Response of Sugarcane and Sugarcane Stalk Borers Sesamia spp. (Lepidoptera: Noctuidae) to Calcium Silicate Fertilization.

Sugarcane is grown extensively throughout the world including more than 100,000 ha in Khuzestan province, Iran. The pink stalk borers Sesamia are key pests of sugarcane in this region, while other stalk borers will occur in sugarcane worldwide. Application of silicon as a soil amendment has provided plant mitigation to both biotic and abiotic stresses. Silicon has been shown to enhance resistance of sugarcane against stalk borers. Field trials were conducted to determine the effects of calcium silicate against infestations of stalk borers Sesamia spp. and on yield quality. Experiments were conducted with three sugarcane varieties CP69-1062, IRC99-01, and SP70-1143 and two rates of calcium silicate (400 and 800 kg/ha). Percentage of stalk damaged, percentage of bored internodes, length of borer tunnel (mm), number of larvae + pupae per 100 stalks, number of exit holes, and cane yield quality were determined. We demonstrate significant reduction on borer population and damage under silicon treatment, but greater reduction in the percentages of stalk damage, bored internodes, moth exit holes, and length of borer tunnel and number of larvae and pupae per 100 stalks were observed in the susceptible variety CP69-1062. Silicon treatment positively affected cane and sugarcane juice quality of for the variety CP69-1062, but not for SP70-1143. We conclude that the benefits of silicon to sugarcane quality and sugarcane resistance to stalk borers are dependent on the sugarcane variety.

Life parameters of Tetranychus urticae (Acari: Tetranychidae) on six common bean cultivars.

It is well recognized that the quality of host plants affects the development and survival of twospotted spider mite Tetranychus urticae Koch. The life table parameters of T. urticae, on six cultivars of common bean (Phaseolus vulgaris L.) (chiti Khomein, chiti Ks21189, red Akhtar, red Ks31169, white Pak, and white G11867) were studied at constant laboratory conditions (27 +/- 2 degrees C, 70 +/- 5% RH and 16:8 L:D). Total development times of immature males and females were significantly influenced by bean cultivar. T. urticae laid significantly more eggs per day on red Akhtar (16.16) than on the other cultivars. The mean generation time ranged from 23.37 to 34.82 d, and a significant varietal effect was seen. Percentage of egg hatchability oftwospotted spider mite ranged from 88.25 to 94.20%. The highest intrinsic rate of increase, was recorded on red Akhtar (0.269 +/- 0.031) and the lowest value was obtained on white Pak (0.129 +/- 0.048). In addition, net reproductive rate and finite rate of increase of the twospotted spider mite had the highest value on red Akhtar: 62.38 +/- 1.05 and 1.30 +/- 1.02, respectively. The lowest values of these parameters were recorded on white Pak as 26.11 +/- 1.40 and 1.13 +/- 1.10, respectively. Doubling time varied significantly on different cultivars and the lowest and highest values were obtained on red Akhtar and white Pak, respectively. Our findings revealed that white beans (Pak and G11867) were less suitable cultivars, suggesting that they are more resistant to the twospotted spider mite than the other cultivars.

Biological study of Plutella xylostella (L.) (Lep: Plutellidae) and it's solitary endoparasitoid, Cotesia vestalis (Haliday) (Hym. Braconidae) under laboratory conditions.

Plutella xylostella (L.) (Lep: Plutellidae), is a destructive pest of brassicaceous crops in the world. Cotesia vestalis (Haliday) is one of most important biological control agents of P. xylostella in the world and Iran. Both of P. xylostella and C. vestalis biology were carried out in laboratory condition. Results showed that development time of immature stages of P. xylostella including egg, Instar I, Instar II, Instar III, Instar IV, prepupa, pupa were 2.39 +/- 0.17, 2.18 +/- 0.17, 2.06 +/- 0.28, 2.14 +/- 0.14, 2.54 +/- 0.12, 0.40 +/- 0.12 and 4.23 +/- 0.23 days, respectively. Longevity of female and male were 28.26 +/- 0.05 and 30.22 +/- 0.05 days. By dissecting the parasitized larvae, the egg incubation period of C. vestalis was recorded 1.73 +/- 0.06 days. In long-term oviposition trials, females laid eggs on P. xylostella larvae for up to 10 days. Larval development of the parasitoid in host only required 6.47 days: the first instar larva required 3.25 +/- 0.047 days; the second instar larva needed 2.78 +/- 0.1 days and the third instar larvae exited the host and pupated in, 0.4 +/- 0.07 days. Prepupal and pupal period of wasp were 1.9 +/- 0.06 and 2.13 +/- 0.09 day, respectively. Unmated female and male longevity of wasp were 16.83 +/- 0.37, 16.25 +/- 0.17 and sex ratio is male-biased. When a mixed group and isolated of instars were presented for parasitoid, the 2nd and 3rd instar larvae were so preferred and the 4th instar was less attractive for selection. In choice experiment, the percentage parasitism of 2nd, 3rd and 4th instars was 78.58, 69.94 and 4.36%, respectively. The rapid oviposition rate, short life duration and high percentage parasitism increases parasitoid potential for suppression of host population. Present results suggest that C. vestalis has considerable potential as a biological control agent for P. xylostella.