What happened? Yesterday, your plants looked lovely. Today, several leaves are rolled up, looking like green cigars. What did this, is it a problem, and what can you do?
Leaf roll (or leafroll) is not the newest thing in Burmese take-out. Instead, it is a symptom that can give you clues about what is going on in your garden. Leaf roll can be caused by environmental stresses , viral infections, fungal infection, pests, or herbicide damage.
If you notice leaves starting to roll on any of your plants, start by asking yourself the following questions:
Physiological or environmental causes of leafroll
Environmental or physiological damage is normally visible near the base of a plant first, as leaves cup upward, toward the leaf vein. These leaves tend to thicken and become leathery, while remaining a normal green color, as the plant tries to protect itself. Environmental damage is a common problem when growing members of the nightshade family, such as tomatoes, peppers, and eggplant. Interestingly enough, bush (determinate) varieties are less likely to exhibit leaf roll than vine (indeterminate) varieties. Symptoms of environmental damage can indicate any of these problems:
Some viral diseases can also cause leaf roll. Viruses often enter plant tissue as insect carriers feed. These carriers are normally aphids, mealybugs, and soft scale insects. Leaf roll viruses can also be spread through infected scion wood. Once infected, vascular bundles become clogged as the viruses reproduce in the nutrient-rich phloem. This reduces water and nutrient flow within the plant, causing stunting, delayed maturity, reduced crop size, chlorosis, necrosis, and leaf roll.
Viral infections affect newer leaves first. Leaves cup upwards and turn pale green. They may also have yellow edges, mottling, and veins may look purplish. This color change is due to damage to the phloem. Infected fruit may start rotting from the inside out.
There are three major types of viral leafroll that warrant concern:
Because these viruses can spread rapidly, over relatively great distances, close monitoring and control are in everyone’s best interest. Once a plant is infected with one of the leafroll viruses, it should be removed and destroyed. There is no cure or treatment. When shopping for plants, choose resistant varieties and put them in quarantine when you bring them home. Controlling carrier pests will also help reduce the likelihood of leafroll affecting your garden.
Leaf curl caused by fungal infections can be particularly destructive, since the disease can be carried in by whiteflies. Peach leaf curl, bacterial blast, and botrytis are common examples. Symptoms include:
As aphids, leaf miners, thrips, mites, scale insects, and mealybugs feed on sap, they can cause leaves to curl. Occasionally, a spider may curl a leaf to create a cocoon, but spiders are Good Guys in the garden, so leave them alone. The real pest when it comes to leaf rolling comes from the larva of certain moths. In particular, California has a problem with moths in the tortricid family. These pests can be found in citrus, pear, plum, apple, almond, apricot, raspberries and other cane fruit, quince, and walnut, plus most ornamentals. Light brown apple moths also fall in this category. Pest damage usually includes ragged edges on nearby leaves and tightly rolled nesting leaves. Inspect fruit and nut trees carefully from March through May for signs of these pests.
The ads make herbicides look so safe and helpful, but they are, in my opinion, anything but. Leaching, overspray, rain splash, a sudden breeze, and the failure to breakdown in the soil as advertised can put many other plants at risk. Symptoms of herbicide damage include:
If you notice leaf rolling on your garden or landscape plants, take a closer look to see if you can figure out what is causing this change. Knowing the cause helps you find a solution that allows your plants stay healthy and productive.
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