Small mistake leads to mighty mite invasion, crop damage

By Samuel Janovici

It started as a minor violation of one of the golden rules of indoor growing: Don’t introduce a new plant into the garden without a reasonable quarantine period and a healthy dose of Azatrol. The new strain was from a friend, a respected grower, so he put the clones of a new variety straight into the main clone room for a few days before moving them to the veg-room.

That was the last chance to notice the spider mites before they traveled into his healthy, bug-free environment to breed in near-perfect conditions.

Spider mites are usually less than 1 mm in size and they produce small, spherical eggs. The hot, dry conditions of an indoor operation are the perfect breeding ground for a population of spider mites. The two-spotted spider mite that infested this crop can hatch in as few as three days, and become sexually mature in as few as five. One female can produce up to 20 eggs per day and live for 2 to 4 weeks, laying hundreds of eggs.

Mites inhabit the underside of the leaf and are not easily seen. The first indication is tiny brown spots circled by small yellow patches. That’s where mites have punctured the leaf surface and sucked the plant’s sweet juices. As the population grows they begin to build webs and can be seen migrating from one feeding area to the next.

Three weeks into the flower cycle, the grower needed help. The crop was infested to a point that webs were going to appear in the next three days, but he still needed three weeks for Urkle and at least five for the new strain, Headband. He sought an organic solution to save as much medicine as possible without using a miticide-insecticide like Avid that would toxify his medicine. Avid is for ornamental plants only.

Since the crop was in its third week of flowering it was impossible to use a horticultural soap. Instead, the grower used large doses of CO2 lasting up to five hours a day for two weeks, dropping the temperatures and the humidity as low as was healthy for the plants. He released Pyrethrin Bombs and increased the air circulation. The plants flourished, but so did the mites. The CO2 and the cold did slow them down and the Pyrethrin would have been more effective sprayed directly on the invaders, but that could have created a mold cycle in the maturing buds.

In the final week of the Urkle the webs began to appear. They were removed with the help of a low-volume vacuum cleaner that wouldn’t harm the buds, but the plants were weakening. Pyrethrin spray was the last resort for the Urkle. The combination helped save that half of the crop. Unfortunately, the Headband was a total loss, but it was a valuable lesson in humility and a reminder to always follow good, safe gardening practices.

Stay safe out there.