Professorville resident Dexter Girton is an avid gardener who began noticing something was eating his crops. When he was convinced it was rats, his engineering background kicked into gear and a night-vision camera he rigged confirmed his suspicions.

"There have always been a few rats in our garden through the year, with a little damage here and there. I had noticed a gradual increase in rat damage for the past four years. But this spring and summer the damage was the worst, by far, in 30 years of gardening. They ate things that were never touched before -- like entire basil plants and green citrus. Usually, they would eat some dried tangerines and a few ripe tomatoes, but this year they ate green and ripening tomatoes, and then they destroyed a lot of pluots ... and pummelos. I wasn't prepared for this and before I could find an effective method to keep them away they had eaten half of the green and ripening tomato crop."

"I've caught 21 (rats) in traps since January but there are many more. I have 11 snap traps and one electronic trap," he said. "The adult rats are smart and avoid the traps while the young rats are more careless, as shown in my (nighttime) video recordings.

"I know the damage was being caused by rats because I use motion-activated night vision cameras to record videos of their behavior. I've been using snap traps, and I've caught 21 since January, but the damage continues. They prefer fruit over any bait I put in the traps.

"This spring I took the approach of excluding them from my tomato plants and fruit trees that are not near fences or buildings." He uses 9,000-volt shock wires that are similar to those used by farmers and ranchers. The shocks don't kill the rats, he says, but "teaches them a lesson." Any more voltage and it would be dangerous to people and pets.

Girton listed all of the 16 fruits and vegetables that rats have damaged in his yard. They range from avocados to basil to peaches, raspberries and tomatoes.

He is not alone. Master gardener Candace Simpson, who lives in Barron Park, started noticing holes eaten in her tomatoes and cucumbers growing in her side yard, and began a hunt for rats. "I started looking around and asking where could these rats be coming from? My neighbors had a very overgrown (lantana) hedge, very tangled and totally dense."

Once she discovered that the neighbor's hedge did have evidence of rats, her neighbors quickly took it out. "I have had no rat damage in my side yard since."

She said rats usually eat holes in fruit or vegetables but will leave it in place and come back the next night to eat more. Squirrels, on the other hand, pick the fruit and take it with them to eat it.

She said cooperating with neighbors is essential. "One person trying to correct the situation in their yard is never going to correct it. "

She said in her own and fellow gardeners' experience, the uptick in rats is partly due to home gardening.

"There's such a new emphasis on growing food. The popularization of the back yard garden," she said. "The overpopulation is due to an abundant food supply and very good places to live. Gardeners may need to get together as small neighborhood groups."

Rats don't necessarily just prefer an overgrown or neglected garden. "It doesn't have to be ugly for a rat to be living there," Simpson said.

While it might be tempting to head to the nearest hardware store to buy traps and poison, Santa Clara County Vector Control District spokesman Jose Colume says not so fast. These districts provide free inspections from expert technicians to help residents.

If you suspect you have rats, Colume, a community resource specialist for the district, says to contact your county vector control district first before calling a commercial pest control company or trying to deal with the problem yourself.

Technicians from the Santa Clara County Vector Control District can inspect the house perimeter and do a back-yard inspection for free. "Our inspectors are very well trained to find entry points and paths," he said.

"If you cannot see the ground, the rats can nest there," Colume said, pointing out that low shrubs, ivy, or generally covered vegetation without good turnover is attractive to rats. Even if you don't have the shrubs, your neighbor might, while you have the food.

"One yard can be the food source and the other yard can be the nest," Colume said.

"Normally it's not very far. These animals don't like to commute."

Technicians set "snap traps" in the most effective places. Snap traps are not dangerous to other animals or wildlife, but will dispose of the rats efficiently.

"We don't advise rat poison," he said. Poisoning rats can be dangerous to other animals and often isn't as effective as traps, especially if the sick rats travel to your neighbor's yard to die.

While composting is an excellent way of recycling, be sure (the bins) don't attract rats, he said. Get a tight-fitting covered bin and secure even the lower portion. Rats, he said, can get through anything with holes larger than a person's thumb.

According to the University of California Agriculture and Natural Resources/ Integrated Pest Management, people don't often see rats, but signs of their presence are easy to spot. In California, the most troublesome rats are two introduced species: the roof rat and the Norway rat.

Norway rats, sometimes called brown or sewer rats, are stocky burrowing rodents that are larger than roof rats. Their burrows are found along building foundations, beneath rubbish or woodpiles, and in moist areas in and around gardens and fields.

Nests can be lined with shredded paper, cloth, or other fibrous material. When Norway rats which weigh up to 18 ounces, invade buildings, they usually remain in the basement or ground floor. Norway rats live throughout the 48 contiguous United States.

Roof rats, sometimes called black rats, are slightly smaller than Norway rats. They weigh about 5 to 10 ounces and they have pointed muzzles. Unlike Norway rats, their tails are longer than their heads and bodies combined. Roof rats are agile climbers and usually live and nest above ground in shrubs, trees, and dense vegetation such as ivy. In buildings, they are most often found in enclosed or elevated spaces such as attics, walls, false ceilings, and cabinets.

FACTOID BOX:

Santa Clara County Vector Control:

(408) 918-4770

email: vectorinfo@deh.sccgov.org

Web site: sccvector.org (you can also download an app here to allow you to send photos directly and receive notifications from the vector control district.

Response should happen in at least 3 business days.

San Mateo County Mosquito and Vector Control

(650) 344-8592

email: info@smcmvcd.org

Web site: www.smcmvcd.org

University of California Agriculture and Integrated Pest Management:

http://ipm.ucanr.edu/PMG/PESTNOTES/pn74106.html