Mango
Blue-striped Nettle Grub
Parasa lepida
Insect
In a Nutshell
- Holes chewed in leaves.
- Loss of whole leaves due to feeding.
Mango
Symptoms
When caterpillars are young, they eat the bottom layer of the leaf. The damage often begins from the tip of the leaves where the eggs are initially laid. They then move to the edges of the leaf and eat a lot of it. As they grow, they eat the whole leaf, starting at the tip and leaving only the middle part of the leaf with visible marks. As a result, the plants are not able to photosynthesize properly, leading to reduced yields in crops. If the attacked plant has fruits they can drop before maturity. Caterpillars can be spotted feeding in groups. Excrement (frass) of the caterpillars is visible.
Recommendations
Organic Control
To control the pest without chemicals, physically removing the caterpillars from affected plants is an option. This should be done using a pair of tweezers or a piece of tape, without touching them directly. Light traps can also be set up to trap and collect adult moths. About 5 light traps may be installed per hectare to effectively control the pest.
Chemical Control
Select the appropriate insecticide for your specific situation, following the label instructions carefully, and wearing protective clothing and gloves when applying it. Spray only if the infestation is severe.
What caused it?
The damage is caused by the Blue-Striped Nettle Grub. They are mostly tropical and can be present all year round. This moth goes through several stages in their life cycle. It starts with the eggs that are laid on the leaves of plants. Once hatched, the young caterpillars begin to feed on the leaves. During growth, they renew their skin several times and replace it with new one. Eventually, they form a cocoon around themselves and pupate. After a period of time, adult moths emerge from the cocoons and start the cycle again. The grubs of this insect have green bodies with three pale blue stripes and grow to be 3-4 cm long. The cocoons look like large seeds with a hard papery shell covered in silk. Female and male moths have a similar colour pattern. They have a yellowish-green head, reddish-brown body, dark red-brown legs and a brown edge on the outer part of the wing.
Preventive Measures
- Infestations are initially limited in one area.
- The caterpillars can be collected by hand and destroyed.
- Look for the cocoons in the same area and destroy them too.
- Look on the trunk, on the leaves and on the ground.
- Cocoons are usually laid side by side.
- Purchase plant material only from clean, accredited suppliers, and preferably material that is certified.
- Blue-striped nettle grub may be moved to new places through plant material contaminated with eggs or larvae.
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