June 26, 2020 - By Helen Willoughby-Peck (UC Master Gardener) - Take a walk in your garden daily if you can. It’s good for you and it’s good for your plants. Observing your plants regularly helps 
control pests that may be beginning to enjoy your tomatoes before you can. When caught early, they are usually easy to control without insecticides or other drastic action.
Any number of pests can invade your tomato plants and other veggies: mites, beetles, thrips, whiteflies, caterpillars, aphids, leaf miners… the list goes on. But don’t be discouraged; tomato plants are hardy. Diligent observation, knowing the difference between good and bad bugs, and dealing with problems promptly will go a long way in pest management without using insecticides.
The tomato hornworm (pictured below), a common and easily controlled pest, can camouflage itself as it looks like a tomato leaf. If you notice sudden defoliation of your tomato plant or large holes gnawed into the tomato fruit, it’s likely a tomato hornworm. They are tricky to find since they blend in so well. Check the leaves and ground below the plant for 
1/16-inch black pellets of excrement…a telltale sign. Look straight up and you will find a hornworm, usually about the size of a finger. Or use a blacklight flashlight at night. The hornworm will appear much brighter than the plant foliage, making them easy to locate. Hand pick them and drop them in a pail of water.
Aphids can be a problem, especially in years with a cooler spring. Look under leaves or on tender new growth for tiny, oval, green, yellowish or black insects and use a sharp spray from a hose to remove them. They are unlikely to reinfest the plant. For heavy infestations, spray them with neem oil, a naturally occurring and less toxic pesticide.
Birds sometimes eat mature tomatoes. Devices, such as reflective tape, can scare birds from your garden as it moves with the breeze.
It is best to accurately identify any concerning pests. Many pests need no control unless infestations are severe and many are kept under good control by natural predators or parasites (other insects that eat them or lay their eggs in them).
If insecticide is needed, use a product specific to the pest. Broad-spectrum insecticides can cause more harm than good by destroying beneficial insects that prey on pests, causing an upset to nature’s insect balance. By destroying beneficial insects, it is possible to see a surge in the pest population.
For assistance in identifying insects and how to best treat specific pests, contact our Helpline at (209) 966-7078 or at mgmariposa@ucdavis.edu. We are currently unable to take samples or meet with you in person but welcome pictures of insects and foliage.
The U.C. Master Gardener Helpline is staffed; Thursdays from 2:00 p.m. - 5:00 p.m.
Serving Mariposa County, including Greeley Hill, Coulterville and Lake Don Pedro
Please contact the helpline, or leave a message by phone at: (209) 966-7078
By email (send photos and questions for researched answers) to: mgmariposa@ucdavis.edu
For further gardening information and event announcements, please visit: UCMG website: http://cemariposa.ucanr.edu/Master_Gardener
Follow us on Facebook at: https://www.facebook.com/mariposamastergardeners
Master Gardener Office Location:
UC Cooperative Extension Office,
5009 Fairgrounds Road
Mariposa, CA 95338
Phone: (209) 966-2417
Email: mgmariposa@ucdavis.edu
Website: http://cemariposa.ucanr.edu/Master_Gardener
