- Author: Lauren Fordyce
It's time for UC IPM's annual insect Easter egg hunt! Can you guess which insects laid the eggs pictured below? Some may be pests, while others may be beneficial. Leave a comment on this blog post with your guesses, or on our Facebook and Instagram posts.
Answers will be posted on Monday, April 1st.
Photo credits:
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Jennifer Carr, University of Florida, Bugwood.org
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Alton N. Sparks, Jr., University of Georgia, Bugwood.org
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Kenneth R. Law, USDA APHIS PPQ, Bugwood.org
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Jack Kelly Clark, UC IPM
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Whitney Cranshaw, Colorado State University, Bugwood.org
- David R. Haviland, UCCE
- Author: Anne Schellman
- Author: Ed Perry
- Why are the leaves on my orange tree turning yellow?
It's common for citrus tree leaves to turn yellow in winter*. Fertilize to provide the tree with nutrients now, then watch as leaves green up in spring. Avoid fertilizing in fall, which encourages new growth favored by pest and can leave the tree susceptible to frost injury.
- How do I know if my oranges are ripe/when should I pick my oranges?
You don't have to pick all your oranges once they ripen. In fact, the best place to store oranges is on the tree, where they stay fresh! Pick as needed, unless temperatures below 28 F are predicted, then you'll want to harvest.
- What is this pest?
Scales and whiteflies suck plant juices and weaken the plant. Ants do two things:
- Protect pests from predators like ladybugs, parasitic wasps (very tiny wasps) and lacewings.
- “Harvest” honeydew (a sticky sugary substance excreted by these pests) for food, in a symbiotic relationship that does not include the gardener.
- Why are my oranges splitting?
The reason this happens is not well understood, although it's often related to changes in weather conditions. However, allowing the soil to dry out too much between irrigations is believed to result in increased splitting. Make sure your tree has a constant supply of moisture by watering monthly during the dry season.
- When should I prune my orange tree?
When pruning deciduous trees like peach, plum or cherry, after leaf drop, don't be tempted to prune citrus! Citrus trees are evergreen and require little if any pruning except to control size. If you'd like to keep a new citrus tree under 5 feet tall, you can carefully prune it in spring to manage the height. This way, you won't need a ladder to pick fruit again!
Avoid pruning in fall or winter, which encourages new growth favored by pests and can leave the tree susceptible to frost injury.
*if your tree leaves turn yellow and it's not winter, this may be a different problem.
- Author: Melissa G. Womack
As gardeners, we're often generous with our garden's bounty. From sharing seeds and plant trimmings to the joy of gifting homegrown fruit and vegetables, gardening is as much about community as it is about growing plants. However, in this season of sharing, we must also remember our responsibility to prevent the spread of pests and invasive species to protect California's diverse ecosystem.
First detected in California in 2008, Asian citrus psyllid (ACP) has been a concern for both commercial citrus growers and home gardeners. ACP poses a significant threat to California's citrus trees, capable of spreading the deadly huanglongbing (HLB) disease, an incurable condition that eventually kills the tree.
Detecting ACP involves looking for a few key characteristics. ACP is a tiny, mottled brown insect about the size of an aphid. Adults are typically 3 to 4 millimeters long and are identified by their distinctive body shape, where the head is narrower than the body, and they hold their wings tent-like over their bodies. They are most active during warm temperatures, and you might notice them jumping or flying when disturbed. The nymphs, the immature form of the psyllid, are yellowish-orange and secrete white, waxy tubules from the back of their abdomen.
Additionally, ACP leaves telltale signs on citrus leaves, such as twisted or curled new leaf growth. They are sap-feeders, like aphids and mealybugs, so they produce honeydew which leads to the growth of sooty mold. Regularly inspecting your citrus trees, especially the new growth, is key to early detection of ACP.
Recent updates to the USDA's Plant Protection and Quarantine citrus map highlights areas that are generally infested with ACP and those which are not. This distinction is crucial for understanding the regulations and eradication efforts in different regions across the state. To find detailed quarantine information by county or zones, visit the California Department of Food and Agriculture (CDFA) ACP Regulation and Quarantine Boundaries website and maps.
Looking at the map pictured above, areas in the southern region of California, south of the Grapevine or San Gabriel and Tehachapi Mountain Ranges, and as far up the coast as Santa Barbara County are considered generally infested. The CDFA does not carry out eradication efforts for ACP in these areas. In areas north of the Grapevine, an ACP detection on a residential citrus tree would trigger an eradication response from the CDFA.
As we approach the holiday season, a popular time for gardeners to share budwood for grafting, it's crucial to understand the importance of not moving citrus planting material between quarantine areas. It is especially important not to move budwood or citrus from Southern California or the Bay Area into California's Central Valley.
To aid in this effort, UC Master Gardener Program resources are available to help educate you about identifying ACP and understanding the quarantine regulations. Here are some key actions you can take:
- Only purchase new citrus trees from reputable nurseries.
- Do not accept tree cuttings or budwood from friends or family.
- After pruning or removing a citrus tree, dry out the green waste or double bag it to help ensure the green waste is disposed of appropriately.
- Control ants in and near citrus trees with bait stations. Scientists have released natural enemies of ACP in Southern California to help keep the pest in check, but ants aid ACP in evading the natural enemies.
The UC Agriculture and Natural Resources ACP website offers an interactive map tool, biological control efforts, and an online calculator for the potential costs of using insecticides. Additionally, the Statewide UC Integrated Pest Management website provides free online training for gardeners and detailed Pest Notes on ACP and HLB disease. Remember, inspecting your citrus trees is vital to prevent the spread of ACP and HLB. If you suspect an infestation, contact the CDFA Exotic Pest Hotline at 1 (800) 491-1899 or your local county agricultural commissioner.
Let's continue to share the bounties of our gardens, but let's do so responsibly, keeping our citrus trees safe and healthy. Together, we can make a difference in the fight against ACP and HLB.
- Author: Luca Carmignani
- Editor: Karey Windbiel-Rojas
- Editor: Belinda Messenger-Sikes
- Post: Gale Perez
How can weed control help with wildfire preparedness?
Given the large amount of rain in the winter of 2022-2023, you might have experienced a surge in annual grasses and fast-growing plants that cover most of the ground around your home and community. In my area, I observed invasive species like wild oats and mustard growing rapidly in the spring, then drying out as summer approached (Figure 1). Dry vegetation poses a major threat to our homes and communities, both in terms of ignition (possibility of starting a fire) and fire path (creating ways for a fire to spread).
Understand fire risks.
Fires require fuel to spread, and any combustible materials, including vegetation, wooden fences, or sheds can serve as fuel. Once ignited, these materials can create a direct fire path toward a residence. Fires also generate embers (small fuel brands transported by the fire plume or wind) that can ignite leaves or debris on roofs and gutters or penetrate directly into a building through vents. Embers can also accumulate near the house, especially within the first 5 feet. You can reduce your home's exposure to flames and embers by implementing defensible space and home hardening strategies. Creating a defensible space involves managing the landscape around buildings (such as houses, sheds, detached garages) to prevent fires from reaching them. Home hardening focuses on improving building components, such as vents, roofs, and gutters, that could reduce exposure to flame and ember ignition. Though it can seem overwhelming to figure out where to begin reducing your home's fire risk, in this article I will walk you through a few simple, cost-effective recommendations that have been shown to make a difference.
How do we build a fire in a firepit? We start by adding the smaller kindling, and then the larger pieces of wood. Why? Because twigs and small branches are easy to ignite, they burn quickly, and they can be used to ignite larger logs. Similarly, dry grasses and herbaceous plants are easier to ignite than other types of vegetation such as big shrubs or trees.
Weeds can be ignited directly by flames, or by embers and sparks landing nearby. A mower hitting a rock or sparks from a power tool can easily ignite dry grasses around your property. Using the firepit analogy, ground fuels such as weeds serve as kindling to spread the fire to larger fuels nearby such as fences, decks, and shrubs. Therefore, removing weeds from vulnerable locations, such as near fences (Figure 2), is a very effective way to prevent ignitions around homes and communities, and reduce potential fire paths. It's easier to remove weeds while they are still green. This reduces the risk of ignition caused by mowers and prevents invasive species from reaching maturity and producing viable seeds.
Weeds and fire paths
In addition to being easy to ignite, dry grass and herbaceous plants can also create fuel continuity. Fuel continuity, or fire path, refers to the way a fire could spread toward a building. There can be both horizontal and vertical paths (Figure 3). Weeds can provide horizontal continuity between shrubs or other combustible materials, increasing the intensity of a fire and bringing it closer to the house. Thus, it is important to create horizontal separations between groups of plants when maintaining vegetation. When burning grass ignites a fence, the fire “climbs up” from the ground, and if the fence is attached to the house, the fire can continue to climb. A fire can reach a building by using this vertical path, often called a “fuel ladder.” The risk of fire spreading to your house can be significantly reduced by removing these potential fire paths, starting with ground fuels like annual grass. However, other sources of ignition, such as embers, may create additional paths. It is therefore crucial to harden house components like vents (for example, by replacing their screens with a metal mesh of 1/8” or smaller) and keep your roof and gutters clean.
What can you do?
Maintaining the landscape and vegetation around your home and community is crucial to preventing losses during a wildfire. Prioritize your actions to reduce the risk of ignition and fire spread around your home starting from the building and working outwards. Below are some recommended actions for creating and maintaining a fire-resilient landscape:
- Remove annual weeds and litter from vulnerable locations such as fences, sheds, siding, and under decks.
- When mowing or removing grass, be careful of sparks from power tools or other machinery, especially near open areas. Make sure you have access to water in case of a fire emergency.
- Break horizontal and vertical fire paths by removing weeds and other vegetation that are easy to ignite (grass, dead twigs, and dry leaves).
- Prune lower branches of shrubs closer to the ground and clean their understory; trim lower limbs of trees that are close to other plants or buildings.
- Mulch can be effective for weed control, but it is also flammable. Do not place mulch in vulnerable locations within the first 5 feet around a structure.
- A fence creates a direct path for fires. If your fence is attached to your house, replace the last 5 feet with a noncombustible section or gate.
- Install metallic 1/8" mesh screens on vents to prevent ember entry.
- Regularly clean roofs and gutters, especially near roof intersections.
- Maintain your landscape throughout the year.
Preventing the ignition of your home during a wildfire is possible, but it requires a combination of home hardening and defensible space strategies. For more information related to wildfire preparedness, check the additional resources below:
- UC ANR Fire website: https://ucanr.edu/sites/fire/
- Reducing the vulnerability of buildings to wildfire: Vegetation and Landscaping Guidance: https://anrcatalog.ucanr.edu/Details.aspx?itemNo=8695#FullDescription
- Wildfire home retrofit guide: https://www.readyforwildfire.org/wp-content/uploads/Wildfire_Home_Retrfit_Guide-1.26.21.pdf
- Combustibility of landscaping mulches: https://naes.agnt.unr.edu/PMS/Pubs/1510_2011_95.pdf
- Landscaping and home hardening: https://defensiblespace.org/
Luca Carmignani is a UC Cooperative Extension Fire Advisor located at the UC South Coast Research & Extension Center in Irvine, CA.
Original source: UC IPM Home & Garden Pest Newsletter :: Summer 2023 issue
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- Author: Luca Carmignani
How can weed control help with wildfire preparedness?
Wildfires are part of California's ecosystems, and they do not have to lead to the destruction of structures and livelihoods. Each of us can contribute to improving wildfire resilience, from individual homeowners and businesses to entire communities. Managing the vegetation and landscape around our homes can play a crucial role in preventing the spread of fires and sources of ignition.
Given the large amount of rain in the winter of 2022-2023, you might have experienced a surge in annual grasses and fast-growing plants that cover most of the ground around your home and community. In my area, I observed invasive species like wild oats and mustard growing rapidly in the spring, then drying out as summer approached (Figure 1). Dry vegetation poses a major threat to our homes and communities, both in terms of ignition (possibility of starting a fire) and fire path (creating ways for a fire to spread).
Understand fire risks.
Fires require fuel to spread, and any combustible materials, including vegetation, wooden fences, or sheds can serve as fuel. Once ignited, these materials can create a direct fire path toward a residence. Fires also generate embers (small fuel brands transported by the fire plume or wind) that can ignite leaves or debris on roofs and gutters or penetrate directly into a building through vents. Embers can also accumulate near the house, especially within the first 5 feet. You can reduce your home's exposure to flames and embers by implementing defensible space and home hardening strategies. Creating a defensible space involves managing the landscape around buildings (such as houses, sheds, detached garages) to prevent fires from reaching them. Home hardening focuses on improving building components, such as vents, roofs, and gutters, that could reduce exposure to flame and ember ignition. Though it can seem overwhelming to figure out where to begin reducing your home's fire risk, in this article I will walk you through a few simple, cost-effective recommendations that have been shown to make a difference.
Fires can start from weeds.
How do we build a fire in a firepit? We start by adding the smaller kindling, and then the larger pieces of wood. Why? Because twigs and small branches are easy to ignite, they burn quickly, and they can be used to ignite larger logs. Similarly, dry grasses and herbaceous plants are easier to ignite than other types of vegetation such as big shrubs or trees.
Weeds can be ignited directly by flames, or by embers and sparks landing nearby. A mower hitting a rock or sparks from a power tool can easily ignite dry grasses around your property. Using the firepit analogy, ground fuels such as weeds serve as kindling to spread the fire to larger fuels nearby such as fences, decks, and shrubs. Therefore, removing weeds from vulnerable locations, such as near fences (Figure 2), is a very effective way to prevent ignitions around homes and communities, and reduce potential fire paths. It's easier to remove weeds while they are still green. This reduces the risk of ignition caused by mowers and prevents invasive species from reaching maturity and producing viable seeds.
Weeds and fire paths.
In addition to being easy to ignite, dry grass and herbaceous plants can also create fuel continuity. Fuel continuity, or fire path, refers to the way a fire could spread toward a building. There can be both horizontal and vertical paths (Figure 3). Weeds can provide horizontal continuity between shrubs or other combustible materials, increasing the intensity of a fire and bringing it closer to the house. Thus, it is important to create horizontal separations between groups of plants when maintaining vegetation. When burning grass ignites a fence, the fire “climbs up” from the ground, and if the fence is attached to the house, the fire can continue to climb. A fire can reach a building by using this vertical path, often called a “fuel ladder.” The risk of fire spreading to your house can be significantly reduced by removing these potential fire paths, starting with ground fuels like annual grass. However, other sources of ignition, such as embers, may create additional paths. It is therefore crucial to harden house components like vents (for example, by replacing their screens with a metal mesh of 1/8” or smaller) and keep your roof and gutters clean.
What can you do?
Maintaining the landscape and vegetation around your home and community is crucial to preventing losses during a wildfire. Prioritize your actions to reduce the risk of ignition and fire spread around your home starting from the building and working outwards. Below are some recommended actions for creating and maintaining a fire-resilient landscape:
- Remove annual weeds and litter from vulnerable locations such as fences, sheds, siding, and under decks.
- When mowing or removing grass, be careful of sparks from power tools or other machinery, especially near open areas. Make sure you have access to water in case of a fire emergency.
- Break horizontal and vertical fire paths by removing weeds and other vegetation that are easy to ignite (grass, dead twigs, and dry leaves).
- Prune lower branches of shrubs closer to the ground and clean their understory; trim lower limbs of trees that are close to other plants or buildings.
- Mulch can be effective for weed control, but it is also flammable. Do not place mulch in vulnerable locations within the first 5 feet around a structure.
- A fence creates a direct path for fires. If your fence is attached to your house, replace the last 5 feet with a noncombustible section or gate.
- Install metallic 1/8" mesh screens on vents to prevent ember entry.
- Regularly clean roofs and gutters, especially near roof intersections.
- Maintain your landscape throughout the year.
Preventing the ignition of your home during a wildfire is possible, but it requires a combination of home hardening and defensible space strategies. For more information related to wildfire preparedness, check the additional resources below:
- UC ANR Fire website: https://ucanr.edu/sites/fire/
- Reducing the vulnerability of buildings to wildfire: Vegetation and Landscaping Guidance: https://anrcatalog.ucanr.edu/Details.aspx?itemNo=8695#FullDescription
- Wildfire home retrofit guide: https://www.readyforwildfire.org/wp-content/uploads/Wildfire_Home_Retrfit_Guide-1.26.21.pdf
- Combustibility of landscaping mulches: https://naes.agnt.unr.edu/PMS/Pubs/1510_2011_95.pdf
- Landscaping and home hardening: https://defensiblespace.org/
[Originally featured in the Summer 2023 issue of UC IPM's Home & Garden Pest Newsletter]
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