The potential of Beauveria bassiana vuill to control rice leaf roller cnaphalocrocis medinalis guenee

The pest presence and environmental condition is very important factor on agricultural production especially manage rice growth in wetland. The purpose of the research is to study the role of Beauveria bassiana Vuill as entomopathogenic fungi against rice leaf roller Cnaphalochrosis medinalis Guenee (Lepidoptera: Pyralidae) in wetland rice field. Experimental research was held in Pest Laboratory, Plant Pests and Diseases Department, Faculty of Agriculture Hasanuddin University in March to August 2018. The source of C. medinalis larval from rice field in Moncongloe Bulu village, Maros district, South Sulawesi. B. bassiana isolate from Disease Laboratory collection in applied concentration 106 cfu to all of the treatment. The result showed in five days after applied B. bassiana the effective treatment control is P4 = C. medinalis sprayed and dipped rice leaves as food of larvae (100%) then P3 = dipped rice leaves into B. bassiana (90%); P2 = sprayed B. bassiana to body of C. medinalis larval (50%) and P1 = control (30%), respectively. The total mortality of C. medinalis after application B. bassiana started at five days in P4, faster than another treatment. The result of research, B. bassiana is very useful and safety manage population of C. medinalis in rice field.


Introduction
Rice (Oryzasativa L.) family Poaceae is an agricultural famous important crop for half world population. Rice was growth approximately on 145 million hectares in 110 country. About 90% rice were growth in wetland and more consumption in Asia. Overall, rice to be an important staple food for 2 billion people on development country [1][2][3]. In 2014, Indonesian rice productivity was reduced 0.63% than 2013. In the recent years, the decreasing of rice harvest because reduced of productivity amount 0.33% [4]. Commonly the main factor reduced of rice harvest is insect-pest and diseases incidence. The one of human effort against insect-pest is insecticides application. Unfortunately, synthetic insecticides as the plant protection material has a negative effect. Synthetic insecticides playing important role as the source of poison in ecosystem, increasing insect-pest resistance, resurgence and endangered status of natural enemies.
In Indonesia, especially in South Sulawesi as the producers of rice, presence the white rice stem borers (Scirpophagainnotata Walker), rice plant hoppers (Nilaparvatalugens Stahl.), rice leaf roller (C. medinalis) and grasshoppers are key pests of the rice in the wetland [5-7]. The rice leaf roller, Cnaphalocrocismedinalis Guenee) (Lepidoptera: Pyralidae), gained the status of a major pest that may cause 30-40% leaf infestation and 20 -30% yield losses to the rice crop [8][9][10]. The effective insecticides available to cope with insect-pest incidence, but this solution is not a long-term strategy because their impact to health and environmental hazards, exposure risks, residual perseverance and The potential of Beauveria bassiana vuill to control rice leaf roller cnaphalocrocis medinalis guenee  [11]. Therefore, in recent years, the focus of C. medinalis has been shifted towards biological control. Earlier researches suggested the possibility of the successful use of BeauveriabassianaVuill [12,13]. B. bassiana as famous entomopathogenic fungi controlled insect-pest in crops around the world. Application of entomopathogenic fungi as the safety way controlled insectpest development. These biofungicides are valued tools for non-chemical pest management strategies. The advantages apply of B. bassiana is: safety for mammals, human health and environment, improve plant health, cheaper and easy to apply [10,14]. Rizwan et al. [15] reported that B. bassiana or white muscardine fungi as the important biological control agent for insect-pest on the tropic. B. bassiana have been effectively used for biological control of aphids, lepidopteran caterpillars and other pests. B. bassiana are active agents against different stages of insect pests. Sivasundaram et al. [12] reported the application of B. bassiana have been decrease number of several insect-pest species with reduced cells and protein synthesis on body of insect target. The purpose of research is to study the role of B. bassiana as important entomopathogenic fungi against rice leaf roller C. medinalis in wetland rice field.

Source of C. medinalis. C.
Medinalis larval as object of research was collected from rice field in Moncongloe Bulu village, Moncongloe district, Maros Regency, South Sulawesi Indonesia.

Source of isolate and pathogenicity test of B. bassiana.
The research used B. bassiana isolate from Phytopathology Laboratory collection, Plant Pests and Diseases Department, Faculty of Agriculture, Hasanuddin University Makassar. The available concentration [1 × 106 colony-forming unit/gram (cfu/g)] of B. bassiana used in order to study the pathogenicity of B. bassiana against the two instar larval of C. medinalis. The tested larval were collected from wetland rice field, starved for 3 h and apply for each treatment [16].
The research conducted in four treatment such as: P1= control (sterilized distilled water); P2 = sprayed B. bassiana suspension to body of C. medinalis larval. Every larval sprayed with 2 ml of B. bassiana suspension with concentration 106 cfu/g inside petridish; P3 = dipped rice leaves into B. bassiana with concentration 106 cfu/g. Treatment used rice young leaves at the food source of C. medinalis. Before dipped in the B. bassiana suspension, the leaves cutting to be small pieces (length 5 cm), cleaning with water and drying. After dipped, the leaves dried and put inside petridish contain C. medinalis larval; P4 = C. medinalis larval and dipped rice leaves as their food were put together inside a petridish. The treatment used dipping rice leaves similar treatment with P3. After 24 hours, C. medinalis larval sprayed with 2 ml of B. bassiana suspension with concentration 106 cfu/g. Ten larval put into every petridish (diameter 8 cm) and used in each treatment. Mortality counts started after 24 hours and recorded for 10 days [13].

Data analysis
All of data treatment of C. medinalis was collected and tabulation. The performance of research data used Analysis of Variance (ANOVA) with DMRT level 95% (α = 0.05). randomly.

Results and discussions
The result showed in five days after applied B. bassiana the effective treatment control is P4 = C. medinalis sprayed and dipped rice leaves as food of larval (100%) then (90%); P2 = sprayed B. bassiana to body of C. medinalis larval (50%) and P1 = control (30%), respectively.    Figure 2 showed in nine days after applied of B. bassiana, all of C. medinalis larval from P2, P3 and P4 died. The finding of research showed treatment combination sprayed and dipped of larval food showed the best treatment in control development of C. medinalis. After 48 hours the application of B. bassiana was visually C. medinalis larval began in-active moved for P2, P3 and P4. It seems C. medinalis in dehydration condition. In the treatment using B. bassiana, suspected that B. bassiana suspension contains beauvericine toxin has been invasion of C. medinalis cell body. The dipping leaves treatment is an effective way to against C. medinalis because B. bassiana contain in larval food then enter to digestive tract. Sun et al. [17] state that beauvericine as toxin from B. bassiana will effective and damage cells at low pH mainly in insect stomach. The visual symptom is C. medinalis larval become in-active after apply the entomopathogenic fungi.
Commonly rice leaf roller C. medinalis hatched from the egg will produce silk thread used to fold leaves of their host plant. During the development, C. medinalis living in scroll and form pupae inside leaves. In addition, rice leaves function as protective leaf folding C. medinalisfrom predators and sunlight. This is a problem controlling presence C. medinalis in rice field because C. medinalis protected by rice leaves. Drop of synthetic pesticides application against C. medinalis will stay more at leaves surface. If larval eating leaves, it will contaminated and caused death [18].
The result of research is microbial insecticides contain B. bassiana have shown promising better action against C. medinalislarval. The data is accordance with finding Ambethgaret al. [19] reported that B. bassiana was the most efficient for biological control of C. medinalis under laboratory condition. B. bassianaas entomopathogenic fungi that recommended in IPM program. Feng et al. and Saravanakumaret al. [20,21] state that the isolated was found easy to culture, cheap and effective control insect-pest in different crop including in wetland.

Conclusions
The result of research showed B. bassiana is very useful as entomopathogenic fungi and effective decrease population of C. medinalis larval. However, further studies are required evaluate their efficacy and compatibility against C. medinalis larval under field condition in various wetland zones at South Sulawesi.