RESPONSES OF SOME AMERICAN CORN HYBRIDS TO NATURAL INFESTATION BY THE CORN STEM BORER, Sesamia cretica Led. (Lepidoptera:Phalaenidae)

M. AL-Khafaji, A.; H. Al-Karboli, H.

	RESPONSES OF SOME AMERICAN CORN HYBRIDS TO NATURAL INFESTATION BY THE CORN STEM BORER, Sesamia cretica Led. (Lepidoptera:Phalaenidae)
IRAQ JOURNAL OF AGRICULTURE
Article 1, Volume 14, Issue 3, 2009, Pages 0-0
Authors
A. M. AL-Khafaji; H. H. Al-Karboli
Abstract
Laboratory and field studies were conducted to evaluate the susceptibility of 10 corn hybrids recently introduced from Texas - USA to Iraq to infestation by the stem borer Sesamia cretica Led. During the spring and fall season of 2005. Preference and Non-preference and Antibiosis were used as criteria in this experiment to evaluate their susceptibility to the stem borer. Results indicated that their was significant differences in females preference to lay eggs on the seedlings. The lowest percentage of eggs were laid on the seedlings of hybrids MSI 4328 and MSI 4391 )3.13, 3.5( for the spring and fall seasons of 2005 respectively, which was significanty different from the highest numbers laid on hybrid MSI 4148 (8.01, 8.71) respectively. There were no significant differences in terms of larval weight and peroids. The larval fed on these hybrids were ranged from 95-156 mg /larvae and 26-33 days respectively. The lowest survival rates of 50% were observed for the larvae fed on the hybrid MSI 4387 compared to 98 % for the local hybrid IPA 5012. The lowest growth index was 1.08 observed for the hybrid MSI 4387 which was similar to that of the well known tolerant hybrid IPA 3001. Weight of pupa emerged from larvae fed on hybrids MSI 4387 and MSI 4317 were 50.6 and 77.0mg which significantly different from those fed on the local cultivars IPA 5012 and IPA 3001 (127.47) and (106.47) mg respectively. The lowest peroids 4 days obsered for larvae fed on hydrid MSI 4387 which was significantly different from larvae fed on other hybrids. Furthermore, adlults emerged from these pupae were small, weak, with slow motion and died after 3-4 days from their emergence. Therefore, it could be concluded that these impressive results encourge to do more field studies on hybrid MSI 4387 to determine its tolerance to the stem borer.

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