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Effect of Artificial Defoliation on Sunflower Yields and Other Characteristics¹

Leaf removal studies were conducted on sunflowers (Helianthus annuus L.) from 1969 through 1971 at Experiment, Georgia, to evaluate the amount of leaf damage sunflower plants can tolerate without yield losses. Leaves from sunflower plants were artificially removed at levels ranging from none to all prior to flowering.

Sunflower seed yields were significantly reduced as a result of partial or complete leaf excision when compared with the undefoliated check. Yields were affected least when leaves 5 through 12 from the top or the top 12 were left on the sunflower plants. Lowest leaves on the plant were more important to seed yield than when only top 4 were left. The oil percent of seed was not affected by defoliation treatments when eight or more leaves remained on plants. Complete and partial leaf removal treatments reduced both seed weight and head diameter compared with the undefoliated check.

Key Words: Helianthus annuus L. • Leaf removal • Excision

² Assistant Professor of Agronomy.

Received for publication January 24, 1972.