Advice for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County
Client's Request (from telephone conversation): Help!... I'm growing tomatoes in an enclosed courtyard. I'm now seeing tomatoes disappearing and some with gnawed portions of low hanging tomatoes. I've heard a lot about voles being quite prevalent this year. Do you think it is voles? Other than the disappearing tomatoes and gnawing, I haven't really seen signs of other “animals”.
MGCC Help Desk Response: Thank you for calling the UC Master Gardener Program Help Desk this morning with your question about your disappearing tomatoes.
On the other hand, rats are excellent climbers and though somewhat larger, look similar to voles. (Voles can be up to 8 inches long, including the tail, and they have a short tail. While rats are much larger than the common house mouse or meadow vole, a young rat is occasionally confused with a mouse. In general, very young rats have large heads and feet in proportion to their bodies, whereas those of adult mice are proportionately much smaller).
Reducing the rat population should be the first step in protecting your tomatoes. Sanitation and making your courtyard less hospitable to rats, can go a long way to reducing the population. If you have bird feeders, either remove them or clean under them daily and take them inside at night. Also, talk with your neighbors about reducing rat habitat, as this is usually a neighborhood-wide problem. (Rat habitat outside of your courtyard might include woodpiles, moist areas in and around gardens, and dense vegetation such as ivy.)
Trapping can also work to reduce the population, but it is difficult to make a permanent dent in the population through trapping alone. Snap traps are the best traps to use as long as you can place them where other animals (squirrels, opossums, and birds as well as your dog or neighbors' cats) can't get to them. For roof rats, the traps should be placed in off-the-ground locations such as branches or fences.
If you use traps, check them frequently for dead rats. Do not touch rodents with your bare hands. Make sure you wash your hands thoroughly after handling traps. Dispose of dead rats by burying them or by placing them in a sealed plastic bag and putting them in the trash.
In the meantime, physical barriers can be used to protect your tomato plants directly. One approach is to erect a 1 foot tall barrier using metal roof flashing (obtainable at the hardware store) all the way around the planting bed. Rats are unable to gain traction on the slippery surface. Alternatively, you could build a small-mesh (no larger than 1/4 inch holes) enclosure around the bed or around each plant. Since rats, especially roof rats, are excellent climbers, the wire mesh enclosure would need to go up the sides and across the top of the plants.
We do not recommend use of rat poisons, especially out of doors, due to risk of harm to wildlife and pets either by eating the poison directly and/or indirectly in eating the rat.
For more information on rat identification and management, see: http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74106.html
And for information on voles see: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7439.html
Hope this information helps you eliminate those disappearing tomatoes. From the inquiries Master Gardeners have received about rats this year you are not alone.
Please let us know if you have further questions.
Good luck with your tomatoes!
Help Desk of the UC Master Gardener Program of Contra Costa County (MCW)
Please Join us at "Fall for Plants" on September 9 for the workshops and the plant sale, Registration is optional, but it'll get you a free plant from the sale. Hope to see you there.
Note: The UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925)646-6586, email: firstname.lastname@example.org, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog (http://ucanr.edu/blogs/CCMGBlog/).
Advice from the Help Desk of the
UC Master Gardener Program of Contra Costa County
Advice from the UC MGCC Help Desk: Thank you for contacting the Master Gardener help desk with your question about compost and rodents.
There are several different designs for compost bins to prevent rodent access, all of which have their benefits and disadvantages. The easiest way to keep rodents out would be a fully-enclosed and elevated tumbling bin, however these bins tend to be smaller than other bins. There are also plastic on-the-ground bins that hold more, but are more difficult to rodent proof, although it's definitely possible. Then there are wooden bins or open compost piles that pretty much cannot be rodent proofed.
There are some steps you can also take to reduce the attractiveness of compost in any container. Since rodents use the bins to find food and often as well a dry and comfortable place to live, make sure you keep the pile moist and turn it regularly. Bury and cover food waste deeply into the compost, making sure you don't add meat, grease or dairy products.
There are other things you can do to reduce rodent population in your yard. Don't feed and/or leave uneaten pet food outside. Cleanup around bird-feeding stations where the birds have scatter food. Clear thick vegetation, especially ground covers. Keep garbage and trash picked up and stored in a container. Seal access to crawl spaces and attics as well as make the area under decks and sheds inaccessible. The goal is to to eliminate rodents' cover and hiding spots.
This year especially, rat complaints at the MGCC Help Desks appear to be quite common. Rats appear to be a bigger problem in our area than are mice, and roof rats are the primary pest. Rats can chew and cause damage inside homes, especially attics and crawl spaces, and they can get into stored foods, especially pet food in garages. In the garden, they can damage fruits and vegetables, sometimes wiping out entire crops. They can also spread diseases to humans and other animals.
The University of California has a good information sheet on rat management for the home and garden: http://ipm.ucanr.edu/PMG/PESTNOTES/pn74106.html. And here are two links to good information about composting: http://anrcatalog.ucanr.edu/pdf/8037.pdf and http://sacmg.ucanr.edu/files/163139.pdf.
Additionally, if you live in Contra Costa County, you can request assistance on rat and mice control from the Contra Costa Mosquito & Vector Control District. While the District won't trap or bait for rats and mice in or around private e homes, they will assist homeowners with rat or mouse problems with advice and a free inspection from one of their state certified technicians to assist in rodent prevention and control (skunks too!). Their web page at http://www.contracostamosquito.com/rats_mice.htm provides the details.
Please let us know if you have more questions.
(all pictures from the Contra Costa Mosquito & Vector Control District)
Help Desk of the UC Master Gardener Program of Contra Costa County (SEH)
Note: The UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925) 646-6586, email: email@example.com, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog (http://ucanr.edu/blogs/CCMGBlog/).