- Author: Help Desk Team
This time of year, as the heat increases and things start to get dusty, you might see a number of webs on your plants. Uh oh. Are these webs a sign of spider mites?
Chances are the webs you see covering the ends of branches are actually created by spiders, a close relative to spider mites, and are nothing to worry about. Spiders are predators of insects, some of which are pests, and the webs are used for capturing prey. According to the UC Cooperative Extension, there are at least 54 families and over 1,000 species of spiders in California (https://ipm.ucanr.edu/natural-enemies/spiders/#gsc.tab=0).
Most spiders are beneficial to your garden. Think of them as a free pest control service and remember that among poisonous spiders only the widow spiders are commonly found in California, and these generally stay hidden in places like cellars or woodpiles. And even though the vast majority of spiders are harmless, that doesn't mean you want them surprising you in the garden! You can learn to recognize the many types of spiders hunting among your plants. Some of the more common web-spinning spiders you might see include:
• Dwarf Spiders: These tiny spiders hunt during the day and produce sheet-like or irregular crisscross webs on plant surfaces. You will find them in the plant canopy and in ground litter. They are common in fields and vegetable crops.
• Cobweb Spiders: Hang upside down in sticky, irregularly spun webs waiting for prey. Most are small and harmless, although widow spiders fall into this category.
• Funnel weavers include the Common House Spider: These spiders hang out in the garden, and on walls and ceilings in the house. They feed during the day and night, hiding and waiting for their prey near the ground in most types of vegetation. They spin funnel shaped webs, often with a flat extension covering the plant or soil. Their webs become conspicuous in morning light after collecting dew.
• Orb weavers or Garden Spiders: Often large and colorful, these spiders spin elaborate webs in concentric circles in the garden. They wait in their webs or nearby for prey to become entangled. Often, we can tell the species of the spider by the pattern woven into their web.
• Sac spiders: Typically nocturnal, Sac spiders live in silk tubes in places such as corners, beneath plants, or on bark, and stalk their prey at night. They occur both indoors and out.
Spiders that don't spin webs include the jumping spiders, lynx, crab and wolf spiders. Like their web-spinning cousins, these spiders are beneficial in your garden, preying on insects and other pests.
Are the webs damaging my plants?
In these photos you can see spider webs on a Daphne shrub, some succulents, and a Japanese Pieris. Notice there is no visible plant damage associated with the webs, although occasionally some dead leaves may get caught in a web, such as with the Japanese Pieris. A closer inspection shows the web hasn't caused the leaf damage — in this case it's sunburn from the recent heat wave.
Try to refrain from using insecticides as they aren't necessarily effective on the spiders, and you risk killing other beneficial insects. You can remove cobwebs from your plants by sweeping or hosing them away, or if inside, with a vacuum cleaner or mop. Instead, learn to recognize the spiders in your garden and you will come to appreciate the antics of the jumping spiders, or the beauty of a web with droplets of dew shining in the early morning.
• Quick Tips about spiders: https://ipm.ucanr.edu/QT/commongardenspiderscard.html
• Video to help you learn to identify spiders: https://www.youtube.com/watch?v=Bs-OUvY8L80.
• Identifying and managing spiders: https://ipm.ucanr.edu/PMG/PESTNOTES/pn7442.html
Help Desk of the UC Master Gardeners of Contra Costa County (RDH)
- Author: Help Desk Team
It's summertime! Our gardens are in full swing, tomatoes are beginning to ripen, berries are mostly done, and everything is lush and green. But beware, your plants can sunburn just like you. Sometimes we all need a little break from the heat, especially in the central and eastern portions of Contra Costa County where daytime temps regularly exceed 90 degrees.
Sunshine is necessary for plant growth, but too much can stress plants. Shade cloth (also called shade fabric) can block excessive sunshine and heat and will:
• Lower temperatures
• Reduce heat stress
• Prevent sunburn
• Reduce evaporation from the soil and the plant
• Reduce water needs
• Extend the growing season
• Expand the type of plants that can be grown
Selecting shade cloth
Shade cloth can block between 20% and 90% of the sun's rays reaching your garden beds, also called the transmission rate. A 30% shade cloth will reduce the sunlight reaching plants by 30% and will let 70% of the sun's rays in. The transmission rates will be shown on the product at the store. Delicate seedlings and cooler season plants (lettuce and spinach) will benefit from more shade (50–60% shade cloth), while sun-loving plants like fruits, tomatoes and peppers would do better with less blockage (20–40% shade cloth). Shade cloth is sold two ways: from a roll with a predetermined width and a length that you choose, or in pre-cut triangle and rectangle shapes. Shade cloth also comes in a variety of colors—black, brown, green, shades of beige, white, and sometimes less-common colors.
Installing shade cloth
Shade cloth can be installed several ways, depending on your garden layout. It can be spread over PVC hoops, also called hoop houses, or other PVC structures and secured with zip ties, ropes/twine, bungee cords, etc.
A triangle or rectangular piece can be installed like a sail attached to building edges or poles over the garden bed in a tent-like structure.
A DIY Frame can be made from fencing, vegetable cages, etc. and shade cloth can be draped and secured over the frame.
Be sure to attach shade cloth securely so that it does not flap or slide out of place because that can damage plants.
The vast majority of commercially available shade cloth is made from petroleum products like polypropylene or polyethylene. You may find shade cloth made from natural fibers such as jute, bamboo, sea grass, etc. but this is less common.
Give yourself and your plants a break from the heat this summer and for many summers to come by investing in some shade. It can help you use less water, prevent sunburn and heat stress, and extend your growing season. Enjoy your summer!
For more information about shade cloth in the garden, see this link: https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=55005
Help Desk of the UC Master Gardeners of Contra Costa County (DLB)
- Author: Help Desk Team
You really do not want voles (also called meadow mice) moving into your garden. They are larger than a house mouse or deer mouse but do not quite reach the size of an adult gopher or rat. Although it is said that they can mature to 5–8 inches long including the tail, they are most commonly on the smaller side of the range. With their charming pudgy shape, beady black eyes, small ears, soft gray/brown fur, and rather short and oddly furry tail, their appearance could be thought of as somewhat cute or endearing. That is, until you experience how quickly they can lay waste to your beloved garden.
When they are not ravaging your garden plants, these rodents spend much of their time hiding in their burrows. They are most likely to be seen during the cooler parts of the day such as dawn and dusk, when they dash from one burrow to another, or scurry from dining on your favorite plant into the safety of their burrows. The burrows have openings that are 1 ½ to 2 inches wide. There are often obvious runways from the burrows where soil is trampled down by their repeated scampering back and forth. Voles will happily burrow into both mulch and soil, and where there are dense weeds or long grasses (a favored habitat), voles will create distinctive tunnels through the vegetation.
Vole populations regularly go through cycles of low to high numbers. Their numbers generally peak each 3 to 6 years or so, but don't count on being able to guess when the next vole invasion will occur. These cycles are not predictable. Their numbers can increase to staggering amounts during a population explosion, soaring to as many as several thousand per acre.
If you have voles in your garden, you already know they eat a very wide variety of plants. Unlike rats and mice that are out and about wreaking havoc at night, voles are active both day and night, and year-round. Also, unlike rats and mice who have favorite foods and tend to go after sweet, ripe fruits and the most succulent vegetables, voles are not terribly picky. They will eat a wide variety of plants including zucchini, cucumber, green bean, tomato, and artichoke. Basil, dill and parsley are some herb plants that may be there one day and gone the next. Flowers such as marigolds, cosmos, yarrow, and sunflower are also part of their menu plan.
Voles do take an occasional break from their feeding frenzy to breed and can have 5 to 10 litters of offspring each year. They can have 3–6 young at a time. One redeeming quality is their short lifespan of just a few months to a year, and the fact that after a season of super high numbers, the population tends to go back to normal.
There are several effective control methods such as habitat modification (make the area less hospitable to them), trapping (setting many, many mouse traps), and exclusion (creating impassable barriers around your garden, your garden beds, or even individual plants).
Vole management
Habitat modification is an effective way to reduce vole damage in the landscape. Remove weeds, heavy mulch, and dense vegetative cover to reduce their food sources and expose them to predators. Voles prefer not to feed in the open so 4-foot buffer strips of open ground can help protect trees or other plants.
Because of the large numbers of voles that can be present during a population explosion, exclusion is often the most important option. Wire hardware cloth with ¼ inch or smaller mesh makes a good barrier if it is at least 12 inches tall. Make sure it surrounds the plants completely and bury it into ground 6 to 10 inches deep. Metal roof flashing, sold in hardware stores, makes a very effective barrier. It comes in rolls with varying widths. Unlike gophers, who dig deep burrows, voles usually dig down only a few inches. They are not very athletic and don't climb or jump very well like rats can, so barriers don't have to be terribly tall to be effective.
Trapping can be effective if vole numbers are low or they are in a small area, but difficult when the population is high. The key is to use many mouse traps at the same time. For detailed directions on how to place traps, see the link below.
Voles are an important part of the natural food chain. They are prey for a variety of predators including hawks, crows, owls, snakes, raccoons, bobcats, foxes, coyotes, opossums, and domestic cats. They may not keep vole populations adequately controlled near homes because of their reluctance to hunt close to homes.
There are toxic baits available, but care must be taken to ensure the safety of children, pets, and nontarget animals such as the predators listed above. See the link below for more information.
This UC IPM (integrated pest management) link is an excellent source for information on identifying and managing voles:
https://ipm.ucanr.edu/home-and-landscape/voles/pest-notes/#gsc.tab=0
This link will help you determine whether damage to your yard is due to voles, gophers or moles:
https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=49119
Help Desk of the UC Master Gardeners of Contra Costa County (SMH)
- Author: Help Desk Team
This post is a rerun from 2023.
Have you noticed tomatoes that have round, water-soaked spots on the bottom? Blossom end rot (BER) is a frustrating problem that can be quite common in vegetable gardens, as it can affect tomatoes, peppers, and squash. You might notice it after a few very hot days. It usually starts on green fruit as a small, discolored spot on the end opposite the stem that might look water soaked. The spot enlarges and tissues dry out, becoming sunken, collapsed, and leathery.
Some tomato varieties, especially paste tomatoes, are affected more than others, but all varieties except cherry tomatoes seem to be susceptible if conditions are conducive. It is more likely to occur earlier in the season when plants are rapidly growing, but it can also show up later in the season when we have hot, dry weather.
Blossom end rot results from a low level of calcium in the fruit and a lack of water balance in the plant. Most of our soils have plenty of available calcium so there is no need to add more. Fluctuations in irrigation and/or heavy application of nitrogen are often the culprits in this condition. To reduce blossom end rot, monitor soil moisture to make sure the root zone neither dries out nor remains saturated. Follow recommended rates for vegetable fertilizers, using organic fertilizers.
Improvement in irrigation practices usually results in the problem going away. Rather than watering on a schedule, you should check the soil to determine its moisture level. Either by digging down into the soil without disturbing the roots or using a moisture meter, check to make sure the entire root zone is moist but not soggy. Use mulch around the plants to help maintain soil moisture, but make sure the mulch isn't right against the base of the plants.
Blossom end rot is not caused by a pathogen, so there are no pesticide solutions.
To reduce blossom-end rot:
• Use cover crops in the off season to increase water-holding organic matter in the soil.
• Irrigate before periods of hot weather.
• Don't disturb the root area.
• Don't over fertilize. Too much nitrogen during the early fruiting period can tie up calcium and make BER worse. Manure, especially poultry manure, can make it worse.
Vegetables affected by blossom end rot are still edible if they haven't begun to get moldy. Just cut away the discolored area.
More information about blossom end rot:
http://ipm.ucanr.edu/PMG/GARDEN/VEGES/ENVIRON/blossomendrot.html
Information about growing tomatoes in the home garden: https://anrcatalog.ucanr.edu/pdf/8159.pdf
Help Desk of the UC Master Gardeners of Contra Costa County (SEH)
- Author: Help Desk Team
Earwigs are one of the most common pests in our gardens. There is a lot to learn about them besides knowing how to prevent the damage they cause.
Fun facts about earwigs:
- Their name probably comes from myths surrounding these insects:
- They sometimes enter peoples' ears when they are sleeping and they sometimes burrow into the brain
- The forceps appendages at their rear ends look like tools to puncture ears for earrings
- The expanded wings of earwigs have the shape of human ears
- The common and abundant earwigs in our gardens weren't even in California 100 years ago.
- Roald Dahl, author of children's books, has a character in George's Marvelous Medicine that urges the grandson to eat a ‘big fat earwig' and tells him how to do it so it wouldn't grab his tongue with the ‘sharp nippers on its back end.
- Roald Dahl also mentions earwigs in James and the Giant Peach where the characters find an earwig inside the giant peach.
- Under their hard, shiny wing covers, they have remarkably large and complex flight wings that spring from folded to flight without muscles. (These wings expand to 10 times larger than when folded.)
- Female earwigs watch over their eggs and newly hatched young, protecting them and keeping them clean until they are old enough to fend for themselves.
Did you know?
- Earwigs are important predators of aphids, mites, nematodes, and other small insects and their eggs.
- Research from Washington State University shows earwigs can be beneficial in apple and pear trees, eating pests but doing minimal damage to the crop.
- They also feed on fungi and decaying plant material.
- They are food for other animals, including birds and lizards.
Tips to control earwigs in your garden:
- Remove their hiding places. Earwigs thrive in dark and moist areas during the day, coming out to feed at night.
- Clean up debris, leaf piles, and decaying plant matter
- Trap them by placing numerous traps throughout your yard.
- Use empty tuna or cat food cans with ½ inch of vegetable oil and a smelly substance such as fish oil or bacon grease. Place these in your garden bed with the top of the can level with the soil. In the morning, dispose of the trapped earwigs.
- Roll up damp newspaper, secure with rubber bands, and place in your garden bed. Next morning, collect them and shake the earwigs into a pail of soapy water.
- Baits such as SluggoPlus can be used, but often they are not effective if the earwigs have other attractive food sources like your tasty garden.
For more information about earwigs, please visit these links:
https://ipm.ucanr.edu/PMG/PESTNOTES/pn74102.html
Ode to an Earwig https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=51351
Earwigs in California (published 1975): https://essig.berkeley.edu/documents/cis/cis20.pdf
Washington State University study: https://www.mdpi.com/2075-4450/14/12/906
Help Desk of the UC Master Gardeners of Contra Costa County (SEH)