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Plantwise Technical Factsheet

white top borer (Scirpophaga excerptalis)

Host plants / species affected
Mangifera indica (mango)
Oryza sativa (rice)
Saccharum officinarum (sugarcane)
Sorghum halepense (Johnson grass)
Triticum (wheat)
List of symptoms/signs
Growing point  -  dead heart
Growing point  -  internal feeding; boring
Leaves  -  external feeding
Leaves  -  internal feeding
Stems  -  dead heart
Stems  -  internal feeding
Symptoms
Early indications of the presence of S. excerptalis on sugarcane include the presence of egg clusters on the upper side of the leaves near the growing point. The egg clusters are usually 13 mm long and covered by brownish-yellow hairs from the anal tuft of the female adult moth. First-instar larvae eat through the rolled leaves which subsequently unfurl, producing a characteristic, repetitive pattern of small holes. The larvae usually penetrate along the midrib of the leaf into the heart of the plant. They tunnel in the midrib for 24-48 hours and emerge through the upper epidermis. Two or three first- and/or second-instar larvae, and on rare occasions third-instar larvae, can be found in the spindle of the stems. The top shoot becomes withered and stunted, whereas the internodes beneath may produce new leaves.

In general, only one mature larva survives in a single stem because of food competition. The larva tunnels into the stem, making a small window near ground level; it then pupates in a cocoon near that opening. Damage is generally most severe in young plants that thrive in a humid environment.
Prevention and control

Cultural Control

Cultural control methods may reduce the borer population but applications are limited. Cultural methods for controlling S. excerptalis and Chilo sacchariphagus in India include the application of nitrogen (Yazdani et al., 1993) and potash fertilizers, and intercropping with spice crops (Varun et al., 1990). The effect of plant-row direction on the incidence of S. excerptalis and Chilo infuscatellus in sugarcane in the pre-monsoon period in India was different for the two species (Singla and Duhra, 1992). Some irrigation schemes may reduce the incidence of first and third broods of S. excerptalis (Singla and Duhra, 1992).

The effect of pulse intercrops on some borer pests of sugarcane and general predators was examined in two field studies in India. In a replicated experiment using black gram, cowpea, green gram and soyabean as intercrops, the incidence of the shoot borer Chilo infuscatellus did not differ significantly with the different combinations and control. The incidence of S. excerptalis was negligible in all combinations. Mean predator numbers did not differ significantly between intercrop and monocrop in these three plots. The importance of factors such as crop combination, temporal and spatial patterns of planting and agronomic suitability for sugarcane pest management in sugarcane-based polycultures is discussed (Srikanth et al., 2000).

Integrated Control

Integrated control of S. excerptalis was studied on sugarcane at Seorahi, Uttar Pradesh, India, during 1993-94 and 1994-95. Control methods included egg mass collection during oviposition by the first and second generations in March and May, and treatment with carbofuran [a hazardous chemical that is not recommended] and the release of Trichogramma chilonis and T. japonicum at 50,000 adults/ha per week during the third generation. A reduction of 5 and 9.5% of the first and second generations, respectively, was observed during 1993-94 and of 16.5 and 5.6% during 1994-95. This reduction in infestation was attributed to egg mass collection. The application of carbofuran and Trichogramma spp. reduced the third generation by 8.2%. Yield was increased by 18.1% with integrated control methods (Pandey et al., 1997a).

IPM methods were applied by Saroj Jaipal (2000) in India. The timely mechanical removal of top borer infested shoots, egg masses and adults helped to reduce the incidence of the most damaging third brood alone by over 50% in all of the cultivars studied. Apart from being completely safe to the environment, expenditure was 3-4 times lower (Rs. 150-250/ha) with this technique than with the chemical treatment (Rs. 1000-1500/ha). It was considered practicable in areas where labour is plentiful and inexpensive, and on small family holdings.

Biological Control

The main parasites of S. excerptalis in India include Stenobracon sp., Isotima javensis, Rhaconotus scirpophagae, Telenomus spp. and Elasmus zehntneri (Gupta et al., 1994; Mukunthan, 1989). T. beneficiens, E. zehntneri and I. javensis did not suppress pyralid populations below the economic threshold in Indonesia (Samoedi, 1988). Stenobracon deesae and R. scirpophagae are the most common parasitoids of S. excerptalis larvae (Gupta et al., 1994); E. zehntneri is less common; I. javensis is found in the pupae.

Field studies conducted in Orissa, India, on the extent of egg parasitization of S. excerptalis on sugarcane revealed that Telenomus dignoides caused an average of 14.6% parasitization. The highest and the lowest rates of parasitization occurred in the first 2 weeks of December and January, respectively (Jena and Patnaik, 1997).

Pseudochirakia was recorded from S. excerptalis for the first time in 1998 (Debjani Dey, 1998).

Tanwar and Ashok Varma (1997) studied the relation between parasitoids and sugarcane cultivars in eastern Uttar Pradesh, India, during 1987-1989. Two egg parasitoids and seven larval parasitoids were recorded but the pest population was not suppressed by parasitism during successive generations. Among the local commercial cultivars screened, BO 91 was the least infested by S. excerptalis and was tolerant under field conditions compared to CoS 7918, Co 1148, CoJ 64 and CoS770.

Trichogramma chilonis, Trichogrammatoidea eldanae and Allorhogas pyralophagus [Parallorhogas pyralophagus] were evaluated against Chilo infuscatellus, and Isotima javensis against S. excerptalis, on sugarcane in Punjab, India. Cane damage by S. excerptalis in fields where I. javensis was released was 10% compared with 22% in the control; 22% of larvae were parasitized in the release field compared with 9% in the control. S. excerptalis and C. infuscatellus were found to be the key pests of sugarcane in the Punjab. S. excerptalis was active from March to October, but most of the damage was inflicted in July-August; C. infuscatellus was active from April to June (Maninder Shenhmar and Brar, 1996).

Mukunthan (1989) collected the eggs and larvae of S. excerptalis. Telonomus sp. caused the highest mortality of the eggs; R. scirpophagae and Isotima javensis attacked the final-instar larvae; and S. deesae and Xanthopimpla pedator attacked the pupal stage.

Tanwar (1990) described the biology of E. zehntneri and a technique for rearing the parasitoid.

The parasitoid Allorphogas pyralophagus [Parallorhogas pyralophagus] was introduced in India and bred successfully on S. excerptalis; however, it did not establish in the wild (Easwaramoorthy et al., 1992; Varma et al., 1987).

Tetrastichus schoenobii was reared in China; a strategy for the conservation and augmentation of this eulophid has been proposed by Pu et al. (1988).

A device was developed to conserve and increase the number of egg parasites of S. excerptalis on sugarcane in Bangladesh, including Telenomus, Tetrastichus and Trichogramma. Naturally parasitized egg masses were collected and posted through a hole made on the internode of a piece of hollow bamboo, known as a parasite booster. The periphery of the hole was smeared with a locally prepared adhesive to stop the larvae of S. excerptalis from crawling out. The boosters were kept in an upright position in a field 6.5 m apart, thus allowing the parasites to fly out and parasitize other egg masses. The device reduced the pest population and enhanced the parasite population; 20% less infestation occurred in a treated field than in an untreated one (Miah et al., 1984).

Stenobracon maculata, I. javensis and Elasmus sp. were collected from larvae, and Pharanus sp. was collected from eggs of S. excerptalis in Indonesia (Samoedi, 1993).

Trichogramma spp. were released against different stem-borers (S. excerptalis, Tetramoera schistaceana and Chilo infuscatellus) in the Philippines. When releases were synchronized with the appearance of the first egg, the rate of parasitism increased to 87.5%. Releases of parasitoids decreased borer infestation to 4.78% in treated fields compared with 77.7% in untreated fields (Alba, 1990, 1991).

Karunakar et al. (1999) found that S. excerptalis was highly susceptible to the nematodes Steinernema glaseri, S. feltiae and Heterorhabditis indicus under laboratory conditions.

The pathogenicity of the fungus Beauveria bassiana was investigated in India (Sivasankaran et al., 1990). Several lepidopterous insects were tested including S. excerptalis. The fungus caused an average of 50-65% mortality of third-instar larvae in different species.

Chemical Control

Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:


Impact
S. excerptalis reduces sugarcane quality and sugar yield (Duhra and Sharma, 1993). The third generation of S. excerptalis causes the highest losses in cane yield, sucrose and commercial sugar; maximum losses occur in autumn-planted cane (Gupta et al., 1993).

S. excerptalis is ranked among one of the major pests of sugarcane in Asia. However, objective assessment of crop losses by S. excerptalis alone are difficult because it usually occurs together with other stem-borers such as Emmalocera depressella [Polyocha depressella], Chilo infuscatellus and C. auricilius in India (Singla and Duhra, 1991); C. infuscatellus in the Philippines (Alba, 1990); and C. saccharipagus in Indonesia (Kalshoven, 1950).

Nevertheless, a number of studies on crop losses have been undertaken in recent years. Manager Singh (1997) studied the effect of S. excerptalis on plant height, number of internodes, weight and CCS of sugarcane in Uttar Pradesh, India, from 1988 to 1989 and 1990 to 1991. Stalk length was reduced by 68 and 30%, internodes by 67 and 29%, cane weight by 86 and 34.5%, and CCS by 25.9 and 13.5%, respectively. Pandya et al. (1997b) recorded the incidence of S. excerptalis on sugarcane in Gujarat, India. An incidence of 45% was recorded at harvest, resulting in 25.2 weight loss and a 22.9% decrease in length. Decreases of 4.3, 5.6, 2.2 and 6.3% in brix, pol, purity and estimated recovery, respectively, were recorded due to S. excerptalis damage.
Related treatment support
 
External factsheets
TNAU Agritech Portal Crop Protection Factsheets, Tamil Nadu Agricultural University, English language
TNAU Agritech Portal Crop Protection Factsheets, Tamil Nadu Agricultural University, Tamil language
BSES Factsheets, BSES Limited, English language
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