By Penny Pawl, UC Master Gardener of Napa County
In the first old house my husband and I lived in in downtown Napa, we had the second floor and access to the attic. When we moved in, we had no idea there were bats in the attic. My first encounter was when I went to mop the floor and there was a funny looking “mouse” in the bucket.
I had just seen a Dracula movie and you can guess what I was thinking. After six years of living with bats and having no insects biting us, we had adjusted well to our fellow tenants. The only downside was cleaning up their guano.
When I visited Morocco a few years ago and camped in the desert, bats started flying around our tent during dinner. They were after the bugs flying around the light; they did not bother the other diners or me. After everyone finished eating, I stayed and watched the bats and tried to get a picture of them. Photographing a flying bat is not easy.
On a trip to Bangkok, I saw beautiful fox-faced bats hanging from the trees that we walked under.
I know we have bats right here in Napa County. I have seen them, and according to what I have read about them, we should be happy they are here. One bat can eat as many as 3,000 insects in one night.
Bats are mammals that give birth to live young. How they do that when hanging upside down is quite a feat.
There are 27 species of bats in California and 7 species in Napa County. Worldwide, there are 1,200 species, including the vampire bats of South America and the fruit-eating bats of Asia. Most of the California species nest in trees, while others nest in caves or rock outcroppings. We don't see them unless we are out at night when they are hunting for insects.
A few bats are also important pollinators. On the East Coast, white-nose syndrome, caused by a fungus, is killing many bats that nest in humid caves. In California we do not have this problem; however, many California bats are killed annually by large wind turbines.
Vineyard owners in California welcome bats because they eat insects that harm grapevines. Several organizations are dedicated to saving bats and educating the public about them.
Bats are said to seek houses or other enclosed spaces when they are reproducing and caring for their young. A few years ago, I purchased a bat house, painted it and hung it as directed on the sunrise-facing side of a tree. Droppings at the base of the tree would indicate that they were resident, but so far, I have not found evidence that they ever moved in.
Some sources advise putting bat houses under a roof overhang, but I have had enough bat guano in my life and decided not to do that. Another option is to hang the house from a pole at least 15 feet above ground. You can find a lot of information online about how to build and erect a bat house.
Some people believe that bats are blind, but this is an old wives' tale. They use both their eyes and ears and have better vision than we do. They are not related to mice. The average lifespan in the wild is 20 years, although one bat was known to live 40 years. They typically produce one bat baby, or pup, each year.
If you see a bat on a bush, on the ground or under bark on a tree, don't pick it up. Bats can carry rabies. A group of rabid bats was recently found on the UC Davis campus. Although fewer than one percent of bats are rabid, you should avoid them just in case. If you are bitten by a bat or get bat saliva on you, see a doctor at once.
Here is some information from UC IPM Pest Notes on bats:
http://ipm.ucanr.edu/PMG/PESTNOTES/pn74150.html
Workshop: UC Master Gardeners of Napa County will conduct a demonstration workshop on “Harvesting Your Compost from a Backyard Pile or Worm Bin” on Wednesday, May 26, from 6 pm to 8 pm, via Zoom. Register to get the zoom link at: City of Napa Compost Workshops
Got Garden Questions? Contact our Help Desk. The team is working remotely so please submit your questions through our diagnosis form, sending any photos to mastergardeners@countyofnapa.org or leave a detailed message at 707- 253-4143. A Master Gardener will get back to you by phone or email.
For more information visit http://napamg.ucanr.edu or find us on Facebook or Instagram, UC Master Gardeners of Napa County.
Which is the better choice for controlling pests in our gardens and vineyards: man-made pesticides with their environmental cost or nature's pest squad in all of its beauty?
Consider songbirds. They eat a wide variety of insects, including aphids and snails. They feed on the ground, in mid-air and from vegetation. Especially during their breeding season, songbirds need a high-protein diet. The nutrition they derive from insects is essential for the growth of nestlings and even for the breeding adults. Could there be an easier, more natural way to control garden pests?
To attract these birds to your garden or vineyard, build some birdhouses. Before you begin, take a look at “Songbird, Bat and Owl Boxes” (University of California Publication 21636). The information is aimed at vineyard managers, but it's useful for homeowners as well.
“Songbird boxes should keep birds safe from predators, protect them from weather extremes, and be placed in a manner that is attractive to native species but not to non-native birds,” the publication says. For recommended box styles and building plans, consult conservation groups, specialty stores, woodworkers or the local grape growers' association.
In natural tree cavities, the songbird nesting success rate is 50 to 70 percent. However, boxes mounted on eight-foot T-posts and protected with a PVC sleeve under each box average a 99 percent success rate.
Barn owls were common before agriculture replaced grasslands. By installing nest boxes, you can help increase their numbers to near the level found in their native habitat. Barn owls have exceptional low-light vision, and their hearing is so acute that they can locate prey by sound alone. Adult barn owls kill and eat the equivalent of a large rat, a gopher or a dozen mice every night. How's that for an effective rodent trap?
Barn owls will readily nest in boxes larger than about two square feet. You can build the boxes from materials such as barrels and beehive boxes. Follow the guidelines in the University of California publication or buy a box from a specialty store.
My husband and I built an owl house for the Master Gardener Demonstration Garden at Connolly Ranch in Napa. We will wait until December to install it, since the owls show interest in newly erected boxes around January and lay eggs between February and April.
Owl boxes should be installed 12 to 20 feet above the ground. Add flashing to prevent predators. You can tell that owls have occupied the boxes if you find undigested matter from their prey. Listen for screeching and clicking sounds at night—another sign that owls have taken up residence.
Sadly, young barn owls have a high rate of mortality. Sixty percent die within the first year, and only two percent survive to 10 years. In captivity, they live more than 15 years. Cars and great-horned owls kill both flying and roosting barn owls. Even more reason to build and install owl houses.
There are 25 species of bats in California. These creatures mainly eat insects, including mosquitos, scorpions and centipedes. Bat houses or roost boxes will attract them.
Bat colonies range from a dozen to thousands, with several species sharing the same roost. They are the only mammal capable of flying. Most bat species will feed on crop pests, making them extremely beneficial to farmers. They rely on echolocation and sight to navigate and hunt for food.
Bats live 10 to 15 years and only have one offspring per year. The pallid bat is California's largest bat. Its large ears are so sensitive they can hear insects several feet away. They feed on the ground and catch their prey in the air. Bats can consume their body weight in insects in one night, and they seldom eat beneficial insects.
Due to the loss of natural roosting sites, bats have declined substantially in both species and number. Bat houses can replace the lost roost sites if sited and mounted properly. To keep bats out of reach of predators, mount houses at least 10 feet off the ground and the same distance away from objects that might block the entrance.
Standard bat houses are usually made of plywood and can accommodate about 300 residents. An open bottom serves as both entrance and exit. Do not paint or stain the inside of a bat house. Bat mothers with young prefer houses that receive morning sun and afternoon shade, or no sun.
It can take up to four years for bat houses to be occupied and up to 10 years to build a colony of several hundred.
For many years, humans have been destroying the habitat of these beneficial creatures. Consider taking the time to install houses for some of nature's pest squad so we can help restore our environment one garden or one vineyard at a time.
Workshop: Napa County Master Gardeners will hold a workshop on “Rose Care” on Saturday, June 4, from 10 a.m. to noon, at University of California Cooperative Extension, 1710 Soscol Avenue, Napa. Join the discussion about spring and early summer rose care, issues and solutions. Learn about integrated pest management for common pests and diseases and how to keep your roses healthy during our current drought. On-line registration (credit card only); Mail-in/Walk-in registration (cash or check only).
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.