Remember when San Francisco 49'ers wide receiver Brandon Aiyuk credited his spectacular 51-yard catch in the 2024 NFC championship game with the Detroit Lions to a ladybug (note that entomologists correctly call it a "lady beetle") landing on his shoe before the game?

Well, those attending the 110th annual UC Davis Picnic Day activities on Saturday, April 20 at Briggs Hall--home of the UC Davis Department of Entomology and Nematology--can also net some luck.

Children are encouraged to take home a couple of the beetles at the UC Statewide Integrated Pest Management Program (UC IPM) booth in the courtyard of Briggs. (Adults can do so, too. Maybe they'll name their beetles "Brandon" and "Aiyuk.")

The ladybug is actually a beetle (Coleoptera), not a bug (Hemiptera). It's associated with good luck because it eats the aphids that try to destroy our crops. It can eat as many as 5000 aphids in its lifetime, scientists estimate.

"These beetles have become a cultural icon of sorts because of their appearance and their beneficial habits," writes UC Davis distinguished professor Lynn Kimsey, former director of the Bohart Museum of Entomology, in her insect fact sheet on lady beetles. "Both adults and larvae feed on aphids and other small, soft-bodied insects...They are ferocious predators on small insects." (See what the UC Statewide Integrated Pest Management Program says about lady beetles.)

Ever seen a close-up shot of a lady beetle eating an aphid? The predator and the prey...

Ever seen a cellar spider snaring and eating a lady beetle? The predator and the predator...one becomes prey.

Ordinarily, the lady beetle's bright red coloration serves as a "warning" to predators. Plus, lady beetles are known to ooze a foul-tasting chemical that tastes so bad that predators leave them alone. This lady beetle engaged in "reflex bleeding," exuding an alkaloid toxin (which did not deter the predator). 

Lady beetles will be just a few of the bugs at Briggs Hall during UC Davis Picnic Day. You'll also see cockroach races, maggot art, and displays featuring ants, bees, walking sticks, mosquitoes, nematodes, butterflies, spiders, whip scorpions, and more.  Check out "bug" activities at Briggs Hall here.  UC Davis Picnic Day is free and family friendly.

In winter it's a normal process to see yellowing leaves and leaf drop. When we see this in other seasons, it indicates a problem. When we see the yellowing leaves on our citrus, we often jump to the conclusion there is an iron or a nitrogen deficiency, but there can be a variety of causes.

Before adding nutrients such as iron or nitrogen, consider things such as the time of year, watering practices, soil pH, general care practices, as well as the pattern of yellowing on the leaves.

Things to check first before adding nutrients:

√ Is it winter with cold soil temperatures?

√ Are rains or irrigation practices causing soil to be waterlogged?

√ Is soil pH alkaline, greater than 7.5?

√ What fertilizers have been applied?

√ What is the pattern of yellowing on the leaves, symptoms in older or younger leaves?

Certain conditions often make nutrients unavailable to plants, even though the nutrient may be present in the soil.

Alkaline soil pH. Soil pH is a measure of soil acidity/alkalinity, with 7.0 as the neutral point. Citrus, like other plants that are adapted to slightly acidic soil, are especially prone to iron deficiency when soil pH is above about 7.5 (alkaline). Alkaline soils hold onto iron, making it inaccessible to plants, even though typically iron is plentiful in most California soils. A pH of around 6.5 is ideal for citrus, but it can tolerate a range from 6.0 to 7.5. Adjusting soil pH needs to be done carefully and slowly to avoid unwanted effects in the garden.

Cold soil and soggy soil limit microbial activity important in getting nutrients to the plants. Microbes need porous soil and a certain temperature range to thrive, which is why chlorosis (yellowing leaves) is more common in winter. Porous soils have spaces in the soil that allow water and air to move easily in the soil. Compacted or clay soils are especially prone to a lack of porosity in cold, wet weather which may persist into spring.

Nutrient imbalances, especially an overabundance of zinc, copper, and manganese, can make iron less available. Causes vary, but imbalances can be due to over-application of certain fertilizers.

Identification: Iron deficiency symptoms: yellow leaves, green veins – primarily in young leaves. Nutritional deficiencies in citrus can be identified by the pattern of leaf yellowing and by noting whether it occurs on old or new foliage. The pattern of yellowing leaves between the small, darker green veins occurs primarily in young leaves. This happens as soils cool, reducing root activity. Other possible causes of that pattern of yellowing include zinc and manganese deficiencies. See the UC Integrated Pest Management website for pictures of various patterns of chlorosis.

What to do about iron deficiency?

Improve cultural practices and the soil environment.

• Make sure to irrigate with sufficient time between waterings to allow soil to dry but still provide enough water. Deep watering once a month is often sufficient, especially in summer.
• Make sure drainage allows roots to have air and water, avoiding waterlogged soil.
• Regularly add compost on top of roots, away from the crown of citrus. The addition of organic matter helps with iron deficiency as the organic matter decays and soil gradually becomes more acidic.
• If there has been a history of regular application of fertilizers, a soil test may be helpful to determine potential nutrient imbalances before applying more fertilizer.
• Iron, manganese and/or zinc deficiencies can be corrected with a foliar (leaf) application of a liquid micronutrient solution as the new growth emerges in the spring. You can also apply micronutrients, such as zinc sulfate or iron sulfate, to the soil. Microelements such as iron and zinc though, need an actively growing root system for uptake. Their soil application should be limited to the summertime.

Identification: Nitrogen (N) deficiency symptoms- leaves pale all over (light green or yellow), especially in older leaves. Nitrogen deficiency starts with older leaves near the bottom of the tree and foliage turns a uniform yellow. Slow growth and uniform yellowing of older leaves are usually the first symptoms of nitrogen deficiency. The causes include a true deficiency of nitrogen, adverse soil conditions, or unhealthy roots.

What to do about nitrogen deficiency in citrus?

Most citrus require regular fertilization with nitrogen. However, there are still conditions that would mimic nitrogen deficiency that would not be fixed by adding nitrogen.

• Wait until the soil is warmer, moist but not soggy, to apply nitrogen. Cold and soggy soil inhibits nitrogen uptake.
• Make sure to water with sufficient time between waterings to allow soil to drain well but still provide enough water to citrus. Deep watering once a month is often sufficient, especially in summer.
• Make sure drainage allows roots to have air and water, avoiding waterlogged soil, which often leads to rot and crown damage.
• Regularly add compost on top of roots, away from the crown of citrus. The addition of organic matter helps with iron deficiency as the organic matter decays and soil gradually becomes more acidic.
• Consider doing a soil test, either from a commercial laboratory or a home soil test kit. If there has been a history of regular application of fertilizers, a soil test may be helpful to determine potential nutrient imbalances and to know the current levels of nutrients such as N,P, K and pH.
• Remember it is possible to over-fertilize, potentially causing problems such as a delay in maturity and a reduction in fruit quality; so when in doubt, fertilize less.

When should citrus be fertilized?

Most mature citrus require regular fertilization with nitrogen.

• Begin nitrogen fertilization in February or March depending on the temperature, when soils are warmer and drier, just before pre-bloom.
• Fertilize only in the spring and summer months.
  • Choose more frequent/small applications of nitrogen that allow more efficient nitrogen uptake, so less fertilizer is required.
  • Or choose the more convenient schedule of three nitrogen fertilizations to be in February, early May and June – Valentine's Day, Mother's Day, Father's Day, with a last application perhaps in early fall.
• Stop applying nitrogen fertilizer if citrus leaf miner severely damages new foliage growth in late summer.
• Aim to go into winter with adequate nitrogen stored in the plant, so when spring comes, the nutrients are already there ready for the blooming period.
• Avoid late-season fertilization
  • It may affect fruit quality, delay fruit coloring and make the rind rough.
  • It stimulates new growth and makes trees more susceptible to frost injury. Subtropical plants, including citrus, develop some resistance to cold damage by going through quiescence, a resting time of no or slow growth when cooler temperatures arrive. Quiescence is induced several weeks after 40-50°F temperatures arrive. But that quiescence can be changed to active growing by pruning or nitrogen fertilization in early winter, increasing the possibility of cold damage.
• Avoid adding too much nitrogen, which can damage plants and cause other problems associated with nitrogen excess. Follow the directions on the package. If in doubt, fertilize less.

What fertilizer should be used?

• Nitrogen is the chief nutrient required by citrus and should be applied each year. Fertilizers commonly contain nitrogen (N), phosphorus (P), and potassium (K), listed as NPK on the fertilizer label. Look for a fertilizer where the first number (nitrogen) is the highest of the three, e.g., 7-3-3; fertilizers formulated for citrus typically have higher nitrogen with lower levels of phosphorus and potassium. Avoid balanced fertilizers such those labeled 10-10-10. The relatively high concentrations of phosphorus and potassium are not needed since they are held in the soil much longer than nitrogen.
• Choose the type that best fits your needs. Nitrogen can be provided as organic matter, inorganic compounds, or commercial slow-release (e.g., suffer-or polymer-coated urea). Some fertilizers add nutrients only; other fertilizers are also amendments that indirectly affect plant growth by improving the physical properties of the soil. You can find more information about fertilizers and amendments from The San Luis Obispo Master Gardeners in their pdf handout.

When we see yellowing leaves in our citrus, we want a quick easy answer. But by taking a more comprehensive look at our citrus, the soil and the moisture levels in the soil, as well as the seasonal temperatures, we are more likely to correctly diagnose the problem and then effectively adjust factors that will result in healthier citrus trees. And fertilizing with the right amount of nutrients, mainly nitrogen, at the right time will promote the health and productivity of citrus while minimizing problems associated with overfertilization.

This blog post is brought to you by the Help Desk of the Master Gardeners of Alameda County.  Subscribe to our blog! 

Have a gardening question?  We'll help.  You  can reach us by:  

• Emailing acmg@ucanr.edu. Please include a photo of the problem, if you can, plus your name, phone number, city and a description of the problem.

• Using our online form.

• By phone, during our office hours, 10 am to noon Wednesday and 11 am to 1 pm Thursday: 510-670-5645. At other times, please leave a message and we'll return your call during our office hours.

• In person at our Hayward office, during our office hours, only by appointment.

Resources 

• Adjusting Soil pH in California Gardens, a free downloadable PDF 
• A Guide to Citrus Nutritional Deficiency and Toxicity Identification 
• Citrus for the Home Gardener  2008 Vincent Lazaneo, Horticulture Advisor 
• Diseases and Disorders of Leaves and Twigs
• Fertilizing Citrus in the Foothills by Cindy Fake
• Iron deficiency UC IPM
• Nitrogen deficiency UC IPM
• When to Fertilize Avocado and Citrus in California

What's a picnic without bugs?

Well, it wouldn't be a picnic at all!

The UC Davis Department of Entomology and Nematology (ENT) is planning scores of displays and activities at Briggs Hall for the 110th annual campuswide UC Davis Picnic Day, to take place Saturday, April 20. 

Think ants, bees, beetles, butterflies, flies, cockroaches, maggots, mosquitoes, nematodes, spiders and scorpions.

And more.

This year, all of the entomology exhibits, including those at the Bohart Museum of Entomology,  will be at Briggs Hall.  (The Bohart Museum headquarters in the Academic Surge Building will be closed on Picnic Day.)

Hours? From 9 a.m. to 5 p.m. The Bohart Museum's pop-up tent in front of Briggs, featuring insect specimens and an insect petting zoo, will be open from noon to 4 p.m. 

The entomology displays traditionally draw some 3000 attendees, said the ENT co-chairs, doctoral student Grace Horne of the Emily Meineke lab, and faculty member and forensic entomologist Robert "Bob" Kimsey. It's all free and family friendly.

Among the crowd pleasers are the cockroach races, maggot art, stick insects, and the Bug Doctor booth. The doctor is always in!

New to the line-up is the “I IUV Bugs,"  an exhibit about plant-insect interactions under ultraviolet light. The "glowing bugs exhibit" is the brainchild of Horne and primarily designed by the Meineke lab, "especially (doctoral student) Marielle Hansel Friedman," Horne said.  "We will have plants from the UC Davis Arboretum Teaching Nursery and local/pet-trade arthropods which glow under ultraviolet light. With this exhibit, we seek to highlight the interplay between light, color, and species interactions." 

Doctoral student Veronica Casey of the Shahid Siddique lab designed the new nematode exhibit. Carla-Cristina "CC" Melo Edwards of the Geoffrey Attardo lab is coordinating the new medical entomology display. "The bumble bee observation hive is unfortunately not ready for the spotlight this year," Horne said.

The list of events and activities in and around Briggs Hall will include:

Bug Doctor
Briggs Hall Entryway
Graduate students will answer questions about insects. What's that bug? Attendees are encouraged to bring an insect or photo for identification.

Cockroach Races
Front of Briggs Hall 
American cockroaches, Periplaneta americana, from Bob Kimsey's forensic lab, race on a specially made track, while roach fans cheer for their favorites. (Sometimes the athletes are named for faculty, friends or bystanders.)

Medical Entomology
122 Briggs Hall
Carla-Cristina "CC" Melo Edwards of the Geoffrey Attardo lab is coordinating the medical entomology display. Her research focuses on investigating the physiological mechanisms underlying pyrethroid resistance in Aedes aegypti (the yellow fever mosquito). 

Diversity of Arachnids
122 Briggs Hall
Doctoral student Emma Jochim of the Jason Bond lab is coordinating an exhibit she created last year to display the diversity of arachnids, such as vinegaroons, whip spiders, tarantulas, and scorpions. "We'll have live animals and fact sheets that will give a general overview of their diversity, behavior, and habitat," Jochim said. "I'll also bring some curated specimens to show what goes into creating a scientific collection and talk about why collections are important for understanding biodiversity. "

Maggot Art
Briggs Courtyard 
Artists--children and adults alike--create maggot art by dipping a live maggot into water-based, non-toxic paint. It's suitable for framing (or at least a spot on the refrigerator door). This event will close at 3 p.m. this year (last year it was at 5 p.m.)

Dr. Death
122 Briggs Hall
Forensic entomologist Robert Kimsey will display and discuss his work in his "Dr. Death" booth. Last year Kimsey pin-mounted and identified flies from various cases and research efforts, and displayed studies on the sequence of development of individual maggots, calling attention to the development and sequence of communities of insect maggots.  "By these means, approximations about how long a person has been dead can be made," he told the crowd.

Entomology at UC Davis
122 Briggs Hall
Displays of insects, including bees, ants and more. Graduate students, faculty and emeriti will staff the tables. 

Bohart Museum of Entomology
Front of Briggs Hall
A pop-up tent, staffed by the Bohart Museum, will include stick insects (walking sticks) and Madagascar hissing cockroaches. "We are excited to be part of the bigger department's offerings," said Tabatha Yang, education and outreach coordinator.  Give-aways are also planned.

Fly-Tying
Briggs Hall courtyard
Fly Fishers of Davis will show attendees how to tie a fly. The recipients take home the flies. 

Insect-Themed T-Shirt Sales
Briggs Hall entryway
Members of the Entomology Graduate Student Association (EGSA), led by president Mia Lippey, will be selling their popular insect-themed t-shirts, including The Beetles.  The T-shirt, EGSA's all-time best seller, is a take-off of the cover of The Beetles' Abbey Road alum. However, instead of the Beatles crossing the road in a single file, four beetles (family names Phengogidae, Curculionidae, Cerambycidae and Scarabaeidae) do so.  

Mosquito Control Booth
Entrance to Briggs (below front steps)
Sacramento-Yolo Mosquito and Vector Control District will be providing information on mosquitoes, answering questions, and handing out give-a-ways, including mosquito repellent. 

UC  Statewide Integrated Pest Management (UC IPM) 
Briggs Hall Courtyard
“We plan to have many of our usual materials on display and will be giving out the live lady beetles (aka ladybugs) again,” said urban and community IPM educator Lauren Fordyce. “We purchase them from a local garden center. In addition to that, we plan to have a prize wheel that adults and kids can spin, answer a question, and win a prize if they answer correctly. We may also have temporary insect tattoos to give away.”

Ranked Third in the Country. The UC Davis Department of Entomology and Nematology is ranked third among  “The Best Entomology Colleges in the United States for 2024" by universities.com.  The department includes 24 active and 19 retired faculty;  28 graduate students (five in the master's degree program and 23 in the doctoral degree program); 47 undergraduate entomology majors (based on the Office of Academic Support and Instructional Services (OASIS)  Student Reports); and a staff comprised of 27 academics (non-faculty), 24 career, and 56 student assistants. Professor and chair of the department is molecular geneticist and physiologist Joanna Chiu.

It's springtime, and many of us are adding new plants to our gardens.  That means it is also a good time to review the principles of creating defensible space around our homes.

Fire is a normal part of the natural environment in California, so if you live in the wildland-urban interface (WUI), it's not so much a question of if, but of when your home will be exposed to wildfire.  With this thought and the devastation of the Camp Fire and other recent Northern California fires in mind, many Butte County property owners may be thinking about creating a fire-resistant landscape around their homes.  Not only is this a prudent course of action, a 2005 revision of the California Public Resources Code (PRC 4291) requires that property owners create 100 feet (or to the property line) of defensible space around homes and buildings.  Defensible space is defined as the area around a structure where the landscape is designed and maintained to decrease fire danger.  Creating defensible space also gives firefighters an opportunity to safely protect your home. 

The key to establishing defensible space is to utilize plants that are fire resistant and judiciously space them both horizontally and vertically. Increasing the space between plants limits the ability of fire to spread.  As a rule of thumb, Cal Fire recommends that on flat ground the space from the edge of one shrub to the edge of the next be twice the height of the shrub.  For example, if shrubs are two feet tall, they should be spaced four feet apart.  If the shrubs are growing on a moderate slope the space between them should be four times the height of the shrub.  The space between trees should be 10 feet from canopy to canopy and increase to 20 feet on a moderate slope.

If a fire reaches the crown of a tree, its heat intensity increases and this can increase the combustibility of surrounding vegetation.  Low tree branches create fuel ladders that allow fires to climb into a tree.  To prevent fires from ‘crowning,' these ladder fuels must be eliminated.  Cal Fire recommends that the lower branches of a mature tree should be pruned to create a clearance of three times the height of the shrubs beneath it.  For example if a shrub is four feet tall, the tree should be pruned so that there is 12 feet of clearance between the top of the shrub and the lowest branches of the tree.  For younger trees, the lower one-third of branches should be removed.

The area that is 30 feet closest to a home is often called the “home defense zone” or, as Cal Fire puts it, the “Lean, Clean and Green Zone.”  In this area, highly flammable fuels should be eliminated or minimized and widely spaced plants should be kept green and well irrigated.  Vegetation in this zone should be comprised of shorter plants such as grasses and non-woody flowers.  If shrubs or trees are planted, they should be fire-resistant plants such as deciduous trees (which shed their leaves in the fall) or non-woody natives and other perennials such as salvias.  Fire-resistant ground covers are also an acceptable choice for this area.  Avoid planting broadleaf evergreens (like holly and coyote bush), conifers (like pines, junipers, cedars, and firs) and palms, because they are highly flammable. 

Applying mulch is a good strategy for conserving soil water, reducing weeds and preventing erosion.  Normally, materials such as wood chips, shredded bark, leaves or straw are used as mulches because these organic materials have the added benefit of enriching the soil and improving its water-holding capacity.  However, organic materials burn, so within the five feet closest to a home, it is recommended that non-combustible mulches of rock, gravel, pavers or broken concrete be used instead of traditional organic materials.

When planning a firewise landscape, the contribution of hardscape features should not be overlooked.  Decomposed granite, cement, asphalt or gravel pathways and driveways make effective firebreaks.  Structures such as patios and masonry walls and water features like pools, ponds, and streams will also impede the advance of a fire. 

Before moving beyond the 30-foot home defense zone, mention should be made of items that do not belong too close to a home.  Most propane tanks should be located a minimum of 10 feet from any structure, and woodpiles should be at least 30 feet away.  A cord of seasoned firewood contains the energy equivalent of approximately 174 gallons of gasoline!  Would you store that much gasoline on your porch?  Also, flammable liquids such as gasoline, paint thinner, and turpentine should be properly stored away from ignition sources and combustibles.

The outer 70 feet of the defensible space is called the “reduced fuel zone.”  As with the home defense zone, plants in this zone should be well spaced horizontally and separated vertically to eliminate fire ladders.   Fire resistant plants should also be used here.  Most surface litter such as leaves, pine needles, and twigs should be removed so that this layer is no more than three inches deep.  Dead annual grasses should be mowed to a height of no more than four inches.  Mature trees without shrubs growing beneath them should be limbed to a height of six feet above the ground.  All plants should receive adequate water and dead branches in trees and shrubs should be regularly removed.  As noted in the UC Cooperative Extension's fact sheet on defensible space, “The goal of brush clearance is not to remove all vegetation.  When done well, cleared areas should still include enough well-spaced and judiciously pruned plants to protect against excessive erosion and provide wildlife habitat.”

If organic mulches are used in the reduced-fuel zone, a 2008 study showed that a mulch of composted wood chips spread two to three inches deep showed the slowest fire-spread rate of the eight mulches tested.  A potential disadvantage of wood chip mulches is that they tend to smolder and can be difficult to extinguish.  In general, fine, stringy mulches such as shredded bark burn more rapidly than larger chunks.

Establishing defensible space can be summarized by the following three R's:  1) Remove dead and dying plant material; 2) Reduce the density of vegetation and ladder fuels; 3) Replace hazardous vegetation with less flammable, well-irrigated fire resistant plants.

Further information on fire safety for homeowners can be found on the Cal Fire website at Home - Ready for Wildfire.  And for property owners who are considering landscaping from scratch, the Sonoma-Marin Saving Water Partnership has developed eight fire-rebuild landscape design plans that are well worth considering (Water Smart Landscape Design Templates - Sonoma- Marin Saving Water Partnership).

For more information on creating fire resistant landscapes, attend our Firewise Gardening workshop on May 2, part of the Master Gardeners' 2024 Spring Workshop Series. For information about all the workshops, and to register, visit our website.  All workshops are free, but registration is required.

Why not buy some plants for your fire-resistant landscape at the Master Gardeners' Plant Sale on Saturday, May 18, 2024? The sale will be held at our Demonstration Garden at Patrick Ranch, 10381 Midway, between Chico and Durham, from 9 am till noon. For more information, and a partial list of plants, see our Plant Sale webpage.  

UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system.  To learn more about us and our upcoming events, and for help with gardening in our area visit our website.  If you have a gardening question or problem, email the Hotline at mgbutte@ucanr.edu or leave a phone message on our Hotline at 530-552-5812. To speak to a Master Gardener about a gardening issue, or to drop by the MG office during Hotline hours, see the most current information on our Ask Us section of our website.