Can Leaves Absorb Pesticides?

Systemic Pesticides

• Unlike contact pesticides that remain as a film on plant surfaces, systemic pesticides are designed as absorbent liquids. Whether watered into soil or sprayed onto foliage, systemic pesticides filter into plants' vascular systems. Depending on a particular plant and particular pesticide mixture, the toxin moves throughout the plant to protect it from pathogens or pests for an extended period. In fact, some systemic pesticides remain in only certain plant parts, such as the leaves, depending on the intended target. Each pesticide has its own specific chemistry; for overall safety, read all labels on a pesticide package before applying the pesticide to your plants.

Uses

• Many herbicides are systemic pesticides that are applied directly on weed leaves and stems. Although not a fast-fix strategy, systemic herbicides slowly maneuver through a weed's vascular system and effectively kill the plant through hormone manipulation. Fungicides follow the same vascular route after entering the leaves to remove burgeoning fungi harming the plant. Traditional systemic pesticides flowing through plants protect them from organism feeding. For example, caterpillars and other leaf-chewing organisms are killed quickly as they feed on leaves and stems made toxic to them by systemic pesticides.

Alternatives

• Maintaining a healthy garden, rather than using harmful pesticides, is one of the best ways to deter pests and pathogens; edible crops retain toxins even after they are harvested and washed. Consistently weed by hand and otherwise keep your garden tidy. Observe your plants frequently, including leaf undersides, so you can remove pests with water instead of toxins. If your garden has a more aggressive pathogen or pest problem, try a removal strategy such as insecticidal soap or horticultural oil. Typically non-toxic, those pathogen- and pest-removal strategies help to avoid widespread pesticide use, and so they help to keep the environment clean.

Beneficial Insect Implications

• Bees and butterflies are the main pollinators of many plants, but pesticides absorbed into leaves often affect such insects' populations. According to the California Department of Pesticide Regulation, pollen and nectar show signs of systemic pesticide residues. As pollinators ingest the nectar, they are poisoned as well. Without widespread insect pollination, many edible crops fail to fruit, causing reduced food sources. Using pesticide alternatives in gardens protects critical pollinators from harm.