 Leaf miner damage is generally attributed to larval feeding or "mining" of leaf tissue between the upper and lower surfaces. Mining of the leaf tissue may cause desiccation (drying), browning and premature defoliation. In certain cases, the leaves may become thin, papery and translucent and the two leaf surfaces can be peeled apart. When examined closely, black pellets can be seen within the tunnels as a result of faecal deposition.
Adult leaf miners can be moths, beetles, or flies, and the tunnelling patterns of their larvae vary depending on the nature of the insect. For example, an aspen serpentine leaf miner creates winding or meandering tunnels whereas a birch leaf miner creates large blotches. Serpentine miners are also known to attack herbaceous perennials such as columbine. For most deciduous ornamentals, leaf mining has a negative effect on appearance rather than on plant health. However, leaf miners also attack an array of vegetable crops and can have a detrimental effect on yield due to defoliation. They are particularly damaging to vegetable crops in which the leaves are consumed such as beet, spinach and Swiss chard.
Adult leaf miners can also cause severe damage to the foliage. Basswood adult leaf miners are beetles that will begin feeding on the upper leaf surface, skeletonizing the leaf tissue. When infestations are severe, entire leaves may appear skeletonized as the tissues dry up. Dead tissue may remain in place but mined leaved usually dry, shrivel and drop off the branch prematurely. Repeated severe infestations will reduce plant health and growth rate and on occasion, can kill a tree.
Source : http://www.umanitoba.ca/afs/hort_inquiries/deciduous_ornamentals/leaf_miners.html |
