by Larry Williams | Aug 20, 2018
Hydrangea leaf spot disease
Photo credit: Larry Williams
It is not uncommon to see leaf spots on your hydrangeas during late summer and fall.
These spots are caused by a number of fungal diseases. Plant fungi and wet weather go hand-in-hand. Florida’s high humidity, heavy dews and frequent rains during spring and summer provide perfect conditions to allow fungal diseases to flourish. Bacterial leaf spots can be part of this foliage disease mix, too.
Common foliage diseases seen on hydrangeas this time of year include Phyllosticta leaf spot, Target leaf spot, Bacterial leaf spot, Botrytis and Cercospora leaf spot.
These foliage diseases are the norm rather than the exception as we move into the wet summer months and on into fall. As a matter of fact, you would be hard-pressed to find any hydrangea in our area without some evidence of infection now.
This late in the year it is more of a “grin and bear it” problem. In other words, it’s too late to do much about the fact that your hydrangea plant has leaves covered in ugly spots. By now many of the infected leaves are turning brown, withering and dropping prematurely from the plant.
Cercospora leaf spot is one of the most common foliage diseases of hydrangeas. Along with most of the leaf spot diseases, it begins as small dark-colored specks on the leaves. The small specks generally go unnoticed. But as the spots continue to slowly enlarge, mostly maintaining a circular shape, they become more obvious. With heavy infection, individual spots can coalesce forming larger irregular shaped brown areas on individual leaves. The individual spots may have a purplish halo with gray center.
There are some fungicides that can help prevent these leaf spots. But you’d have to begin treatment early in spring before any leaf spots exist and spray the plant every 10 to 14 days during favorable disease development (humid, rainy weather), which is pretty much our spring and summer months. These types of diseases are prevented, not cured. That’s the “grin and bear it” part of waiting until now.
The fungus survives on infected leaves. So, the best thing to do now is to remove and dispose of infected leaves. Also, be careful to not wet the leaves when irrigating the plants during the growing season.
New leaves of spring should be spot/disease free as they emerge. But the cycle of life for these leaf spot diseases will again result in spotted/diseased leaves on your hydrangeas next summer and fall without persistent treatment.
The good news is that these leaf spot diseases normally do not cause permanent/long-term damage for hydrangeas. They just make the plant look ugly.
by Matt Lollar | Jun 4, 2018
Normally we think of rust as something that deteriorates metal, but a number of different fungal rusts can affect plants in the garden. Rust disease can affect corn plants, cedar trees, and even blueberry bushes. Just like the broad range of plant species that can be plagued by rust, there are a number of species of rust fungal spores floating around and ready to infest your garden. This article will focus on leaf rust of blueberry.
Blueberry leaf rust on the top of a leaf. Photo Credit: Philip Harmon, University of Florida/IFAS Extension.
Leaf rust of blueberry in Florida is caused by the fungus Pucciniastrum vaccinii. Although the common name of the disease is “leaf rust”, the disease can also infect the stems and fruit of blueberry plants. The disease causes small, round spots visible on the tops of leaves. Spots will multiply and the leaves will eventually yellow and fall off. Young stems and green fruit can also become infected as the disease progresses. Bright orange lesions will form on stems and fruit as the thousands of microscopic spores conjoin. The clusters of spores are easily wiped or washed off of plant material. When spores dry out, they become airborne and can be transferred to nearby plants.
Blueberry leaf rust on fruit. Photo Credit: Philip Harmon, University of Florida/IFAS Extension
The rust fungus thrives in hot, humid, wet conditions. A number of cultural practices can be adopted to reduce disease progression and survival.
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Irrigation
Disease persistence can be reduced by limiting the amount of water that contacts the plant leaves. Water the base of plants or install drip irrigation for your bushes rather than watering from overhead. If overhead irrigation is the only option, then water plants in the morning rather than in the evening. This allows the leaves to dry out over the course of the day.
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Pruning
Removal of approximately 25% of the oldest canes in late winter before spring growth begins will stimulate the production of new canes and should result in plants with canes of different ages and will provide a good mix of vigorous branching and fruit production. Moderate summer pruning can also improve yield and shoot growth. When pruning, cut out vigorous shoots that are growing well beyond the desired canopy height and are in the interior portion of the bush. This will promote a more open growth habit and help with air circulation on the remaining plant material. Some vigorous canes developing from the ground and growing on the outside of the bush can be topped to stimulate branching and flower bud formation.
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Mulch
Pine bark mulch helps with establishment of young plants and helps keep soil pH low in existing plantings. A layer of aged pine bark 3 inches deep extending about 2 feet out from the plants will provide a good growing medium for surface feeder roots. Pine straw can be used if pine bark is unavailable. Mulch also moderates soil temperature, helps keep weeds at bay, and adds organic matter to the soil. Make sure to keep mulch raked back about three inches away from the plant canes to provide good air circulation to the roots.
Hopefully this article has given you some tips to have a good blueberry crop for years to come. For more information on growing blueberries in Florida, please visit the University of Florida/IFAS EDIS Publication: Blueberry Gardener’s Guide.
by Matt Lollar | Apr 23, 2018
Recently, an Extension Agent in the Florida Panhandle received a picture of some mushrooms popping up in a client’s garden. These particular mushrooms were in a spot where leftover mushroom compost had been dumped. The compost was previously used to grow oyster mushrooms and the client was hopeful that she had more oyster mushrooms growing in her yard. Unfortunately, the lab results came back stating the mushrooms in question were Armillaria spp.
Armillaria spp. in the garden. Photo Credit: University of Florida/IFAS Extension.
Armillaria spp. cause root rot of trees and shrubs throughout the world. The fungus infects the roots and bases of trees, causing them to rot and eventually die. Some species of Armillaria are primary pathogens that attack and kill plants, but most are opportunistic pathogens that are attracted to unhealthy or stressed plants. Fruiting structures of the fungi can be recognized by the clusters of yellow to brown-colored mushrooms that emerge during wet conditions. However, the mushroom caps sometimes never form and the plant material needs to be inspected more thoroughly to find the disease culprit. Infected plants may have wilted branches, branch dieback, and stunted growth and should be removed and replaced with resistant species.
White mycelial fan under the bark of a root infected with Armillaria tabescens. Photo Credit: Ed Barnard
Management – The best method for controlling Armillaria root rot is with proper plant installation and maintenance. Planting plant material at the proper depth will allow the roots to breathe and reduce the opportunity for the roots to rot. Pruning tools should be sanitized between plant material. Proper irrigation and fertilization will also reduce the risk of plant disease and root rot. Lastly, you can choose to plant a diverse landscape with resistant species.
For more information on Armillaria root rot and a comprehensive list of resistant species, please view the EDIS publication: Armillaria Root Rot
by Matt Lollar | Mar 20, 2017
A type III fairy ring. Photo Credit: Alex Bolques, Assistant Professor, Florida A&M University
Mushrooms often are grouped in a circle in your lawn. This is due to the circular release of spores from a central mushroom. “Fairy Ring” is a term used to describe this phenomenon. Fairy rings can be caused by multiple mushroom species such as Chlorophyllum spp., Marasmius spp., Lepiota spp., Lycoperdon spp., and other basidiomycete fungi.
Occurrence
Fairy rings most commonly invade your yard during the summer months, when the Florida panhandle receives the most rain. The mushrooms cause the development and spread of the rings by the release of spores. Spores produce more mushrooms and are similar to the seed produced by plants.
Fairy Ring “Types”
Fairy rings can be seen in three forms:
- Type I rings have a zone of dead grass just inside a zone of dark green grass. Weeds often invade the dead zone.
- Type II rings have only a band of dark green turf, with or without mushrooms present in the band.
- Type III rings do not exhibit a dead zone or a dark green zone, but a ring of mushrooms is present.
The size and fill of rings varies considerably. Rings are often 6 ft or more in diameter. The fill of a ring can range from a quarter circle to a semicircle or full circle.
Cultural Controls
The rings will disappear naturally, but it could take up to five years. Although it is possible to dig up the fairy ring sites, it is a good possibility the rings will return if the food source (buried, rotting wood or other organic matter) for the fungi is still present underground.
In some situations, the fungi coat the soil particles and make the soil hydrophobic (meaning it repels water), which will result in rings of dead grass. If the soil under this dead grass is dry but the soil under healthy grass next to it is wet, then it is necessary to aerate or break up the soil under the dead grass with a pitchfork or other cultivation tool.
Rings of dead turf due to fairy ring fungi. Photo Credit: University of Florida/IFAS Extension.
Chemical Controls
Effective fungicides include products containing the active ingredients azoxystrobin, flutolanil, metconazole, pyraclostrobin, and triticonazole.
Fungicides inhibit the fungus only. They do not eliminate the dark green or dead rings of turfgrass and do not solve the dry soil problem.
A homeowner’s guide to lawn fungicides can be found at the University of Florida/IFAS Extension Electronic Data Information Source (EDIS) website (http://edis.ifas.ufl.edu/document_pp154).
by Daniel J. Leonard | Jun 22, 2016
Gardeners in Northwest Florida were blessed this spring with conditions conducive to great gardening, mild weather and plenty of rain. However, with those pleasant conditions has come an unusually high occurrence of Fireblight. Cases of Fireblight have been brought into our office almost daily this spring/early summer!
Mature ‘Bradford’ Pear infected with Fireblight
Fireblight is a difficult to control, rapidly-spreading disease caused by a bacterium (Erwinia amylovora) that affects many fruit trees, especially apple and pear but is also seen on quince, crabapple, hawthorn, loquat and photinia. Fireblight is generally noticed in late winter and early spring during periods of frequent rainfall as the plant begins to bloom and leaf out. The bacterium enters the plant through the opening flowers causing them to blacken and die. The disease then makes its way down the infected stem, destroying newly developing twigs along the way. Most homeowners notice the problem at this point in the progression; the new shoots have died, turned black and hold on the plant, giving it the tell-tale “burned” look. Homeowners also generally notice sunken lesions, or cankers, that form on the infected stems.
So, with a problem as unpredictable and destructive as Fireblight, what can one do to prevent it or combat its spread? There is no one method that can prevent or cure a Fireblight infection but there are several precautions homeowners can make to mitigate its effects.
- Plant resistant species and/or resistant cultivars of susceptible species, such as pear and apple. Under conditions like we’ve had this year, no pear or apple is immune but these cultivars have some proven resistance:
- Edible Pear: ‘Keiffer’, ‘Moonglow’, ‘Orient’
- Apple: ‘Anna’, ‘Dorsett Golden’
- Ornamental Pear: ‘Bradford’, ‘Cleveland Select’
- Remove infected and dead wood when the tree is dormant. Make a clean cut at least 12” below the last sign of infected wood and dispose of it. It is always a good practice to sanitize your pruners between cuts on a diseased tree. Also, there is little evidence to suggest that pruning out diseased wood on actively growing plants has much effect on further disease spread as long as conditions are still suitable for Fireblight formation.
- If you have noticed Fireblight on your trees in the previous year, it is good practice to make a preventative spray of a copper fungicide prior to the plant breaking dormancy.
- During bloom, streptomycin may be applied every three or four days for the duration of the bloom cycle to prevent infection. Consult the label for required days between spraying and consumption.
Fireblight is bad news in a fruit orchard but homeowners can take heart in the fact that the condition is not always fatal, especially if the preventative measures outlined above (proper cultural practices, proper pesticide use, and planting of resistant cultivars) are taken!
