Whole plant and cellular response of wild garlic (Allium vineale L.) to thifensulfuron-methyl

Field, greenhouse and laboratory experiments were conducted to investigate whole plant and cellular response of wild garlic to thifensulfuron-methyl.

Thifensulfuron-methyl activity on wild garlic was evaluated as influenced by rate and time of application, antagonism and sequential application. Phytotoxicity to small grains was also assessed. Thifensulfuron-methyl at 9 g ai ha⁻¹ was the lowest rate observed that suppressed aerial bulblet production greater than 90% when compared to the standard treatment of 2,4-D. Suppression was greatest at the 35 g ai ha⁻¹ applied in late March to early April. The lowest rate for reduction of underground bulbs was 35 g ai ha⁻¹ applied in late March.

Tank-mixing metribuzin at 210, 420 and 630 g ai ha⁻¹ with thifensulfuron-methyl antagonized the letter's activity on wild garlic aerial bulblet suppression. Reduction in underground bulb and aerial bulblet weight was antagonized by tank-mixing metribuzin with thifensulfuron-methyl. The antagonism of thifensulfuron-methyl only occurred for rates of 4 to 9 g ai ha⁻¹ and was totally overcome at 17.5 g ai ha⁻¹.

Sequential applications of thifensulfuron-methyl followed by metribuzin at 12 or 24 h or metribuzin followed by thifensulfuron-methyl at 12 or 24 h did not result in antagonized activity of thifensulfuron-methyl on wild garlic whole plant growth or aerial bulblet production. The lower rates of thifensulfuron-methyl followed at 12 h by metribuzin at 630 g ai ha⁻¹ was antagonized as evidenced by increases in underground bulb weights.

Thifensulfuron-methyl decreased bulb quality, shoot weight, number of roots per bulb and root and shoot length even at 4 g ai ha⁻¹ in the greenhouse. The addition of 420 g ai ha⁻¹ to all rates of thifensulfuron-methyl reduced the letter's ability to inhibit shoot growth. Thifensulfuron-methyl applied at rates up to 35 g ai ha⁻¹ was not phytotoxic to wheat or barley.

Thifensulfuron-methyl reduced shoot and root growth of aerial bulblets in sterile culture. The amino acids valine, leucine and isoleucine were inconsistent in overcoming the effects of thifensulfuron-methyl on aerial bulblet growth. All concentrations of thifensulfuron-methyl except 0.001 rag L⁻¹ inhibited growth of soft offset bulbs following 10 d of exposure. The addition of valine, leucine and isoleucine did not totally nullify the activity of thifensulfuron-methyl on soft offset bulb growth.