IPM For The Herb Garden

Designed as an alternative to the rampant use of insecticides in agriculture, Integrated Pest Management has proven to be an effective means of promoting healthy growth in the backyard garden as well. Learn more about how you can implement this technique in your herb plot.

Even under the best of care, your herb garden may be affected by pests or disease at some point. It can be difficult to choose the right moment and method to deal with these problems that arise, but implementing an Integrated Pest Management {IPM} strategy can help get your garden on the right track. With its multipronged approach of prevention, observation, identification, and control {if necessary}, IPM can have a significant impact in any garden, large or small, and will reward you with healthy, thriving plants with minimal impact to the environment.

The concept of IPM was first explored by American scientists and agriculturalists after World War II. They recognized that the synthetic pesticides being developed at the time should only be employed in instances where it was clear that a commodity crop would be lost to insects. Using these chemicals when the threat wasn’t critical could prove potentially damaging to the environment – and would not likely reduce the economic risk to the grower. Determining if and when to use pesticides became the backbone of the IPM strategy. By the 1970’s, Integrated Pest Management was commonly used in commercial agricultural.

Nowadays, the management strategy targets all types of pests; insects, mammals, birds, invasive plants, and weeds, as well as plant disease. Controls may be organic, cultural, physical, or biological in nature, with chemical controls used only as a last resort. And as IPM is employed in larger farms and nurseries, many home gardeners are realizing that it can work in their own backyard plots.

Preparing Your Garden

It may seem obvious, but stress-free plants are healthy plants. There are several ways to minimize stress for the herbs in your garden.

Location: One of the most important elements to consider is siting. When you purchase a plant or prepare to sow seeds, plan carefully as to where you will place it in the garden. Don’t just cram it into an available space, no matter how tempting. Do your research; know how much sunlight each plant needs and determine if it can tolerate an exposed windy area if that’s what the site experiences. Find out what type of soil it prefers, and how much water and fertilizer it relies on. Make sure your new plant will have enough room to grow to comfortably reach its mature size. Is your plant an annual or perennial; will it stay in the same location for many years or will it die with the first frost? Once you’ve taken all of these things into consideration, then you can make a decision about the optimum location for your plant and dig accordingly.

Siting a plant in an area that lacks proper requirements may provide an open invitation to pest problems down the road. Poor conditions will weaken your plant, making them unable to withstand or combat pest issues.

Best Plants: Some species naturally resist disease and pests better; others are bred to have these capabilities. Opting for resistance species or cultivars may help minimize widespread damage or loss to your plants. For example, cultivars of lavender such as ‘Munstead’ and ‘Phenomenal’ resist disease better than some other lavenders, and if you are not too picky, can save you a lot of hassle. Meanwhile, entire plant families, including most members of the Allium family, are pest resistant, giving you plenty of options.

Proper Maintenance: How you look after your herbs will also minimize stress. Applying supplemental water and fertilizer at the proper time and in the correct amounts is critical to success. Remember that each individual plant will have its own needs – not all plants like the same treatment. If you are unsure about how to nurture a specific plant, consult the plant label {if you purchased it at a store} or check with the horticulturist on staff at your local garden center.

Weeding: Make sure to keep up with this task will reduce competition from other plants. Get them when the soil is damp and the weed plants are immature and small. {This is another reason why it’s so important to monitor your garden on a regular basis – you can catch these encroaching plants before they get too large.} Don’t forget deadheading and pruning; done correctly and at the right time, they will open up air circulation around the plants and minimize the risk of some bacterial and fungal infections.

Protection: Offering a barrier from the elements in the form of mulching can contribute to a perennial’s longevity in cold climates. Fall clean-up is also important – while it isn’t necessary to cut back perennial herbs {unless you want to}, raking up any pest-infested leaf litter or diseased fruit will prove vital to limiting the spread of unwanted problems.

IPM for garden

Monitoring the Environment

No matter how well you look after your plants, you will occasionally encounter factors that you cannot control. As you spend time interacting and caring for your plants in the garden, be on the lookout for anything out of the ordinary. Do you see evidence of insect chewing or egg-laying? Perhaps you see the adult insect themselves. Are the leaves mottled and discolored, or the stems shriveled? Does a large clump of weeds threaten to take over a spot where you have planted? Successful IPM depends on continuous observation; if you inspect your plants each time you go out to water, weed, deadhead, or prune, you can catch potential problems before they grow huge and difficult to deal with. Using a hand lens or magnifying glass for closer examination may be useful to distinguish details. Don’t forget to look at the undersides of leaves, a favorite spot for insects to hide.

Taking a few macro photos with a digital camera may also come in handy. If you do not already keep a garden journal, jot down a few notes about what you see and the garden’s general conditions, such as the time of year and the weather. This will give you something to reference in the future. Bring a few small plastic bags with zipper closures or recycled glass jars if you wish to collect specimens – an insect, perhaps, or a damaged leaf – to take to an expert.


Identifying Trouble Spots

If your plants seem less vigorous than normal, you will need to identify the problem. This is the trickiest part of IPM, but it’s critical in order for the rest of the strategy to work properly. Sometimes it’s easy to identify the issue – for instance, you will see a massive conglomeration of black aphids gathered on the stems of your chervil plants, or you will notice that the leaves of your basil suddenly sport the same white patches of powdery mildew that your tomatoes had a few years back.

Other problems may not be as familiar to you, or the symptoms may hint to several potential issues. The yellowing of leaves, for example, may indicate bacterial infection, a nutrient deficiency, or over-watering.

Sometimes what we think is a problem actually poses no threat. You might spot a scaly black insect on your sweet cicely plants and fear the worst when the strange creature turns out to be the larval form of a ladybird beetle, a well-known beneficial insect. Misidentification can lead to errors in controlling or treating the problem, which may prove even more detrimental to the plant.

Check out books from the public library or search knowledgeable online resources, such as websites of university extension offices, to assist you with ID. Your local garden club or horticultural society may have several master gardeners in their membership who can also help you. Consult with the experts at garden centers and nurseries in your area.

If the problem involves an insect, remember that bugs take on many forms depending on where they are in their life cycle, which will cause their appearance to differ. {This also matters if you have to control insect pests; flying, hard-bodied adults are usually harder to get rid of than crawling larvae.}

Taking Control

Once you have properly identified the problem affecting your plants, it may be time to take action. The operative word is “may,” as the IPM strategy operates on the principle of employing controls only if the damage to the plants is so severe that you fear its loss or, if you sell plants for food or ornamental use, the damage to the plant renders it unsaleable at market. The age of the plant may also influence your decision. A very young, tender plant attacked by a pest or disease may not recover as well as a mature plant might.

Physical Controls:  Should you determine that the losses would be significant, you have several solutions at your disposal. If you need to deal with insect pests immediately, physical controls such as hand-picking can be highly effective if you have the time and can tolerate this unsavory task. You will need to hand-pick insects every few days to reduce the population. Wear gloves and remove large insects with your fingers, dropping them into a bucket of water mixed with liquid dish detergent. {If you are targeting caterpillars, first make sure they are not larvae of beneficial butterflies.} You can wipe some insects, such as aphids, from leaves and stems using a damp cloth. You can also remove aphids and other pests such as mites from large plants and trees using a blast of water from the garden hose.

Pruning is another physical control that can help reduce problematic damage, such as diseased or even severely pest-infested stems and branches. There is a danger, however, of removing too much surface area, which can harm the plant’s ability to photosynthesize and grow. Take care that you only prune as much as is required to control the pest.

Depending on the pest, you may need to erect barriers around your plants. These can come in the form of collars to protect young basil plants from cutworms, row covers to protect against leafminers, or fences to keep deer and rabbits out of your herb garden.

Biological Controls: Perhaps not as well-known as physical controls, biological controls can come in handy in some situations. Certain beneficial insects, such as ladybird beetles, spiders, lacewings, and some parasitoid wasps, will feed on pest insects in the wild. If you are growing herbs in a greenhouse setting, you might consider purchasing ladybird beetles for release inside the building to control aphids, mealybugs, scales, or spider mites. Lacewings will control aphids, leafhoppers, spider mites, and thrips. If you wish to encourage more beneficial insects to your outdoor herb garden, choose plants that attract them, such as angelica, fennel, and calendula. Birds, bats, snakes, and frogs are also considered biological controls, as they eat many insect pests. Remember that you do not want to completely eradicate all pests in your garden – the beneficials need something to eat!

If you grow annual herbs and other plants, crop rotation can help reduce the risk of soil-borne diseases and pest infestations. The easiest way to do this is to avoid planting members of the same family in the same spot year after year. You want to mix it up; plant new cultivars and species alongside your usual favorites every year or so.

Companion planting is another way to control pests and diseases. By growing specific combinations of plants together, one plant will either repel insects from the group or act as a so-called “trap crop,” which attracts pests away from the desired plants in the group. Potentially useful herb companion planting combinations include sage and rosemary, anise and coriander, basil and oregano, chamomile and alliums, chives and dill, and catnip and hyssop.

Chemical Controls: As organic gardeners, we shy away from synthetic chemical herbicides, fungicides, and pesticides. But that does not mean we have zero options. You will need to do a little research to find the right combination of substances for the problem at hand. Keep in mind that although these sprays and solutions may be organic, they are not completely “safe.” As they target pests, they also negatively impact the beneficial insects in our yard. They can also pose a risk to the soil and to other plants. Wear gloves and always keep them out of the reach of children and pets. The Xerces Society for Invertebrate Conservation has some great information about organic herbicides and pesticides. Go to xerces.org and type “organic approved pesticides” into its search bar to find out more.

Don’t forget to write down any results or observations in your garden journal for later reference. Part of Integrated Pest Management involves keeping track of successes and failures so you can build on them or troubleshoot in successive years – thereby enjoying the best of the growing season.