Orchid Blossom Midge

Today on my first field trip in Barbados I learned about a new disease called the Orchid Blossom Midge, it is a recently arrived pest to orchid growers. I have found some information in regards to the disease that I would like to share with my readers.

The orchid blossom midge is a member of the gall midge family (Cecidomyidae), so named for the galls that form in plants attacked by some species during their larval stage. The orchid blossom midge is polyphagous (feeds on many types of plants) and will attack orchid buds and flowers. This can cause bud blast, as well as damage and deformity to the developing floral tissues. Because the midge larvae flourish in conditions with high humidity and require a damp medium in which to pupate, they thrive under conditions ideal for growing orchids.

Life Cycle - The small, flying adult midges lay large quantities of eggs in flower buds. The eggs and developing larvae are virtually undetectable inside the closed bud, until the damage from the feeding larvae becomes evident - Midge larvae are small (approximately 7/64–1/8 inch [2.5–3 mm] in length), white, and resemble fungus-gnat larvae in appearance. At maturity, larvae jump from the plant to the surface of the potting medium by curling and uncurling their bodies in a springlike fashion for propulsion. They then burrow into the top layer of the medium to pupate. The tiny adult flies emerge about three weeks later. Symptoms Evidence of possible orchid blossom midge infestation includes bud blast, brownish spots that appear chewed, holes in buds and floral tissues, and fungal infections that may follow in areas damaged by the midges. The midge larva is most prevalent in temperate areas and can be identified by their presence inside unopened flower buds. Under favorable conditions, this pest can become entrenched within 14 days. A serious infestation can be devastating, rapidly destroying an entire flowering if left unchecked Controls - Remove all damaged, molding or dropped buds. Eradicate weeds in the growing area, as well as in and around plants - Applications of pesticide may be useful, such as Diazinon granules to the medium to eradicate burrowing larvae and Orthene (used with a penetrant such as LI 700) to foliage and buds to control egg-laying adults and larvae. - Biological controls, such as Hymenopteran predatory wasps, have proven effective against other gall midge species, and may be useful for C. maculipennis as well.