Nature’s Balancing Act
Having had a mild winter here in the Pacific Northwest, there may be an increase in pest and/or disease pressures occurring in our landscapes and gardens this season. We can take control of these issues involving pathogens and insect pests while avoiding the use of synthetic chemicals with steps that follow a simple, thoughtful process: scouting, identification, actions, and long-term ecological management.
Scouting:
Gardeners intuitively scout when they go into their growing areas and make observations. Using a systematic approach, set an intention to do this on a weekly basis. Begin by looking at the entire growing area, noticing patches that are sparse, stunted, or discolored. Also scout randomly within the entire edge, middle, and back of the garden bed, making a zigzag pattern. When looking at the individual plant, start at the ground and move in an upward spiral up the main stem, then outwards along branches to the leaf tips, checking both the underside and top of leaves. Scouting on a regular basis can be a proactive approach to catching issues early.
Identification:
Symptoms of an herbivore pest can present as puncture holes or bite marks, unusual residues or textures left behind, and sometimes as wilted or yellowing on plant parts. Many pathogens are fungal organisms, who commonly present symptoms on a leaf or stem as a discolored, rounded spot or lesion that can have a bullseye of different textures or colors. A common pathogen that affects many plants in our growing region is Phytophthora, a water mold that acts like a fungus. There are many distinct species of Phytopthora, and they may present differing symptoms based on the plant host. Some general above ground symptoms can include necrotic spots or blotches, often where water collects on leaves. Below ground symptoms often result in plants with minimal feeder roots with the remaining roots appearing dark and decayed. Look for areas in your garden where water collects and may not be draining; standing water is a potential location where Phytopthora will spread.
Diagnosing pests and pathogens is complex and can feel overwhelming. Some pests and pathogens only attack specific species of plants; some have a broader range. If you have an issue or concern, identify the plant species, collect data about when and what you are noticing, take lots of photos of what is happening to the plant. Sometimes the issue is a plants response to a change in the environment. Utilize resources such as Master Gardeners and your local Extension Office for advice or explore the Pacific Northwest Pest Management Handbook online. They can guide you in effective identification of the cause and treatment of the problem.
What is amazing about plants is that they have evolved a range of natural defenses that we as gardeners can encourage. Plants with thick, healthy cuticles, which are a waxy outer layer, act as the first line of a defensive barrier that protects from insect bites or pathogen entry. Sometimes plants will drop off all their affected leaves in response to an attack and bounce back the following year. Some plants can also produce chemical elicitors that deter insects or reduce further damage. In some cases, they even release signals that trigger defensive responses within the plant itself and, to a degree, in neighboring plants. These types of defenses do take a toll on the plant’s resources; that’s where we as gardeners can assist.
Action:
If you do notice signs of a pest or disease, small, thoughtful actions can go a long way. Begin by removing and disposing of the most affected plant material; this can help slow the spread. Check that the plant is receiving appropriate water (neither too much nor too little) and improve air circulation with pruning if foliage is dense. In some cases, simply rinsing plants with water or hand removing insects can reduce populations.
It is also important to pause before taking more intensive action. Not all damage requires intervention, and some level of pest activity is a natural part of a healthy ecosystem. Monitoring the situation over time can help determine whether the issue is increasing, stabilizing, or resolving on its own.
Long-Term Ecological Management
Healthy gardens start with healthy soils. Feeding your soil with organic material is an essential element in plant health overall. This organic material can come from leaving leaf litter and plant material to overwinter, providing a food source for soil microorganisms to break down. With a healthy microbial ecosystem in place, an entire food web is established that results in a good overall structure for quality soils. This in turn allows water to move through the soil, releasing nutrients that are available for plant uptake. When trying to build soils, adding a layer of organic compost on top of the litter adds to slow-release fertilization and more fuel for soil health. Covering bare soils with wood chip mulch adds another layer to soil maintenance by protection from erosion, water retention, and weed suppression. These processes mimic nature, where soils are rarely found free of natural litter material.
Increasing overall biodiversity below and above ground provides a healthy ecosystem. The higher population of insect pests that we may meet this season can be viewed as a food buffet for beneficial insects and pollinators. Holding off on winter clean up until consistent spring warming is ideal for allowing beneficial insects to hatch. Often, beneficial insects in the juvenile stage are the highest consumers of pests. Providing them with the time to continue through this life stage is essential to effective pest management. Planting your landscape with flowering perennials or hedgerows is another way to increase biodiversity and attract beneficial insects and pollinators that will consume pests. A diverse plant palette keeps pathogens localized and contained within smaller areas as many diseases are specialized towards specific species. A monoculture of one plant family or species can be devastated by a pathogen.
Following a more natural approach to gardening can help our plants survive these more extreme climate events and changes. Often, getting results following these practices can feel slower, but they do intensify and develop over time. Patience is key; nature is often adjusting to find an equilibrium.
–Written by Ann Mackey, Horticulturist
