Philippine Journal of Science 133 (2): 103-108, December 2004 ISSN 0031 - 7683

The Preference, Acceptability and Suitability of Ichneumonid , Eriborus argenteopilosus Cameron (:) on the Different Larval Stages of Cotton Bollworm, Helicoverpa armigera Hubner (Lepidoptera: Noctuidae)

Leonardo T. Pascua*1 and Miriam E. Pascua2

1Cotton Research Center Cotton Development Administration, Batac, Ilocos Norte 2College of Agriculture and Forestry Mariano Marcos State University, Batac, Ilocos Norte

The preference, acceptability and suitability of Eriborus argenteopilosus Cameron on different larval stages of Helicoverpa armigera Hubner were studied. First (2-3 day old) and second instar larvae were the most preferred and accepted, while the second instar larvae were the most suitable host for E. argenteopilosus. Third and older instar larvae of H. armigera showed aggressive behavior, hence, hindering parasitization.

Keywords: Cotton bollworm, parasitization, larva, parasitoid introduction evolved the ability to assess the host and modify the oviposition process accordingly (Mathews and Mathews The success of survival of progeny after egg 1978). Therefore, the ovipositing female parasitoid often deposition depends on the selection of a suitable host. spends considerable time and energy in inspecting the Doutt (1959) enumerated four steps for a successful host prior to oviposition. parasitoid-host relationship: host habitat selection, host location, host acceptance and host suitability. Vinson The behavior, development, morphology and (1975) considered the first three steps to be the host ecology of parasitoids are influenced by selection process. host characteristics such as age, size and general physiological state (Lawrence 1990). For example, The successful development of the parasitoid host location and acceptance by ovipositing female depends on behavioral host defense, competition with parasitoids are influenced by chemical cues emanating other parasitoids, host toxins, pathogenic infection, from the host. host sensitivity and nutritional suitability (Vinson and Iwantsch 1980). With this, many parasitoids have Larval host acceptance and suitability by hymenopterans generally show a parabolic trend *Corresponding author: [email protected] in relation to host age but the parasitoid’s duration

103 Pascua LT & Pascua ME of development usually decreases. The parasitoid artificial diet. The number of pupal cocoons and the size, proportion of females produced and level of female progeny from each age group were recorded. superparasitism increase with host age at the time of The experiment was replicated eight times except for parasitization (Mellini 1986a and 1986b). Mortality of the set up with first larval instars which was repeated the parasitoid is higher when a small host is parasitized four times. Replications were set up at different times compared to a large one (Mellini 1986b). The female using a Randomized Incomplete Block Design. parasitic wasp Tiphia popilliavora controls the sex of their eggs laid in the beetle host, Popilla (Brunson 1937). Host stage preference The wasp lays fertilized female eggs in third instar host larvae and non-fertilized male eggs in second instar In the screen house, first (one day old and 2-3 day hosts. The parasitoid Campoletis perdistinctus prefers old), second, third, fourth and fifth instar larvae of H. two to five day-old Helicoverpa larvae (Lingren et al. armigera were separately exposed to the parasitoid in 1970; Nikam and Gaikwad 1991) and third instar larvae a choice test. of Spodoptera (Isenhour 1985), while Campoletis sp. prefers early instar larvae of H. armigera (Cacayorin In each replicate, six hills of cotton plants (flowering et al. 1993). stage) distanced at 1 m were covered with a muslin cloth cage measuring 1 x 5 x 1.5 m. A hill of cotton The cotton bollworm Helicoverpa armigera plant represented one treatment (age group) where (Hubner), a serious pest of cotton in the Philippines, the assignment of treatments was at random. In each attacks growing tips and reproductive plant parts like hill of cotton plants, twenty larvae were placed on the squares, flowers and bolls causing a reduction in growing tips. A mated parasitoid was introduced in the seedcotton yield by 28 to 97% (Catedral 1982; Damo cage during 24 h. After this period, larvae of H. armigera and Domingo 1996). Filipino farmers depend mostly on were transferred into compartmentalized rearing pans the use of synthetic insecticides to control H. armigera and fed with artificial diet formulated by Deang (1971). in their cotton crops. Alternative control measures are The number of cocoons from each age group was now the focus of research and the use of biological recorded. The treatments were replicated eight times control agents is the first priority. except for the set up with first larval instar (one day old) which was replicated four times. Replications were set Eriborus argenteopilosus (Cameron) is a potential up at different times using a Randomized Incomplete biological control agent of H. armigera. It was identified Block Design. as a key mortality factor of H. armigera on cotton (Pascua and Pascua 2002a). A series of researches on its biology is deemed necessary, thus the study was conducted to determine the most preferred, most suitable and acceptable stage of H. armigera for Results parasitization by E. argenteopilosus. Host stage acceptance and suitability (No-choice test) The number of E. argenteopilosus cocoons recovered after exposure of different larval instars of Materials and Method H. armigera to the parasitoid in a no-choice test varied significantly (P< 0.01; Fc=186.0) (Table 1). Eriborus Host stage acceptance and suitability argenteopilosus parasitized more than 60% of the first (2-3 days old) and second instar larvae, whereas In the laboratory, first instar (separate one day old only 19% of the third instar larvae and 1% of the fourth and 2-3 day old), second, third, fourth and fifth instar instar larvae were parasitized. larvae of H. armigera were separately exposed to E. argenteopilosus in a no-choice test. The development period of E. argenteopilosus from larval hosts being parasitized during the first (2-3 days Twenty larvae of each age group were placed in old) instar larvae (20.2±0.9 days) was not significantly a plastic container (8.5 cm diameter, 6 cm height) different from that of hosts being parasitized during the containing artificial diet developed by Deang (1971). A second (19.2±0.9 days), the third (18.6±0.6 days) and plastic container represents one treatment (age group). the fourth (18 days) instar. The container was covered with muslin cloth. A mated parasitoid was introduced in each plastic container The sex of E. argenteopilosus emerging from larvae for 24 h. After exposure to the parasitoid, larvae from parasitized at the fourth larval instar was female. The different age groups were separately transferred to percentage of female E. argenteopilosus emerging compartmentalized rearing pans and were fed with from hosts parasitized during the third, second and first

104 Preference, Acceptability and Suitability of Wasp on Different Larval Stages of Cotton Bollworm

Table 1. Parasitization of Eriborus sp. on different larval stages of Helicoverpa armigera in a no-choice test Dead Dead Eriborus Parasitized Eriborus Development Period H. armigera larvae unparasitized Parasitized Female Larvae* Cocoons* of Eriborus (days) Larval Instar larvae larvae Progeny* Exposed Recovered (%) (%) (%) (%) (%) Mean±SD Range

First (day-old) 80 46 27.8 0.0 0.0c 0.0

First(2-3 days old) 160 158 3.2 7.0 66.5a 59.5a 48.5b 20.2±0.86 19-22

Second 160 155 1.9 0.01 60.0a 60.0a 53.6b 19.2±0.84 18-21

Third 160 148 4.0 0.0 18.9b 18.9b 60.4a 18.6±0.64 18-20

Fourth 160 80 0.0 0.0 1.2c 1.2c 100.0a 18

Fifth 160 51 0.0 0.0 0.0c 0.0c

*Means marked with the same letter are not significantly different using Duncan Multiple Rating Test

(2-3 days old) instar of H. armigera declined from 60 Eriborus argenteopilosus that emerged from to 49. The percentage female progeny emerging from third and fourth larval instar of H. armigera were all larvae parasitized at different larval host stages was females, while those emerging from the second were significantly different (Table 1). 61% and from the first (2-3 day-old) instar were 43.8% females. Host stage preference (Choice test)

When E. argenteopilosus females were given a choice among larval stages of H. armigera, they Discussion parasitized 48.6 % of the second, 43.5% of the first (2-3 In a situation where different larval instars are days old), 7.2% of the third and only 0.7% of the fourth present, the ovipositing female parasitoid spent time instar larvae (Table 2). The number of E. argenteopilosus and energy in locating and discriminating potential that emerged was significantly higher (P< 0.01;Fc=62.2) hosts. In the field, however, such as in the early when first (2-3 days old) and second instar larvae were stage of the cotton crop, early instar larvae are the parasitized than on those other larval instars. First (one only available hosts (Pascua and Pascua 2002a). day-old), fourth and fifth instar larvae of H. armigera had Further, at later stages with overlapping generations, high mortality rates because few larvae were recovered the percentage of early instar larvae is higher than after their exposure to E. argenteopilosus. Only few older ones (Pascua and Pascua 2002b; stable age parasitized larvae died: three larvae of the first instar (2-3 distribution of H. armigera). These situations might days old) and two larvae of the third instar. help the reduction on the cost of host location of

Table 2. Parasitization of Eriborus sp. on the different larval stages of Helicoverpa armigera in a choice test Dead Dead Number of Total number No. of Female Larval Instar H. armigera larvae unparasitized parasitized parasitized of parasitized Eriborus Progeny of larvae larvae larvae* larvae** cocoons* Eriborus Exposed Recovered (%)* (%)*

First (day-old) 80 39 3 0 0c 0.0c 0c

First (2-3 days old) 160 155 3 2 60a 43.5a 58a 43.8b

Second 160 159 2 3 67a 48.6a 64a 60.5b

Third 160 152 0 0 10b 7.2b 10b 100.0a

Fourth 160 95 0 0 1c 0.7c 1c 100.0a

Fifth 160 82 0 0 0c 0.0c 0c

*Means marked with the same letter are not significantly different using Duncan Multiple Range Test **not including the dead parasitized larvae

105 Pascua LT & Pascua ME

the parasitoid. In addition, early instar larvae of H. A longer development period of E. argenteopilosus armigera are located on the terminal buds or on the and a lower percentage female offspring were obtained periphery of the plant canopy (Pascua and Pascua when first instar (2-3 days old) and second instar larvae 2002a). Early instar larvae also cause insignificant were exposed to the female parasitoid than offsprings damage because they usually feed on the terminal from wasp parasitizing older host larval stages. buds and newly-developed leaves. Therefore, the However, offsprings from parasitizing first (2-3 H. armigera larvae should be parasitized by the days old) and second instar larvae had higher percent parasitoid at their first and second instars. The delay parasitization larvae and more cocoons produced than of parasitization allows the larvae to grow older where older stages. they become less attractive to the parasitoid. This increases the probability of low parasitization by E. Host selection by the parasitoid is not limited to argenteopilosus because of the tendency of older the choice whether to oviposit or reject the host. It larvae to move to squares and bolls at the lower part also involves decisions regarding the sex allocation of the canopy, hence, becoming less accessible to of their offspring when exposed to hosts of different the parasitoid. instars. Many hymenopterous can control the sex ratio of their offspring (Flanders 1939; van Dijken Smaller hosts defending themselves against et al. 1989; Ueno and Tanaka 1997) and this is related parasitization probably cause lesser injury to to their reproductive strategy (Hamilton 1967; King the parasitoid than older ones. This is why E. 1987). Eriborus argenteopilosus laid more female argenteopilosus prefers equally first instar (2 to 3 days eggs in larger hosts. Similar results were obtained by old) and second instar larvae for oviposition than later Brunson (1937), Sandlan (1979), Charnov et al. (1981), instars. This preference might be based on the ease to Charnov (1982), van den Assem et al. (1984), King oviposit in younger larval instars, resulting in shorter (1987,1988), Heinz and Parella (1990), van Dijken et al. duration of oviposition which is critical for time limited (1991), Heinz (1996 and 1999), Mayhew and Godfray parasitoids. Asobara tabida is also more successful (1997), and Kraaijeveld et al. (1999). Sex allocation in attacking younger than older larvae of Drosophila is a parental investment of parasitoids in relation to (van Alphen and Drijver 1982). The response of the the fitness of their offsprings. If a large parasitoid host to parasitization is violent wriggling (Mathews emerging from a large host has increased fitness, 1974). In this case, the insect host is able to resist the then a female parasitoid should maximize fitness by attack (van Alphen and Drijver 1982). In our study, allocating her female offsprings to larger hosts and her third, fourth and fifth instar larvae made aggressive male offsprings to smaller hosts (Charnov 1979). Larger movements towards E. argenteopilosus causing female offsprings live longer, have higher searching the female parasitoid to stop ovipositing or to move efficiency and oviposition success, and more eggs laid away from the host larvae. Larger hosts can defend than smaller ones (Visser 1994; Ueno 1999). Also, Kishi themselves better than smaller hosts (Kouame and (1970) and Sandlan (1979) found that females suffer Mackauer 1991). higher mortality than males in small hosts. Developmental time of the parasitoid is influenced The sex ratio of offspring from the female E. by the host instar (Hopper and King 1984). In this study, argenteopilosus parasitizing second instar larvae is E. argenteopilosus developing from younger hosts had female biased (53.6 % and 60.5 %). A female-biased a longer development period than those developing from sex ratio of the parasitoid is favorable as it leads to high older hosts. Harvey and Thompson (1994) had similar pest mortality. Males only mate and do not contribute results with Venturia parasitizing Plodia sp. larvae of to pest mortality (Hassel et al. 1983; Comins and different instars. The development time of parasitoids Welling 1985). is longer in younger hosts because the development of the larvae is slower than those developing in matured In Pieres rapae, the blend of chemicals in both hosts (Vinson and Iwantsch 1980). quantity and quality emitted by feces of different larval instars exhibited an instar specificity (Agelopoulos et al. The quantity and quality of nutrients consumed 1995). Can E. argenteopilosus discriminate the potential during the larval host period dictates the development hosts in long range through volatiles coming from the time and the state of health of the parasitoid. Older host insect and its products? If so, this is advantageous host larvae supply more nutrients to the parasitoids to the parasitoid because it saves time in host location than younger larvae resulting in faster growth and and the chances of rejecting the located potential hosts development. However, early stage to mid-stage larvae maybe minimal. The steps in host location could be may readily supply abundant hemolymph trehalose shortened when the parasitoid rejects or accepts the and other nutrients (Lawrence 1990) making them also host and it goes directly to the potential host. Unlike if suitable for the development of the parasitoid. the parasitoid can not discriminate the potential host in

106 Preference, Acceptability and Suitability of Wasp on Different Larval Stages of Cotton Bollworm

long range, the parasitoid inspects all potential hosts Comins H & Wellings P. 1985. Density related parasitoid then it rejects or accepts. The time and energy of host sex ratio: Influence on host-parasitoid dynamics. J location and chances of rejecting the potential host might Ecol 54:583-594. be higher than in situations where in the parasitoid can Deang RT. 1971. Life history and morphology of discriminate the potential host. Nevertheless, research Helicoverpa armigera (Hubner) reared on synthetic on this aspect should be taken into consideration. diet and topical toxicity of five organic insecticides to the insects [M. S. Thesis]. College, Laguna, Philippines: University of the Philippines Los Baños. Acknowledgments Dijken M van, Alphen J van & Stratum P. van. 1989. Sex allocation in Epidinocarsis lopezi, a local mate Special thanks are expressed to the Cotton competition. Entomol Exp Appl 52:249-255. Research and Development Institute (now the Cotton Development Administration) for funding the research, Dijken M van, Neuensschwander P, Alphen J van & to Dr. Isagani G. Catedral, Dr. Eugenio D. Orpia, Jr. Hammomd W. 1991. Sex ratios in field population and Mr. Yolando M. Madriaga for their support on of Epidinocarsis lopezi, an exotic parasitoid of the the conduct of the experiments, to Prof. Dr. Joop van cassava mealy bug in Africa. Ecol Entomol 16:233- Lenteren, Dr. Arnold van Huis, Dr. Epifania O. Agustin, 240. Dr. Sosimo Ma. Pablico and Dr. Rey Velasco for their Doutt R. 1959. The biology of parasitic Hymenoptera. helpful comments and editing this paper, and Dr. Rob Ann Rev Entomol 4:161-182. Zwart for identifying Eriborus argenteopilosus. Flanders SE. 1939. Environmental control of sex in hymenopteran insects. Ann Entomol Soc Am 32:11- 26. References Hamilton W. 1967. Extraordinary sex ratios. Science Agelopoulos N, Dicke M & Posthumus M. 1995. Role 156:477-488. of volatile infochemicals emitted by feces of larvae Harvey J & Thompson D. 1994. Some factors affecting in host searching behavior of parasitoid Cotesia host suitability for the solitary parasitoid wasp, rubecula (Hymenoptera:Braconidae): A behavioral Venturia canescens (Hymenoptera: Ichneumonidae). and chemical study. J Chem Ecol 21:1789-1811. Norwegian J Agric Sci Suppl 16. 321-327. Alphen J Van & Drijver R. 1982. Host selection by Hassel M, Waage J & May R. 1983. Variable parasitoid Asobara tabida (Braconidae: Alysiinae), a larval sex ratios and their effect on host-parasitoid parasitoid of fruit Drosophilidae species: Host dynamics. J Animal Ecol 52:889-904. selection with Drosophila melanogaster as host. Netherlands J Zool 32:215-231. Heinz K. 1996. Host selection and sex allocation behavior among parasitoid throphic levels. Ecol Assem J van den, Putters F & Prins T. 1984. Entomol 21(3):218-226. Host quality effects on sex ratio of the parasitic wasp Anisopteramalu calandrae (Chalcidodea: Heinz K. 1999. Host size-dependent sex allocation Pteromalidae) Netherlands J Zool 34:33-62. behavior in a parasitoid; implications for Catolaccus grandis (Hymenoptera:Pteromalidae) mass rearing Brunson MH. 1937. The influence of the instar of the prgrames. Bull Entomol Res 88(1):37-45. host larvae on the sex of the progeny of Tipihia popilliavora. Science 86:197. Heinz K & Parella M. 1990. The influence of host size on sex ratios in the parasitoid Diglyphus begini (Hymenoptera: Cacayorin N, Solsoloy A, Damo C & Solsoloy T. 1993. Eulophide). Ecol Entomol 15:391-399. Beneficial regulating population of insect pests of cotton. Cotton Res J (Phil.) 6:1-8. Hopper K & King E. 1984. Preference of Microplitis croceipes (Hymenoptera: Braconidae) for instars Charnov. 1979. The genetic evolution of patterns of sexuality: and species of Heliothis (Lepidoptera: Noctuide). Darwinian fitness. Am Naturalist 113:465-480. Environ Entomol 13:1145-1150. Charnov E. 1982. The theory of sex allocation. Isenhour P. 1985. Campoletis sonorensis Princeton: University Press. (Hymenoptera: Ichneumonidae) as a parasitoid of Charnov E. Los-den Hartogh, R., Jones, W. and van Spodoptera frugiferda (Lepidoptera: Noctuidae); den Assem.1981. Sex ratio evolution in a variable host stage preference and functional response. environment. Nature 289:27-33. Entomophaga 30:31-36.

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