Posts Tagged: rodent damage
Rats in Your Orchard
The roof rat (Rattus rattus), sometimes called the black rat, is a common vertebrate pest in citrus, avocado and other yummy tree orchards. It builds leaf and twig nests in fruit trees or nearby trees, or it can nest in debris piles or thick mulch on the ground. This agile, sleek rat has a pointed muzzle, and a tail that is longer than the body and head combined.
Be sure to identify the species of rat present to avoid killing nontarget or protected species. Be aware that endangered native kangaroo rats (Dipodomys spp.) and the riparian woodrat (Neotoma fuscipes riparia) resemble pest rats, but are protected by law. Unlike the hairless, scale-covered tail of roof rats, the tails of kangaroo rats and the riparian woodrat are covered with fur. The riparian woodrat is active mostly during the day, and its tail is somewhat shorter than the combined length of its body and head. A kangaroo rat's tail is noticeably longer than its body and head combined. Kangaroo rats are nocturnal, but unlike Norway rats and roof rats, which move on all four legs, kangaroo rats hold their front legs off the ground and travel by hopping on their hind legs.
Rats gnaw on electrical wires, wooden structures, and fruit on trees. After harvest, they damage fruit in bins, chewing on the bins and leaving excrement. Rats are active throughout the year, and mostly at night.
To help manage rats, reduce shelter and nesting sites of rats. Eliminate debris and wood piles. Store materials neatly and off the ground. Thin and separate non-crop vegetation around orchards where feasible. Exclude rats from nearby structures by properly sealing entry ways.
Baits and rat-sized snap traps placed in trees are the most effective control measures. 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. Secure anticoagulant wax blocks in a bait station before placing in trees on limbs 6 feet or more above the ground. Placing the wax blocks in a bait station will prevent chunks of the anticoagulant wax from dropping to the ground and creating a hazard.
Be aware that certain types of single-dose rat baits for use inside buildings are not labeled for use outdoors in orchards; these are hazardous to wildlife and should not be used.
For more on the subject see:
http://icwdm.org/handbook/allPDF/RO_B125.PDF
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74106.html
and another blog:
//ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=16880
roof rat
rat damage to citrus
OH, rats!
When I was a kid, I had a pet rat. The offspring of “Rat Olympics” medal winning parents, she was friendly and athletic. A smart rat, I trained her to perform several tricks. She was a domesticated rat and my pet. The wild rats that have been using our vegetable garden as their cafeteria, are pests.
![purple eggplant nibbled on by rats, showing damage of the nibbling purple eggplant nibbled on by rats, showing damage of the nibbling](http://ucanr.org/blogs/USS/blogfiles/8820.jpg)
There are many public health issues associated with wild rodents and any pest problem is best dealt with early, before it gets out of control. The two most common rat species in California are the Norway rat (Rattus norvegicus) and the roof rat (R. rattus). Sanitation, rat proofing, and population control are the three main aspects of managing a rat problem.
The first sign of my rat problem was early in spring: vanishing bok choy (Brassica rapa chinensis). The outer leaves of the young leafy clusters were disappearing one by one over the course of a few nights. The amount of damage could not have been caused by insects and no evidence of slugs or snails was visible. Since they are active at night, I suspected rats. I constructed 24-inch tall cylinders of hardware cloth to protect the plants. After a few nights of experimenting with methods for securing the cylinders to the ground, the leaves remained undamaged. Hungry rats will find a way around obstacles, so I buried the hardware cloth about an inch deep and used garden staples to hold it in place. The bok choy was now rat proofed.
![Adult Norway rat Adult Norway rat](http://ucanr.org/blogs/USS/blogfiles/8821.jpg)
Things to consider when choosing a control method:
Rodent baits contain poisons that are also toxic to pets, wildlife, and humans. It may take several days for the poison to work allowing the rat (or mouse) the opportunity to find an inconvenient place to die like inside a wall or under a deck. The carcass may still contain active poison that could be harmful to cats, dogs, or wildlife that might consume it.
Glue or sticky traps are usually ineffective and rats can drag them around as they struggle to escape. Glue traps can be dangerous for wildlife such as birds and reptiles, and small mammals like kittens.
Trapping with a spring type trap is recommended by UC IPM as the most effective. It may be labor intensive, but it works. Over the summer, we controlled more than twenty rats in our garden. We religiously set the traps in the evening and unset any unused traps in the morning. Why not leave traps out all the time? Dogs, cats, and wild birds looking for food could be injured by the traps, and that is definitely not the intention.
For more information on managing rats, including trap setting strategies, visit the UC IPM website for Pest Note number 74106 http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74106.html