Holes in Plant Leaves? Causes, Common Pests & Easy Organic Solutions

Every rooftop gardener knows that wistful moment when you climb the stairs to the terrace with a steaming cup of tea, all set to admire the morning greens, only to freeze in horrified dismay. That beloved patch of spinach, brinjal, or the rose bush has been mangled beyond recognition in the night, as if some vandal had taken a shooting range to your leaves. Green lace hangs from the stems.

After all, life on the rooftop is an expedition for your plants. Sun, wind, even wild animals take their toll. But when there are holes in the leaves, it’s not difficult to guess what has been doing the nibbling. Just take a close look at the pattern of damage, and you can identify the miscreant.

Here are some detective tips for the rooftop gardener who wants to single out the culprit damaging his leaves and what to do about it.

Leaves riddled with dozens of tiny, round, shotgun-type holes

The Perpetrator: Flea Beetles

These are about the size of a sesame seed, usually jet-black or bronze. Give them a gentle touch, and they will spring away like fleas, using their hind legs. If you see fleas leaping off your plants, that’s usually a sure sign that they are flea beetles. They have a voracious appetite for the leaves of all your vegetable crops and are most prevalent in the hot season.

Each adult flea beetle can lay six to eight eggs in a day, and they hatch in five to seven days. A few dozen pinprick-size holes in the leaves may not worry you if the plant is healthy, but young plants may wilt and die if they lose too much chlorophyll.

What to do:

Sprinkle some wood ash or diatomaceous earth on the leaves; flea beetles hate the texture and avoid the plant. Yellow sticky traps placed near the base of the plant can also capture them.

Big, bony, irregular holes, sometimes leaves missing altogether.

The Perpetrator: Caterpillars on night shift.

When leaves are stripped of big, ragged pieces, or the whole leaf is missing by morning, it is likely to be caterpillars. Because the terrace is an open space and moths fly around quite freely, they may have laid eggs on the leaves the previous night. The eggs hatch into fat green caterpillars that hide on the leaves, well-concealed against the green of the stems.

If you suspect caterpillars to be the cause of the damage, take a good look at the leaves for droppings. Look closely at the upper surface of leaves just below the damaged spots, and you are likely to see some small, dark, peppery-like bits. If you look up, facing the direction from which the droppings have fallen, you may see a caterpillar clinging to a leaf vein or a stem, waiting for the night to fall.

What to do:

The best way to get rid of caterpillars is to have a good look at the leaves in the morning and pick them off by hand. If you have many potted plants, it may be a good idea to spray the leaves with an organic neem oil solution in the evening hours. It leaves behind a bitter taste for the caterpillars.

Neatly punched-out semicircular holes on leaves.

The Perpetrator: Leafcutter bee

Sometimes, the leaves of your rose or bean plants are decorated with beautifully punched-out semicircular holes, almost as if someone had used a hole punch to make pretty patterns. What is even more surprising is that the leafcutter bee is actually a beneficial insect. This bee slices out little semicircles from the leaves to make little leaf pockets to line her nest with.

What to do:

Take no action! She only takes a few leaves at a time, and she rarely strips a whole plant of its leaves. In fact, she is your friend, and you should leave her alone. This is a great incentive for you to let her help herself to a couple of leaves here and there. Her reward? She pollinates all your favourite rooftop flowers.

Discoloured spots on leaves that ‘drop out’

The Perpetrator: The ghostly fungus

Sometimes you might feel that there is no pest at all because you don’t see any holes or chewed-up leaves. Nevertheless, when there are discoloured, almost dead-looking spots with a ring of thin, weak-looking tissue around them, it is likely to be a fungal infection.

What happens is that spores land on wet leaves. If you are watering your plants in the evening, there may be some moisture on the leaves, which encourages the spores to germinate on them. The spores are minuscule, so they are barely visible, but the infection takes hold, and the plant begins to starve that part of the leaf of nutrients. This causes a round, dead-looking patch on the leaf, which finally dies and drops off, leaving a ‘shot-hole’.

What to do:

Avoid watering on leaves. Water only the roots, and avoid watering in the evening. The best time to water your plants is early in the morning. The spores will then die in the hot sun.

Torn edges with veins split and frayed

The Perpetrator: Wind and heat

Rooftops are windy places, and if your plants have broad leaves, such as gourds, papaya and beans, you may find that they have been whipped against uneven pot edges, bricks and sticks. Within a few days, the wind and sun will curl the edges of these leaves into browned, split strips.

What to do:

Make clusters of your potted plants so that they provide cool shade for one another. Stake the plants properly so that the stems are protected against the wind. You might even want to hang a light green shade cloth to protect your plants from searing heat and biting winds.

A Rooftop Gardener’s Quick Guide

A few simple measures are enough to prevent most pests and diseases in your rooftop garden. First, water your plants at sunrise when the sun is not very hot. Watering in the early morning ensures that your plants have enough water to get through the day, and any water that has fallen on the leaves dries up within a few hours.

Every fortnight, spray your plants with an organic neem oil solution. The spray will protect the plants from pests without harming the bees. To prepare the solution, add a teaspoon of neem oil and a drop of liquid dish soap to a litre of warm water. Shake well and spray the leaves on alternate evenings.

Grow companion plants such as orange marigold and basil to scent out unwanted visitors.

A good way to get rid of aphids and whiteflies is to grow these strongly-scented annuals such as marigold or basil among your vegetable plants. Their pungent aroma repels many insects.