By Marta Lynch, PHS Farm Manager, Norristown Farm Park
Home vegetable gardens are a wonderful way to enjoy fresh produce throughout the growing season. However, growers are often faced with the challenge of pests that can damage or even destroy their crops.
First and foremost, when we talk about pests in the garden, it is important to remember that our garden is an ecosystem that is made up of a complex network of biological organisms (i.e., plants, animals, fungi, etc.) and their physical environment. The environment and these organisms are constantly interacting and influencing one another to create a delicate and ever-evolving balance of life. When we use pest management methods, we are impacting the balance of this complex network.
Fortunately, there is a system for dealing with these pests called Integrated Pest Management (IPM), which is a science-based approach that takes this whole ecosystem into consideration. It is not a single method for controlling pests, but rather a decision-making process to incorporate into your gardening. IPM principles include:
Most insects in your garden will cause no harm or even be beneficial. For this reason, it is crucial to learn what pests affect the crops you have and what the damage looks like. The Organic Gardener's Handbook of Natural Insect and Disease Controls by Barbara W. Ellis, Fern Marshall Bradley, and Deborah L. Martin is a great resource. You can work backward, first seeing the damage, and then narrowing down what type of pest might have caused it.
When trying to ID an insect, remember that insects go through metamorphosis and can look extremely different at each life stage. Once you have an ID, learn the life cycles and host plants of the pests you have in your garden and region. This knowledge empowers you to make the best management decisions. Some common pests in the Philadelphia region include Leaf miners (both allium and beet/spinach), Colorado potato beetle, Cabbage white butterflies, Cucumber beetle (both striped and spotted), Harlequin beetles, Tomato horn worm, Flea beetles, Root maggot flies (both cabbage and onion), Squash vine borer, Mexican bean beetle, and many more.
Frequent monitoring of insects and evaluation of damage in your garden is the building block to a good IPM program. At least once a week, you should be walking through your garden and observing it in great detail. What insects are present and what life stage are they in? How many of these insects are you seeing? Where are they located? Do your plants have any physical damage? If so, how much? Evaluate what you are seeing and ask yourself whether it warrants taking action.
Sometimes seeing a couple of pests or a small amount of damage does not always mean control methods are needed. For example, if you find a tomato hornworm on your plant, and it has only eaten one branch, consider leaving it to get parasitized by a Braconid wasp, thus supporting the Braconid wasp population in your garden. However, if a tomato hornworm has eaten half of your tomato plant, action may be necessary.
Prevention is the first line of defense in IPM, and some simple strategies can prevent pest populations from becoming a threat. Some strategies/tools used include adding beneficial insect/organism habitat, using pest/disease resistant plant varieties, planting early/late (to offset with pest life cycles), practicing crop rotation, reducing pest habitat by keeping your garden weeded and cleaning your garden at the end of each season, and more.
Once you have identified your pest(s), monitored and evaluated the damage, and preventative controls are no longer effective, you can consider using a combination of biological, cultural, physical/mechanical, and chemical management tools. You always want to first choose a control method that has the lowest amount of risk to other organisms and the environment. Often cultural (for example pulling out all brassicas in the month of July to disrupt the harlequin beetle life cycle) or physical/mechanical methods (using bug netting to cover plants) will pose the lowest risk. Biological control is using natural enemies — predators, parasites, and pathogens — to control pests. Examples include Green Lacewing larvae, Ground Beetles, and Minute Pirate bugs. Arbico Organics is a great resource for determining what biologicals can be used to control certain pests.
When all else fails, you can use a chemical control. These can be extremely effective but can also pose a higher risk to other organisms and the environment. It is important to use chemical controls prudently, as overuse can lead to pests developing pesticide resistance. When choosing a chemical control, know if it is a targeted or broad-spectrum chemical. Using organic chemicals does not always mean safety for other organisms. Pyrethrin and copper sulfate are organic chemicals that are extremely effective in killing your targeted pests, but also kill your beneficial insects and pollinators. Well-timed and targeted use can reduce the potential harm to other organisms.
In total: a good IPM program will look different for each garden since each garden has its own unique ecosystem. Identifying, monitoring, and evaluating your garden pests year after year will allow you to learn the rhythm of pest pressure in your garden and make better-informed decisions going forward. And remember not to be discouraged if you lose crops to a pest -- that is more data to inform future preventative tools and strategies! By employing IPM principles, you can ensure that you are making more environmentally friendly pest management decisions while ensuring a bountiful harvest from your vegetable garden. We wish you happy growing!