Chiggers

(Question)

We have a garden on the harbour in Burlington, facing south with a bad infestation of chiggers.  What do you recommend to get rid of them?

(Answer)

We are sorry to hear that your garden has a chigger infestation.  The itch caused by the larvae of this mite can be infuriating.

Chiggers, Eutombicula spp. spend most of their life in moist soil.  The adult chigger lays its eggs in soil in early Spring.  After they hatch, the microscoptic larve climb onto surrounding vegetation and wait for potential hosts to wander by.  They then jump onto the hosts (which include mammals, birds, reptiles, and even some amphibians), find a tender spot of skin to attach themselves onto, and start feeding.  They inject into the skin a chemical that liquefies skin cells for consumption, and it is this chemical that causes the tremendous itching the host feels.  After feeding, the larvae drop onto the ground, where they develop into nymphs and later adults.  Adult chiggers die shortly after mating and egg-laying.  There are 2-3 life cycles per year, and chiggers that become adults in the Fall will overwinter in the soil or leaf debris, and reproduce the next Spring.

Chiggers generally prefer a warm, moist environment with overgrown vegetation, or shady, damp sites around stream banks, trees, and berry thickets.  They can also become established in a lawn.  The best long-term control is achieved through habitat reduction.  Prune trees, shrubs and any overgrown vegetation to let in more sun, and mow the lawn more frequently.  Clear all vegetative debris and weeds from flower beds or in and around compost bins etc… in order to reduce the protective covers for both chiggers and any small mammal hosts of the chigger larvae.  This is especially important in the fall as it will help reduce the number of overwintering adults and therefore reduce the initial population.

If mice, voles, moles, rats or other such mammals are present in your garden, it may be wise to contact a pest control company in order to address this issue, as chiggers need these hosts in order to survive.

To determine the exact location and level of infestation, one method is to put a piece of black cardboard, edge-side up, on the ground.  The chiggers, if present, will climb up and congregate at the top of the cardboard, appearing as miniscule yellow or pink dots.  Remember to wear protective clothing and use an insect repellent containing DEET before carrying out this exercise.  Showering and lathering with lots of soap after working in the garden is advised, as well as laundering any clothing, worn in the garden, in hot water.

While it may be temtpting to use insecticides, the Toronto Master Gardeners do not recommend chemical control.  If the infestation is severely hampering enjoyment of your garden, we suggest you contact the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) to see if they have suggestions for other methods of control.