Spider Mites Eating Up Your Profits? In commercial grow operations, plant pests are one of the top causes of decreased profitability contributing to poor plant health, quality, and yields. One such pest that should be at the top of a commercial growers most “unwanted list”, is the spider mite. These tiny arachnids can rapidly infest crops, causing tremendous amounts of damage by extracting plant liquids, and in some cases spreading disease. The most common spider mite found in a greenhouse is the broad mite, as well as the carmine spider mite, cyclamen mite, the Lewis spider mite, and the two-spotted mite.