One of the best ways to control a pest population is to catch it before it becomes a full fledged pest infestation. Using proper monitoring practices and skilled scouting is essential to catching a potential issue in your cannabis crop. This will be a mini three-part series - this first post will cover what types of pest damage and signs to look for, part two will focus on pest identification, and the final post will suggest tools and practices for catching pest bug populations before they turn into infestations.
Integrating monitoring into day-to-day activities of watering, de-leafing, and transplanting will reduce the amount of time that you need to dedicate to the task. Many of the pests that attack cannabis are small and often go un-noticed until plant damage is present. Plant damage to look for:
Caused by the two-spotted spider mite, stippling occurs when the pest pierces the leaf from the underside with their long, needle-like mouth parts. The mite vacuums out the sap, the leaf tissue collapses, and a small spot is created at each feeding site.
Scratching is caused by the Western Flower Thrip. This pest scratches the top side of leaves to find a satisfactory feeding spot. Then, using brute force, they punch a hole in the leaf and eat the contained sap. This damage will have an almost reflective, slivery appearance caused by the dried sap that is left behind.
Aphid damage is much more subtle than spider mite or thrip damage. The aphid does eat sap from the leaves but is much more delicate and when the plant starts showing signs of wilting, yellowing, and leaf curling the infestation will already be in full swing. One of the early signs of aphids in your grow, are the presence of their exoskeletons. As the aphid grows it must shed it's outer layers to make room for its new, larger body. These 'casting' will appear as white debris that can be removed with a wipe or shake from the leaves.
The damage caused by root pests is near invisible but can cause nutrient deficiency and wilting in your plants. Pests such as Fungus Gnat larvae and Rice Root Aphids eat the small root hairs of a plant. This inhibits the plant's ability for nutrient and water uptake causing wilted leaves. Checking the roots during transplants is an easy way to catch root pests.
Long winding lines on your leaves is the work of a leaf miner. There are multiple species of insect larvae who create this type of damage. Adults lay eggs on the surface of the leaves and the hatched larvae dig their way into the leaf. They then begin to eat their way through leaf tissue staying cocooned between the upper and lower surface areas.
Hole damage is almost always a sign of caterpillars in your grow. The title of the popular kids book 'The Hungry, Hungry Caterpillar' is an accurate description of caterpillar behaviour. An infestation of caterpillars can easily defoliate an entire crop in a few days. The good news is that caterpillar damage is easy to spot. If you don't see and caterpillars the may be coming out at night as some species are nocturnal.
Webbing created by two-spotted spider mites is a sign of a full blown infestation. If webbing is found, immediate and large scale control will be needed to control the population. The webbing will inhibit the growth of the cannabis plant.
Black sooty mold develops from the honey dew secreted by pest bugs such as aphids and white flies. The honey dew will sometimes also attract ants so be on the lookout.
As we always say prevention and early detection are crucial. Please feel free to print our quick pest damage reference guide below!