BIOLOGY OF PHRA GMA TAECIA CASTANEAE HUBNER, THE GIANT BORER OF SUMATRA, INDONESIA ABSTRACT

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1 BOLOGY OF PHRA GMA TAECA CASTANEAE HUBNER, THE GANT BORER OF SUMATRA, NDONESA Boedijono Wirioatmodjo Sugar Experiment Station, Pasuruan, ndonesia ABSTRACT Phragmataecia castaneae Hubner is the dominant species of stem borer in sugar cane.'observations on its biology were made in the laboratory at an ambient temperature of approximately 32 C and a relative humidity of approximately 74%. Data are provided on the headwidths of larval instars and on the duration of the immature stages. The mean duration of the life cycle from egg to adult was 107 days. The average number of eggs laid per female was 330. The potential finite rate of population increases per day is NTRODUCTON At least four species of lepidopterous stem borers are known affecting sugarcane plantings on newly cleared land in Sumatra. These are the pyralids Chilo sacchariphagus Boyer and C. auricilius Dudg., the noctuid Sesamia inferens Walk and the cossid Phragmataecia castaneae Hubner. The last mentioned species was determined by the Commonwealth nstitute of Entomology. P. castaneae is generally the dominanr species in grown-up cane fields consisting more than 90% of the borer population. Although it is known from Europe to South East Asia, little seems to be known about this moth. This paper covers studies on the general biology of P. castaneae carried out in North Sumatra. EXPERMENTAL PROCEDURE The experiments were conducted at Tanjung Morawa, 12 km from Medan. Sugarcane is grown in rainfed areas, on alluvial soils and an altitude of f 20 meters. The average annual rainfall is 1810 mm. Most of the work was carried out in the laboratory at an ambient temperature of * 0.79'~ and a relative humidity of 74.87%. Eggs were placed in glass tubes. Freshly emerged larvae were maintained individually in vials containing leafsheaths of young cane stalks. Food was changed every two days. Pupae were placed individually in plastic tubes. Adult moths were kept in muslin cages containing dry cane leaves

2 1653 ENTOMOLOGY Egg, R ESU LTS Freshly laid eggs have a creamish white color turning light brown after several days and becoming grey one or two days before hatching. Eggs are oval in shape, 1.8 mm long 0.8 mm thick (Fig. 1). FGURE 1. Phragmataecia castaneae Hubner., egg batch and larva.! i Eggs were laid in patches consisting of one or more rows on the edges of old dry leaves still attached to the cane or on dead hearts leaves. The edges were then folded and secured to the leaf blades. A one centimeter row consisted of 9-12 eggs, depending on the way of attachment, i.e. either side by side or end to end. The longest observed row was 15 cm. The incubation period was 9-10 days. Larvae After hatching, the larvae grouped together for several hours around the egg patches. Then they dispersed by crawling, or became windborne on silken threads. Some larvae bored directly into the plants without digpersing. They entered the opening between the leafsheath (usually number + 3) and the stem. Three to seven days later the larvae bore into the stem. A single larva may destroy several nodes, averaging 2.28 f 0.95 nodes before pupating inside the stem. The color of a full grown larva is pinkish white with four reddish spot on each segment. Ten instars were observed during rearing (Table 1). On the basis of head-width, the growth increment between instars approximated to The mean total duration of the instars was * 2.06 days. The length af a full grown larva may reach 5.5 cm for females and 4 cm for males. The duration of the pre-pupal stage observed during the study was about two days.

3 B. W ROATMODJO 1654 TABLE 1. Headwidths and duration of the various instars of Phragmataecia castaneae Hubner. lnstar Headwidths Duration (mm) (days) Mean Range Mean Range ll V V V 2.OO V Vlll X X Pupa The pupa is typically protectedwithout the palpus maxilla and the proboscis is rudimental (Fig. 2). The spiracle of the first abdominal segment is not visible. At first the color is light yellow. After a few days the colir gradually becomes darker until finally it turns to dark brown (Fig. 2). FGURE 2. Phragmataecia castaneae Hubner, moths and pupae (left: male; right female). A few hours before emerging, the pupa wriggled itself to the exit hole. When the moth emerged, half of the pupal skin protruded outside. This habit distinguished it from the other lepidopterous,borers. The average length of females and males

4 were cm and 2.53 f '0.26 cm respectively,and the average duration of the pupal phase was * 1.3 days. Adult \ \ Emerging occurred during the afternoon. The moth, which is grayish brown in color has a rudimental proboscis. The antenna of the female consists of 45 annuli, which two third are bipectinate. Three fourths of the male antenna are bipectinate and the apical part is unipectinate. 7- :. -*, Length of the female body was 3.d cm and that of the male was 2.18 f 0.09 cm of 50 specimens examined, the average wing span of female and male were, respectively, 4.90 f 2.77 cm and 3.75 * 0.15 cm. To determine the potential egg-laying capacity, a record was made of the number of eggs laid and the number of ripe eggs or discernable oocytes which remained in the ovaries after the death of the moth. Females laid about 90% of the potential fecundity. n the laboratory, females survived only for about three days. The average number of eggs laid was f The relationship between fecundity (~fand pupal length (X was shown in the following regression equation Y = X The correlation coefficient r = was significant at 0.1% level. southwood4 has used fecundity data to calculate tl-re potential rate of increase of sugarcane borers. To calculate these values it was necessary to determine the maximum reproductive rate (Rm) which is equal to the mean maximum fecundity (F) per ifemale and the fraction of females (f $) in the adult population. With a mean actual fecundity'(not maximum fecundity as in Southwood) per female of and a female fraction of 0.59, the maximum rate of reproduction was \ The potential rate of increase in the absence of mortality is expressed as r = loge Rm/T, where T is the sum of the mean duration of immature stages, preoviposition period and half of the egg laying period. Antilog, rp is an expression of the potential finite rate of population increase per day. With a mean duration of the borer generation T = 99, the values of rp and antilog, rp is an expression of the potential finite rate of population increase per day. With a mean duration of the borer generation T = log, the values of rp and antilog, rp were and respectively. DSCUSSON The incidence of the giant borer affecting sugarcane plantings was first observed in 1976 on newly cleared land in Sumatra. ~hompson', during his visit in Sumatra, donsidered this as the same species which badly attacked sugarcane in Malaysia, i.e., P. gummata. Specimens sent to the Commonwealth nstitute of Entomology were identified as Phragmataecia castaneae Hubner. This species has never been recorded before in ndonesia. ~alshoven* mentioned only Phragmatae 1

5 1 cia Hamps, infesting sugarcane in the mountains. Little seems to be known about P. castaneae although it is known from Europe to Southeast Asia; in fact the Review of Applied Entordology has only four references to it since 1913 reat at head'). While the life cycle of the larvae feeding on the common reed in Central Europe occupies two years, the life duration in / Sumatra is much shorter, i.e. about 80 days. n Lepidoptera, adult fecundity is usually related to the size of pupae (Williams7). Data obtained during the study revealed that the pupal weight can be used to predict fecundity. The value of rp is comparable with those of Southwood4, who obtained a rp of for Castnia, the giant borer of Guyana. The relatively smaller rate of potential finite daily rate of increase, compared to those of the pyralids, is the result of its longer life cycle. The number of instars observed was ten. Larger numbers of instars occurred occasionally during insectary rearing. pathak3 has pointed out that the number of moults increases under stress conditions. The growth increment between instars based on head,width approximately to 1.1. This is less than 1.4 which is typical of many lepidopterous larvae (~i~~lesworth'). REFERENCES 1. Greathead, D. J. (1978). Personal communication. 2. Kalshoven, L. G. E. and Van Der Vecht (1950). De Plagen Van De Cultuurgewassen in ndonesia. W. van Hoeve's, GravenhageBandoeng 1065 pp. 3. Pathak, M. D. (1968). Ecology of common 'insect pests of rice, Ann. Rev. Ent. 13: , 4. Southwood, T. R. E. (1969). Population studies of insect attacking sugarcane. n Pests of sugar cane (Ed. by J. R. Williams eta/.). Elsevier, Amsterdam, Thompson, H. A. (1977). Laporan peninjauan ke kebun-kebun percobaan proyek pengembangan indu,stri gula. Departemen Pertanian, Direktorat Jendral Perkebunan, 33 pp. (Unpublished report). 6. Wigglesworth, V. B. (1965). The Principles of nsect Physiology. Methuen, London, 434 pp. 7. Williams, J. R. (1963). The reproduction and fecundity of the sugarcane stalk borers, Proceras sacchariphagus Boyer. (Lep., Crambidae). Proc. SSCT. t

6 1657 ENTOMOLOGY BOLOGA DEL PERFORADOR GGANTE DE SUMATRA, NDONESA, PHRAGMATAECA CASTANEAE HUBNER Boedijono W irioatmodjo RESUMEN Phragmataecia castanea Hubner es la especie. predominan te de perforador en la caaa de azucar. Se realiza~on algunas experiencias de laboratorio a temperatura ambiente k 320~: y humedad relatiya de + 74%. Este trabajo ofrece datos sobre 136 dimensiones de las cabezas de las larva en 10s distintos estadios, mi%-como la duracion de vida de 10s adultos. El promedio del ciclo de vida del huevecillo a1 adulto fue de 107 dias. El promedio de huevecillos ovipositados por hembra fue de 330, y el aumento potencial de poblacion de dia