Citrus Trees and Roof Rats: A Phoenix Season Guide

If you live in an older Phoenix neighborhood, odds are you've got a citrus tree or your neighbor does. Those trees are one of the best things about living here. They're also why roof rats took hold in the Valley. University of Arizona Extension notes roof rats especially like oranges, eating the pulp out of hanging fruit and leaving the empty rind. When the problem first showed up around Arcadia in 2002, that hollow fruit is how people noticed.

You don't need to cut down the tree. You need to manage the fruit, trim the tree off the roof, and pay attention to what the rest of the yard is offering.

Why fall and winter are rat season

Most Valley citrus ripens from late fall through winter and into spring, depending on the type, and grapefruit and some oranges can hang on the tree for months. That's a long, steady buffet. Maricopa County Vector Control staff have tied the fall crop to rising roof rat activity, and cooler nights bring rats closer to the house, so winter is when a lot of people first hear the attic. If that's you, see what roof rat control involves.

The rest of the year still counts. Roof rats don't take the summer off. They just go looking for water instead of fruit. A rough calendar for a Phoenix citrus yard looks like this.

• October and November: fruit starts to color. Trim palms and thin hedges now, before the crop is ready
• December through March: peak fruit. Pick as it ripens and clear the ground every morning
• April and May: strip the last fruit off and check the roofline for gaps
• June through September: heat sends rats toward water. Fix drip leaks and bring pet bowls in at night

The fruit plan

None of this is hard. It just has to happen every week during the season, not once in January when you finally notice the hollow ones. Extra fruit is better off with the neighbors, a food bank or the green bin than hanging on the tree.

• Pick fruit as it ripens instead of letting it hang
• Walk under the tree each morning and pick up any drops
• Strip all leftover fruit at the end of the season
• Put fruit scraps in a closed bin, not an open compost pile

Palms, oleander and the wall tops

Citrus is the food. Palms, hedges and walls are the housing and the roads. Roof rats nest in palm crowns and thick evergreen shrubs and travel along block wall tops and power lines. Trim palm skirts and dead fronds at least once a year, thin the oleander, bougainvillea and ivy along the back wall, and keep branches several feet off the roof. Bring pet food and bird seed in before dark, and fix the drip emitters and sprinkler heads that leak. The yard and citrus tree rat control page covers what a tech can add outside.

Roof rats follow the old citrus. In Phoenix that means Arcadia, the big irrigated lots of North Central and the older homes around Encanto Park. Across the Valley, older parts of Mesa, south Scottsdale and Tempe see the same thing. Newer subdivisions with young trees see fewer citrus rats, but not zero. The trees grow up.

When picking fruit isn't enough

Noise in the attic, droppings in the garage, or hollow fruit that keeps showing up after a few weeks of cleanup means it's time to call. A tech can set traps, put locked, tamper-resistant bait stations where they make sense, and work on closing the roof gaps. If rats have been living up there a while, plan on attic cleanup after they're gone.

Never put loose poison in the tree or on the ground. Owls, hawks, dogs and cats can all get sick from loose bait or from eating a poisoned rat. Get your neighbors in on the fruit picking if you can, because rats move between yards on the walls. The call checklist shows what's useful to have ready when you phone.

See also: Citrus Tree & Yard Rodent Control, Roof Rat Control, Rodent Exclusion