Leaf Roll

Leaf roll is not the newest thing in Burmese take-out.


Instead, leaf roll is a symptom that can tell you a lot about what is going on in your garden. Leaf roll can be caused by several different factors:
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• environmental stresses 
• viral infections
• fungal disease
• pests
• herbicide damage

Evaluating leaf roll damage

If you notice leaves starting to roll on any of your trees, shrubs, garden or landscape plants, start by asking yourself the following questions:
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• Are the leaves rolling upward or downward?
• Which leaves are rolling? Are they new or old? On the top or bottom of the plant?
• Is it only on one side that leaves are rolling?
• Are other parts of the plant showing symptoms?

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Photo of tomato with leaf roll (Clemson U.)

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Environmental damage

Environmental damage is normally visible near the base of a plant first, as leaves cup upward, toward the leaf vein. These leaves tend to be leathery, while remaining a normal green color. Environmental damage is a common problem when growing tomatoes. 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:  
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• too much moisture
• too much sunlight
• too much nitrogen
• too much pruning
• root damage
• transplant shock

Viral infections

Some viral infections can also cause leaf roll. This is especially true for tomatoes, potatoes, and grapes. 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. The rest of the plant may look stunted, and infected fruit may start rotting from the inside out. Infected plants are goners and should be removed right away to prevent spreading the disease to nearby plants. Be sure to disinfect tools with a 1 part bleach to 9 parts water solution and keep weeds away from the area. This is to reduce the number of insects that may reinfect the garden bed.


Fungal diseases

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:

• red blisters
• twisted, rubbery leaves
• ultimately, leaves turn white as the fungi start reproducing
• infected leaves fall earlier than normal and should be destroyed

Pests

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 we 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. This pest can be found in citrus, pear, plum, apple, almond, apricot, caneberries, 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.


Herbicide damage

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:

• downward cupping leaves
• twisted leaves
• stems that twist or turn white
• deformed fruit

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 to thrive!