Leaf Miner

He leaf miner It is a small fly that lays its eggs inside the leaves; when they hatch, the larvae emerge and create galleries or mines inside the leaves, giving rise to its name.

High relative humidity conditions are conducive to egg-laying, but, as with other insects, it is the ambient temperature that truly influences population development. Egg-to-adult development can take approximately 25 days at 20°C and about 15 days at 25°C.

Another factor influencing the development of leafminer populations is the cultivated variety. Generally, these insects do not cause significant infestations in indoor cannabis, but they are becoming increasingly common in outdoor and greenhouse crops in subtropical regions.

The larvae are responsible for the damage to plants by creating mines or galleries in the mesophyll of the leaves. The larvae are very active throughout their development, burrowing into the leaves with their chewing mouthparts.

Typically, leafminer larvae move within the leaf where the egg was laid, but they can migrate through the petiole when a food source is insufficient. The resulting mines destroy the photosynthetic organs of the cannabis plant.

Adult females also damage the plant, making feeding punctures and leaf punctures. These punctures are perforations made only by adult females on the upper surface of the leaves, while the male does not possess a piercing apparatus.

Explanatory video: Leaf miner

Control method

Prevention is more complex for outdoor crops because the plants are exposed to attack by these insects. Under favorable weather and varietal conditions, these insects can develop into veritable plagues.

In greenhouses, insect netting should be used to reduce the number of insects entering the premises.

Treatments with neem oil and garlic extract can be quite effective as repellents.

Attacks on indoor crops are less frequent, as gaining entry into the facilities is more difficult. Identifying their presence is simple: look for feeding mines and punctures.

Removing the infected leaves would solve the problem on a small scale.

When a severe infestation of leaf miners occurs in a crop, due to the insecticide resistance these phytophagous insects are able to develop, the smartest solution is biological control, using parasitic wasps. Diglyphus isaea y Dacnusa sibirica.

Removing host plants such as weeds is a common practice for preventing these insects.