Sunday, June 16, 2013

Stanhopea Pests

Stanhopea are relatively pest free orchids when compared with other genera.  The common pests are snails/slugs and spider mites.  For me the snails/slugs are a constant battle, and are the more serious pests.  These mollusks can damage new growth, inflorescences, and flowers.  They usually do not have any more of an impact on a plant other than cosmetic damage, though long term damage can occur if they continually eat new growth and prevent the plant from growing well.

Bush snails (orchid snails)

I use metaldehyde based snail and slug bait (e.g. That’s It) to control these pests that is a granular form, and doesn’t leave a meal residue in the pots and baskets. I also have been recently trying “Sluggo Plus” suggested by a blog visitor.  This product breaks down into iron and phosphorus which plants benefit from, and it is less environmentally damaging. "Sluggo" seems to be a good product to use and does not adversely impact children, pets, and wildlife in the amounts used as directed.

Spider mite spots on leaves of Stanhopea.
Spider mites on underside of plant
leaves. From Got Pests? website
Spider mites can be a problem for Stanhopea and are generally noticed when light yellow spots appear on the leaves in large numbers.  I have had very few problems with spider mites in my collection perhaps because I grow most of the Stanhopea outdoors where spider mites have to deal with predators.  That being said, environments that are low in humidity and dry often allow plants to harbor spider mites. The best control I have found for these is to apply a rosemary oil based mite control (e.g., SNS-217) to the leaves and pseudobulbs every few weeks.  This treatment removes the spider mites and then you can ensure that they don’t return by increasing humidity in the environment and checking your plants often to spray again when necessary.  These rosemary oil based sprays are organic and pose less of a threat to pets and wildlife.

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