Planting Herbs for Bug Control in Maryland
Answered by: Conrad Richter
Question from: Laura Ivey
Posted on: April 21, 2002

I am about to start living in a part of Maryland which is renowned for its bug life - mosquitoes, chiggers, fleas, ticks, no-see-ums - which make it difficult to be outdoors in the mornings and evenings, i.e. the cool parts of the day in summer. So I am thinking about sowing herbs which smell bad to bugs in what passes for lawn (3 acres), planting shrubs and trees with similar effect around the perimeter and in the marshy culverts which serve to drain the soggy places. The state will spray for bugs, too, but it seems to me I would like to do my part naturally, too.

The property is full sun, sandy soil, high water table, high humidity in summer, winters are mild. For example, no snow at all last winter, and few days in a row below freezing. Loads of hungry deer. Deer don’t like to eat things that smell bad, so it may be that bug repellent plants will also not taste good to deer. Native species which might help are eastern red cedar, and a number of things which increase the bird life. Already am building a purple martin apartment house, bats already live there, so I am thinking about improving the plant life.

I know that pennyroyal works in my garden in Washington D. C., but I am sure there is a longer list! Any ideas? Any information on seed suppliers (bulk seeds that is)?

While it is true that some herbs can have repellent effects when growing in an area infested with mosquitos and other pests, just how effective they are depends on what your expectations. If you are looking for complete absence of biting insects, that is not going to happen with herbs. But if you are hoping for a reduction, even a slight one, then herbs may help.

You can read answers to previous questions about mosquitoes in the "Q&A" section of our website (http://www.richters.com) by searching for "mosquito".

I am not aware of an exhaustive listing of herbs useful for environmental biting insect control. There are references here and there in books and other sources, mostly anecdotal in nature. The subject has not, in my opinion, been studied properly in controlled studies, at least not in any systematic way among the aromatic herbs.

Certainly, members of the mint family are worth considering. So, yes, pennyroyal (a member of the mint family) may well work. Lemon thyme may be another good candidate from the mint family but it cannot be grown from seeds and it is expensive to establish over large areas using plugs. You might consider yarrow and tansy, members of the daisy family, also: these can be established easily and relatively cheaply from seeds.

One of the challenges for environmental pest control using herbs is the need to vaporize the essential oils that likely are responsible for the repellent effects of herbs. Often aromatic herbs do not release their essential oils to the air until the leaves are crushed. It may be necessary to consider having some animals that grazing or at least move around in the area so the oils can escape into the air as the plants are trampled on.

There is an InfoSheet on deer-tolerant herbs on our website in the "Richters InfoCentre" section. There is not much deer will not touch in a famine season, so this list is really a guide to what to expect in a good season when the deer have food choices. Whether any of the herbs on this list are actually deer-repelling herbs, I don’t know. Again, I don’t think that systematic studies have been done to test the herbs and their deer repellent properties.

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