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Tomato Hornworm   (Manduca quinquemaculata ) and   Tobacco Hornworm (Manduca sexta)

Where indicated, photos can be enlarged.

Robins may even be turned off by this very large, very ugly, very combative larva. 
If you see missing leaves or tips of branches, fruit with bite marks, and feces at the base of the plant, it's there!   They normally hide underneath a leaf stem, as the photo below illustrates.  Begin spraying with BT (Bacillus thuringiensis), a non toxic form of biological control, at the first sign of larva or leaf damage.   They should be picked off immediately, because even one worm can decimate the growing tips of a plant before the Bt is effective.  Click on the image below to see what this ominous-looking creature looks like up close.  It is appropriately named for the horn on its tail.

Hornworm on Pepper      Hornworm and Mike's Finger

 

Memorize this moth in case you're lucky enough to see it in the daytime.

moth_sphinx_usgs_small.jpg (1866 bytes)

Photo courtesy of USGS

It is the nocturnal Five Spotted Hawk Moth,  sometimes called sphinx moth,  or hummingbird moth, because they have a 4" proboscis.  Their wingspan is 3"-5".  In the larval stage, they are called the tomato hornworm.  If you miss the warning signs, as Planter did, and  the worm reaches the ominous size of 3" long and 3/4" thick, it is probably too late to save what remains of your tomato plant. 

It eats the leaves and the fruit and can defoliate the plant in a matter of days.  When we first started our garden here in NH, we lost over 75% of our table tomato plants,   including the growing tips of the plant.  Damage to the Romas and cherry tomatoes was not as severe. 

If the larva has some white cocoons attached to its back.   These are wasp larvae that feed off the hornworm larvae.   Since the infected hornworm stops eating, I leave it on the plant long enough for the beneficial parasite to mature.      

hornworm_wasp.jpg (6413 bytes)

Perhaps due to a very wet summer in 2003, the hornworm did not appear until the first week of August.  It took only about 10 days for the wasp larvae cocoons to appear.  The larvae were completely desiccated within days, perhaps because they were immature.    That's what organic gardening is all about!  

Know Their Life Cycles

Life History: In late spring, the adult moth lays eggs on the underside of tomato leaves. The eggs hatch in 6 to 8 days and the larva passes through five or six stages before reaching full growth in 3 to 4 weeks. The full grown larva wander from the garden and burrow into the soil where they transform into the pupal stage. The hornworm remains in the pupal stage in the soil all winter.

Tip:  Turning the soil in the fall will expose hornworm pupae to weather and predators.

The moths emerge from the pupa within 2 to 4 weeks. The emerging moth makes its way to the soil surface and mates. The females begin to deposit eggs on the tomato plants for the next brood of hornworms.

Natural Enemies: There are a number of natural factors that help control the hornworm. One of the most common parasites in home gardens is a small wasp. Occasionally, hornworms are seen with a number of white projections protruding from their bodies. These are the cocoons of the small parasitic wasps. The wasp larvae feed inside the hornworm during its life span and kill the host upon emergence. Do not kill parasite-infected hornworms.

Control: Dust and sprays should be applied evenly, thoroughly covering all the foliage. Control is most effective during July and August. Hand picking or snipping the hornworms in half with scissors gives good control on infested plants in the home garden. Insecticides may also be used to control hornworms.

Gardeners are advised to examine vines frequently from early July on into August for hornworm eggs and small caterpillars, and to begin control measures as soon as they are seen. If sprays or dust are applied on time, a second treatment probably will be unnecessary.

For recommended insecticides see a current issue of BR 1158, "Insect and Disease Control in the

Home Vegetable Garden."

Univ. of VT Extension Service

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Hosts: Primarily tomato but can also attack eggplant, pepper, and potato.

Description: The larval stage of this insect is a 3 1/2 to 4 inch long pale green caterpillar with white and black markings. There is also a brown form but it is not as common. One of the last abdominal segments has a spine-like red or black horn that that gives this insect its' name. The adult is the Sphinx moth; a grayish-colored insect with a wing spread of 4 to 5 inches.

The larva is the damaging stage and feeds on the leaves and stems of the tomato plant and leaving behind dark green or black droppings.

Recommendations: This insect is parasitized by a number of insects. One of the most common is a small braconid wasp. Larva that hatch from wasp eggs laid on the hornworm feed on the inside of the hornworm until the wasp is ready to pupate. The cocoons appear as white projections protruding from the hornworms body. If such projections are seen, leave the hornworms in the garden. The wasps will kill the hornworms when they emerge from the cocoons and will seek out other hornworms to parasites.

Handpicking is an effective control in small gardens. Bt (Bacillus thuringiensis) and other insecticides may also be used to control hornworms, but it should be applied when the hornworm is still small, before it does major damage to the plant.

References:

1. Tomato Hornworm, Cornell University Extension Service

2. Ortho Problem Solver, Ortho Information Services, pg 776

Last Update: 5/97

Kansas State Univ. Research and Extension

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These 4 inch, green worms have a prominent horn on the rear end and can eat much foliage. The insects make a clicking sound when the plant is shaken. Use Rotenone(1), Sevin(0 to 3), Pyrethrin(1) and Bacillus thuringiensis.

Mich State Univ. Database

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Shinx de la tomate

Manduca quinquemaculata

DESCRIPTION and LIFE HISTORY

* indicates damaging stage

Adult (12 cm wingspan):

"Hawk" moth; greyish brown; sips nectar; emerges from pupa in late spring.

Egg:

Round, greenish; laid singly on undersides of leaves

* Larva (10 cm):

Green with oblique white bars; "horn" on rear end; may resemble curled up leaf (locate by dark

green droppings on ground below); feeds ravenously for 3-4 weeks, then pupates.

Pupa (7 cm):

10-12 cm deep in soil; dark brown hard, spindle-shaped; overwinters as pupa.

Generations/Year:

1-4: 1 in northern range

DAMAGE

Attacks TOMATO, TOBACCO, POTATO, PEPPER, EGGPLANT an related weeds.

Eats leaves (mostly) and fruit.

CONTROL:

Handpick and drop in soapy water unless covered with small white cocoons (braconid parasites - an effective natural control); eliminate crop residues right after harvest (reduces overwintering populations); spray young larva with Bacillus thuringiensis1 (or rotenone, as a last resort);  trap adults with black light; repel with marigold, borage and parsley as companion plants.

1 Sold as Dipel (r) ~ and Thuricide(r)

Ecological Agricultural Project, McGill, CA