Roof Rats in Palm Trees and Fruit Trees in San Diego

Why palms attract roof rats

Many palms planted in San Diego, including the tall fan palms that line streets and the queen palms common in yards, hold dead fronds that hang down in a skirt. That skirt is dry, shaded and hard for predators to reach. Roof rats nest in it and use the trunk as a highway. Date palms and other fruiting palms add food.

A palm next to the house, or one whose fronds brush the roof, gives rats a direct route to the roofline. In neighborhoods like Coronado, Point Loma, Pacific Beach and North Park, rows of palms let rats travel from yard to yard without touching the ground.

Why fruit trees matter

Backyard citrus, avocado, loquat, fig and stone fruit trees are everywhere in San Diego, from older Lemon Grove and Chula Vista lots to La Jolla gardens. Roof rats eat the fruit on the branch and on the ground. Classic signs:

• Oranges or lemons hollowed out on the tree, with just the peel left hanging
• Avocados gnawed open, with the seed chewed
• Bark stripped from branches
• Droppings on the ground or on fences under the tree

Many backyard citrus trees hold fruit for months, which keeps rats fed through much of the year.

Trim the trees

• Remove dead palm fronds and keep the skirt cleaned up; tall palms may need a tree service
• Cut back branches so nothing is within 4 feet of the roof, as the county advises
• Thin dense lower branches on fruit trees so rats have less cover
• Cut back ivy, bougainvillea and other vines on fences that connect to the house
• Keep palms and trees from touching power lines that run to the house, which is a job for the utility or a qualified tree service

Trimming does not remove the rats in the neighborhood, but it takes away the bridge to your roof.

Clean up the fruit

• Pick ripe fruit promptly instead of letting it hang
• Pick up fallen fruit every day during the season
• Do not leave fruit in open bins or compost piles; the city's green bin takes food scraps, and its guidance says to keep the lid closed
• Store harvested fruit indoors or in closed containers

If you have more fruit than you can use, give it away early rather than letting it drop.

Seal the roof

Even with trimmed trees, rats can reach the roof from fences and utility lines. Seal the roof edges they would use: open tile ends at the eaves, torn vent screens and gaps where rooflines meet. The county's rule is to seal openings larger than a quarter. See rodent exclusion.

Trapping in the yard

Snap traps along fence tops and under trees catch rats before they reach the house, but outdoor traps can catch birds, lizards and pets. Put them inside covered boxes or short lengths of pipe, secure them and check them daily. See best rat and mouse traps.

When the problem is next door

If the palms or fruit trees belong to a neighbor, start with a conversation. Offer to share the cost of trimming branches that hang over your roof. In the City of San Diego, the Municipal Code requires property owners to keep their land free of weeds, rubbish and waste, and the city's code enforcement section takes requests for investigation if a property is neglected. See trash and yard rules.

Through the seasons

Roof rats breed most of the year in San Diego's mild climate, but the yard changes with the seasons. Backyard citrus often holds fruit through winter and spring. Summer heat inland pushes rats toward irrigated yards and shade. In late summer and fall, many homeowners notice more activity as young rats spread out to find new nests. Plan trimming before the busy months, and keep up fruit cleanup whenever trees are bearing. A quick look under each fruit tree once a week for hollowed fruit and droppings tells you whether rats are still using it.