By Gregory Covello, A.C.E.
(Associate Certified Entomologist)
Winter is normally a time when our focus on pests in the garden is at its least. The majority of the insect world is taking a break from visiting our gardens, orchards, and farms. However, not all pests take a winter vacation. The time is now that we take a look for signs of common rodents.
During the winter months most of the resources that rodents rely on dwindle. However, if you utilize winter cover crops, some of the much needed food sources for rodents still may exist throughout the winter. Inspect your grounds for trails or burrows that mice and rats may leave behind. Check for disturbances in leaf litter, soil, and vegetation. Trails will occasionally have rodent droppings present as well which will help you properly identify what rodent may be paying you a visit. Mice have pointed droppings approximately ¼ inch and rats have rounded blunt droppings approximately ¾ inch.
House Mouse (Mus musculus)
The most common winter pest is the house mouse (Mus musculus). The house mouse is a small rodent about 3-4 inches (head to tail) in length as an adult. Most commonly this type of mouse will have grey fur. The house mouse is classified as an omnivore however plant material is its primary choice diet. Any plant material can provide the house mouse with the nourishment it needs to survive the colder months. If a winter cover crop strategy is used, make sure you are inspecting your ground cover. Winter greens not only provide the house mouse with food, but a good ground cover provides the house mouse with shelter from the harsh cold environment.
Another pest that growers commonly encounter in the colder months is the Rattus norvegicus. This rodent is referred to by many common names including the brown rat, Norway rat, common rat, and sewer rat. Despite the common name “brown rat”, the Rattus norvegicus can and commonly does have grey fur as well as brown fur. An adult rat is about 15-20 inches (head to tail). A brown rat is the epitome of an omnivore. There is very little that a rat will not eat. Gardeners and growers that have encountered brown rats would agree that corn is a commonly unrecognized favorite food. Unlike the smaller house mouse, the rat needs an ample water supply to survive through the rough winter months.
Integrated Pest Management Strategies
If you have identified either of these common winter pests roaming your grounds, it is time to implement (or revisit) an IPM (integrated pest management) strategy. Without a good IPM plan in place, the rodent population will be doing the majority of the blooming come the spring. Both mice and rats have quick reproductive cycles. Now is the time to manage outdoor populations of rodents as breeding often ceases during winter months. Remember, as with any IPM plan, the use of pesticides should be reserved as a last step. Start by removing harborage sights such as leaf litter and old abandoned equipment. (Spare tires, a broken down tractor, unused storage containers, etc) Search for any items that may be accumulating water and remove them. If weather permits, inspect and turn your mulch piles. Mulch may contain numerous sources of food if the pile isn’t properly managed. Monitor burrows by collapsing them or filling them with soil. If the burrows reappear within a few days, you have confirmed activity.
Often landscape modification and good grounds maintenance is enough to expose mice and rats to predation. If these winter visitors still persist after implementing a cleanup strategy, trapping should be considered as the next step. As a final step, rodenticide baits and powders can be utilized. Be aware of local and state laws before applying any pesticides, or contact Viking at 1-800-618-2847
Now is the time to get an early start to the growing season this year by implementing your winter rodent IPM plan.
Editor’s note: Gregory Covello, ACE is an Associate Certified Entomologist and District Manager for Viking Pest Control based out of Warren, Somerset County. He is a back yard gardener and hobbyist bee keeper. He can be reached at firstname.lastname@example.org.