Wednesday, June 25, 2008

Greenhouse and Nursery - Leaf Miner in Garden Mums

Garden mum growers should be on the look out for a number of pests. On is the serpentine leaf miner. The following is information on this pest.

Different species of leafminers feed upon different plants. Leafminers may be either wasp, fly, moth or beetle species. One of the more common leafminer species is Liriomyza trifolii that infests many floral and vegetable crops, especially members of the Compositae family. This species attacks chrysanthemum, and gerbera daisy. It caused serious problems in the cut mum industry in the 1980's and was notoriously difficult to control.

Growers of garden mums should be on the lookout for the damage caused by this species. Look for narrow mines that wind around the leaves, with some brown tip dieback. Herbaceous perennial growers have also noted seeing Liriomyza leafminer damage on Helenium, Leucanthemum, and Gaillardia as well as others in recent years.

Adult leafminer flies puncture holes in the leaves as they lay eggs. Look for white specks from these egg laying punctures. (See photo). Leafminer adults may be confused with shore fly adults. However, adult serpentine leafminer flies have yellow markings on their abdomen whereas shore flies do not. With a hand lens, you can also see a cannon-shaped ovipositor or egg-laying device on the females rear end.

As the larvae feed, winding (serpentine) mines develop. Leafminer larvae are in a protected location as they feed between the upper and lower leaves making control difficult. If only a few plants are affected, removal of infested plants or leaves may help. Some greenhouse growers use yellow sticky tape or ribbon to help mass trap out leafminer adults. Once larvae are inside the mines, often insecticides with systemic or slightly systemic (translaminar) activity work best such as acephate (Orthene).

Information from the New England Greenhouse Update.

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