Irrigation is not a ‘set and forget' thing. Your watering schedule should be adjusted each season (at least four times each year) as water needs in the landscape vary greatly from season to season. Seasonal adjustments allow us to adapt to changing weather conditions, plant growth patterns, and water availability. If your irrigation system isn't adjusted with the seasons, your plants can suffer from overwatering in the winter or underwatering in the summer.

As seasons change through the year, your plants' needs will change, too. For example, a 15-foot wide Chinese pistache tree (Pistacia chinensis) growing in Concord needs 52 gallons of water each week in July, 24 gallons per week in October, and only 8 gallons each week in January. Adjusting irrigation according to the season can decrease water use by half and your plants will be healthier.

You can calculate how much water your landscape should have for best growth. Look up the water needs of your plants in this database: https://ccuh.ucdavis.edu/wucols-db. Determine how much water is needed for each of your plants throughout the year here: https://puddle-stompers.com/waterwonk/how-much/index.php

Even knowing what your plants ‘should' need, it's best to test your soil occasionally to make sure the water you apply is getting to the right place. To test the depth of your watering, use a soil sampling tube or a small trowel to dig down 6–8 inches deep and observe the moisture level at the bottom of the hole. Get your hands dirty and learn what your soil feels like with varying moisture levels.

There can be substantial water waste when automatic watering systems are left to run on their own. Some systems come with a rain sensor function that will automatically turn off the system when it rains and others are smart controllers that adjust the schedule based on environmental factors. It might be time to upgrade your controller to take advantage of these benefits.

Some additional reminders for good irrigation practices:

Apply the right amount of water
Overwatering is more common than underwatering and can lead to more disease problems.

Water plants deeply and infrequently
The entire root zone should receive water, but let the soil dry partially in between to reduce the chance of root rot and other diseases.

Water early in the morning
Cooler temperatures and less wind will reduce evaporation, especially if using sprinklers or above-ground systems.

Avoid runoff
This happens often in clay soil and the water is simply wasted. Cycle the irrigation giving enough time for each cycle to be absorbed.

Regularly maintain your irrigation system
Check for leaks or damaged parts that could be wasting water and preventing water from getting to the right place.

Apply mulch
A 2- to 4-inch layer will reduce evaporation, minimize weed competition, and improve the soil.

See these links for more information on irrigation:
https://sonomamg.ucanr.edu/Drip_Irrigation/Drip_Irrigation_in_Different_Landscape_Situations/
https://sonomamg.ucanr.edu/Drip_Irrigation/

Help Desk of the UC Master Gardeners of Contra Costa County

Q: Can I use the graywater from my washing machine to water my vegetable garden and fruit trees?

A: There are two key considerations, discussed below, relating to the use of graywater in the garden: what is meant by the term graywater and on what plants to use it.

Graywater Definition

Graywater is untreated, non-disinfected household wastewater that does not include toilet waste. It may be sourced from showers, baths, and washing machines. Untreated water from sources such as kitchen sinks and dishwashers, which may have properties that encourage pathogens, is called dark graywater. Water from toilets and washing machines used to launder diapers or chemically contaminated clothing is called black water. Only graywater should be used in the landscape.

Graywater Usage

Graywater can be safely used to water landscape plants and orchard trees. Because graywater can contain bacteria and viruses that cause illness, it should not be used to grow vegetables if the edible portion may come in contact with the soil. For example, graywater should not be used for growing asparagus, beets, carrots, cucumbers, lettuces and other salad greens, garlic, onions, potatoes, melons, squash, bush beans, radishes, turnips, unstaked tomatoes, or strawberries. Crops not touching the ground like staked tomatoes, peppers, and eggplants should be OK.
https://ccmg.ucanr.edu/files/289340.pdf

Laundry Detergent Considerations

When using laundry rinse water to irrigate plants, your choice of household products will affect the composition of the graywater. The wrong products can adversely affect plants and soils. It is best to avoid using products that contain sodium or sodium compounds, bleach, or boron, as these can result in an alkaline soil condition that suppresses healthy soil biologic activity and is poorly tolerated by many plants.

Although the UC Master Gardener Program of Contra Costa County cannot recommend any products, the FAQ page on Greywater Action's website (https://greywateraction.org/greywater-faq/) lists some products that are plant friendly. These are generally biodegradable, non-toxic, and salt and boron free. The Ecology Center in Berkeley has also evaluated several cleaning products for compatibility with graywater systems. Consult their website at https://ecologycenter.org/factsheets/ for a current list of products. (Click on the link to Greywater-Compatible Cleaning Products.)

Other Considerations

Some key takeaways excerpted from our Marin Master Gardener colleagues are listed below. https://marinmg.ucanr.edu/BASICS/CONSERVE_WATER_-_ENERGY/Graywater/
Do:
Water ornamentals with graywater which is often rich in nutrients.
Check your plants first—Acid-loving plants won't tolerate salts found in high pH graywater and evergreen trees are often more salt-sensitive than deciduous trees.
Alternate graywater irrigation with fresh water to minimize salt build up.
Watch what you put in the wash. Use biodegradable pH balanced, sodium-free, boron-free, chlorine-free products in the washing machine and for bathing.
Apply graywater directly to the ground—don't allow it to be sprayed on plant surfaces.
Use graywater within 24 hours after collecting to minimize bacterial growth.

Don't:
Don't let graywater come in contact with skin.
Don't use on root vegetables such as carrots and onions.
Don't use on lawns unless the graywater is delivered below the surface. If sprayed on the surface, people or pets may come in contact with it.

I hope this helps. Please don't hesitate to contact us with any further questions. Good luck with your tomatoes and fruit trees!

Help Desk of the UC Master Gardeners of Contra Costa County (GD)

A poet once said, “A weed is but an unloved flower.” Sometimes though, a weed, an insect, or a four-legged critter can become a dangerous pest. In a state like California where so much of our economy is agriculturally based, these pests can wreak havoc. In our home gardens they threaten our landscape and ornamental plants and make the creation of natural areas a significant challenge when they displace native plants and wildlife.

Exotic and Invasive

California's native ecosystems were uniquely adapted to our Mediterranean climate, with its dry summers and wet winters. However, as the population changed and grew with immigration alongside increased international travel and commerce, new species of plants, many bringing insects and pathogens with them, were imported from Asia and Europe (often inadvertently) and introduced into the landscape. These exotic plants sometimes failed and sometimes flourished. Sometimes we move them unwittingly from state to state as we travel. The result is that some exotics have become invasive, spreading through the native ecosystem.

You might recognize some of these pests. The pathogen that causes sudden oak death was accidentally introduced on nursery stock and is estimated to have killed more than 1 million oak and tanoak trees over the last decade. In addition to disease, invasive plants can change the composition of soil as scotch broom does by adding nitrogen to the soil, or outcompete shallow rooted native species during dry summer months as the star thistle does with its deep root system.

Of special concern currently is the Asian Citrus Psyllid (Diaphorina citri), a tiny insect that attacks all varieties of citrus, and is a vector for the bacterium that causes Huanglongbing (HLB) disease. An infestation can spread quickly and there is no cure for HLB. Although the psyllid is rarely seen in Northern California, it has become a serious problem in Southern California where it arrived from Mexico in 2008 and is slowly spreading north. The USDA notes that HLB “has devastated millions of acres of citrus production around the world, including in the United States.” http://ipm.ucanr.edu/PMG/PESTNOTES/pn74155.html

Asian Citrus Psyllid

Steps to Take to Stop the Spread

We can all have an impact on the spread of invasive species into our ecosystem.

1. Become familiar with invasive pests, how to identify them, and where to find information. The UC IPM website is a good source of information about managing exotic and invasive pests. https://ipm.ucanr.edu/Invasive-and-Exotic-Pests/

2. When you see suspicious organisms, get help identifying them. Contact your local UC Master Gardener Program Help Desk or Agricultural Commission to report invasive species and to get help with managing them. https://www.cdfa.ca.gov/plant/

3. Inspect new plants carefully before planting them. When possible, plant native species — they are better adapted to our climate, support butterflies and other pollinators, and are less likely to have pest problems! https://plantright.org/

4. Don't bring plants into California from outside the state, and don't purchase invasive plant species. This includes planting gifts from friends across the country into your garden, and ordering online from nurseries that are outside of California. https://www.cal-ipc.org/

5. Buy your firewood where you burn it. Many pest insects and pathogens move with firewood. Don't move it far from its source. http://www.firewood.ca.gov/

To learn more about the invasive species prevalent in California, their impact and how to address them, the UC IPM website is a wealth of important information. We can all make a difference in protecting our beautiful state.

Scotch Broom

Yellow Star Thistle - Courtesy of Joseph DiTomaso

Source your firewood locally

Help Desk of the UC Master Gardeners of Contra Costa County (RDH)

Do your tomato plants suffer from lack of vigor, yellowing leaves, and poor fruit production? These symptoms are associated with many different problems, including lack of soil nutrients, excess salts in the soil or irrigation water, poor drainage or waterlogged soil, or a variety of plant diseases.

Trying to figure out what has gone wrong in your garden may not sound like much fun, but it is a necessary and important part of gardening. The more information we have, the easier it is to diagnose the problem when our hopes for a bountiful garden turn to disappointment. A gardener may change how they care for ailing plants by applying more or less water, fertilizing, or even spraying with pesticides or fungicides. Often nothing they do makes a difference, the plants continue to fail, and many eventually wither and die.

If this describes your experience growing tomatoes, you may find that a wilt disease could be the culprit. Armed with the information in this article, you can determine whether a wilt disease is a problem in your garden.

What is a wilt disease?

Verticillium wilt and Fusarium wilt, also called vascular wilt diseases, are soil-borne fungal diseases that infect susceptible plants through the roots, growing into and plugging the water-conducting (vascular) tissues. This causes the plant to be unable to take up sufficient water needed for healthy growth. Verticillium and Fusarium cause similar symptoms in their hosts.

Once these pathogens are in the soil, they are difficult to manage as they can survive in the soil for many years and possibly decades without living host plants. There is nothing that can be done for plants that are already infected with either Verticillium or Fusarium wilt. There are no fungicides available for application to the plants that can be used to control these diseases.

Verticillium wilt is widespread and very destructive and is common in our area. It is estimated that over 300 plant species throughout the world are susceptible. The pathogen responsible for the disease in tomato plants is Verticillium dahliae. This fungus favors moist soil and relatively cool (55–75° F) soil temperatures.

Early symptoms include a progressive yellowing of older leaves and wilting of shoot tips at the top of the plant during the warm part of the day.

Later, leaf margins curl upward, and leaves often drop off. Any fruit produced is usually small. The wilting becomes progressively worse, and although plants may not die, their condition can be so poor that it is not worth the effort to try to keep them going. Verticillium wilt will also infect several other common garden plants.

The list is a long one, and includes many garden vegetables as well as shrubs, trees and ornamentals. Below are links to lists of plants that are susceptible to Verticillium and Fusarium wilt.

Verticillium wilt symptoms on tomato leaves

Fusarium wilt presents with symptoms that, while not identical, are quite similar to Verticillium wilt. Although it is not as widespread as Verticillium, Fusarium is also a common disease in tomatoes. It differs from Verticillium wilt in that the Fusarium oxysporum pathogen has several forms which are host-specific. This means that the specific Fusarium fungi, Fusarium oxysporum f.sp. lycopersici, only causes disease in tomato plants.

Unlike Verticillium wilt which has a very wide host range, the strain of Fusarium that infects tomatoes will not cause disease in other plant species. It can infect many different non-tomato crops, including melons, pepper, and sunflowers without causing any symptoms, and will persist in both tomato and non-tomato plant residue in soil. Infection and disease development in Fusarium wilt are favored by warm soil temperatures (80° F) and low soil moisture.

The symptoms of this disease are bright yellow leaves that commonly appear first on just one side or one branch of a plant. The leaf symptoms will also often appear as yellowing on just one side of a leaf, delineated by the central vein. These symptoms are distinctive and can be very helpful in making a diagnosis. The foliage yellows, wilts, then turns brown and dies. Older leaves are affected first, followed by death of the entire plant.

Fusarium wilt symptoms on tomato plant

Disease confirmation

To confirm the diagnosis of a wilt disease, cut open one of the lower stems of the affected plant. If the vascular tissue inside the stem has turned brown or darkened (in contrast to the white or pale green color inside a healthy stem), it is a good indication that the plant has one or the other of these fungal diseases.

If you confirm the presence of the disease, you should remove the infected plant (including as much of the roots and plant debris as possible) and dispose of it in the garbage or your green waste bin. Don't compost it yourself since home compost piles rarely reach and maintain temperatures hot enough to kill the disease pathogens.

vascular discoloration typical of both Verticillium and Fusarium

How did this disease get into my garden?

Both Fusarium and Verticillium fungi can be introduced on infected transplants, seeds, and tubers, or spread on equipment contaminated with infected soil. Wood chip mulch that comes from an infected tree can also spread the Verticillium fungi from one area to another. Because it can also survive in the digestive tract of horses and other animals who have consumed infected plant material, animal manures can sometimes be another source.

What steps can I take to keep these diseases from spreading throughout my garden?

• Do not transplant plants from one area to another. Moving soil, even a very small amount, can spread the disease.
• The fungi can also be transported on equipment such as shovels, trowels, etc. Thoroughly clean and disinfect tools used in the infected garden bed before using them in other areas of your yard or garden. First wash or brush off any soil or plant debris, then disinfect your tools with alcohol. You can either wipe or dip them in a solution that is 70–100% alcohol. Isopropyl alcohol is widely available and can easily be found in many stores.
• More on products used to sterilize garden tools, and their pros and cons: https://gardeningsolutions.ifas.ufl.edu/care/tools-and-equipment/disinfecting-tools.html

I suspect that I may have a wilt disease in my garden. Will I still be able to grow tomatoes and other vegetables?

Choosing disease resistant tomato varieties is a way for gardeners to prevent the losses due to wilt diseases. Many disease-resistant hybrid tomato plant varieties have been developed and are available to the home gardener. They can be found at our yearly Great Tomato Plant Sale, in seed catalogs, and at local garden centers. The letters V and F following the variety name in seed catalogs, on seed packets, or plant labels denote varieties that are resistant to Verticillium and Fusarium wilts.

It is unfortunate that nearly all heirloom tomato varieties are susceptible to wilt disease. Heirloom tomato varieties would be better grown in containers with fresh potting mix or in a garden area that has not developed the pathogens (for example, an area in which you have never previously grown tomatoes or other crops that are vulnerable to the wilt diseases).

In addition to tomatoes, several vegetable plants including peppers, eggplants, potatoes, squash, and melons can suffer from Verticillium wilt. The Fusarium fungus specific to tomatoes will only affect tomatoes and will not cause disease in other vegetables. If you plan to grow other vegetables in the same garden bed where a tomato plant suspected of having Verticillium wilt has grown. Check the links below or do an internet search to determine whether the variety you want to grow is susceptible to the wilt diseases. For example, you can search “is broccoli susceptible to Verticillium wilt?”

Soil solarization is another method that can be used to reduce the amount of these pathogens in the soil. It involves heating the soil by covering it with clear plastic for four to six weeks during the summer. It is most effective when day length at its longest, and temperatures are high.

Links to additional information:
• Soil solarization: https://ipm.ucanr.edu/PMG/PESTNOTES/pn74145.html
• Verticillium wilt: http://ipm.ucanr.edu/PMG/GARDEN/VEGES/DISEASES/tomvertwilt.html
• Fusarium wilt: https://ipm.ucanr.edu/PMG/GARDEN/PLANTS/DISEASES/fusariumwlt.html
• Plants resistant or susceptible to Verticillium wilt: https://depts.washington.edu/hortlib/resources/ucdavis_verticillium.pdf
• Plants susceptible to Fusarium wilt: https://extension.usu.edu/pests/research/fusarium-verticillium-wilts

To find great gardening info, a list of previous blog postings, and information on our Great Tomato Plant Sale go to our website: https://ccmg.ucanr.edu/

Help Desk of the UC Master Gardeners of Contra Costa County (SMH)