The Sugarcane Top Borer
Damage: Young larvae bore into the midrib, leaving red markings and small holes on the leaves. Then the larvae tunnel in the upper portion of the stem, resulting in drying of the central shoot, causing “dead heart”. With the death of central shoot, side branches start growing from a lower node, giving a characteristic “bunchy top” appearance to the plant. Up to 25% mortality of shoots and 40% stunting has been recorded in northern India.
Life cycle: Adult moths are creamy white in colour with crimson coloured anal tuft of hairs in females. Males are slightly smaller, with a wing span of 25-30 mm. Fecundity is 150-300 eggs per female. Eggs are dull white, oval, laid in overlapping clusters of about 30 eggs on the under surface of the leaf and covered with buff coloured hairs derived from the anal tuft of female. Incubation period is 5-7 days. After hatching the larvae bore into the midrib and tunnel towards the stem for 24-48 hours and then enter the stem. Full grown larva is 25-30 mm long dull creamy white having shorter legs. Larval period is 25-40 days. Pupation takes place inside the stem in a chamber constructed by the larva just above the node. Pupal period is 10-20 days depending on temperature. Hibernation takes place in the larval stage.
Distribution: This is a widely distributed species all over the Indian subcontinent and also occurs in Indonesia, Japan and Philippines.
Control: Egg masses and infested portions should be collected and destroyed. Chemical control is not satisfactory although 0002% malathion, endosulfan or carbofuran if timed with egg laying gives some control. Dusting with 10% BHC, dieldrin or endrin or 3% carbofuran timed with moth emergence is recommended.
Biological control was successfully attempted by CIBC (Commonwealth Institute of Biological Control) by mass release programmes of exotic species of Trichogramma. The following parasitoids have been recorded on this pest:
Egg parasites: Tetrastichus sp., Trichogramma intemedium, T. minutum.
Larval parasites: Goniozus indicus, Stenobracon deesae, Amauromorpha accepta schoenobii, Isotima javensis, Syzeuctus sp., Sturmiopsis infenens.
Pupal parasites: Tetrastichus ayyari, Xanthopimpla pedator.