by
Lu Zhongxian, Zheng Xusong, Zhejiang Academy of Agricultural Sciences, Hangzhou, China and Zhu Pingyang, Plant Protection Station, Jin Hua City, Zhejiang province, China
![A: Experimental set up to evaluate sesame flowers on Chilo. B: Experimental set up to evaluate effects of sesame on Trichogramma.](https://ricehopper.wordpress.com/wp-content/uploads/2013/03/pic-1-parasitoids.gif?w=540)
A: Experimental set up to evaluate sesame flowers on Chilo. B: Experimental set up to evaluate effects of sesame on Trichogramma.
Sesame flowers have been found to be nectar rich and provide food and shelter resources to natural enemies such as the hymenoptera parasitoids (Gurr et al 2011). The growing of sesame plants on rice bunds is an ecological engineering practice that have high potential. Sesame flowers were found to significantly improve the searching of planthopper egg parasitoids, Anagrus. As egg parasitism is vital, growing of sesame flowers have significant effects on insecticide reduction and planthopper populations .
At the same time nectar is also a food resource for Lepidoptera pest species, such as leaf folders and stem borers. We further investigated this issue and measured the effects of sesame flowers on both parasitoid and pest species.
Longevities of larval parasitoids, Apanteles ruficrus and Cortesia chilonis improves significantly (more than 30%) when fed with sesame flowers compared with water. For the egg parasitoid, Trichogramma chilonis the differences were as large. (Table 1).
Table 1: Longevities (in hours) of 3 species of parasitoids fed with water and sesame flowers
Parasitoid |
Sex |
Water |
Sesame |
Prob |
Apanteles ruficrus |
Female |
52.1 |
68.1 |
0.027 |
Male |
48.6 |
67.0 |
0.005 |
|
Cotesia chilonis |
Female |
49.9 |
69.2 |
< 0.001 |
Male |
57.1 |
61.7 |
< 0.001 |
|
Trichogramma chilonis |
Female |
37.6 |
42.9 |
< 0.001 |
Male |
33.8 |
44.2 |
< 0.001 |
![Lepidoptera pest species. A = Chilo suppressalis. B = Sesamia inferens. C = Marasmia exigua. D = Cnaphalocrocis medinalis](https://ricehopper.wordpress.com/wp-content/uploads/2013/03/pic-2-expt-set-up.gif?w=540)
Lepidoptera pest species. A = Chilo suppressalis. B = Sesamia inferens. C = Marasmia exigua. D = Cnaphalocrocis medinalis
For the 3 Lepidoptera pest species, leaf folder, Cnaphalocrocis medinalis, leaf folder, Marasmia exigua and stem borers, Sesamia inferens and Chilo suppressalis longevities were not significantly different or only slight different when fed with sesame flowers and water (Table 2).
Table 2: Longevities (in hours) of 3 species of Lepidoptera pests fed with water and sesame flowers
Lepidoptera pest species |
Sex |
Water |
Sesame |
Prob |
Cnaphalocrocis medinalis |
Female |
137.4 |
140.3 |
>0.05 |
|
Male |
107.7 |
117.0 |
>0.05 |
Marasmia exigua |
Female |
132.3 |
126.2 |
>0.05 |
Male |
126.2 |
112.3 |
>0.05 | |
Sesamia inferens |
Female |
149.3 |
139.8 |
>0.05 |
Male |
137.7 |
153.2 |
>0.05 | |
Chilo suppressalis |
Female |
131.8 |
136.2 |
>0.05 |
Male |
135.7 |
131.8 |
>0.05 |
![Lepidoptera pest species. A = Chilo suppressalis. B = Sesamia inferens. C = Marasmia exigua. D = Cnaphalocrocis medinalis](https://ricehopper.wordpress.com/wp-content/uploads/2013/03/pic-3-pests.gif?w=540)
Lepidoptera pest species. A = Chilo suppressalis. B = Sesamia inferens. C = Marasmia exigua. D = Cnaphalocrocis medinalis
We also measured eggs laid by the pest females and found that for the leaf folders, the sesame flowers had significant effects while for the stem borers, there were slight negative effects (Table 3).
Table 3: Eggs laid per female of 3 pest species when fed with water and sesame flowers.
Lepidoptera pest species |
Water |
Sesame |
Prob |
Cnaphalocrocis medinalis |
0.10 |
0.77 |
0.001 |
Marasmia exigua |
1.05 |
4.60 |
<0.001 |
Sesamia inferens |
133.6 |
117.0 |
> 0.05 |
Chilo suppressalis |
77.3 |
70.3 |
> 0.05 |
Laboratory studies fully support the selection of sesame to enhance Anagrus spp parasitoids (Zhu et al 2013). These results suggest that sesame flowers have more positive effects in enhancing other hymenoptera parasitoids than on increasing pest species. This is further support for the use of sesame in ecological engineering practices.
Reference
Zhu Pingyang, Gurr, Geoff, Lu Zhongxian, Heong, K.L., Chen, Guihua, Zheng, Xusong, Xu, Hongxing, Yang, Yajun. 2013. Laboratory screening supports the selection of sesame (Sesamum indicum), to enhance Anagrus spp. parasitoids (Hymenoptera: Mymaridae) of rice planthoppers. Biological Control 64, 83 – 89.