Answer: Earwigs are among our least favorite insects, but they do serve a positive function of eating aphids in the garden. If you have a heavy infestation of aphids, this could be helping to attract the earwigs. Aphids can be treated with insectidical soap, devoured by lady bugs, or knocked down with a strong spray of water frome the garden hose. I would not suggest washing them off in your case however, since earwigs like moisture.
Earwigs tend to build up in an area with decaying organic matter combined with constant moisture. Watering regularly at night, a wet spell of weather, overly thick organic mulch, and decaying plant material can all make an area attractive to them. If you can make the area less attractive to the earwigs, they should decline in number.
Pull mulch several inches away from plant stems, keep mulch layer only about two inches deep, avoid watering at night, and direct excess surface moisture, such as runoff from gutters, away from the planting area. Keep the mulch several inches away from any building foundation as well.
Deadhead spent flowers and remove any damaged diseased or rotting foliage from the garden as soon as it occurs. Fluff the mulch with a rake to help it dry out after rainy spells. Avoid daily sprinkling or light watering in dry weather, instead, water deeply less often.
Next, you can try catching and trapping them. Although time consuming, hand picking at night by flashlight can help bring a population back to manageable levels. When the population is very high you will also have some success trapping them in rolls of damp newspaper or cardboard tubes sealed at one end, filled with drinking straws set parallel to the tube, and set at intervals around the garden. Each morning, shake out the rolls to dislodge the earwigs that will have taken shelter inside and dump them in a bucket of soapy water.
Sevin is a typically recommended chemical control for this garden pest, but a dust should not be so visible if applied correctly, meaning very lightly, with a duster applicator made for the purpose. This would be a less toxic control than diazinon (an outdated chemical being phased out of use by the government) and mothballs are simply not recommended for garden use. If you use carbaryl (the ingredient in Sevin) or any chemical control as a last resort, be sure to read and carefully follow the label instructions and cautions.
I would suggest, since the problem seems to be extreme, that you also consult with your county extension for suggestions as to what to do to prevent them from possibly entering adjacent buildings such as your house or garage since they will sometimes come in through a basement or along a slab foundation. Your county extension should also be able to advise you of the most up to date chemical controls recommended in your state if the other methods are not working for you.
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