MONITORING SUGARCANE MOTH BORERS IN INDONESIA: TOWARDS BETTER PREPAREDNESS FOR EXOTIC INCURSIONS. Pasuruan, Indonesia

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1 MONITORING SUGARCANE MOTH BORERS IN INDONESIA: TOWARDS BETTER PREPAREDNESS FOR EXOTIC INCURSIONS By NADER SALLAM 1, ETIK ACHADIAN 2, ARI KRISTINI 2, MUCHAMAD SOCHIB 2, HERWAN ADI 2 1 BSES Limited, Gordonvale, 2 Indonesian Sugar Research Institute, Pasuruan, Indonesia nsallam@bses.org.au KEYWORDS: Moth Borers, Chilo, Scirpophaga, Indonesia, Sugarcane. Abstract SUGARCANE moth borers were surveyed on 931 farms across Java, Indonesia in Five moth borer species caused varying levels of damage to sugarcane plantations: Chilo auricilius, C. sacchariphagus, Scirpophaga excerptalis, Sesamia inferens and Tetramoera schistaceana. The first three were the most abundant. All five species caused dead hearts in sugarcane, with S. excerptalis (top borer) being responsible for the majority of dead heart symptoms in both young and mature cane. Chilo species (stalk borers) cause dead hearts only in young cane and later tunnel inside cane stalks and damage the internodes. Farms managed by sugar factories suffered more S. excerptalis dead hearts than those managed by individual growers. This may be the result of crop diversification and shorter crop cycles practiced by individual farmers. In addition, S. excerptalis dead heart symptoms were more common in older ratoons, indicating progressive build up of infestation in older crops. C. sacchariphagus was more widespread in Java than C. auricilius, with the former species preferring irrigated areas while C. auricilius was more abundant in drier areas. S. excerptalis was equally abundant in both irrigated and rainfall areas. Parasitoid species recovered were Cotesia flavipes from C. sacchariphagus, Diatraeophaga striatalis from both Chilo species, and Rhaconotus roslinensis, R. scirpophagae, Stenobracon sp., Elasmus sp. and Isotima sp from S. excerptalis. All moth borers have a high potential of colonising sugarcane in Australia, especially in central and north Queensland where climatic conditions are similar to conditions in their area of origin. Knowledge of the distribution and dynamics of these pests is essential to the development of sound Incursion Management Plans to ensure better preparedness for any incursion into Australia. 181

2 Introduction In Indonesia, the sugarcane industry is an important source of income, with 58 sugarcane factories processing 30 Mt of cane grown over ha, mostly on the island of Java. Numerous pests and diseases attack sugarcane crops in Java and productivity and profitability are significantly reduced due to periodic heavy infestations and cost of pest control. However, very few published studies have looked at the range of sugarcane pests and diseases in Indonesia and no data are available on their impact on sugar production in that country. This paper reports on preliminary results of a pest survey conducted as a part of a joint research project between the Australian Centre of International Agricultural Research (ACIAR), the Indonesian Sugarcane Research Institution (ISRI) in Java and BSES Limited in Australia (Magarey et al., 2010). The project aims to survey sugarcane pests and diseases in Java over two years, with special focus on moth borers, which are major pest species not only in Indonesia but in all cane-growing areas except Australia and Fiji (Harris, 1962; Legaspi et al., 1997; FitzGibbon et al., 1998). So far, the Australian sugar industry has been free of major moth borers, but several borer species occur in neighbouring countries and it is in Australia s interest to collaborate with research organisations in these countries and maintain comprehensive pest monitoring and surveillance programs. Prior to studying the impact of moth borers on cane productivity in Java, we needed first to identify the range of borer species on that island, study their geographical distribution and examine aspects of their biology and ecology. Our study focused on investigating the geographical distribution of moth borer species in Java and on relating surveillance results to factors such as crop age, locality (region) and farm management practices. This information will lead to better assessment of the economic impact inflicted by each of these species on cane productivity and will assist in the establishment of species-specific management strategies in Java. This information is also important for improved sugarcane biosecurity in Australia and to ensure the establishment of a quick and accurate emergency response strategy in case of a borer incursion. Materials and methods We surveyed 931 farms that supply to 30 sugar factories across Java for species of stalk borers during April 2008 April Of these farms, 620, 226 and 85 belonged to the main three regions of East, Central and West Java, respectively. In one field on each farm, all plants in ten 10-metre transects were checked for symptoms of moth borer infestation. Fields examined represented a range of crop ages (in months), crop classes (plant cane or ratoon crops) and management systems (factory-managed or growermanaged), and covered all sugarcane growing regions in Java. Plants showing boring symptoms either in the leaf, shoot, stalk or the growing point were recorded. Shoots, stalks and growing points were dissected and the pest species responsible for the 182

3 detected damage was identified directly or, if no borer was found, by the feeding pattern on the leaves, the shape of the feeding tunnel, the shape of the exit hole and the presence or absence of a dead heart. Any borer larvae collected were taken to the laboratory and bred out until they produced an adult moth or a parasitoid, in which case the parasitoid was identified and rate of parasitism recorded. Information on crop age, class and farm management was obtained and used in the data analysis as independent variables with pest species and infestation levels as dependent variables (SAS, 2003). Climates at Pasuruan and Bogor were matched with those in major canegrowing areas of Australia using the program CLIMEX as used by FitzGibbon et al. (1999). Results and discussion Species identification and damage symptoms We found five species of moth borers belonging to four families: Chilo auricilius and C. sacchariphagus (Lepidoptera: Crambidae), Scirpophaga excerptalis (Lepidoptera: Pyralidae), Sesamia inferens (Lepidoptera: Noctuidae), and Tetramoera schistaceana (Lepidoptera: Tortricidae). Both S. inferens and T. schistaceana were very rarely encountered and were not included in the data analysis. The following are observations on the identification and damage symptoms of these pest species. Chilo auricilius (stalk borer) This pest causes dead hearts in young cane and damages internodes in advanced crops. The larval stage is distinguishable by the five dark longitudinal lines along the body, while damage symptoms can be distinguished by the transparent feeding marks early instar larvae cause on young leaves before they unfold. Feeding by mature larvae causes a thin, straight feeding tunnel inside the internode (Figure 1), while the moth s exit hole is neatly round. Chilo sacchariphagus (stalk borer) Similar to C. auricilius, this pest causes dead hearts in young cane and damages internodes in advanced crops. The larval stage can be distinguished by the four longitudinal stripes formed by the spots on the dorsal side (Kalshoven, 1981). Unlike C. auricilius, feeding by young larvae leaves a line of holes on young leaves, while mature larvae cause irregular tunnels inside the internodes (Figure 1). The moth s exit hole is oval in shape. Scirpophaga excerptalis (top borer) Feeding by young S. excerptalis larvae leaves parallel horizontal rows of shot holes that become apparent when young leaves unfold (Figure 1). Unlike species of Chilo, larvae of S. excerptalis do not tunnel in cane stalks and so do not damage the internodes, but instead move down the plant top towards the growing point, mainly causing a dead heart and a bunchy-top appearance of shoots (Arora, 2000). Sesamia inferens (shoot borer) This species is mainly a pest of rice and is rarely found infesting sugarcane in Java. It was found occasionally during the general survey in East and Central Java but not in West Java. This species is a shoot borer and causes dead hearts in young cane 183

4 plants (Figure 1). Larvae are distinguished by their purple or pink dorsal colour and white ventral colour (Kalshoven, 1981; David et al., 1991). Tetramoera schistaceana (shoot borer) This species was found occasionally in all the three regions of East, Central and West Java. Tetramoera schistaceana is an early-shoot borer which mainly causes dead hearts in young plants (Williams, 1978; Cheng and Wang 1997). In mature plants, larvae feed externally on the internodes and around the buds but usually cause minor damage (Figure 1). Fig. 1 Damage symptoms of Chilo auricilius, Chilo sacchariphagus, Scirpophaga excerptalis, Sesamia inferens and Tetramoera schistaceana (from left to right). Infestation levels Figures 2a-c show damage levels for C. auricilius, C. sacchariphagus and S. excerptalis in 30 sugar factories across Java. C. auricilius was responsible for low damage levels in a number of sugar factories through Java, but it was mainly widespread in Pesantren Baru sugar factory (East Java) where infestation resulted in an average of 3.3 bored internodes per 10 m row. This was significantly higher than damage levels caused by this species in all other sugar factories, where infestation levels ranged between damaged internodes per 10 m row (F = 17.49; df=29,901; P<0.0001). On the other hand, damage by C. sacchariphagus was found in all sugar factories across Java, with significantly higher damage levels in Sumberharjo and Jombang Baru sugar factories (F= 9.44; df=29,901; P<0.0001) where infestation levels averaged 3.2 and 3.1 bored internodes per 10 m row, respectively. Most sugar factories had more than 0.2 bored internodes per 10 m row. This species was the main cause of bored stalks in Java, with an overall average of 1.13 bored internodes per 10 m row, compared to 0.19 bored internodes per 10 m row caused by C. auricilius (F= ; df=2, 2790; P<0.0001). S. excerptalis was present in all sugar factories across Java, and it was the main cause of dead heart symptoms in young and mature plants in Java. Damage levels ranged between dead hearts per 10 m row, with 15 sugar factories recording more than 1.5 dead hearts per 10 m row. Overall, S. excerptalis caused an average of 1.4 dead hearts per 10 m row across Java, which is significantly higher than mean dead hearts caused by C. sacchariphagus and C. auricilius (0.13 and dead hearts per 10 m, respectively) (F=293.87; df=2,2790; P<0.0001). In addition, this species was also the main cause of leaf damage symptoms due to borers, with an 184

5 overall average of 0.33 damaged leaf tops per 10 m row across Java. This was significantly higher than leaf damage caused by C. sacchariphagus and C. auricilius (0.27 and bored leaf tops per 10 m, respectively) (F=77.76; df=2,2790; P<0.0001). Borer infestations varied according to crop age (in months) and crop class (plant cane or successive ratoons). Infestations by C. sacchariphagus and C. auricilius resulted in dead hearts and leaf damage symptoms in younger cane, but mainly caused bored internodes as the crop aged. However, for S. excerptalis, there was a tendency towards both leaf damage and dead hearts being more apparent as the crop aged and in older ratoons, with 5 th and 6 th ratoons showing significantly more dead hearts than earlier ratoons or plant cane crops (F=3.87; df=6,924; P=0.0008) (Figures 3 and 4). Data analysis also showed that S. excerptalis damage varied according to farm ownership, with farms managed by sugar factories suffering significantly more dead hearts (1.82 per 10 m row) and leaf damage (0.42 per 10 m row) than an average of 1.23 dead hearts and 0.27 leaf damage per 10 m row in farms managed by farmers (F=13.44; df=1,929; P=0.0003; F=8.81; df=1,929; P=0.0031) (Figure 5). This is probably because individual growers tend not to grow as many ratoons as the sugar factories. In addition, individual farmers tend to diversify their crops and do not rely solely on sugarcane and this is likely to interrupt the pest s life cycle. However, this correlation with farm ownership was not significant in most cases for C. sacchariphagus and C. auricilius damage. C. sacchariphagus damage symptoms were more prevalent than those caused by C. auricilius in irrigated cane plantations, where crops receive larger quantities of water compared to areas relying only on rainfall (Figure 6), indicating that C. sacchariphagus may be more adapted to wetter regions whereas C. auricilius may be more tolerant of drought. This agrees with studies by Suhartawan (1998), who observed that high humidity was correlated with increased infestation levels by C. sacchariphagus. The status of different populations of C. sacchariphagus needs confirmation. The species is often treated as three subspecies: Chilo sacchariphagus sacchariphagus (Bojer), Chilo sacchariphagus stramineellus (Caradja) and Chilo sacchariphagus indicus (Kapur), or alternatively as several phylogenetically young species (Bleszynski, 1970). Different populations show considerable variation in behaviour across their natural range. For example, despite C. sacchariphagus being mainly a pest of sugarcane, it has been reported to attack maize and sorghum in Madagascar, Mauritius and Reunion (Betbeder-Matibet and Malinge, 1968; Williams, 1983), while Chundurwar (1989) reported it to be a key pest of sorghum in some parts of China and Mallik et al. (2003) reported it as a pest of rice in eastern India. However, it has never been observed in any of these crops in Java, despite their availability and proximity to sugarcane plantations (Etik Achadian, personal observation). A recent DNA study by Lang et al. (2004) showed phylogenetic differences among populations from India and Thailand compared to those from 185

6 Mauritius and Reunion (which were probably introduced from Java in the mid 1800s (Bleszynski, 1970; Williams, 1983)). Hence, further genetic studies are required to clarify the status of the C. sacchariphagus complex. Similarly, while our survey suggests that C. auricilius is a less abundant stalk borer compared to C. sacchariphagus in Java, it was recognised by Indonesian scientists to have been more widespread than C. sacchariphagus in Java in the early 1990s and its status seems to have changed in recent years (Joko Pramono, personal communication). In addition, C. auricilius is considered to be one of the most damaging sugarcane pests in northern India and it is also recorded to feed on rice and considered to be one of its key pests in Bangladesh and parts of India and China (Husain and Begum, 1985; Meng et al., 1997; Neupane, 1990). Yet C. auricilius is not recorded as a significant pest of rice in Java, and has always been known to mainly feed on sugarcane until Hattori and Siwi (1986) reported it feeding on rice in Java and South Kalimantan. Again, DNA phylogenetic studies are needed to assist in the understanding of each of these pest species and, ultimately, ensure the establishment of pest management strategies that are accurate and pest specific. (a) C. auricilius Dead heart Leaf damage Bored internodes East Java Cantral Java Wast Java (b) C. sacchariphagus 2.5 Dead heart Leaf damage Bored internodes East Java Cantral Java Wast Java 186

7 (c) S. excerptalis 2.5 Dead heart Leaf damage East Java Cantral Java Wast Java Fig. 2 Mean damage caused by a) C. auricilius, b) C. sacchariphagus and c) S. excerptalis in 30 sugar factories across Java. (a) C. auricilius Dead heart Leaf damage Bored internodes Crop age (months) (b) C. sacchariphagus 3.0 Dead heart Leaf damage Bored internodes Crop age (months) 187

8 (c) Fig. 3 Comparison of mean damage caused by (a) C. auricilius, (b) C. sacchariphagus and (c) S. excerptalis at different crop ages across Java Plant cane 1R 2R 3R 4R 5R 6R * * Dead heart Leaf damage Bored internodes Dead heart Leaf damage Bored internodes Dead heart Leaf damage C. auricilius C. sacchariphagus S. excerptalis Fig. 4 Comparison of mean damage caused by C. auricilius, C. sacchariphagus and S. excerptalis in plant and ratoon crops across Java. (*) indicates significant difference within the same category and borer species. Fig. 5 Comparison of mean damage caused by C. auricilius, C. sacchariphagus and S. excerptalis in farms owned by the sugar factory or by individual framers in Java. (*) indicates significant difference within the same category and borer species. 188

9 Fig. 6 Comparison of mean damage caused by C. auricilius, C. sacchariphagus and S. excerptalis in irrigated and rainfed cane plantations across Java. (*) indicates significant difference within the same category and borer species. Fig. 7 Climatic match index showing percentage of climatic similarity between the townships of (a) Pasuruan and (b) Bogor in Indonesia to selected cane planting areas of Queensland and New South Wales, Australia. Parasitoids Two main parasitoids attacked C. sacchariphagus larvae Diatraeophaga striatalis Townsend (Diptera: Tachinidae) and Cotesia flavipes (Hymenoptera: Braconidae). However, C. flavipes was not recovered from C. auricilius despite it 189

10 being widely regarded as a key parasitoid of this species across Asia (Nair, 1958; Butani, 1972; Nigam, 1984; Tanwar and Varma, 1996). Mohyuddin (1991) stated that a local Indonesian strain of C. flavipes was encapsulated in C. auricilius in Sumatra, but a strain from Thailand was introduced and this resulted in high rates of parasitism of both C. auricilius and C. sacchariphagus. Our results suggest that encapsulation may remain a problem in Java, where C. auricilius has proven to be an unsuitable host for C. flavipes even when larvae were stung by parasitoids in the laboratory (Etik Achadian, unpublished data); more work is needed to investigate this problem. For S. excerptalis, four parasitoids attacked the larval stage Rhaconotus roslinensis Lal., Rhaconotus scirpophagae Wilkinson, Stenobracon sp. (Hymenoptera: Braconidae) and Elasmus sp. (Hymenoptera: Elasmidae) while one species attacked the prepupal stage, Isotima sp. (Hymenoptera: Ichneumonidae). All parasitoids were responsible for low parasitism levels, and more work is required to investigate ways of improving their impact in cane fields in Java. Climate matching Figure 7 show indices matching climatic conditions in Pasuruan (East Java) and Bogor (West Java) to selected cane-growing areas of Queensland and New South Wales. The matching indices demonstrate the climatic similarity of those two regions to areas in central and north Queensland. Conclusions It is likely that the Indonesian moth borers would quickly colonise areas of tropical and subtropical regions of Queensland if introduced and it is important to be prepared for any sudden incursion. Incursion Management Plans have been developed by BSES Limited, and these contain comprehensive dossiers on the biology, ecology and management of world moth borers, including the Indonesian species (Sallam and Allsopp, 2008 a, b). In addition, our study highlighted some behavioural variations between Indonesian moth borers and other populations of the same species across the species range in Asia and Indian Ocean islands. Hence, detailed DNA phylogenetic studies are required to clarify the status of the moth borer complex in Asia. Moreover, information gained during this work highlights the importance of further studying pest/natural enemy relationships in the sugarcane ecosystem in Java, and investigating reasons for the failure of Cotesia flavipes to parasitise larvae of Chilo auricilius. There is also need to examine the range of similar natural enemies in Australia to determine whether they can exploit exotic pest species for their development. A study is currently underway to test the indigenous Australian parasitoid Cotesia nonagriae (Olliff) (Hymenoptera: Braconidae) against exotic moth borers (Kate Muirhead, personal communication). In light of the information highlighted through this work, it is advised that moth borer monitoring in Indonesia should continue and be considered a key part of any management program. This will ensure accurate targeting of the correct pest species, and will enable the timely detection of any change in pest status and distribution over time. Information obtained during this general survey and an ongoing monthly survey will improve our knowledge of the nature of these pests, and 190

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