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#1 2018-12-26 19:16:51

Dick_Grimshaw
Moderator

Rice stem borer control using vetiver as a "dead end" trap plant.

Application of vetiver grass Vetiveria zizanioides: Poaceae (L.) as a trap plant for rice stem borer Chilo suppressalis: Crambidae (Walker) in the paddy fields by LU Yan-hui, ZHENG Xu-song, LU Zhong-xian
State Key Laboratory Breeding Base for Zhejiang Sustainable Pest and Disease Control, Institute of Plant Protection and Microbiology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, P.R.China

Here is a summary of the research todate:

Studies have shown that the net income for farmers planting trap plants grew by an average of 10–30% (Hokkanen 1991).

Results of our lab have revealed that the best planting period of vetiver in rice fields is from late March to early April with the planting area accounting for 6–10% of the total area. (Ed: probably less in the field particularly if planted around field boundary)

After transplanting of the rice crop, the water and fertilizer management is consistent with the conventional management of rice. Vetiver can remain in the fields after the harvest of early rice and doesn’t need to be re-planted in the late rice period and following year.

If the damage by rice borers is under the economic threshold, the application of pesticides can be avoided (Zheng et al. 2008).

The results showed that most of the volatiles were common to both rice and vetiver and the relative levels were similar.

The results indicated that the lethal effect of vetiver on C. suppressalis larvae focused on two aspects. Firstly, vetiver contained toxic active substances which have a lethal effect on C. suppressalis larvae. Larvae gradually lost the metabolic detoxification capacity by inhibiting the activity of detoxification enzymes CarE and P450 in larvae and ultimately led to death. Secondly, V. zizanioides is deficient in nutrients compared with rice. The C. suppressalis larvae showed nutritional imbalance after feeding vetiver, impacting the activity of digestive enzymes, resulting in digestive disorders and eventually death.

Biennial vetiver had a stronger controlling effect on C. suppressalis than annual vetiver.

It was concluded that biennial vetiver is effective in controlling Chilo suppressalis in rice for up to 20 m from the planted row.

The reduction rate of C. suppressalis varied from 76.2% to 92.6% depending on the distance from the vetiver rows. The reduction rate of C. suppressalis in the rice fields 25 m from the vetiver strips was also around 80%. The average insect reduction rate reached 84.2%, indicating that in addition to the technological measures of biodiversity conservation, the controlling effect of C. suppressalis was effective with vetiver rows at 50 m spacing and vetiver clusters at 4 m spacing along the rows.

The average density of overwintering C. suppressalis larvae in vetiver field was 13.8 per 100 clusters while that in control field was 85.4 per 100 clusters. The reduction rate of C. suppressalis was 83.8% (Fig. 2).

The survey results on the natural enemies showed that the numbers of egg parasitoids of rice stem borers Telenomus and Trichogrammatidae and other larval stage wasps in vetiver planting field were significantly higher than that in the control field (Fig. 3).

The number of Telenomus and Trichogrammatidae, other parasitic wasps in vetiver fields was 2.8, 1.7, 0.8 times higher than in control field.

Using vetiver as a trap plant to control rice C. suppressalis is a current research hot spot. Our main research has focused on the control of this insect species by vetiver for many years. We integrated and applied green management of C. suppressalis based on the trap plant vetiver on early rice in the main rice growing fields of Zhejiang Province. C. suppressalis was the most serious pest and rice crops in this region have suffered from infestation for years. This management strategy has great significance in the sustainable management of C. suppressalis in rice and reduction in the use of chemical pesticides.

PLEASE NOTE:  (1) the recommended distance between lines of vetiver is abut 20 meters.  Vetiver planted down just one side of a paddy field is unlikely to be effective, as there will be nothing to attract the stem borer moth on the other side, so the moth can invade from the unprotected side. Thus it is important to plant vetiver  around the complete perimeter of the field. If the field is wider than 40 meters then a line of vetiver will need to be planted down the middle of the field.  Also note that within the line spacing of plants can be as much as 5 meters (of course at such wide in-line planting distances the vetiver will not do much for land stabilization!)  (2) the real impact of the vetiver occurs from the second year onwards.

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