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Title: LEAF CHARACTERISTICS AND SURFACTANT AFFECT PRIMISULFURON DROPLET SPREAD IN THREE BROADLEAF WEEDS

Author
item SANYAL, DEBANJAN - UNIV OF MASSACHUSETTS
item BHOWMIK, PRASANTA - UNIV OF MASSACHUSETTS
item Reddy, Krishna

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2005
Publication Date: 3/30/2006
Citation: Sanyal, D., Bhowmik, P.C., Reddy, K.N. 2006. Leaf characteristics and surfactant affect primisulfuron droplet spread in three broadleaf weeds. Weed Science 54:16-22.

Interpretive Summary: To achieve effective weed control by postemergent herbicides, the herbicides have to come in contact and retain on the leaf surface prior to absorption into plant. Leaf surface characteristics of weed species and surfactant play a major role in herbicide efficacy. Scientists from Department of Plant Sciences, University of Massachusetts and Southern Weed Science Research Unit, Stoneville, MS have examined the leaf surface, epicuticular wax content, and spray droplet behavior on common lambsquarters, common purslane, and velvetleaf to understand the relationship between the leaf surface characteristics and the spray droplet behavior on the leaves. Glands and trichomes were present on both the adaxial and abaxial leaf-surfaces of velvetleaf. Common purslane had neither glands, nor trichomes on either side of the leaf. Common lambsquarters did not have any glands or trichomes, but it had the globular bladder hairs on both adaxial and abaxial leaf surfaces. Stomata were present on both adaxial and abaxial leaf surfaces in all three weed species. Common lambsquarters leaves had the highest epicuticular wax content, followed by common purslane, and velvetleaf. There were no significant variations in the spread of the1 l droplet of distilled water and primisulfuron (without adjuvant). The spread of primisulfuron with Induce and primisulfuron with Silwet L-77 were higher on the velvetleaf than on common lambsquarters or common purslane leaf. In all the three species the droplet spread was much higher with Silwet L-77 than with Induce. These results showed a relationship between leaf-surface characteristics and the spread area of the spray droplet.

Technical Abstract: Laboratory studies were conducted to examine the leaf surface, epicuticular wax content, and spray droplet behavior on common lambsquarters (Chenopodium album L.), common purslane (Portulaca oleracea L.), and velvetleaf (Abutilon theophrasti Medicus) to understand the relationship between the leaf surface characteristics and the spray droplet behavior on the leaves. Adaxial and abaxial leaf surfaces of the three weed species were examined using the scanning electron microscopy. Glands and trichomes were present on both the adaxial and abaxial leaf-surfaces of velvetleaf. Common purslane had neither glands, nor trichomes on either side of the leaf. Common lambsquarters did not have any glands or trichomes, but it had the globular bladder hairs on both adaxial and abaxial leaf surfaces. Stomata were present on both adaxial and abaxial leaf surfaces in all three weed species. Common purslane had much lower number of stomata per unit area of leaf as compared to velvetleaf or common lambsquarters. Common lambsquarters had the highest epicuticular wax content on the leaf surface (395.17 g cm-2 ), followed by common purslane (164.33 g cm-2 ), and velvetleaf (65.17 g cm-2 ). The spread of 1 l droplet of distilled water, primisulfuron solution (without adjuvant), primisulfuron solution with Induce (0.25% v/v), and primisulfuron solution with Silwet L-77 (0.1% v/v) were determined on the adaxial leaf surfaces of each of the weed species. There were no significant variations in the spread of the1 l droplet of distilled water and primisulfuron (without adjuvant). The spread of primisulfuron with Induce and primisulfuron with Silwet L-77 were higher on the velvetleaf than on common lambsquarters or common purslane leaf. In all the three species the spread of the droplets were much higher with Silwet L-77 followed by the primisulfuron with Induce. These results showed a relationship between leaf-surface characteristics and the spread area of the spray droplet.