Leek Moth: the Second Generation
For the last couple of years leek moth has become an annual problem. There is no biological or chemical solution and the only way to try and minimise the problem is by understanding the life cycle of the little pests (the moderator of this site would not let me call them what I really want to call them).
Thanks to the RHS website for the following info:
The Leek moth (Acrolepiopsis assectella) is mainly a problem in southern England but it is spreading north. The adult leek moth is an inconspicuous very small (5-6mm) brown moth. Its larvae (caterpillars) feed on leeks and similar crops. The caterpillars feed within the foliage and stems or bulbs of leeks, onions and related vegetables. Main symptoms: white patches on leaves, with young plants rotting and dying. Small caterpillars may be seen in the plant tissues. Leek moth caterpillars are creamy-white with brown heads and small legs.
Symptoms
Control
The female moths can be prevented from laying eggs by covering susceptible plants with horticultural fleece, or an insect-proof mesh such as Ultra-Fine Enviromesh. Crop rotation should also be practiced to prevent potential build-up of moth populations under the fleece. Look for the white, net-like silk cocoons on the foliage and squash them.
None of the pesticides currently available to amateur gardeners for use on leeks and onions will give effective control of leek moth.
Biology
Initially the caterpillars mine the foliage but the older larvae bore into the stems and bulbs. When fully fed, the caterpillars are 11 mm long. They come out of the plant and pupate within net-like silk cocoons that are spun on the foliage. Adult moths emerge in autumn and overwinter in sheltered places.
In my experience the leeks will recover to an extent, but it is best to grow them under fleece or insect mesh if possible.
Thanks to the RHS website for the following info:
The Leek moth (Acrolepiopsis assectella) is mainly a problem in southern England but it is spreading north. The adult leek moth is an inconspicuous very small (5-6mm) brown moth. Its larvae (caterpillars) feed on leeks and similar crops. The caterpillars feed within the foliage and stems or bulbs of leeks, onions and related vegetables. Main symptoms: white patches on leaves, with young plants rotting and dying. Small caterpillars may be seen in the plant tissues. Leek moth caterpillars are creamy-white with brown heads and small legs.
Symptoms
- White patches developing on the foliage where the caterpillars have eaten the internal tissues.
- Tunnels in the stems of leeks and bulbs of onions, shallots and garlic.
- Affected plants often develop secondary rots and young leek plants may be killed.
Control
The female moths can be prevented from laying eggs by covering susceptible plants with horticultural fleece, or an insect-proof mesh such as Ultra-Fine Enviromesh. Crop rotation should also be practiced to prevent potential build-up of moth populations under the fleece. Look for the white, net-like silk cocoons on the foliage and squash them.
None of the pesticides currently available to amateur gardeners for use on leeks and onions will give effective control of leek moth.
Biology
- The Leek moth has two generations during the summer with larvae damaging the plants:
- From the first generation in May-June.
- And the second generation in August-October.
- The second generation is the more numerous and damaging.
Initially the caterpillars mine the foliage but the older larvae bore into the stems and bulbs. When fully fed, the caterpillars are 11 mm long. They come out of the plant and pupate within net-like silk cocoons that are spun on the foliage. Adult moths emerge in autumn and overwinter in sheltered places.
In my experience the leeks will recover to an extent, but it is best to grow them under fleece or insect mesh if possible.
Submitted by John, plot 16
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