Why are roof rats a citrus-belt problem in Phoenix?
Maricopa County Environmental Services says most roof rat activity in Arcadia, central Phoenix and Ahwatukee is tied to older citrus. Mature orange, lemon and grapefruit trees give roof rats food and cover, and the county urges residents to clear ripening citrus. The first Valley roof rat was found in hollowed-out Arcadia citrus.
In Arcadia, the groves ran from 1919 to the mid-1950s, watered through the Arcadia Water Company's concrete pipes, and then ranch homes on large lots replaced them. Mature citrus survived on those lots and is still flood-irrigated, so the trees are still there for the rats.
Salt River Project runs flood irrigation about every 14 days from April to September and about every 28 days from October to March. In Arcadia that water is what keeps the mature citrus growing. The same delivery is documented for South Mountain Village's agrarian properties, but not for Encanto, Maryvale or other neighborhoods, and this page does not claim it there.
How do roof rats get onto my roof?
Roof rats travel along power lines, rock fences, tree branches and palms, and they use irrigation canals and food around homes. Gaps under the eaves and unscreened roof vents are the openings the county tells residents to close. A technician traces which of these routes your house offers.
Look at your house the way a rat does. A branch that touches the roof is a ramp. A power line that comes to the eave is a highway. A block wall or rock fence that meets the house gives them a stepping route off the ground.
Palms and tall trees matter too, because they put a route within reach of the roof. A technician will usually flag one that sits close to the house.
When are roof rats most active?
Roof rat activity increases in cooler weather, according to county-reported guidance, which is why calls often pick up in winter. Maricopa County urges residents to clear ripening citrus, and the best time to act on fruit is before it ripens rather than after the rats have found it.
Scorpions are active about March through October, so the cooler months are when roof rats take over the conversation. A homeowner who has watched for scorpions all summer may be surprised by a different animal in the attic in January.
A technician can set up before the cooler weather arrives. Picking fruit when it is ripe, and not leaving fallen fruit under the tree, is the simple step the county itself recommends.
What is different in the older neighborhoods?
Older homes in central Phoenix, such as the pre-war houses of Encanto-Palmcroft, have attic and eave entry points, and central Phoenix is a county-named roof rat area. Tempe and South Tempe residents have also reported roof rats, going back to at least 2010, so the pressure is not limited to the citrus belt.
Encanto-Palmcroft has 330 homes dating from 1927, most of them from the 1930s and 1940s in Spanish Colonial and Tudor Revival styles on large lots. Encanto houses like that have roof lines, eaves and mature landscaping that give rats shelter and ways in.
In Arcadia, the trees are the draw and the roofs are ranch-style on large lots, so the technician looks at the fruit and the branches first.
Ahwatukee sits against the north edge of South Mountain and is also named by the county. South Mountain Village keeps farms, nurseries, canals and flood-irrigated properties, which is a different setting from a tract subdivision, and a technician looks at each lot on its own terms.
