By: Kristi Waterworth
Quince, the once beloved, but then largely forgotten orchid staple, is making a comeback in a big way. And why wouldn’t it? With colorful crepe-like flowers, a relatively small size and a great big pectin punch, quince is the perfect fruit for the orchardist who makes their own jams and jellies. But it’s not all fun and games in the world of jelly; it’s also important to know a little bit about the common diseases of quince trees so you can catch them before your quince becomes seriously sick. Treating a sick quince is much easier if you can do it in an early stage of illness. Read on to learn more about common quince disease problems.
Diseases of Quince Trees
Quince tree illness is usually not too serious, but most warrant some type of treatment. Pathogens can ruin harvests and weaken plants, so knowing how to treat quince tree diseases can be a valuable skill for the long-term health of your plant. These are some of the most common problems you’re likely to encounter:
Fire blight. Pear growers will be familiar with fire blight. This bacterial nuisance is also a problem for quince. You may notice blossoms appearing water-soaked or rapidly wilting. Nearby leaves follow, wilting and darkening while remaining attached to the plant, giving it a scorched appearance. In wet weather, infected tissues may ooze a creamy liquid and mummy fruits remain firmly attached after the end of the season.
Often, you can cut out the infected material, rake up all fallen debris to prevent reinfection and treat your plant with copper sprays during dormancy and again just prior to bud break to end the cycle. It may take a few years of diligence, but your patience will be rewarded.
Leaf spot. There are several leaf spot diseases that can affect quince. They may appear as large or small spots on leaves, but are largely cosmetic in nature. The best plan is to clean up all fallen debris from around your tree to remove any fungal spores, prune the inner canopy to increase air circulation and, if the spots are plentiful, spray with a copper fungicide when leaves emerge in the spring.
Powdery mildew. Powdery mildew is a fungal disease that looks like your plant has been lightly dusted with powdered sugar in the night. In ornamentals, it’s not a serious disease, but in fruit trees it can cause dwarfing, distortion and scarring of new growth, even damaging the fruit itself. It’s definitely something to treat. Luckily, you treat it just like leaf spot. Open up the canopy, increase the airflow around each branch, get rid of any debris that might be harboring spores and apply a fungicide to help kill the fungus back.
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Diseases in Junipers
Junipers (Juniperus spp.) are a family of woody, cone-bearing, evergreen plants. Ranging in size from 4 inches to over 50 feet in height, these plants are popular in the home landscape as ground covers, screens, hedges and windbreaks, among other uses. They grow best in full sunlight and well-drained soil and are tolerant of a wide range of soil types. Junipers are susceptible to a number of diseases that may detract from their beauty or cause plant death.
Cedar hedges are affected by both Keithia and Seiridium blights. Keithia blight causes small, circular holes to appear on leaves. The edges of the holes are black at first but turn white. Affected leaves wither and fall off, leaving the lower branches of the tree bare. Keithia is caused by a fungus which can be killed by applying a fungicide every 2 weeks during the spring and early summer fungicides containing fixed copper, zineb and mancozeb work best. Less severe is the Seiridium blight, characterized by small cankers on leaves and twigs, eventually causing the affected shoots to die. Fungicide treatment can resolve the problem if necessary, but this blight is not a serious problem on most varieties and may not warrant treatment.
IDENTIFYING SHRUB DISEASES
Homeowners strive to maintain healthy plant life in their gardens and landscapes, but oftentimes shrubs suffer casualties, or fall ill from disease for a variety of reasons. From too little watering to pest infestation, proper disease identification is crucial to the survival of your shrubs. Depending on the specific type of shrub affected, the disease, diagnosis and treatment will all vary.
Similar to humans, when the needs of shrubs are not met, a decline in health will result. A landscape professional, trained and knowledgeable about plant health, can inspect and diagnose sick shrubs but for those determined to do a little self-diagnosing, here are some fundamentals to get you started.
Begin your prognosis by eliminating improper growing conditions or shrub pests as the culprits for your shrub’s demise by looking for gnaw marks or stripped leaves, which will indicate rodents, rabbits, or deer. Once you are certain your shrub isn’t being eaten by bugs or animals, you can move on to analyzing the type of disease. When diagnosing shrub disease, there are two categories for which your “ick” will be classified: abiotic or biotic. Abiotic diseases are man-induced diseases that involve non-living factors such as lack of space for root growth, prolonged levels of water toxins, or extreme heat, light or soil pH levels. There are a host of resources on those topics. Let’s explore the biotic causes of woody-shrub diseases that are scientifically or biologically-induced, such as fungi, bacteria, viruses and nematodes.
Identifying the Disease in Woody-Shrub Fungus Materials
It’s important to note that you should identify your infected shrub first as not all diseases affect one type of plant. This will help narrow down your market of diseases to identify. Be sure to check the trunk, leaves, branches and roots to note the specific symptoms from which your shrub is suffering. There are numerous types of shrub diseases so let’s explore some of the most common biotic diseases and symptoms of what to look for when diagnosing your sick shrubs and how to treat each disease.
Fungus: Powdery Mildew Fungus
This common type of disease is a fungal growth that leaves a white powder on surfaces of shrub foliage.
- Remove parts of the shrub that are infected with the disease.
- Prune shrubs to improve air circulation.
- Hold off on all fertilization until the disease has been altered and the plant health has improved.
- Water the shrub from under the plant in order to reach roots directly.
- A fungicide should be applied. Tip: An application will likely need to be reapplied seven-14 days later to ensure the health of the shrub is rectified.
Bacteria: Fire Blight
This common type of bacteria leaves twigs and branches on shrubs wilted and blackened. Often, the affected branches will bend over into the shape of a shepherd’s crook.
- Dormant season: prune the infected areas of the shrub.
- Tip: Be sure to clean pruning tools in-between shrub cuts.
- Growing season: refrain from pruning shrubs due to the chance it could spread the disease, instead remove infected shrub from the landscape.
Symptoms include browning shrubbery and vegetation, which may cause undergrowth to die and/or fall off the plant. Root systems will be affected and plant growth will be stunted.
- Do not use a chemical application to treat plants.
- Remove infected plant from the landscape.
- Protect other shrubs through water and fertilization.
Virus: Rose Mosaic Disease
You will notice signs of this virus if your shrub experiences color changes in its leaves, specifically a mosaic pattern of light or dark greens. Additional symptoms and signs include stunted growth and uncommon color changes.
- Remove the infected shrub to prevent the spread of disease.
- Tip: It’s important to be on top of insect management because Rose Mosaic Disease can spread through your landscape from insects feeding on additional health plants.
Many people focus on the health of their plants in the summer and then that attention wanes. It’s important to be proactive to prevent shrub disease throughout the year. Be aware of the following factors that are all important to good plant health:
- Proper air circulation and ventilation
- Use of native plants (planting the right plant that will survive the culture of your landscape, i.e. choosing shrubs that will withstand the harsh winter temperatures or extreme heat during the summer months of your locality)
- Proper sunlight
- Be sure water is not sitting on the leaves of the plant
- Plant resistant cultivators (plant disease resistance will protect plants from pathogens)
While these are some of the most comment shrub diseases, there’s a laundry list of other culprits that can be detrimental to your plants. A landscape professional can help identify problem posers and identify an appropriate treatment plan – and recommend steps to ward off disease before it strikes.
Photos courtesy of Sun Valley Landscaping, Omaha, NE.
How to cure a quince tree
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T he 20-year-old quince tree in Donald Sherlock’s Hampshire garden has been stricken by rust in recent years. Spraying is useless, he says, as is ignoring the disease in the hope that it will cure itself. Is it the end for the poor thing? And is there any point in replacing it?
Also known as quince leaf blight (Diplocarpon mespili), this is a common fungal disease of quinces and is almost uncurable. A tree tends to start the year well and blooms beautifully, but by July its leaves become spotty and start to fall off. The whole tree can defoliate by August, most of the branches leafing at the tips before autumn, although some may die. The disease is worse in wet, cold years, when even the fruit becomes ugly and spotty.
As Donald says, fungicide treatment is ineffective, so all he can do is clear up the fallen leaves, cut off dead shoots in winter, kill the weeds and remove some of the turf underneath the tree so that it can be fed with a general fertiliser each spring.
And the future? He could soldier on or replace it on a different site with a newer variety with greater disease resistance. 'Vranja’ is popular, but new varieties from Eastern Europe such as 'Lescovaka’ and 'Krymsk’ are also pretty tough.