- 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: Lauren Fordyce
It may be after Labor Day, but some of your plants may still be wearing white, breaking that long-standing fashion “rule”! While many of us don't adhere to this old rule for our wardrobes these days, you may care about white stuff on your plants this time of year.
There are several white colored pest insects and diseases that you could be noticing on your plants.
Scales
Several types of scale insects are white. Each has their own host preferences, or plants they feed on.
- Cochineal scales feed only on cacti, usually prickly pears. On the outside they are white and waxy but have bright red bodies. If you scrape them off, you'll notice a red stain left behind.
- Cottony cushion scale feeds on a variety of woody ornamental plants. Common hosts in California are citrus, cocculus, nandina, and pittosporum. Adult scales are elongated and fluted.
- Euonymus scale feeds on many different plants but can be a serious pest to Japanese Euonymus (Euonymus japonica). Immature males are white and elongated with a brownish-yellow area at one end.
See the UC IPM Pest Notes: Scales to learn more about these and other scales and how to manage them.
Mealybugs
Mealybugs are whiteish-gray, oval, wax-covered insects. They can be found on many different plants, from fruit trees to houseplants, often hiding in protected places like branch crotches.
Powdery mildew
Powdery mildew often appears as white powdery spots (fungal spores) primarily on the tops of leaves. It can infect fruits and fruit trees, vegetables, and landscape plants in shady conditions when temperatures are between 60 to 80 degrees.
Whiteflies
Whiteflies are tiny insects with white, waxy wings and yellow bodies. They feed in large colonies on the undersides of leaves and have a very wide host range, including trees, vegetables, houseplants, and flowers.
Hackberry wooly aphids
This introduced aphid species infests Chinese hackberry and other hackberry (Celtis) plants. Hackberry wooly aphid adults appear in white, fuzzy masses on shoot terminals and leaves.
Spittlebugs
Adult spittlebugs are often brown, but they produce a white, foamy excrement on plants that looks like spit. They are known to feed on just about any plant.
Mushrooms
Many fungi produce white fruiting bodies that may pop up in your lawn, mulched landscape beds, or on trees and stumps. Puffballs and other fungi in lawns are mostly just a nuisance. However fungi on trees can sometimes cause wood decay and harm trees.
For more help diagnosing a plant problem or identifying a pest, see the UC IPM Plant Problem Diagnostic Tool or contact your local UC Master Gardeners.
- Author: Lauren Fordyce
The new year brings new webinars from the UC IPM Urban and Community Program! Mark your calendars and register now for these informative presentations, held every third Thursday from 12:00-1:00pm PST.
January 19, 2023: Houseplant Problems – Is your houseplant not doing so well? Want to learn how to be a better plant parent? Join us to learn about some common pests and problems of houseplants, and how you can prevent and control them. Presented by Lauren Fordyce, Urban and Community IPM Educator. Register for this webinar
February 16, 2023: Dealing with Pantry Pests – Pests can sometimes get into our pantries and food. Join us to learn how you can prevent and control these pests at home. Presented by Karey Windbiel-Rojas, Associate Director for Urban & Community IPM/Area IPM Advisor. Register for this webinar
March 16, 2023: Preventing Pest Problems at Seeding – Damping off and fungus gnats are common pests encountered when starting seeds indoors. Join us to learn how to prevent seedling problems and grow healthy transplants. Presented by Lauren Fordyce, Urban and Community IPM Educator. Register for this webinar
April 20, 2023: Aphids, Scales, and Mealybugs, Oh my! – Honeydew producers can create a mess when they infest houseplants, garden, or landscape plants. Join us to learn how to identify, prevent, and control these troublesome pests. Presented by Karey Windbiel-Rojas, Associate Director for Urban & Community IPM/Area IPM Advisor. Register for this webinar
Can't make a webinar? Don't worry, all presentations are recorded and posted on the UC IPM YouTube channel! More webinars will be announced in early 2023.
Follow us on social media @ucipmurban for the latest IPM content and news.
[From the UC IPM blog Pests in the Urban Landscape]
1. Aphids
These insects may be small, but they can quickly build up large populations. With many different species in California that feed on vegetables, flowers, fruit trees, and woody ornamentals, aphids are a common sight in landscapes and gardens. Year after year, aphids continue to hold the top spot. Learn more about aphids and their management in Pest Notes: Aphids.
2. Fungus Gnats
3. Thrips
Another tiny insect sometimes found on houseplants, thrips are slender insects about the size and shape of a dash printed in a newspaper. They suck out the cell contents, leaving a discolored speckling on leaves or stunting plant growth. For more about thrips monitoring and management, visit our Pest Notes: Thrips.
4. Mealybugs
If you've found soft, oval insects that are white in color with wax filaments on your indoor or outdoor plants, it is likely you have mealybugs. These wingless insects are often found in clustered colonies. In yards and gardens, handpicking, pruning, or high-pressure water sprays can reduce populations. For small infestations indoors, spot treatments may help reduce populations. For houseplants with severe infestations, consider disposing of the plant. Find additional information in Pest Notes: Mealybugs.
5. Carpet Beetles
6. Peach Leaf Curl
Peach leaf curl can affect the blossoms, fruit, leaves, and shoots of peach and nectarine trees. The symptoms of the disease first appear in spring, when distorted red foliage emerges. However, focus management for nonresistant varieties in the late fall and early winter, after leaves drop. Read more about this disease in our Pest Notes: Peach Leaf Curl.
7. Clothes Moths
New to the top ten list this year were clothes moths. These pests tend to hide when disturbed, so you may not realize you have an infestation until after the moths have already damaged fabric, fur, or feathered items. Some clothes moths make webs while others are casemaking moths. Regularly monitoring and cleaning clothing and storage areas can help prevent or reduce infestations. Find more identification and management information from Pest Notes: Clothes Moths.
8. Springtails
9. Whiteflies
Whiteflies are not actual flies but are tiny insects that are often found on the underside of leaves, feeding on the phloem of many different plants. Certain species can cause significant loss in vegetable gardens; other species found in fruit trees are less damaging. Both adult and immature whiteflies also attack houseplants. Management information can be found in Pest Notes: Whiteflies.
10. Scales
Scales are small, legless insects that look like tiny scabs on the stems, leaves, or fruit of plants. While some scale species can weaken a plant when abundant, other species do not appear to damage plants at all. Think you have a problem with these insects? Visit our Pest Notes: Scales for identification and management options.
/h3>/h3>/h3>/h3>/h3>/h3>/h3>/h3>/h3>/h3>We all encounter pests in our homes, gardens, and landscapes, but which ones are most popular in California? While we can't say for certain, website traffic to UC IPM's Pest Notes gives us a glimpse of popular pests. Here are the top ten most frequently viewed publications in 2021.
1. Aphids
These insects may be small, but they can quickly build up large populations. With many different species in California that feed on vegetables, flowers, fruit trees, and woody ornamentals, aphids are a common sight in landscapes and gardens. Year after year, aphids continue to hold the top spot. Learn more about aphids and their management in Pest Notes: Aphids.
2. Fungus Gnats
This pest has become more popular in recent years, perhaps a result from growing numbers of houseplant enthusiasts. Fungus gnats are small flies that often infest soil and potting mix. They can be a common houseplant problem with larvae, or immatures, damaging roots and stunting plant growth when present in large numbers. More information on these frustrating flies can be found in our Pest Notes: Fungus Gnats.
3. Thrips
Another tiny insect sometimes found on houseplants, thrips are slender insects about the size and shape of a dash printed in a newspaper. They suck out the cell contents, leaving a discolored speckling on leaves or stunting plant growth. For more about thrips monitoring and management, visit our Pest Notes: Thrips.
4. Mealybugs
If you've found soft, oval insects that are white in color with wax filaments on your indoor or outdoor plants, it is likely you have mealybugs. These wingless insects are often found in clustered colonies. In yards and gardens, handpicking, pruning, or high-pressure water sprays can reduce populations. For small infestations indoors, spot treatments may help reduce populations. For houseplants with severe infestations, consider disposing of the plant. Find additional information in Pest Notes: Mealybugs.
5. Carpet Beetles
Immature carpet beetles feed on natural fibers such as wool, silk, or furs. The adults may be brought into the home on cut flowers or when they fly in through open doors, windows, or holes in screens. Regular cleaning of rugs, upholstered furniture and can prevent infestations or reduce damage. Check out the Pest Notes: Carpet Beetles for more information.
6. Peach Leaf Curl
Peach leaf curl can affect the blossoms, fruit, leaves, and shoots of peach and nectarine trees. The symptoms of the disease first appear in spring, when distorted red foliage emerges. However, focus management for nonresistant varieties in the late fall and early winter, after leaves drop. Read more about this disease in our Pest Notes: Peach Leaf Curl.
7. Clothes Moths
New to the top ten list this year were clothes moths. These pests tend to hide when disturbed, so you may not realize you have an infestation until after the moths have already damaged fabric, fur, or feathered items. Some clothes moths make webs while others are casemaking moths. Regularly monitoring and cleaning clothing and storage areas can help prevent or reduce infestations. Find more identification and management information from Pest Notes: Clothes Moths.
8. Springtails
Springtails made an unexpected appearance on this year's top ten list. These are small, jumping insects that can be found near kitchen sicks and bathtubs as well as in the soil of indoor houseplants. They often appear in the spring and early summer but can be found year-round in moist environments. They get their name because they jump when disturbed. Learn more about this pest in Pest Notes: Springtails.
9. Whiteflies
Whiteflies are not actual flies but are tiny insects that are often found on the underside of leaves, feeding on the phloem of many different plants. Certain species can cause significant loss in vegetable gardens; other species found in fruit trees are less damaging. Both adult and immature whiteflies also attack houseplants. Management information can be found in Pest Notes: Whiteflies.
10. Scales
Scales are small, legless insects that look like tiny scabs on the stems, leaves, or fruit of plants. While some scale species can weaken a plant when abundant, other species do not appear to damage plants at all. Think you have a problem with these insects? Visit our Pest Notes: Scales for identification and management options.
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