|Freeman, Thomas - NORTH DAKOTA STATE UNIV|
|Chu, Chang Chi|
Submitted to: National Research and Action Plan for Silver Leaf Whitefly
Publication Type: Abstract Only
Publication Acceptance Date: December 30, 1998
Publication Date: N/A
Technical Abstract: B. argentifolii prefers ST474 cotton over DPL5415. Adults/eggs/nymphs on leaves were: ST474, 19.4 adults/leaf, 15 eggs/cm2 leaf disk (LD), 4.1 nymphs/cm2 LD vs. DPL5415 with 7.6 adults/leaf, 0.9 eggs/cm2 LD, & 0.4 nymphs/cm2 LD. 7 Leaves along stem examined: leaf 1, youngest, is at apex & leaves 3-20 located at lower nodes. Ave. leaf size 11cm2. Examined leaf area, areole area, number terminal vein endings, mucilage ducts per unit leaf area, leaf thickness, distance from lower epidermis to phloem tissue, & number of trichomes per unit leaf area. Leaf 20 smaller/thinner than 10 or 15. Thickness/phloem depth likely major characteristics responsible for variety selection by whitefly, similar in ST474 & DPL5415, & do not explain preference of one variety over the other. Differences between young & old leaves, due to normal leaf expansion, may explain why younger leaves preferred. Leaf 1 of both varieties had phloem located 50 microns from lower epidermis but was up to 130 microns deeper in leaf 15; a depth too great to be reached by adults & nymphs. Varieties similar in vascular pattern, areole area, & number of terminal vein endings per unit area; but significant differences between leaves of different ages. Areole area smaller in young leaves so adults & nymphs can reach phloem tissue from almost any position on leaf surface which may account for preference of young leaves over more mature leaves on same plant. Mucilage glands per unit area did not differ between ST474 & DPL5415 & likely do not play a major role in variety selection by whiteflies. Number of elongated trichomes significantly different between the two cotton varieties & may be related to why whiteflies prefer ST474 over DPL5415.