Buctril / bromoxynill

WSSA Resistance Group: 6

Crop/non-crop registration: Field corn, wheat, oats, barley, rye, triticale, seedling alfalfa, flax, turfgrasses for sod or seed, garlic

Sensitive weeds: Many annual BLW (broadleaf weeds): wild buckwheat, smartweed, lamb's-quarters, wild mustard kochia, cocklebur, velvetleaf, nightshades (but most effective before 5-leaf stage).

Application method: POST

Absorption & Translocation: Absorbed by foliage and moves very little within the plant.

Mode of Action: Inhibition of photosynthesis and ATP formation by blocking electron transport.

Metabolic pathway inhibited: Inhibition of photosynthesis by binding to the QB-binding niche on the D1 protein of the photosystem II complex in chloroplast thylakoid membranes, thus blocking electron transport from QA to QB;this stops CO2 fixation and production of ATP and NADPH2 which are required for plant growth; however, plant death often results from other factors (e.g. lipid peroxidation).

Basis of Selectivity: Differential spray retention, uptake and degradation in tolerant species.

Symptoms: Basically a foliar contact herbicide; causes blistered (mottling) or necrotic spots within 24 hours and extensive destruction of leaf tissue later (4-7 days); chlorosis may appear afterwards around the necrotic areas of leaves; susceptible seedlings become extremely brittle and eventually disintegrate.

Residuality: Essentially none; short (< 1month).

Toxicity: Oral LD50 = 440 mg/kg - very toxic (BUCTRIL = 779 mg/kg - moderately toxic).

Additional comments: Formulation includes a wetting agent to improve the spread of droplets on leaf; although bromoxynil is not an effective soil-applied herbicide, crops such as turnips, peas and beans should not be seeded for 1-week following application; crop injury (leaf scorch) may develop if plant is under stress (high temperatures or high humidity) within 2 or 3 days before or after application; in corn, problems arise if application followed by a period of cool, wet weather, however, yields are generally not affected.

Images above: Bromoxynil (POST) on redroot pigweed. Note: the mottling and numerous necrotic spotting (left). Bromoxynil (POST) on soybean (right).

Images above: Bromoxynil (POST) on common lambsquarters. Bromoxynil (POST) on broadleaf weeds.

Image above: Bromoxymil (POST) on broadleaf and grass crops and weeds.