First of all, what the heck is relative humidity and secondly why is it important?
Relative humidity is a way of describing how much humidity is present in the air, compared to how much there could be. For example, the meteorologist on your local news station likely uses the relative humidity as a measurement to describe the weather in and around where you live.
When the temperature is warm, more water vapor can be present in the air than when it is cold. The relative humidity can tell you if the air feels dry or not. The value is usually written in percent, where 0% means that the air is totally dry, and 100% means that it is so watery that mist or dew is about to form. So when weather man Dan says the relative humidity is going to be 90% you know to bring an extra shirt to put on after your stroll in the park.
Now that our mini science lesson is over, what does that all mean in relation to your cannabis crop, the bugs you want there, and the ones you don't?
Relative humidity effects the reproduction of both pest insects as well as beneficial insects. Many of the pest insects, such as spider mites, thrive in the same relative humidity levels that are best known for flowering cannabis. Most beneficial insects, however, do not cycle well in these conditions. The chart below lists the ideal relative humidity for all the beneficials used for the most common cannabis pests.
IDEAL RH% FOR BENEFICIAL INSECTS
| Beneficial Insect | Temperature | Relative Humidity |
| Adalia Bipunctata | 24-28°c | 70-80% |
| Aphidoletes Aphidimyza | 21-25°c | +70% |
| Chrysopa Carnea | 15-30°c | n/a |
| Aphelinus Abdominalis | 21-25°c | 60-80% |
| Aphidius Colemani | 21°c | 60-80% |
| Aphidius Matricarae | 18-25°c | 60-80% |
| Aphidius Ervi | 18-25°c | 60-80% |
| Hypoaspis Miles | 12-18°c | +85% |
| Nematode Steinernema Feltiae | 5-25°c | 100% |
| Atheta Coriaria | 21°c | 60-90% |
| Phytoseiulus Persimilis | 21-29°c | +70% |
| Amblyseius Californicus | 16°c | 40-60% |
| Feltiella Acarisuga | 27°c | 60-95% |
| Amblyseius Andersonii | 20-25°c | 85% |
| Orius Insidious | 21°c | 60% |
| Amblyseius Cucumeris | 18-20°c | 70-80% |
| Amblyseius Degenerans | 15-25°c | 60-85% |
| Amblyseius Swirskii | 25-28°c | 70% |
Our recommendation? Treat your plants for pest bugs when they are seedlings, clones, or small plants in veg. Typically the humidity levels in these stages of cannabis plant growth are higher and lend positively to beneficial reproduction. Not to mention that treating smaller plants, preventatively, is easier on the pocket book then treating an infestation on large plants in flower. Preventing pest damage before it even starts can only benefit final yields and product quality.
If you are looking for more information you can read about each of our beneficial bugs here.