Effects on hawthorn the year after simulated spray drift

Area of Science:

• Agricultural Science
• Environmental Science
• Botany

Background:

• Off-target herbicide movement is a concern for non-target plants.
• Current risk assessments often rely on short-term laboratory studies.
• Perennial plants in the spray drift zone may experience overlooked effects.

Purpose of the Study:

• To evaluate the long-term effects of herbicide exposure on hawthorn (Crataegus monogyna).
• To assess the impact of metsulfuron-methyl applied at off-target levels.
• To highlight potential deficiencies in current non-target plant risk assessment protocols.

Main Methods:

• Metsulfuron-methyl herbicide was applied in five dosages to individual hawthorn trees.
• Application occurred at two phenological stages: bud stage and early flowering.
• Five endpoints (leaves, buds, flowers, green berries, mature berries) were counted the year following exposure.

Main Results:

• All measured endpoints (leaves, buds, flowers, berries) showed significant reductions with increasing herbicide dosage.
• These effects were observed in field conditions across multiple locations.
• The study demonstrated significant impacts despite uncontrolled variables like herbivory and pollination.

Conclusions:

• Herbicide exposure, even at levels simulating off-target movement, can cause significant, lasting damage to perennial plants like hawthorn.
• Short-term laboratory studies may not adequately predict real-world impacts on non-target species.
• Risk assessments need to incorporate long-term field data for perennial plants in spray drift zones.