Analyzing the Significance of Photoperiod on Fitness of Sugarcane Aphid, Melanaphis sacchari, on Sorghum
Abstract: Little is known of the biology of sugarcane aphid, Melanaphis sacchari (Zehntner), that became a persistent pest of sorghum, Sorghum bicolor (L.) Moench, in North America in 2013. Understanding fitness of sugarcane aphid in relation to environmental conditions would aid in understanding how aphids develop and evaluating sorghum for resistance to this major insect pest. Effect of three photoperiods of 14:10, 13:11, and 12:12 light:dark hours were evaluated on sugarcane aphids on susceptible ‘Tx399 x RTx430’ sorghum at daily light (day) and dark (night) temperatures of 30 and 20°C in an incubator. A sugarcane aphid from a pure colony was put individually into a clip cage, with two clip cages per each of four plants in six pots. When each aphid produced a nymph, the mother was discarded and the nymph retained and allowed to mature and produce offspring until it died in the clip cage. Nymphs produced were counted and removed each day. The pre-reproductive period was ∼53% longer (6.6 days) at 14:10 light:dark hours than at the other photoperiods. The reproductive period at 14:10 was 13.9 days, 2 days longer than at 13:11 (11.8 days). The post-reproductive period averaged 17.0 days at 13:11, 6.6 days longer than at 12:12 (10.4 days). Total fecundity at 13:11 (87.7 aphids) was 22 aphids more than at 12:12 (65.7) and 32 more than at 14:10 (56.2). Developmental times and fitness of sugarcane aphids differed significantly at the different photoperiods. Photoperiod should be considered when evaluating sorghum for durable resistance against sugarcane aphids.
Ethan Triplett* and Dr. Bonnie B.Pendleton
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