Keep the enemy at bay | Daily News
Pest threats

Keep the enemy at bay

What pests and diseases do is, they prevent a good harvest. They undo all the good work done in the home garden and bring down the morale of the entire household. After all the meticulous work done by the home gardeners, these pests and diseases lay waste to the garden.

Green Thumbs speaks to Agriculture Instructor, Agriculture Instructors Office, Homagama, Indika Gunasena on identifying the Pests and Diseases that undo the work of a home gardener.

Indika Gunasena

“We know that for most of this year, people have been confined to their homes because of Covid19. We know that people devoted most of their time to maintaining home gardens that provided a bountiful supply of fresh food. They were encouraged to grow vegetables and fruits. So when a home gardener is unable to harvest that is upsetting. This is why it is essential to know about pests and diseases. First, we need to identify these pests and diseases and then control them,” said Gunasena.

When we take diseases there are mainly three. Fungal Diseases, Bacterial Diseases and Viral Diseases. From these, Fungal diseases are the most common. This is very common in the Wet Zone and throughout the island. However, if you take Cucurbits plants such as Snake Gourd, Bitter Gourd and Karawila, they are mainly attacked by viral diseases. The symptom is leaf curling. What these diseases do is, they change the plant physiology. It contaminates the plant. It prevents the normal functions/ processes of the plant.

“These diseases occur due to environmental problems. That is when the rainfall is in excess and when the plant media is unsuitable. Of course, sanitation issues result in bacterial problems. If you take viral diseases, these occur through transmission methods such as the wind and animals,” stated Gunasena

Nutritional deficiencies

Another problem the Home Gardener has to deal with is nutritional deficiencies. These deficiencies happen due to problems in the soil, water logging and climatic conditions. It is also due to environmental problems, such as when you keep a sun loving plant in the shade. The plant is not able to absorb the nutrients.

“Pests are another big threat to the home garden. Pests can be divided into two. Pests that are visible to the naked eye and pests that are not visible to the naked eye. Now Pests that can be seen by the naked eye can be controlled but pests that cannot be seen with the naked eye are a little difficult to control,” explained Gunasena.

If you take Mites and Ticks, these cannot be seen with the naked eye. And what they do is they suck in the contents of the leaf causing big problems. Pests that can be seen by the eye are snails, rats and bugs. If you take the leaf eating caterpillar, that is a Pest that can also be seen with the naked eye.

“Stem-borer is another problem in the home garden that causes a lot of destruction. It can attack banana plants. Another big threat is the White Fly. It spreads viruses. If you take Eggplant, Chili, Capsicum and Tomato, viruses are transmitted to these plants by the White Fly. It is a tiny white fly and it is a very dangerous pest and it must be controlled,” pointed out Gunasena.


We are told that Caterpillars have chewing mouthparts. If left unchecked, Caterpillars are known to severely damage a crop as they feed on a variety of plants. Some Caterpillars consume entire leaves and others just nibble holes in them. Some feed on the leaf surface, scraping away the top layer and causing damage. Some caterpillars feed voraciously and are known to strip a plant nearly bare.



Red Spider Mites

The tiny mites live under leaves and suck sap, causing yellow mottling. Fine webs are sometimes visible.

Gall Mites

These microscopic mites suck sap and cause abnormal growths. These include raised pimples or clumps of matted hairs on leaves, or enlarged buds. Most are harmless and can be tolerated.


Bagworms are the larval form of a moth that attacks evergreens and other trees. The worm inside each bag feeds on the evergreen bush or tree, building a case around itself for protection from predators. The case is made from bits of the plant the insect is feeding on and slowly enlarges over time as the insect grows. Females lay eggs in the bags in late fall.

Japanese Beetles

Japanese beetles aren’t picky about what flowers they chew and even attack the otherwise pest-proof purple coneflower.

Leaf Miner

Leaf miners create discolored blotches or surface trails on leaves. Most leaf miner damage is relatively harmless and can be left untreated.

Winter Moth

In spring, the leaves of fruit trees are webbed together and hide green caterpillars inside. Holes are visible when leaves expand.


Aphids leave a sticky substance called honeydew on plants, which can allow black fungus to grow.

Viburnum Beetle

Both the adults and larvae eat holes in the leaves.


This tiny black sap-sucker, known as ‘thunder fly’, causes white patches on the petals and leaves of indoor plants, and also peas, leeks, onions and gladioli.

Vine Weevil Larvae

Small cream grubs with a brown head feed on plant roots, especially those growing in containers or with fleshy roots. This can cause plants to suddenly collapse.

Adult Vine Weevil

The adult beetle is nocturnal, flightless and makes notches in leaves.

Cabbage White Caterpillars

These voracious eaters decimate brassicas and nasturtiums.

Tomato Moth

The tomato moth damages fruits.

Rose Slug

A rose slug is the larvae or immature stage of a rose sawfly. It’s easy to overlook on roses, until its feeding begins to damage leaves. Rose slugs feed on leaf undersides, out of sight, nibbling on leaf tissue — the part between the veins. When they’re done eating, leaves resemble skeletons. Usually when gardeners spot rose slug damage, they think their roses have a disease because leaves are speckled and have holes in them. Sawfly larvae are not slugs or caterpillars, but a different type of critter.


When grasshoppers hit your garden, nothing is safe. These insects chew their way through leaves, flowers and fruits without stopping, eating up to half their body weight per day.

Sawfly Larvae

The caterpillar-like larvae devour the foliage on plants such as roses, gooseberries and Solomon’s seal. Leaf rolling is usually the first sign of sawflies.


Mostly beneficial, earwigs are nocturnal and feed on dahlia, chrysanthemum and clematis flowers.

Cabbage Looper Caterpillar

This pest is very destructive due to its voracious consumption of plants in the cabbage family.