The Latest Dirt - May 2024

Can you tell me what's eating my beautiful tomatoes? Squirrels?

By Susan Heckly

Thank you for contacting the UC Master Gardener Program Help Desk and for sending a photo of your poor tomatoes.

If the tomatoes were still on your plants and not moved a distance away when you discovered this, it's rats doing the damage. Squirrels are more likely to remove the tomato and carry it to a nearby location to eat — often, you will find only a small part of a tomato. Rats will cling to the plant or the plant's support and eat the tomato in place, with much of the damage being on the top, like that on the red and green tomatoes in your photo. Rats are one of the most common pests we deal with in urban and suburban gardens. Birds can also do damage, but triangular bite marks would show on the fruit, and there isn't usually this much damage to an individual tomato.

Also, the time of day that the damage occurs will help you figure this out. Squirrels are active only during the day, while rats are active at night or during dusk and dawn.

Caging is a great way to protect plants. You need a metal mesh with holes no larger than ½ inch to exclude rats and squirrels. The caging would need to enclose the plants completely. You may be able to protect plants from rats with something a little easier. While it's reported that rats can jump up three feet, in my experience, most do not. I've had luck excluding rats with a 2-foot-tall smooth metal fence around my tomatoes. As long as they can't gain a toehold on the smooth metal, they cannot scale the slick surface.

Rat control is difficult and needs to be neighborhood wide. Roof rats (the most common rat in our area) can travel 200 feet a night looking for food. There are things you can do to reduce the attractiveness of your property. The most important is sanitation. Remove wood piles and debris where rats could find shelter. Ivy and other dense ground covers or vines are ideal habitat for rat nests. Remove or thin them if you have this in your yard. Make sure your home is sealed by securing your roof and attic vents. Close off the space under decks and sheds. Don't leave pet food or birdseed out at night and clean up any that may have spilled during the day. Also, talk with your neighbors about reducing rat habitat.

Trapping can work to reduce the population, but it is difficult to make a permanent dent through trapping alone. Snap or electronic traps are the best, but make sure to place them where other animals (squirrels, opossums, birds, outdoor pets) can't reach them. Since rats are wary of new objects in their territory, place unset but baited traps out for several nights before setting them. Wait until the rats are taking food from the traps. Wear gloves when setting traps to keep your human scent off. My experience with trapping was catching many of the younger, less intelligent ones, leaving the older genius rats to continue multiplying.

This link is to more information about managing rats: https://ipm.ucanr.edu/home-and-landscape/rats/pest-notes/
This one is for info about squirrels: https://ipm.ucanr.edu/home-and-landscape/tree-squirrels/pest-notes/

I hope this information helps. Let us know if you have more questions.