LEAF MINERS

Leafminers on greenhouse crops are larvae of small flies (Diptera) in the family Agromyzidae. There are about 150 species of leaf miners in this family that have been recorded from cultivated plants. A diagram of a typical leaf miner life cycle is shown in (Figure 1.) . There are four life stages: egg, larva, pupa and adult. The pupal stage normally occurs off the plant -- in potting media, under benches, etc. At present, there are two main leaf miner pest species on greenhouse ornamental and vegetable crops, Liriomyza trifolii (Figure 2.) and L. huidobrensis (Figure 3.) . Occasionally another species, Amauromyza maculosa (Figure 4.) has been found infesting garden chrysanthemums, but to date there have been no widespread infestations. Both L. trifolii and L. huidobrensis can infest a very wide range of host plants in greenhouses and outdoors.

Leaf miner adult females puncture leaf surfaces with their ovipositors (egg-laying devices). Both sexes feed on the fluids that ooze from these punctures. Eggs are deposited in some of the punctures. Leaf punctures are one of the methods used to detect an infestation, and are shown in Figure 5 and Figure 6. After hatching from the eggs, larvae feed between the upper and lower leaf surface, making trails or mines (Figure 7) . Leaf mines of L. trifolii are easily seen from above, but sometimes the mines made by L. huidobrensis are best seen from below. Mines made by A. maculosa tend to be blotch-like. Leaf mines detract from a plants appearance and heavy infestations can kill plants. So, at the very least, leaf miners can make plants look terrible. At worst, plants can be killed.

Leaf Miner Management

There are both chemical and biological control options for leaf miners. The key aspect of management is to detect the infestation before it becomes too difficult and costly to deal with. Plant inspection is one detection method. Another method is to use yellow sticky traps, placed slightly above crop height (Figure 8) . Use 4 to 8 traps per acre. If traps are used, one must have the ability to distinguish between leaf miners and the other small flies (e.g. shore flies) that are attracted to yellow. The chart below (Table 1),includes both chemical and biological controls, and their application rates. A new product, not yet registered in greenhouses, but on outdoor ornamentals is Conserve SC. If an infestation is well-established, it will be necessary to make a series of applications, at 7 to 10 day intervals. Do not use the same pesticide, or pesticide combination, more than three times in sequence.