The Organic Gardener: Embracing Biological Controls for a Healthier Garden

Organic gardening demands patience and a willingness to work with nature rather than against it. Even the most dedicated organic gardeners occasionally feel the urge to reach for herbicides when invasive plants like goutweed or poison ivy take hold, or when Japanese beetles descend en masse just before a garden party. Yet, as we learn more about ecological balance, we discover that organic solutions often outperform chemical ones—especially for persistent problems.

Learning from the Experts

Each winter, the Ecological Landscaping Association (ELA) hosts a conference where researchers, landscapers, and gardeners share cutting-edge ideas. One standout presentation came from Dr. Richard Casagrande of the University of Rhode Island, who spoke on biological control of invasive species. His research demonstrates that for certain pests, introducing carefully vetted natural predators works better—and more sustainably—than any spray.

How Biocontrol Works: The Purple Loosestrife Example

When gardeners hear that foreign insects are being released to control invasive plants, a common fear arises: “What happens when they finish off the target? Will they eat my delphiniums next?” Dr. Casagrande explained that the process is anything but haphazard. The University of Rhode Island operates quarantine labs with security comparable to the White House perimeter.

Scientists first study the invasive species in its native habitat. Purple loosestrife, introduced from Europe in the early 1800s via ship ballast, is kept in check there by over 120 insect species, 14 of which are host-specific—meaning they feed exclusively on loosestrife. Before any insect is released, it undergoes rigorous testing to ensure it won’t attack crops like corn, wheat, or soy, or native relatives of the target plant.

Digging out purple loosestrife is a backbreaking task; its massive root system regenerates from fragments, and each mature plant produces millions of seeds that remain viable for years. Even burning fails to eradicate it. Since 1994, introduced leaf-feeding beetles (Galerucella spp.) have reduced loosestrife stands to about 10% of previous levels. As the plant population drops, so does the beetle population, creating a self-regulating cycle. Similar programs are underway for phragmites and other invasives.

Tackling the Lily Leaf Beetle

Dr. Casagrande has also applied biocontrol to the lily leaf beetle, a stunning but destructive pest that has devastated oriental and Asiatic lilies. The adult beetle is bright red with black trim, about 3/8 inch long, while its larvae cover themselves in excrement to deter predators. Researchers have introduced tiny parasitic wasps from Europe that target the beetle’s larvae. At test sites in Rhode Island and Massachusetts, and established release sites in New Hampshire and Maine, these parasitoids are successfully suppressing beetle numbers.

What the Home Gardener Can Do

• Trust the process. Biological controls are coming; they take time but offer lasting results.
• Abandon the spray. Herbicides and insecticides may kill individual pests but never eliminate the population—and they harm beneficial insects.
• Choose resistant varieties. Lilies like ‘Black Beauty’ are less attractive to lily leaf beetles.
• Hand-pick diligently. Removing beetles twice daily can prevent larvae from appearing altogether.

Organic gardening means accepting that we are not in total control. Sometimes we must wait, tolerate some damage, and trust that nature’s checks and balances will prevail. The birch leaf miner is now a minor nuisance thanks to biocontrol, and purple loosestrife is no longer a threat in many areas. Stay the course—be organic.