Insects and Fungal Disease in Hawaii

Mites (polyphagotarsonemus latus, broad mites), whitefly and armored scale are the three bugs that will present the biggest issues for marijuana growers in Hawaii.

For mites and scale I've found proactive spraying with Avid (a miticide made by Syngenta - Avid 0.15EC) is the best way to control and eliminate outbreaks.

Although pricey (approx. $95 for 8 oz) it only takes 2ml to treat an entire gallon of water so that small bottle should last years.

Even though this product claims to breakdown over 30 days I never apply it to flowering plants. That way none of the consumable material at harvest would have been exposed to it. Avid has a systemic effect that lasts long enough to be effective if you give the plants one last application before sending the batch into the budding cycle.

To treat, make a mixture (2-3ml per gallon) and place into a pressure sprayer. Before using, wear full protective clothing; long sleeves shirt and long pants with socks and shoes. Also add gloves and full facial protection. Should any get onto your skin, wash off the affected area with water immediately.

Apply the Avid mix to every part of the plant; the leaves (top and bottom) to stop the mites and the stems to keep the scale at bay.

Whiteflies are a little challenging to deal with as they tend to be far more resistant to chemical solutions.

For this bug one must be on guard and act the moment the first signs show themselves. Neem oil sprays can be somewhat effective for killing the eggs, but the best way to eliminate them is to use a vacuum and painstakingly work your way through the plant, sucking off each "mini colony" you can find on the leaves.

Concentrate on the undersides of the plant as whitefly try to shield themselves from sunlight. The use of yellow sticky traps can help lower populations significantly in the battle to control this pest.

Powdery mildew is a fungal disease that is also common to Hawaii. It is far more prevalent during the winter rainy months.

Most cannabis varieties are fairly resistant providing they are in a well ventilated area.

A very effective fungicide called Eagle 20EW made by Dow Agro Sciences can be used proactively if powdery mildew proves to be an issue. Use as directed and wear protective clothing as this product is also systemic like the miticide.

I would also not recommend using this product during the flowering phase.

Fundamentally the reason I advocate for fast flowering plants (8 weeks or less) is to afford bugs the least opportunity to infect and establish their colonies on the plants. We do not want to spray the plants with any chemicals during the flowering phase so as to avoid ingesting those toxins ourselves upon consuming the end product after harvest. Furthermore, fast maturing plants grow smaller buds making them much less susceptible to bud rot (Botrytis cinerea/gray mold).

There is not much one can do to prevent bud rot other than growing a different cannabis variety or harvesting the existing one prematurely.