Predatory mite sachets are the first line of defence against pests in most good IPM plans. However, in order for them to effectively suppress pests, they need to be handled properly. Below I will discuss what predatory mite sachets are, how they work, and what you need to do to get optimal results!
What are they? Predatory mite sachets are essentially mini breeding systems that contain all life stages of mites. Multiple generations are bred in the sachets for 5-8 weeks, slowly emerging on to the plant over time in search for pests. They work best at the start of the season as a preventative control method when pest populations are low.
How do they work? Most predatory mite sachets consist of 3 main components: yeast, feeder/host mite, and the predatory mite.
Step 1: Sterilized bran is mixed with a yeast mixture, which will be a food source for the feeder mite. The yeast thrives in a shaded and humid environment (RH 70% or more). This is why it’s so important to place sachets inside the plant canopy where humidity is higher, and temperatures are cooler than ambient climate.
Step 2: Feeder mite will feed on the yeast and build its population in the sachet.
Step 3: Predatory mite use the feeder mite as its food source to create multiple generations inside the sachets. Sachets normally last 4-6 weeks before requiring a replacement but if they're not handled properly they may only last for up to 2 weeks.
How to get the most out of predatory mite sachets?
To achieve optimal results the most important factor is humidity. If there isn’t enough moisture the yeast will dry up and end the entire food chain. The predatory mite eggs and larval stages are also very sensitive to low humidity, constant dry conditions will significantly decrease the egg hatchability rate. The relative humidity for sachets needs to be at least 70% or higher.
Tips to keep humidity high:
- Place sachet inside the plant canopy where humidity can be up to 25% higher and 2-5 °C cooler than the ambient climate.
- Don’t hang sachets in areas with strong winds from ventilators/fans
- Avoid direct sunlight, it dries the sachets microenvironment and creates excessive heat which can kill the mites quickly.
- Don't make the release hole bigger for faster release as this will reduce the moisture in the sachet and shorten its life span significantly.
A. van Westreenen , N. Zhang, J. C. Douma, J. B. Evers, N. P. R. Anten, L. F. M. Marcelis (2020) Substantial differences occur between canopy and ambient climate: Quantification of interactions in a greenhouse-canopy system, DOI: https://doi.org/10.1371/journal.pone.0233210
Rosemarije Buitenhuis, Erik Glemser & Angela Brommit (2014) Practical placement improves the performance of slow release sachets of Neoseiulus cucumeris, Biocontrol Science and Technology, 24:10, 1153-1166, DOI: 10.1080/09583157.2014.930726