- Author: Ben A Faber
Hot off the internet, a new edition of Topics in Subtropics, articles from UC subtropical horticulture folks
Topics in Subtropics Volume 25 Spring 2024
Jul 9, 2024
Fatemeh Khodadadi, Editor
Topics in this issue:
- Effectiveness of Asian citrus psyllid management in huanglongbing treatment zones in residential Southern California
- Managed honeybees in a wet year
- Threats to citrus orchards in California by synergistic effects of dry root rot and phytophthora root and crown rot
- Microbial Safety in Avocado Farms
- How Much Fruit is Up there?
- Tiny Troublemakers: How Geminiviruses are affecting California's Crops
- Citrus Leprosis Disease – Staying alert on potential threat to California's citrus industry
Download (3,620KB PDF)
https://ceventura.ucanr.edu/Com_Ag/Subtropical/
AND THERE"S LOTS MORE TO READ FROM THE ARCHIVES
https://ceventura.ucanr.edu/Com_Ag/Subtropical/?newsletterlist=3197
![topics in sub masthead topics in sub masthead](/blogs/blogcore/blogfiles/107742.png)
- Author: Belinda Messenger-Sikes
Have you been seeing a lot of defoliated sycamore trees recently? Sparse foliage and early leaf drop on sycamore trees might be due to anthracnose. The cool, wet spring in many parts of California provided the perfect conditions for this disease. Anthracnose is a common fungal disease sometimes called leaf, shoot, or twig blight. It can cause twisted, distorted branches in American sycamore, some varieties of London plane trees, and California sycamore trees. Sycamore anthracnose is primarily an aesthetic concern since it usually doesn't kill established trees.
Symptoms
Take a close look at the fallen leaves for the characteristic irregular blotches caused by this disease. Anthracnose can cause leaf spots, cankers, and wilting of young leaves in the spring (Figure 1). Emerging leaves turn brown and die. On older leaves, irregular spots or brown blotches begin on either side of the main leaf vein. The lesions spread, covering much of the leaf surface. Extensive twig or shoot blight occurs when young, growing shoots are killed. New shoots grow back from lower on the branch, eventually causing the branch to look gnarled with a “shepherd's hook” appearance (Figure 2).
Springtime disease
The fungus overwinters on infected sycamore twigs and dead leaves., The disease is most severe during wet years when temperatures during the leafing-out period are below 55°F. The disease is not a problem in hot, dry weather. While the first flush of leaves might be lost to the disease, the canopy will regrow as the second flush of growth matures.
Management
Sycamore anthracnose is best managed by cleaning up fallen infected leaves to prevent the spread of the spores to the following year's new growth. Rake and dispose of fallen leaves and twigs during the growing season and in the fall. Prune and dispose of infected twigs and branches in the fall or winter. Avoid sprinkler irrigation that keeps trees wet. When planting sycamore trees in gardens and landscapes, choose resistant cultivars.
Fungicides do not reliably control sycamore anthracnose in California. By the time you see symptoms, it's too late to treat since fungicides effective against the disease are preventive (before the symptoms appear), not eradicative (after the disease symptoms appear). In landscape and residential settings, chemical spray applications are usually not practical due to the size of the trees and the high potential for pesticide drift.
Most sycamore trees will fully recover from defoliation caused by anthracnose, so the best option could be to just rake up the fallen leaves to reduce disease inoculum for the following year.
For more information about anthracnose, see the UC IPM Pest Notes: Anthracnose.
[Originally published in the Summer 2023 Issue of the UC IPM Green Bulletin Newsletter]
/h2>/h2>/h2>- Author: Belinda J. Messenger-Sikes
What is that weird wormlike thing in your garden? A slug? An earthworm? It may be neither—it it might be a land planarian. Land planaria are also called terrestrial flatworms and hammerhead worms. They are often colorful, such as the blue garden flatworm (Caenoplana coerulea) or patterned with stripes, like the shovel-headed garden worm (Bipalium kewense).
Land planaria are generalist predators of earthworms, slugs, and other mollusks. They capture prey by wrapping their bodies around it and engulfing the prey with mucous. Planaria mouths are not at the end of their body like most animals, but on the underside near the middle of their body. Unlike slugs, land planaria do not have tentacles (such as eyestalks), which is a useful way to distinguish them. Like snails, they are hermaphroditic, meaning each individual has both male and female reproductive organs and can mate readily with any other worm of the same species. Land planaria can also reproduce by binary fission, which is when one individual planarian splits into two. You may remember an experiment from middle or high school science laboratory where a planarian cut in half regrows into two separate planaria.
These animals need moisture, so they live in wet environments. Examples include under rocks and logs, in plant pots and mulch, under bushes, and along streambanks. In nurseries, they are commonly found under plant pots. After heavy rains, they might be found on sidewalks and driveways.
Do land planaria cause problems?
Land planaria may be considered minor pests, but they don't damage plants or harm people. They can sometimes reduce earthworm populations in natural environments. Land planaria have very few predators since their mucus is distasteful. While some species (B. adventitium and B. kewense) produce a neurotoxin, they cannot inject it into pets or people and are only toxic to small animals when eaten. Some species can carry rat lungworm, an internal parasite. Wash your hands thoroughly after handing land planaria to avoid these problems.
Some land planaria are invasive, but their impacts on the environment and native flora and fauna will depend on the species, their prey preferences, and where they are introduced. In most cases, there is little impact. Invasive land planaria may present problems in the future since it is easy for land planaria to reproduce and spread.
Eradication of land planaria from a landscape is difficult, if not impossible. Cutting up planarians to kill them doesn't work since new individuals will grow from each section. They can be killed with salt or by submerging them in rubbing alcohol, but this is impractical for large numbers of planaria. There are no registered pesticides for land planaria and using a molluscicide to control them is ineffective and may be illegal, since land planaria are flatworms and not snails or slugs (mollusks).
[Originally featured in the Spring 2023 issue of UC IPM's Home & Garden Pest Newsletter]
- Author: Belinda J. Messenger-Sikes
The jumping worm, Amynthas agrestis, is an invasive earthworm capable of harming native forests that has been recently reported in some areas of California. This pest devours leaf litter and other organic matter, changing soil texture and nutrient availability to a point where some plants may be unable to survive. Its feeding can lead to a decline in diversity and population of native plants and other organisms within forests.
Although these worms are native to eastern Asia, they have been detected in dozens of states; including Massachusetts, New York, Wisconsin, and Minnesota. Jumping worms have since moved west to Washington and Oregon and were detected in California in 2021. The California Department of Food and Agriculture (CDFA) has labeled the jumping worm as an A-rated pest, meaning it can cause economic or environmental harm if it becomes established in the state.
In nurseries, any jumping worms that are present are likely to be found underneath pots sitting on the ground or on landscape fabric. In forests, they tend to be near the surface, just under accumulations of leaf litter, unlike other earthworms.
How do you know if it's a jumping worm?
The jumping worm, also called the crazy worm or snake worm, can be distinguished from other earthworms by a milky-white band (the clitellum) wrapping all around and flush with its body near the head as well as its characteristic “jumping” when disturbed. Jumping worms have been known to propel themselves off the ground and thrash when disturbed, almost like a provoked snake. Jumping worms are firm, smooth, and glossy, but not slimy. They are dark gray or brown in color, darker than other earthworms. This darker pigmentation helps protect them from sunlight since they live closer to the surface than do other species. Adult jumping worms are usually 4-5 inches long, tend to occur in large numbers, and are most noticeable in late summer or early autumn when most are fully mature. In the fall, adults produce cold and drought resistant cocoons (a hardened egg capsule) before dying. One worm can produce many cocoons without mating. The next generation of jumping worms overwinters in these mustard seed-sized cocoons, which hatch and develop into new worms in the spring.
How do jumping worms spread?
Jumping worms live in leaf and plant litter. The tiny egg cocoons look like small bits of dirt so can easily be moved by raking leaves or by transporting mulch, potting mixes, and potted plants. Jumping worms can be spread to natural areas on soil particles attached to hiker's boots, through movement of plant material sold by nurseries where the worm exists, or even by anglers if they use adult jumping worms as fish bait.
Prevent the spread of the jumping worm
Prevention is by far the best approach to managing jumping worms. Don't buy or use jumping worms for fishing bait, vermicomposting, or gardening. Learn how to recognize jumping worms and pass along the knowledge. Check new mulch, compost, and soil for evidence of jumping worms. Before you buy new plants, take a close look at the potting soil. If jumping worms are present, you will see their telltale, coffee ground-like castings on the soil surface. Buy bareroot plants whenever possible. When gardening, keep an eye out for jumping worm adults and their castings.
What if you find jumping worms?
If you discover jumping worms, contact CDFA or your local agricultural commissioner's office to report the finding. If the CDFA confirms the worms are jumping worms, work with them to focus on preventing the spread of the worm. Don't move materials such as compost, mulch, topsoil, or plants known to have jumping worms to new locations. Always clean dirt and debris off your equipment and shoes before leaving an area infested with jumping worms. Dispose of all contaminated soil and castings in the trash. Kill worms by freezing or leaving them in a plastic bag out in the sun, then discarding.
Jumping worms and their cocoons are unable to survive temperatures above 40°C (104°F). Increasing soil temperatures above this threshold for three days through soil solarization is one way to manage jumping worm populations. Be aware that re-infestation of the area may occur due to cocoon presence in areas beyond the treatment zone. Soil used for potting can be temporarily placed in plastic bins and exposed to direct sunlight.
Do not try to control jumping worms with pesticides. There are currently no registered pesticide products for this pest. Using pesticide products not intended or labeled for the jumping worm is illegal and can kill beneficial earthworms and cause harm to the environment.
Further Reading
https://ag.umass.edu/landscape/fact-sheets/jumpingcrazysnake-worms-amynthas-spp
https://blogs.cdfa.ca.gov/Section3162/wp-content/uploads/2021/12/Amynthas-agrestis_ADA_PRP.pdf
https://hort.extension.wisc.edu/articles/jumping-worms/
https://www.invasivespeciesinfo.gov/terrestrial/invertebrates/asian-jumping-worm
[Originally featured in the Spring 2023 issue of UC IPM's Home & Garden Pest Newsletter.]
/h2>/h2>/h2>/h2>/h2>
- Author: Anne Schellman
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