When do you most love to be in your garden? A spring or summer morning comes to mind, or maybe a fall afternoon. Most gardeners spend plenty of time in the garden during the day; by observing as they tend to the plants, they are well aware of soil conditions, sunlight patterns, and microclimates, as well as the various creatures that inhabit the space. But what is going on in your garden at night? Maybe it's a bit of a mystery. Investigating that can add another dimension to your gardening.
What nocturnal animals may visit your garden at night? Raccoons, opossums, bats, owls, toads, and frogs are common, and there is a whole range of insects not commonly seen during the day, including nocturnal beetles and moths (more about moths below). Gardens sound different at night too. Insects you might hear include crickets, katydids, and grasshoppers. With fewer predators about at night, it makes sense that many insects are active then. A spring night would be an ideal time to spend some time enjoying your garden, becoming attuned to the sights, sounds, and scents that you won't encounter during the day. Ifmosquitos make you hesitant to venture outside at night, remember that eliminating standing water in your yard, wearing long sleeves, and using mosquito repellent will help control them. The Centers for Disease Control and Prevention (CDC) recommends repellents containingDEET orPicaridin.
Moon Gardens
One way to increase enjoyment of your garden is to include plants that reflect moonlight. Before air conditioning, moon gardens were popular for outdoor parties, and they can be just as delightful today. Planning a garden for nighttime use isn't difficult. Any white or pale-colored flower will glow at night, helping to create a romantic, magical setting, and some have the added bonus of a scent that's stronger at night. The Carolee Shields White Flower Garden at the UC Davis Arboretum includes summer daphne (Daphne x transcaucasica), southern magnolia (Magnolia grandiflora), Argentine rain lily (Zephyranthes candida), and calla lily (Zantedeschia aethiopica). Another popular night-blooming plant is garden phlox (Phlox paniculata 'David'). Plants native to San Joaquin County with white or pale flowers are virgin's bower (Clematis ligusticifolia), dune primrose (Oenothera deltoides), yerba mansa (Anemopsis californica), and tricolor gilia (Gilia tricolor); they support several species of moths and other insects. The lovely white Douglas iris (Iris douglasiana ‘White') is a California native local to coastal regions, but it can be grown in moist, shady areas inland.
Nighttime pollinators
How important are moths as pollinators? While some flowers close at night (this is called floral nyctinasty), most do not, and nighttime pollinators take over for the day shift. Moths, bats, beetles, and even some bees are in this nocturnal group. A study by University College London found that moths are better at pollinating than previously thought; their hairy underbellies are very good at collecting pollen. Adding to their value, moths tend to migrate, and they can carry pollen up to 1,000 miles, increasing the genetic diversity of the plants they visit.
Some plants that have co-evolved with moths have characteristics that make them more attractive to nocturnal moths. Their white or pale flowers make them more visible at night and their scent may be stronger at that time. Until recently, researchers have focused primarily on daytime pollinators, sonighttime pollinators are an area that needs further study. The recent awareness of protecting daytime pollinators from pesticides is important, but it can have unintended results. For instance, some farmers spray pesticides at night to prevent bees from coming into direct contact with them, unfortunately not realizing the harm they are causing to moths, an often-disregarded group of pollinator heroes.
Light Pollution
In addition to the threats that all pollinators face—habitat loss, pesticide exposure, disease, and invasive species—moths and other nighttime insects are affected by light pollution. The disorientation caused by artificial lights can cause moths difficulty in finding mates and evading predators, with studies showing that moth mating and plant visitation is markedly decreased in areas with artificial lights.
As gardeners, we can help nocturnal pollinators by:
- Removing lights that serve only a cosmetic purpose
- Using motion-sensing lights that remain off unless someone is nearby
- Using shielding around outdoor lights that prevents light from escaping upward, and directing light to pathways rather than at plants or trees
- Closing curtains at night so indoor lighting doesn't spill outside
It's just a matter of becoming more aware of the light in our yards at night and considering ways to minimize or eliminate it.
We can all enjoy lesser-known, wonderful aspects of our gardens by spending time there at night, learning which insects and animals inhabit the space and which flowers are attracting pollinators. A spring evening is a good time to do this.
Resources:
CalScape (California Native Plant Society)
https://calscape.org
Firefly-Friendly Lighting Practices (Xerces Society)
https://www.xerces.org/sites/default/files/publications/19-055_Firefly_Friendly_Lighting_FS_web.pdf
Hit the Lights! The Impacts of Artificial Light on Ecosystems with Shannon Murphy, Pacific Horticulture Garden Futurist
https://pacifichorticulture.org/articles/hit-the-lights-the-impacts-of-artificial-light-on-ecosystems-with-garden-futurist-shannon-murphy/
Into the Night: Shedding Light on Nocturnal Pollinators (University of Arkansas)
https://aaes.uada.edu/news/night-pollinator/
Insects of the Night (Sonoma State University Center for Environmental Inquiry)
https://www.youtube.com/watch?v=rRCFgOs25S8
Mosquitos (UC IPM)
https://ipm.ucanr.edu/PMG/PESTNOTES/pn7451.html
The Night Shift: Moths as Nocturnal Pollinators (Xerces Society)
https://xerces.org/blog/the-night-shift-moths-as-nocturnal-pollinators
Why is there a moon garden in the arboretum? (UC Davis Arboretum)
https://arboretum.ucdavis.edu/sites/g/files/dgvnsk1546/files/inline-files/Moongarden.pdf
As spring unfurls its vibrant tapestry, local nurseries beckon with a kaleidoscope of colors, inspiring garden enthusiasts to bring life to their landscapes. However, successful gardening is not just about choosing aesthetically pleasing plants; it requires a deep understanding of your planting zone and the nuanced world of microclimates. This comprehensive guide aims to delve into the intricacies of these two critical elements, providing insights into plant selection, optimal growing conditions, and landscaping success.
THE MEDITERRANEAN CLIMATE: A UNIQUE ECOLOGICAL TAPESTRY
Geographical Distribution: 1. Mediterranean Basin: This is the eponymous region, covering countries such as Spain, Italy, Greece, and Turkey. Coastal areas along the Mediterranean Sea experience the classic Mediterranean climate. 2. California, USA: The state of California is home to vast stretches of land with a Mediterranean climate, especially in regions like the Central Valley, Central Coast, and parts of Southern California. 3. Chile: Central Chile, including cities like Santiago, features a Mediterranean climate due to its proximity to the Pacific Ocean. 4. Southwestern Australia: Coastal areas in the southwestern part of Australia, including Perth, exhibit Mediterranean climate characteristics. 5. Cape Town, South Africa: The Cape Town region at the southern tip of Africa experiences a Mediterranean climate, contributing to the unique biodiversity of the Cape Floral Kingdom
Distinctive Seasonal Patterns: Winters in Mediterranean climates are typically cool and wet, featuring infrequent freezing temperatures. This season provides a crucial source of moisture for the ecosystem. In contrast, the long, dry periods of summer and fall are marked by warm to hot temperatures and limited rainfall. This prolonged dry spell contributes to the unique challenges and adaptations of the local flora.
Native Flora Adaptations: Native California plants, including those in San Joaquin County, have evolved over time to thrive in this specific climate. These adaptations enable them to endure the seasonal fluctuations and water availability inherent to the Mediterranean climate. The flora has developed mechanisms to conserve water during the arid summers, contributing to the region's ecological resilience. Natives from other Mediterranean climate groups also adapt well to our landscapes and gardens. These websites are excellent resources:
California Native Plant Society: Calscape website, a database of 7,936 plants native to California—https://calscape.org/
Mediterranean Plants Database: Euro Med PlantBase website—https://europlusmed.org/cdm_dataportal/search
DISCOVERING YOUR PLANTING ZONE
Some benefits of using the Sunset Western Garden Book for your plant choices: it offers a wide range of plant recommendations, including trees, shrubs, flowers, and vegetables, with details on each plant's characteristics, and cultural care requirements; and it offers ideas and inspiration for creating beautiful and functional landscapes, including plant choices for various microclimates within your garden.
The Sunset Climate Zones include the following regions: California, Texas, Oklahoma, Washington, Oregon, Idaho, New Mexico, Arizona, Nevada, Wyoming, Utah, and Colorado.
Considering the San Joaquin County region, the Sunset zone is 14, the United States Department of Agriculture (USDA) cold hardiness falls under zone 9B, and the American Horticultural Society (AHS) heat zone is 8. Knowing these specific zones provides a solid foundation for tailored plant selection and care that aligns with your local climate.
The USDA zones divide North America into zones based strictly on the average annual extreme minimum winter lows. Nurseries use USDA hardiness zones on plant tags to indicate a minimum low temperature that a plant can survive. The USDA Zones—updated in November 2023—indicate an increase of 2.5 degrees Fahrenheit in temperatures across the United States.
To check your Sunset Climate Zone, go to: https://sunsetplantcollection.com/climate-zones/
To check your USDA Cold Hardiness Zone, go to https://planthardiness.ars.usda.gov/
To check your AHS Heat Zone, go to https://ahsgardening.org/about-us/news-press/cool_timeline/heat-zone-map-developed/
Understanding your planting zone is crucial, not only for choosing the right plants but also for determining the best time to plant vegetable crops and gauging the suitability of certain fruit trees and berries for your area.
EXPLORING MICROCLIMATES: CLIMATE VARIATIONS WITHIN YOUR LANDSCAPE
DEFINING MICROCLIMATES
Microclimates are small-scale, localized climates that differ from the surrounding larger climate. Various factors contribute to the development of microclimates, creating a complex tapestry of temperature, humidity, and other environmental conditions within a confined area. These factors can be influenced by both natural elements and human activities.
CAUSES OF MICROCLIMATES
Topography: The lay of the land, whether flat, sloping, or hilly, significantly impacts temperature and precipitation distribution. Valleys may trap cold air, creating cooler microclimates, while hilltops may experience more wind exposure and temperature fluctuations.
Proximity to Water Bodies: Bodies of water, such as lakes, rivers, or oceans, play a vital role in shaping microclimates. Water, with its high heat capacity, leads to milder temperature variations in areas nearby.
Urban Heat Islands: Human activities in urban areas can lead to the formation of microclimates known as urban heat islands. The abundance of concrete and asphalt surfaces in cities absorbs and retains heat, causing localized temperature increases.
Vegetation: The type and density of vegetation in a specific area can influence its microclimate. Trees provide shade and transpire water, cooling the surrounding air. Dense plantings of trees may create cooler and more humid microclimates, while open grasslands may allow for greater temperature fluctuations.
CHARACTERISTICS OF MICROCLIMATES
Temperature Variations: Microclimates often exhibit distinct temperature variations compared to the broader regional climate. Some areas may be warmer due to exposure to sunlight and reduced wind, while others may be cooler, influenced by factors like shade or elevation.
Humidity Levels: Humidity can vary significantly within microclimates. Areas with dense vegetation or proximity to water bodies may have higher humidity, while open spaces or regions with intense sunlight may experience lower humidity levels.
Wind Patterns: The presence of obstacles, such as buildings or hills, can disrupt wind patterns and create unique microclimates. The windward sides of structures may experience higher wind speeds, while leeward sides may be sheltered, affecting temperature and moisture levels.
Precipitation Patterns: Microclimates can also influence precipitation distribution. Rain shadows, created when mountains block the passage of moist air, result in drier microclimates on the leeward side. Conversely, coastal areas may experience increased precipitation due to the proximity of water bodies.
PRACTICAL IMPLICATIONS FOR LANDSCAPING
The UCCE Marin Master Gardeners have crafted a highly valuable downloadable spreadsheet, conveniently printable for your use. This tool serves as a practical aid in systematically assessing your landscape, enabling you to pinpoint and understand the specific microclimates within your garden. Entitled the “Garden Site Microclimate Evaluation Form,” this resource empowers you to make informed observations and strategic decisions for optimizing your gardening experience. https://ucanr.edu/sites/MarinMG/files/47782.pdf
Plant Selection: Understanding the microclimates within your landscape is crucial for selecting suitable plants. Different species thrive in specific sun/shade requirements, and have their own preferences for temperature and humidity ranges. Choosing plants adapted to the microclimate of a particular area ensures better growth and longevity.
Water Management: Microclimates can have varying water requirements. While some areas might be naturally moist, others might be prone to dryness. Efficient water management strategies, such as drip irrigation or rainwater harvesting, can be tailored to the specific needs of different microclimates.
Microclimate Design: Knowledge of microclimates allows for intentional design choices. Planting trees strategically can provide shade and cool specific areas, creating comfortable outdoor spaces. Additionally, structures like pergolas or windbreaks can be strategically placed to modify wind patterns and temperature.
Microclimate Awareness for Urban Planning: In urban planning, understanding microclimates is essential for creating sustainable and comfortable living spaces. Incorporating green spaces, optimizing building orientations, and using reflective materials can mitigate the impact of urban heat islands and enhance overall livability.
HARNESSING MICROCLIMATES
Beyond the broader classifications of planting zones, most gardens and landscapes harbor microclimates—localized pockets influenced by diverse environmental factors. Recognizing and leveraging these microclimates can significantly enhance gardening success. Here are some examples:
Shade Trees and Overhead Structures: These areas provide ideal planting spots for shade-loving plants. On frosty evenings, these spots tend to be a few degrees warmer than open ground, offering protection to delicate plants.
South and West Walls: Masonry and stucco south- and west-facing walls absorb solar energy during the day and release it at night. This warmth is particularly beneficial for heat-loving vegetables, helping them thrive even on cooler summer days. However, on hot summer days, the heat generated during the hottest part of the day may be too hot for some plants.
North Walls: These areas receive minimal direct sunlight, making them perfect for woodland plants like ferns that thrive in shaded conditions.
East Walls: These surfaces generally receive up to half a day of sun, less intense than west-facing walls.
Eaves: Eaves can provide frost protection for delicate flowers, preserving their beauty during chilly nights.
Sloping Grounds: These areas tend to have warmer airflow than hilltops or valleys below, making them ideal for growing citrus trees and other heat-sensitive plants.
Dry Banks: Drought-tolerant plants are well-suited for planting in dry bank areas, as they can thrive in low-water conditions.
Cold Air Pockets: Low-lying areas often trap cold air, making them suitable for plants like tulips that require chilling to encourage blooming. These pockets are also conducive to growing fruit trees and berries that need cold periods for fruit production. Understanding and strategically utilizing these microenvironments allows for intentional and informed plant placement, fostering optimal growth conditions.
CASE STUDY: MICROCLIMATES IN A RESIDENTIAL GARDEN
To further illustrate the practical implications, let's explore a hypothetical residential garden and examine the microclimates within it:
South-Facing Terrace: The south-facing terrace receives ample sunlight throughout the day, creating a warm microclimate. This area is suitable for sun-loving plants that thrive in higher temperatures. However, the increased sunlight also leads to higher evaporation rates, necessitating more frequent watering.
North-Facing Slope: The north-facing slope, being shaded from direct sunlight, experiences cooler temperatures. This microclimate is ideal for shade-loving plants that prefer a more temperate environment. The soil in this area may retain moisture better due to reduced evaporation.
Wind-Exposed Courtyard: A courtyard exposed to prevailing winds may experience increased air movement. While this can help prevent stagnation and reduce the risk of diseases in plants, it may also lead to higher transpiration rates. Wind-resistant plants and windbreaks can be strategically placed to balance these factors.
Proximity to a Pond: If the garden features a pond, the microclimate around it may have higher humidity levels. This is beneficial for moisture-loving plants and can create a more comfortable environment. However, careful consideration of drainage is essential to prevent waterlogged soil.
In the intricate world of landscapes, microclimates are the subtle influencers that shape the diversity and resilience of ecosystems. Recognizing these localized variations in climate is paramount for anyone involved in landscaping, gardening, or urban planning. By understanding the causes and characteristics of microclimates, individuals can make informed decisions to optimize their outdoor spaces, foster plant growth, and create harmonious environments that balance the dynamic interplay of weather patterns within a confined area.
As we continue to explore the nuances of microclimates, we unlock the potential to cultivate thriving and sustainable landscapes that reflect the beauty of nature's complexity. Armed with knowledge about both planting zones and microclimates, gardeners can embark on a journey that goes beyond aesthetics, creating spaces that are not only visually appealing but also ecologically sound and resilient. As you step into your garden, envision the intricate dance of climate zones and microclimates, and let it guide you towards a season of abundant growth and natural harmony.
Resources:
Secrets of World Climate, Mediterranean (Geodiode)— https://geodiode.com/climate/mediterranean
UC Davis Global Soil Health Portal—https://soilhealth.ucdavis.edu/climatic-zones/mediterranean
How to Determine Your Garden Microclimate (Washington State University Extension)— https://s3.wp.wsu.edu/uploads/sites/2077/2020/03/FS181E-Determining-you-gardens-microclimate.pdf
The first point of necessity is when you plant your seeds. The seedlings start to emerge and most times it is almost impossible to identify those tiny leaves. Having them labeled in either the nursery seed starting trays or in the directly-sown garden bed will take the guess work out of it. Use popsicle or tongue depressor sticks, craft sticks, plastic knives/spoons/forks, or reuse the nursery's white plant labels while the little seedlings are taking root. These are very inexpensive and most times reusable. There is plenty of room to add the planting date too.
As the plants grow and are ready to be planted into their place in the garden, larger garden markers will come into play. Here is a list of items to use; it is a great way to recycle things you might otherwise have thrown in the trash and to give them a new purpose.
Broken clay flower pot shards
Clay flower pots used upside-down
Clothespins
Corks
Old retired hand tools
Paint stir sticks
Plastic spoons, forks, and knives
Popsicle or tongue depressor sticks
Rocks and bricks
Vintage dishes and tea cups
Vintage coffee pots
Wood sticks (check your local home improvement store's lumber-cutting department for scrap wood, inexpensive or possibly free)
Window blind slats
Wooden kitchen spoons
The list goes on; use your imagination, and find items that might be perfect for signage while also making whimsical garden décor. The colder winter months are the best time for getting your signs made, so they will be ready for your new spring garden.
Here are some supplies you may need to help you create plant labels: paint and brushes, permanent markers, glue, nails, screws, twine, wire, metal sticks, and any tools you will need. Also, UV varnish is recommended to spray or brush over the painted designs and lettering to help preserve them.
Your creations can be as simple as writing the names on a small wood board to painting creative designs and lettering. Painting carrots, tomatoes, vines, and flowers is simple and makes for a quaint look. It is up to you to choose the style depending on your creative ability, and to decide if you want a plainer look or a fancy creative one.
Wooden stakes and rocks look great together. Or use all clay pots of varying sizes. Turn them upside down, write the name of your plants on them, and place them on a stake.
For a vintage-style garden, look for an old metal watering can. Again, name your garden, “Grandma's Garden” if you wish. Add markers such as vintage metal cans, vintage silverware, or any vintage find that can hold a name.
If you have children or grandchildren, this is a great way to get them interested in gardening. Some kids love to craft, so get them involved in making their own little signs. Small wooden signs and rocks can be painted easily depending on their age. Make a small garden plot and allow them to care for a few plants. A wood sign such as “Ellie's Garden” with her handprint would make any kid a happy gardener. Or give a child a small garden tool with their name on it to decorate their little garden. Transforming a rock into a ladybug or bee is always a fun project for children or even adults. Also, a child's trowel for them to use can be decorated, and do not forget they will need garden gloves.
If you have a grouping or rows of certain vegetables or flowers, paint one larger sign for them. And where there may be only one or two plants, a smaller individual sign can be sufficient.
Check thrift stores and garage sales, or check with family and friends that might be getting rid of things you can recycle.
Have fun creating some garden markers for your plants. When friends visit your garden, the signs will be interesting and educational. Happy gardening!!
- Author: Sue Davis, Master Gardener
Spring is here—that time of renewal and joy as we wander our gardens and take stock of what works and what needs a “tune-up.” Sometimes, at this time of year, the number of things to be done in our gardens can seem overwhelming, but attention to just one or two chores per week can lead to both a feeling of control and a beautiful gardening experience.
April Ideas
ONE – First, make the garden and landscape ready for the new season! Check all the sprinklers and drip lines to be sure they are working properly and not wasting water. There is a comprehensive spring tune-up guide for sprinklers in the 2010 April-June Master Gardener newsletter which can be found here.
THREE – Now is the time to fertilize lawns and many garden plants. Cane berries, citrus, fruit trees, palms, and heavily flowering shrubs will flourish with slow-release fertilizer products. Maintaining good fertilization can keep your plants vigorous and help prevent pest problems. Lawns will thrive with the application of fertilizer now. Use a balanced slow release or organic fertilizer according to the directions on the package; do not apply more than instructed to avoid polluted runoff. Organic fertilizers react more slowly but will eventually provide a lush result. If crabgrass has been a problem in past years, consider a pre-emergent/fertilizer mix. Help preserve our waterways by avoiding getting granules on hardscape surfaces.
FOUR – This is a great time of year to plant citrus trees if there is a vacant, sunny spot in the landscape. Make a hole about twice the width of the root ball. Build a cone of soil in the center of the hole tall enough so the new plant will be level with the surrounding soil when placed on top of it. Gently remove the plant from its pot. Use fingers to gently uncoil and separate any bunched-up roots. If the root-ball is solid, use a clean knife to score four ½-inch deep cuts around the sides and one on the bottom. Set the roots atop the cone, refill the hole and water thoroughly to eliminate air pockets. The beginning of the root flare on trees should be visible at or above the surrounding soil. Add a 2- to 3-inch layer of mulch around the plant, keeping the mulch several inches away from the trunk.
In May
ONE – Prune a couple of things this month. Winter-flowering shrubs (e.g., camellias) need to be pruned prior to the formation of next year's flower buds. Pruning pine terminals to direct growth in young plants and retard growth in more mature plants should only be done during candling (new shoot growth) during late spring to early summer, so May is usually an opportune time.
THREE – Aerate lawns this month. Lawns that get a lot of heavy fool traffic develop compacted soil, which makes it difficult for water, fertilizer, and oxygen to reach the grass roots. If a screwdriver can't be pushed up to its handle into the turf, it's time to aerate. Use an aerator that either produces a core or a water wash to dig holes; spike aerators just add to soil compaction. If using a machine aerator, be sure to mark and avoid all sprinkler heads. Some machine aerators require a lawn to be moist, but not soggy. Irrigate a day or two before aeration if soil is dry.
FOUR – Fill out vegetable gardens with transplants of tomatoes and peppers. The middle of May is a great time to plant seeds of pumpkins, beans, corn, squash, cucumbers, and melons. For interesting and unusual fall decorations, consider growing pumpkins or winter squash that are not the ordinary jack-o-lantern choice. Beef up a flower garden with a little height. Shorter bedding plants get the front row spot followed by tall, upright bedding plants and finished with some summer-blooming vines grown on a sturdy structure that is set in the garden at the same time planting occurs. It is difficult to add the structure once the plant needs it. As the vine grows, train the shoots to the support with self-gripping Velcro, plant tape, or twist ties. Start with flowers in six packs. Planted in May, these little gems will explode with summer color in a few weeks. If instant color is needed, think about 4-inch pots instead.
June Notes
ONE – Clean up mummies (dried, shriveled fruits) and old fruit and nuts in and under trees to avoid harboring pests, and deter borers by deep-watering trees. Paint the trunk and scaffold branches of young trees with white interior latex paint diluted with an equal amount of water to protect them from sunburn.
THREE – Bees are essential pollinators. A variety of flower shapes and colors will attract bees to a garden. Look for flowers and plants that are native to this area for growing ease, adaptation to the local climate, and to serve as an attractant to native bees and honeybees. Planted near or among a vegetable garden, flowers attract bees for pollination and a bountiful harvest.
FOUR – Still have a lawn and wonder just how much water it needs during the hot summer months in the valley? Lawns need about two inches of water per week during the summer heat. To determine lawn sprinklers' output, place several flat-bottomed containers (such as tuna fish cans) around the lawn, turn on the sprinklers for a half hour and then measure the water in the containers. Adjust the sprinkler coverage if needed and reset the amount of time they water according to the results of the timed test. Water lawns and the rest of the landscape early in the day to reduce water wasted due to evaporation and be cognizant of appropriate days to water if applicable. Better yet, start thinking about how to minimize or eliminate the lawn in your landscape to save water in California's dry climate.
Deep-water established plants often enough to prevent wilt and promote deep rooting as temperatures start to rise. Check the soil moisture around roots with a moisture meter probe or by digging down with a trowel. Soaker hoses apply water directly to the soil with minimal evaporation.
Subscribe to our Seasonal Landscape IPM Checklist for Northern San Joaquin Valley. It is delivered straight to your inbox monthly with timely reminders to help prevent or reduce landscape pests and plant problems.
Information for this article was gathered from:
www.ipm.ucdavis.edu
www.sunset.com/garden
www.farmerfred.com
A Valley Gardener's Journal by San Joaquin Master Gardeners
CA Month by Month Gardening by Claire Splan
- Author: Trish Tremayne, Master Gardener
Question:
I have heard of a disease that has devastated citrus in Florida. Is it in California, and if so, how can we protect the citrus trees in our yard?
Answer:
The disease you are referring to is called Huanglongbing—HLB for short—or citrus greening disease. The HLB disease has decimated the Florida citrus industry, causing billions of dollars in economic damage and thousands of lost jobs. Within four years of its arrival, 60,000 acres of trees were affected with HLB.
The bacterium is spread by the Asian citrus psyllid, Diaphorina citri. There is no cure for the disease; once the tree is infected, it can die in as little as 5 years. The Asian citrus psyllid (ACP) arrived in Southern California from Mexico in 2008. The ACP has now been found in many parts of California, including Southern CA, the Central Coast, the San Joaquin Valley, and the Bay Area. The disease was first found in southern California in 2012. The only way to stop the spread of the disease is to stop the spread of the psyllid. Host plants are all citrus species
and ornamental plants in the Rutaceae family (e.g. box orange, Indian curry leaf, and orange jasmine).
The best thing a home gardener can do toprevent the spread of HLB is to obey quarantines set in place and to keep a lookout for the insect and report it to the California Department of Food and Agriculture (CDFA) Exotic Pest Hotline at 1-800-491-1899. San Joaquin county is currently under quarantine for ACP.
Here's what to look for:
The adult psyllid is about the size of an aphid, 1/6 to 1/8 of an inch long. It has mottled brown wings with a clear margin that breaks up the pattern, red eyes, and a pointed rear end. The short antennae have black tips with
two small, light brown spots on the middle segments. It feeds at a 45-degree angle with its tail end in the air. It lays its yellow or orange, almond-shaped eggs on new plant growth, nestled in the crevices of unfolded leaves. The nymphs are wingless and will molt four times before becoming an adult. They feed on the young soft leaf tissue of the plant. As they feed, they produce a large amount of sugary liquid or “honeydew.” They also produce white, waxy, curly tubules with a bulb on the end to help clear the sugary waste from their bodies. This is unique to the Asian citrus psyllid.
Trees should be inspected monthly and especially during periods of active plant growth or "flushing." Due to the small size of the psyllid, using a magnifying glass or hand lens will make inspection
Encourage beneficial insects that eat the psyllid, including lady beetle adults and larvae, syrphid fly larvae, lacewing larvae, and minute pirate bugs. Some spiders, birds, and other general predators also feed on adult psyllids.
Don't move citrus fruit or plants outside your area. The main way the insect spreads is from people transporting infested plant material. Buy citrus trees only from a reputable, licensed nursery. Double-bag clippings from citrus and other host plants or allow them to dry out thoroughly prior to disposal to avoid moving the psyllid and HLB-infected plant material.
References:
https://www.cdfa.ca.gov
http://californiacitrusthreat.org
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74155.html
https://ucanr.edu/sites/ACP/
https://cisr.ucr.edu/invasive-species/asian-citrus-psyllid
https://anrcatalog.ucanr.edu/pdf/8205.pdf