Posts Tagged: roof rats
Disappearing Tomatoes
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: ccmg@ucanr.edu, 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 (//ucanr.edu/blogs/CCMGBlog/).
What a Mess: Roof Rats in Orchards
The roof rat (Rattus rattus, a.k.a. citrus rat, fruit rat, black rat, or gray rat) is an introduced species of rat native to southern Asia. It was brought to America on the first ships to reach the New World and has spread around the world. This rat is the same species that carried the bubonic plague around the world and is also the reservoir host for murine typhus.
The roof rat is a common vertebrate pest in citrus and nut orchards. In citrus, it builds leaf and twig nests in trees or it can nest in debris piles, thick mulch on the ground, or in shallow burrows under the tree, especially in hot weather. In nut orchards, roof rats often nest around the base of trees. In livestock feed yards and barns, roof rats often burrow under feed bunks or into hay bales. Adult roof rats are 12-14 inches long (30-36cm) and weigh 5-10oz. (150-250g). The sleek rat has a pointed muzzle and hairless scale-covered tail that is longer than the body and head combined. They are the most active at night.
DAMAGE
Rats gnaw on electrical wires, wooden structures, and fruit and nuts on trees. They can also girdle limbs or stems, leading to mortality to part or all of a tree. Roof rats often feed on citrus, avocados, and other fruits, sometimes leaving hollow fruit skins hanging on the tree. After harvest, they damage fruit and nuts in bins by chewing them and leaving excrement. Rats are active throughout the year, and mostly at night.
MANAGEMENT
Cultural Control
Because roof rats are such good climbers and swimmers it is hard to completely exclude them from your grove or orchard.
Your fruit trees should be isolated, not touching fences, overhead wires, or the branches of other trees. Roof rats will run along fence stringer boards or support poles, phone and cable TV wires, and tree branches to reach your fruit tree. Lower branches of the tree should not touch the ground. A low-hanging skirt of drooping branches give the rats additional access routes and provides them with protective cover while feeding. Prune tree skirts so that the ground under them is open and visible. This lack of cover makes the rats uncomfortable and more susceptible to predators.
Sanitation is also important. Use or remove all fallen fruit. Reduce shelter and nesting sites of rats. Eliminate debris and woodpiles. Store materials neatly off the ground. Thin and separate non-crop vegetation around orchards where feasible and remove dead wood from fruit trees, especially citrus and avocado.
Monitoring and Treatment Decisions
Baiting *Be sure to identify the species of rat present to avoid killing nontarget or protected species.*
The use of elevated bait stations containing 0.005% diphacinone*-treated oats (sold at some county agricultural commissioner's offices) is highly effective at controlling roof rats in orchards. Secure bait in a bait station before placing in trees on limbs 6 feet or more above the ground. Placing the bait in a secure bait station will prevent bait from dropping to the ground and creating a hazard. Bait stations should also prevent nontarget animals from feeding on the bait. Bait can only be applied during the non-bearing season, so growers must take a proactive approach to managing problematic rat populations.
Trapping
Rat-sized snap or wooden box traps placed in trees are also effective, although a more time-consuming control option. Do not use glue board traps outdoors, as birds, lizards, and other nontarget wildlife may be trapped. Rats are wary, tending to avoid baits and traps for at least a few days after their initial placement. Fasten traps to limbs and bait them with sweet fruit or nut meats, but do not set the traps until after bait is readily eaten.
Be aware that certain types of rat baits for use inside buildings are not labeled for use outdoors in orchards; these are hazardous to wildlife and should not be used.
Roof Rats
When my friend Donna told me that roof rats were eating all her persimmons, I was incredulous. Roof rats? And what a mess they made, too! Eating half the fruit (the half you didn’t see), so that when you reached to pick it, your unsuspecting fingers sank into squishy soft, wet flesh, rather than the firm cool surface you had been expecting. She eventually had her husband put out large snap traps for them, traps that resembled oversize baited mousetraps, and her problem ended for this season.
So it’s my turn now. While cleaning up the windfalls under my unknown species apple tree (perhaps a variety of Red Delicious) I came upon what initially looked like edible windfalls which I collect and use, and some lovely firm fruit still hanging. But only half of the apple was there – the rest had been eaten on the tree. Oh dear. Roof rats…so that’s what my dog was barking at some nights ago. She was actually trying to climb that apple tree. At this point I’m reluctant to put out traps. I may have to, but I’m hoping that my dog’s presence will deter future foraging. We’ll see about that!
For more information about dealing with roof rats, see this link http://ipm.ucdavis.edu/PMG/PESTNOTES/pn74106.html.