Street
Sulphur Springs, Texas 75482