Sampling adult male populations of undalis (:Pyralidae) in cabbage using virgin-females baited sticky trap

A. Sivapragasam, Asma Ahmad and Rafi Abdullah Strategic, Environment and Natural Resources Research Center, MARDI, Serdang, Selangor, Malaysia

Abstract The activity of adult males of (Fabr.) in a cabbage field was determined using a sticky trap baited with two laboratory-reared one-day old virgin females. The daily activity pattern of H. undalis, based on the number of males trapped, was also determined at hourly intervals in four crop areas. The relationship between trap catches, larval populations on the cabbage plants and amount of rainfall was examined. Trap catches of adult males of H. undalis were consistently high suggesting that immigration could be an important factor influencing the dynamics of the H. undalis population on cabbage. There was a poor relationship (r = 0.03) between trap catches and larval populations in the field. Rain also did not influence trap catches. Daily activity of male , based on trap catches, suggested a bimodal pattern with a higher peak between 5.30 h to 6.30 h and a relatively smaller around 20.30 h.

Key words: Hellula undalis, cabbage, virgin-female, trap, activity

Introduction H. undalis were examined using virgin-females baited Amongst the pests which inflict serious damage sticky traps. The latter method was used by Shirai and to head cabbage, Brassica oleracea var. capitata, Kawamoto (1990) to examine flight distances of H. particularly in the lowlands of Malaysia, is the cabbage undalis. The use of virgin females is necessary as the webworm (CWW), Hellula undalis (Fabr.) (Syed et sex pheromone, identified as an aldehyde (E11, E13)- al, 1992; Sivapragasam, 1994). Crop life tables on 11,13-hexadecadienal (Arai et al, 1982; Ando et al., cabbage indicated that this pest is responsible for about 1988), has not been commercially available as yet. 41 percent of total mortality of plants during the preheading stage (Sivapragasam, 1994). One of the Materials and Methods major problems contributing to the pest status of H. Adult activity on cabbage undalis is the fact that there is no economic threshold This study was conducted in a cabbage (var. K-K cross) level for H. undalis to initiate insecticidal treatments. plot at the experimental field at MARDI, Serdang, Thus, a single larva boring into the growing shoot of which was surrounded by other non-cruciferous plants the cabbage plant during the preheading stage, can such as tomato, beans and fruit trees. The cabbage plot result in either the death of the plant or produce two measured 12.0 m x 12.5 m with about 500 transplanted or more small-sized heads that are not marketable. cabbage plants grown using recommended agronomic Consequently, control measures initiated against this practices. Except for the preplant insecticidal spray, pest are preemptive and employed chemical which was done one week before transplanting, no insecticides on a weekly or twice weekly basis. The insecticides were used on the cabbage plants in the frequent use of pesticides elevates the cost of field. production and increases selection pressure towards The activity of H. undalis adult males in the field resistance development (Sivapragasam, 1994). This was monitored using a trap which had two laboratory- poses a major problem for the implementation of the reared one-day old virgin females (Shirai and integrated pest management programme for cabbage Kawamoto, 1990). The design of the trap was similar in the lowlands (Syed et al, 1992). to the one used for trapping the diamondback Understanding the behaviour and ecology of H. (Reagron PlumaR) (Irfan et al, 1991). Both the adult undalis in the field could contribute towards the females were confined in a small cage measuring 10.0 effective management of H. undalis. Amongst the cm in length and 3.5 cm in diameter constructed with important ecological factors that need to be 14 mesh plastic wire screen. A 10 % honey solution investigated are that of understanding adult activity was provided as food for the adults. The cage was then in the field. Although some information on adult hooked to the inside top portion of the trap. The inside activity of H. undalis in the field had been reported bottom of the trap was covered with a thin polyethylene elsewhere (Yamada, 1981; Shirai and Kawamoto, sheet held in place by clips and sprayed with a sticker 1990), such information is lacking in Malaysia. In this (KinryuR, SDS Biotech). The trap was then mounted study, the activity of the adult male population of on a wooden stake and set at a height of 0.5 m above

Poster Papers 335 the ground in the center of the cabbage field. The base larval populations on cabbage could have contributed of the wooden stake was sprayed regularly with sticker to the adults trapped, it does not account for the to prevent predacious such as ants from getting relatively high number of adults trapped after this into the trap. Considering the size of the cabbage field, period. In any case, larval survival to adult is generally only one trap was used in this study. The number of very low ( ca 1 %) for H. undalis under field conditions H. undalis male moths in the trap was recorded and (Sivapragasam, 1994). There was also no significant removed daily. The females in the small cage were relationship (r = 0.22; P >0.05 ) between mean weekly replaced weekly using laboratory-reared females. trap catches at time t and the number of larvae on 10 Trapping was done from four days before transplanting cabbage plants at time t + 2. cabbage until harvest of the cabbage. Daily records of Rain did not seem to influence the activity of the temperature and rainfall were also made using the moths (Figure 2) as indicated by the low correlation meteorological station at MARDI, Serdang during the (r = 0.03) between the number of adults caught and duration of the experiment. To correlate trap catches the incidence of rainfall. with the larval population, the number of larvae on 40 The daily trap catches, based on the mean from cabbage plants in the same field was also counted. For four locations, suggested a bimodal activity pattern; sampling, the cabbage field was divided into four the first and higher peak from 5.30 to 6.30 h and a subplots and ten plants selected randomly in each relatively smaller peak at 20.30 h (Figure 3). quadrat were sampled in situ at 3 to 4 day intervals from 7 days after transplanting until harvest. Discussion Trap catches of adult male H. undalis were higher than Daily activity pattern of adults that expected from the field population of larvae, The daily activity pattern of the H. undalis males was suggesting possible immigration of moths into the determined at hourly intervals using one-day old virgin cabbage plot. The relatively high numbers of adult female moths in the trap described above. One trap catches vis-a-vis the low larval numbers on cabbage was placed at four different locations in the MARDI suggested that the local population of the larvae on Research Station, which also included a plot planted cabbage had little influence on the subsequent trap with cabbage. Preliminary trapping studies had shown catches. Considering that local dispersal of H. undalis the presence of moth in all the four locations. The was common (Shirai and Kawamoto, 1990), one major experiment was repeated on five separate days which source of the immigrant population on cabbage could had no rain and quite similar temperature conditions. be from its ubiquitous weed host, Cleome However, wind speed and direction were not recorded. rutidosperma (D and C.). The latter is a common denizen in areas cultivated with vegetables in Serdang Results (Sivapragasam, 1994). One possible explanation for Male moth catches showed random fluctuations with the fluctuating numbers trapped could be related to no apparent relationship to the larval populations in the age of virgin females. We found a significant the field (Figure 1). Trap catches were already high correlation (r = 0.98; P< 0.01) between the age of even before any H. undalis larvae were recorded on females and the numbers trapped with fresh females the cabbage, i.e. <20 days after transplanting cabbage. generally attracting higher number of adults and their Similarly, at the later stage of the crop, i.e. after 40 attractancy reducing with age. days, adults trapped were also high. Although the local

Number of larvae/40 plants Number of adults trapped 50 Hellula adult Hellula larva 80 40

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40 20

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Figure 1. Trends in larval numbers and trap catches for Hellula undalis on cabbage

336 Proceedings: The Management of Diamondback Moth and Other Crucifer Pests Number of males trapped Rainfall (mm) 50 50 Hellula adult Rainfall (vertical bars) 40 40

30 30

20 20

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0 0 51015202530354045505560 Days Figure 2. Fluctuations in daily adult trap catches and rainfall

Mean number of male moths/trap 8 Moths/trap

6

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0 17.30 18.30 19.30 20.30 21.3022.30 4.30 5.30 6.30 7.30 8.30 Time (h) Figure 3. Hourly mean trap catches of Hellula undalis

Although rain may be important during the early absence of the commercial pheromones, this approach larval stages of H. undalis, it may not be so against could be useful in detecting and monitoring adult the other stages (Sivapragasam, 1994). Kawamoto et populations of the moth especially in areas where al., (1987) however reported that temperature is more crucifers are grown. Besides pheromone traps, other important for flight activity of H. undalis and the traps, such as the mercury vapor lamp (Sasaki, 1986) optimal temperature for this purpose is about 20 °C. and light traps (Yamada, 1981), have also been used However, in the Malaysian lowlands, minimum for trapping H. undalis. However, the attractancy of temperatures exceeded the latter value. either sex to these traps has been reported to be very Talekar et al. (1981), also reported that in H. low. undalis adult emergence was predominantly at night. This is quite similar to that reported for the References diamondback moth Plutella xylostella (Ashihara, Ando, T., Y. Ogura and M. Uchiyama (1988). Mass spectra 1977). But, the reason for the higher activity of the of lepidopterous sex pheromones with a conjugated moths towards dawn needs to be investigated in the diene system. Agric. Biol. Chem., 52(6): 1415Ð1423. future. Arai, K., T. Ando, A. Sakurai, H. Yamada, T. Koshihara and N. Takahashi (1982). Identification of the female sex Although pheromone traps have been useful to pheromone of the cabbage webworm. Agric. Biol. predict and time the initiation of control measures (van Chem., 46(9): 2395Ð2397. Steenwyk et al, 1983), this study suggested that the Ashihara, W. (1977). A laboratory bioassay method of the virgin female baited sticky traps per se might be sex pheromone of the diamondback moth, Plutella limiting as a reliable predictive tool. However, in the xylostella (L.). Jpn. J. Appl. Entomol. Zool. (21) 171Ð 172.

Poster Papers 337 Irfan, U., M. Maryati, W.H. Loke and S.A. Rahman (1991). Sivapragasam, A. (1994). Biology and population dynamics Influence of pheromone trap colour on Diadegma of Hellula undalis (Fabricius)(Lepidoptera: Pyralidae) semiclausum (Horstmann). Paper presented at the on lowland cabbages. Ph. D. Thesis, University of International Conference on Biological Control in Malaya., 223 pp. Tropical Agriculture. Organised by the National van Steenwyk, R.A., E.R. Oatman, N.C. Toscano and J.A. Coordinating Committee on Biologcal Control and Wyman (1983). Pheromone traps to time tomato Malaysian Plant Protection Society, p. 121 (abstract). pinworm control. California Agriculture, 37 (7/8): 22Ð Sasaki, Y. (1986). The prevalence of occurrence and control 24. in the summer seedling Italian with isoxanthion Syed, A.R., W.H. Loke, A. Sivapragasam, I. Fauziah, U.B. to the cabbage webworm, Hellula undalis. Bull. Cheah, Md. M. Jusoh, A.K. Hussan and O. Yusof Kanagawa Agric. Exp. Stn., 38, 14Ð18 (in Japanese, (1992). Integrated pest management package for English summary). effective control of Plutella xylostella on cabbage in Shirai, Y. and K. Kawamoto (1990). A mark-recapture Malaysia. Final report on AVNET Phase 1 for the experiment for male adult cabbage webworm, Hellula Working Group on DBM-IPM, Lembang, Indonesia undalis Fabricius (Lepidoptera: Pyralidae). Appl. Ent. 22Ð26 Sept., 1992. Zool. 25(1): 127Ð129. Talekar, N.S., W.F. Shiao and Y.H. Lin (1981). Insect pest Shirai, Y. and K. Kawamoto (1991). Laboratory evaluation control in summer Chinese cabbage in Taiwan. In: N.S. of the flight ability of female adults of the cabbage Talekar and T.D. Griggs (eds.): Chinese cabbage: webworm, Hellula undalis (Lepidoptera: Pyralidae) and proceedings of the First International Symposium 1981, reproductive success after flight. Bull. Natl. Res. Inst. AVRDC Shanhua, Tainan, Taiwan, China. pp 163Ð172. Veg. Ornam. Plants and Tea, Japan, Ser. A, 4: 31Ð40. Yamada, H. (1981). Seasonal life history of the cabbage webworm, Hellula undalis. Bull. Veg. Ornam. Crops. Res. Stn., A8, 131Ð141 (in Japanese with English summary).

338 Proceedings: The Management of Diamondback Moth and Other Crucifer Pests