Kartohardjono, A. and M. Arifin. 2007. Control of rice army worm using virus formulation (MsNPV) on rice, pp. 56-59. In L. Sulistyowati et al. (Eds.) Proceedings of The 1st International Conference on Crop Security 2005, Crop Security for Food Safety and Human Health. Malang, September 20th – 22nd, 2005. Agriculture Faculty, Brawijaya University, Malang, Indonesia.
Arifin Kartohardjono and Muhammad Arifin
IIRR, Sukamandi and Balitbiogen, Bogor
ABSTRACT
Rice field is often destroyed by many insects pest. Among some pest which cause significant damage and reduce yield significantly is rice army worm, Mythimna separata (Noctuidae, Lepidoptera). Method of control which does not contaminate the environment is by using biological agent, virus. The objective of this study are to: 1) obtain method of control of army worm which does not contaminate the environment by using biological agent virus MsNPV; 2) find effective concentration, formulation, dosage and efficacy of virus MsNPV as biological agents to control rice army worm. The study was conducted in the laboratorium, green house and rice field in Bogor, West Java during Planting Season 2003 and Planting Season 2004. These studies consists of some activities, they were: I) concentration test of virus MsNPV; II) formulation technique and test of the effectiveness; III) test of dosage effectiveness of MsNPV and IV) test of efficacy against rice army worm on rice plant. Result from these studies shows that: 1) virus MsNPV formulation effectively cause mortality of rice army worm on rice plant; 2) concentration test on 3rd to 5th instar larvae on const. 105 to 109 PIB/cc caused larvae mortality until 70-86%; 3) formulation test on talc, kaolin and gypsum respectively caused larvae mortality around 22 to 33%; 4) dosage formulation 1, 2 and 3 gram MsNPV per 1 l water to larvae rice army worm shows the same effectivities; 5) talc formulation shows more effectivity as compared with gypsum and kaolin formulation; 6) Efficacy of MsNPV against larvae rice army worm on 3 and 6 days after application caused the higher mortality.
Key words: MsNPV, rice, rice army worm.
INTRODUCTION
During two decades rice production already stagnant. While rice field always destroyed by many insect pests there were key pests and potential pests. The key pests which often destroyed rice field are rice stem borers, hoppers, and rat. And the potential pests which reduced significantly of production, high, wide with sudden infestation are rice army worm, Mythimna separata, (Lepidoptera: Noctuidae). The infestation is higher when dry season comes earlier or when there was dry period during wet season (Kalshoven, 1981). lnfestation in 1996 around 5,290 ha and in 1998 until 23,807 ha while in 2002 around 12,114 ha. The wider infestation in 2001 existed in South Sulawesi around 2,448 ha and in West Java around 2,335 ha (Direktorat Bina Perlintan, 1994). Some methods are already conducted to control rice army worm; they were mechanical & pysical control, cultural control, biologycal control and chemical control. The chemical control was applied when the rice army worm population was high, but using this method will contaminate the environment and the price of insecticide is expensive. Control method which is sound to the environment are by using biological control; this control method used their biological agents. Some biological agents which is often used in biological control are entomopathogenic fungi, bacteria and virus. Some studies have been conducted by using virus; SlNPV which is used to control army worm on soybean, Spodoptera litura and HaNPV used to control army worm on cotton, H. armigera (Arifin et al., 1999; Indrayani, 1996). On rice army worm also found virus as an entomopathogenic (Kartohardjono, 2003). So it is urgent to study this virus to be used as a biological agent of rice army worm.
In USA before pesticide was used, the EPA (U.S. Environmental Protection Agency) farmer must have information about: a) its active ingredient; b) its result of effication test; c) its safety to human life and the environment; c) its analysis method about the residu; e) the label about the active ingredient conten; f) method of application and g) method of safety in emergency condition (Upholt et al. (1973 in Maddox, 1975). The objective of this paper were to: 1) obtain method to control rice army worm which is sound to the environment by using biological agent virus MsNPV; 2) obtain effectiveness concentration, formulation, dosage and efficacy of virus MsNPV to control army worm on rice.
MATERIALS AND METHODS
The studies were conducted in the laboratorium, green house and rice field in Bogor West java in the planting season 2003 and 2004. The studies consist of some observations which mention below.
Concentration Test of Virus MsNPV
After virus virulence is known (value of LC 5O), than studies were conducted to detect effective concentration of Particle Inclusion Bodies (PIB) per cc, among 105; 106; 107; 108; 109 PIB/cc and control. Each concentration were applied to one-month-old rice plant in a plastic pot then covered with milar plastic. Each rice plant were inoculated with 20 army worm larvae 3rd-4th instar in randomized block design with 4 replications. Observation on total larvae and mortality of larvae were conducted 3 days after application (dap) then continued until the larvae become pupae. Collected data mortality on larvae were analyzed and compared with DMRT 5%.
Formulation Technique and Test of the Effectiveness
Suspension or supernatan virus which was collected were formulated for effective concentration. Concentration of particle inclusion bodies per cc (PIB/cc) used for each formulation based on the result of previous study was LC 70%. Material used for formulation consist of 3 main components in comperasion were a) supernatant virus 33%; b) carrier (1. kaolin/lactosum; 2. talk/CaCO3 and 3. gypsum) 95% each and c) molases 5% then mixed. After all material are mixed then dried and wind blewed in room condition for 24 hours. After completely dried the material mixture were ground using mortar then filtered using small mesh filter. Formulation made were ready for use, each material formulation were tested by applying to one month old IR 64 rice variety in plastic pail. Then each plant were inoculated with 15 larvae of rice army worm 3rd to 4th instar and covered with plastic milar. Randomized block design, was used with treatment were: a) talc; b) gypsum; c) kaolin and d) control, each treatment were replicated 3 times. Observation were conducted on 3 days after application (dap) to total and death larvae rice army worm found every 3 days until the larvae become pupae. Data collected were analized and compared using DMRT 5%.
Test of Dosage Effectiveness MsNPV
Each virus formulation talc (CaCo3); kaolin (laktosum); gypsum on effective concentration (107 PIB/cc) were tested in gram per liter water. Each formulation were tested on one month old IR 64 rice variety in plastic pail in three dosage, they were 1; 2; 3 gram per 1 l water. The treatment were 10, including control and replicated 3 times arranged in randomized block design. Application were conducted in each rice plant then inoculated with 15 rice army worm larvae 3rd-4th instar and covered with plastic mylar. Observations were conducted on 3 dap to total and death of rice army worm larvae were found every 3 days until the larvae become pupae. Dosage effectivety were found from analized data and compare used DMRT 5%.
Test of Efficacy MsNPV against Rice Army Worm
Effication test was conducted on talc formulation with dosage 2 gram/1 l water. Application were conducted on one month old Ciherang variety in plastic pot then each plant were covered with plastic milar. Time of inoculation as treatment were conducted at 0, 3 and 6 days after application including control (without application). After application each plant were inoculated with 15 rice army worm larva 3rd-4th instar. The design was Randomized Block Design with 3 replications. Observations were conducted on 3 dap to total and death of rice army worm larvae were found every 3 days until the larvae become pupae. Effication of MsNPV shown from analyzed data and compare used DMRT 5%.
RESULT AND DISCUSSION
Concentration Test of MsNPV virus
The concentration test against 3rd-4th instar larvae army worm on first observation (3 dap) shows that the percentage of larvae mortality was around 41-50% while on control 19% (Table 1). There are significant difference between treatments and control. But between teatments there are not significant difference. In the following observation 6 dap the percentage of larvae mortality increase into 61-77%. The higher mortality was found at concentration 105 and 109 PIB/cc. ln the last observation 9 dap the percentage of larvae mortality become 70-86%. The higher mortality was still found at concentration 105 and 109 PIB/cc, each 86.77%.
Formulation Technique and Test of the Effectiveness
The virus suspension for formulation was made at effective concentration which is 107 PIB/cc. The carrier and other material used are talc, gypsum, kaolin and molases 5%. Formulation made are shown in Figure 1, each formulation was tested against 3rd-4th instar army worm larvae on rice plant in plastic pot including control. From the observation at 6 dap the percentage of larvae mortality around 15-28% and control 6.7% (Figure 2). The higher mortality was respectively found on gypsum, kaolin and talc. On the following observation 12 dap the mortality increased on gypsum, 33%; talc, 22% and kaolin, 23%.
Test of Dosage Effectiveness MsNPV
Dosage effect of each formulation has been shown from the first observation (3 dap) and it's significantly different between treatment and control (Figure 2) with c.v. 31%. The value of c.v. is high because the larvae mortality is still in variation. Among each dosage in each formulation are not significantly different. On the following observation at 9 dap the larvae mortality increase on talc >90%, while on gypsum and kaolin around 70% and it was significantly different with control (11%). The value of c.v. on last observation are 20%, it showed that mortality of larvae was not so varied. The highest larvae mortality were found on talc with dosage 1; 2; 3 gram/1 l water.
Test of Efficacy MsNPV against Rice Armyworm
Effication test shows significant difference between treatment and control. The percentage of larvae mortality at inoculation after treatment (0 dap) was less as compared with inoculation at 3 and 6 dap on all periode of observation otherwise some are not significantly different (Table 2). After application rice leaf was still wet with spray solution so the effect was still low (16.7-43.3%). While at inoculation 3 dap rice leaf was already dry so the effect on larvae mortality increase 21.7-85% as compared with inoculation at 6 dap the larvae mortality 35-63.3%.
Effectivity of NPV suspension was shown from PIB per cc, the result from this study indicated that 105 and 109 were most effective otherwise at 107 it already caused mortality of armyworm larvae quite high (Table 1). The effective concentration is based on formulation made, when the formulation is already made, the mortality should be as good as concentration used. Material commonly usecl for biological insectiside are talc, gypsum and kaolin (Figure 1).
Test on these three formulation shows that talc caused 22% larvae mortality, gypsum 33% and kaolin 20% (Figure 2). On soybean MsNPV at dosage 9 x108 PlBs/m2 formulated with laktosum powder it caused mortality of army worm Spodoptera litura, 79-81% (Arifin et al. 1999). The application of this formulation used water, talc is easier diluted on water compared to gypsum and kaolin. Test dosage of these formulation 1; 2 and 3 gram per 1 litre water wasn't significantly different, but the use of talc can cause larvae mortality up to 90% (Figure 3). The HaNPV in the field at dosage 200 ml/ha and 100 ml/ha effective decrease H. armigera up to 100% at one to two weeks after application (Bejo, 2001). Efficacy of formulation after application until 6 days still caused 60% larvae mortality (Table 2).
CONCLUSION
1. Virus MsNPV formulation effectively caused mortality of rice army worm on rice plant;
2. Concentration test on 3rd to 5th instar larvae on const. 105 to 109 PIB/cc caused larvae mortality until 70-86%;
3. Formulation test on talc, kaolin and gypsum respectively caused larvae mortality around 22 to 33%;
4. Dosage formulation 1; 2 and 3 gram MsNPV per 1 l water to larvae rice army worm shows the same effectivities;
5. Talc formulation shown more effectiveness as compared with gypsum and kaolin formulation;
6. Efficacy of MsNPV against larvae rice army worm on 3 and 6 days after application caused higher mortality.
REFERENCES
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Direktorat Bina Perlindungan Tanaman. 2003. Evaluasi serangan organisme pengganggu tanaman padi selarna 5 tahun (1989-2002). Dirjen Tanaman Pangan dan Hortikultura, Jakarta.
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