Tomato Hornworm: Bug Hit List

Have you ever gone out into your garden and seen your tomato plants leaves riddled with holes? You could have a Tomato Hornworm infestation. These guys are the real life hungry hungry caterpillar and, though arguably cute for a pest, they can be very damaging as they eat through your plants! They can chew wholes through leaves, eat small stems, and take chunks out of your fruit. Even thought they are large they are hard to see on your plant because they take shelter during the day and are active at night. Carefully read below to learn how to identify them and what to do if you do have them in the garden.

Identification: 

Adult Moths are brown/grey and nocturnal, you are not likely to see them flying around your garden unless you do a night time scout walk. They come out of the ground as adult moths in the spring and mate and lay their eggs. Eggs can be found on the leaves, both on top and the underside, and are green and smooth. The caterpillars are green, white, and sometimes a little yellow making them hard to spot even when fully grown. They have a distinctive horn like appendage on one end giving them their name, hornworm. 

Host Plants:

They're favorite plant is the tomato though they have been found to eat off of potatoes, eggplant, and peppers. 

The Damage:

They often eat the tender new growth and leaves near the top of the plant leaving behind holes, or taking the whole leaf. In their wake, they leave a trail of small black or dark green pellets which can be used to identify them. They often are found in groups and can quickly eat away the leaves putting the plant into a stressed state and reducing the production. 

Prevention Options:

One thing you can do before the season starts is cultivate the area you will plant tomatoes. If you cultivate before planting you may kill the pupae (stage between caterpillar and moth) and caterpillars that may be growing and taking refuge in the soil. As always if prevention fails you can always take responsive action.

Physical Controls

Get your kids or friends and play a difficult game of "I spy with my little eye the Hornworms"! Get in your garden and get searching, make sure you are looking under leaves as the caterpillars like to take cover and hide during the day (you aren't the only one looking for them, birds also love them because they are such a big snack). Pick those caterpillars off your plants and kill on sight. I think a game of who can find the most hornworms in the garden should be a summer staple in a house with children and a garden!

Pesticide Options:

One pesticide we've discussed before is Spinosad which can also be used for tomato hornworms. It is a compound derived from micro-organisms found commonly in soil and effects the insects nervous system. This being said it's good to know that it can also effect bees, especially when freshly applied so use sparingly or, if possible, not at all. 

Another natural pesticide is Bacillius thuringiensis var. kurstaki (Bt) a bacteria that targets only caterpillars, but the caterpillars must digest it to have any effect. 

Whatever you choose to do, make sure you are taking the time in your garden to be on the look out for damage and pests so that you can take action, and as always you can call with questions and concerns!