I’m back again with another entry in the Know your enemy series, this time I’d like to talk about Franklinellia Occidentalis, or the Western Flower Thrip.
This particular pest is more economically damaging for people that grow ornamental flowers, but in the cannabis space they can be a real nuisance due to their fast ability to spread and the potential difficulty in controlling their reproductive cycle. Furthermore, they generate a surprisingly large amount of excrement that they will leave everywhere they go, which could potentially vector bacteria and contaminate your flowers in the event of a large infestation.
Biology:
Thrips have a six stage life cycle: Egg , two larval stages , prepupal, pupal, and Adult. Larvae and adults are found in the foliage and are the stages that are damaging to the plant, however in order to pupate they drop down and burrow into the soil. This adds an additional dimension to your control plan, because if you don’t do anything to treat the soil you’re a lot less likely to be able to get a firm grip on a problem.
The first signs you’ll find of an infestation are silverfish-gray scratches on your foliage, their feeding method is termed “rasping” and they leave very distinct scars on your leaves, as well as clusters of black specks which mark their excretion sites.
Controlling thrips should come along nicely with your overall IPM program for your grow. Most chemicals that you would be using regardless are also effective against thrip and many beneficial insects will also control thrip in addition to others. The main predators of thrip that I make use of are:
Amblyseius Cucumeris – This mite is an excellent predator of early stage thrips. Specifically eggs and the first larval stage. Its not large enough to consume the second larval stage and adults, however it is an integral part of the control plan for its ability to manage the beginning of their reproductive cycle. Available in slow release sachets for preventative dispersion
Orius Insidiosus – One of my personal favorite predators, they are excellent at controlling all life stages of thrip and they are capable of flight and thus are highly mobile. Its also quite easy to establish and maintain a banker system for these insects so if anyone is curious about that just drop me a comment or a DM and I can walk you through it. Release throughout the grow, they spread quickly although they are hard to spot again once dispersed.
Dalotia Coriaria – Also known as “Rove Beetles” these are my favorite soil dwelling predator and will be terrific at managing the pupal stage of thrip in the soil. I have also worked out an effective way to breed these insects as well that I would be happy to share if anyone is interested. Its a lot of work and I have since stopped, but over 1.5 years after stopping the breeding program im still finding them in the greenhouse so they seem to have become firmly established.
Hypoaspis Miles – Everyone’s favorite soil mite, also excellent at controlling soil pests. Not as flashy as the Rove beetles, but that’s not their fault.
Chemical Controls:
Really any biological insecticide should be effective as canopy treatments vs. Thrip. Azadirachtin, Grandevo, Botaniguard, etc all good. For treating the soil, I usually drench with Molt-X and beneficial nematodes. Both of which are pretty compatible with soil predators (For all intents and purposes just meaning <25% pop kill so take that for what it is)
Lets get a discussion going, how do thrip impact you guys?
Additional image of adult thrip caught in the act: