Thrips are one of the most common pests in greenhouse cannabis crops. They are fast-moving small insects that feed on the plant sap. Despite being weak flyers, thrips can also act as disease vectors. If ignored, thrips can be a serious problem especially in the early stages of plants life (seedlings, cuttings, etc)
The Life Cycle of Thrips
Thrips develop through the following stages: egg, larval, prepupal, pupal and adult. An adult can live up to 30 days and can lay up to 10 eggs per day. Thrips insert their eggs into soft plant tissues, including flowers, leaves, and stems. The larval stage develops on the leaves, and the prepupal and pupal stages often develop on the growing medium. The pupa is a non-feeding stage during which the wings and other adult structures are formed.
The first step in controlling thrips is identifying them. Thrips are very small about 1.5mm in length. They can be dark or light depending on its life stage and species.
Signs of thrip damage on Cannabis plant
Both larva and adult stages feed on sap on the plant surface. They're found on the underside of the leaves, leaving white/yellow marks on the surface. The damage appears as white or yellow speckles on the leaves, unlike the feeding of mites and aphids which appear in random order. In severe cases, you can see black dots, which are thrip droppings.
Here are some examples of what thrip damage looks like on cannabis crops:
Thrips prefer to feed on buds, and new leaves, when scouting for thrips look there first. If the thrips outbreak is not controlled, the plant will become stunted and will affect the harvest.
How to control thrips on Cannabis plants?
- Conduct regular scouting and place yellow sticky traps to monitor thrip infestation
- Clear any weeds or fallen leaves from the plant that can provide shelter to thrips.
- Change the grow media when starting a new crop, used media can have thrip pupae that will hatch and reinfest the plant.
- Thrips are more commonly found during spring since they are attracted to flowers and other plants that are grown in the spring. Stay extra vigilant during this time.
- Thrip may also travel on clothes from outside that was in contact with the insects. Always change your clothes before entering the grow room.
Orius has a reputation in the agriculture industry for being one of the most effective biological control solutions against thrips. It is an aggressive predator that can control all stages of thrips, except the egg stage since it is laid inside the leaf. Adults can kill about 50 or more thrips a day.
Orius insidiosus 500 or 1000 adults with buckwheat hull in 4 oz bottle
Dicyphus is better known for controlling whiteflies but also feeds on thrips. It can control the nymph and pupa stages of thrips. It is a tough bug and has a long life and can establish in crops easily.
Dicyphus Hesperus (Mirid Bug) 250 adults with buckwheat hulls in a 4oz bottle
Swirskii is a microscopic mite that has a big appetite for its size. It prefers nymph stages of thrips and can consume up to 6 first instar thrips per day. It can also control other pests such as whiteflies, and various pest mite species such as spider mite.
Amblyseius swirskii available in 50K, 10K, or 5K mites in a cardboard shaker tube
Cucumeris is another microscopic mite that looks very similar to Swirskii. It prefers immature stages of thrips and can kill about 4 thrip larvae in a day. A complete life cycle takes 10-12 days. Cucumeris should be used earlier in the season as a preventative, it is not that effective later in the season when the temperatures are higher since the thrips life cycle is too fast. Use swirskii during this time for control.
Neoseiulus Cucumeris available in 50K & 20K mites in a cardboard shaker tube
Dalotia coriaria works very well against pupating thrips in the soil. These beetles are highly active in the soil and can fly from plant to plant, allowing them to quickly establish their population in various environments.
Dalotia coriaria (Atheta) 1000 adults mixed in buckwheat hulls for quick application.
|AtheLiv 1000 Breeding Pail Dalotia coriaria breeding pail contains all stages of the beetle, multiplying over time to create a long term introduction to the crop.|
Below is a breakdown of all the beneficial insects that can be used against thrips and what stages they control.