Competitive interaction between Cotesia kazak and Hyposoter didymator, exotic parasitoids of Heliothis armigera

Abstract

Competitive interaction between two introduced parasitoids ofHeliothis armigera (Hb.) i.e. the braconid Cotesia kazak Telenga and the ichneumonid Hyposoter didymator (Thunb.) was studied in the laboratory. C. kazak and/-/, didymator individually parasitized about 55~ H. armigera larvae, the combination of the two parasitoids gave more than 7507o parasitism. C. kazak was found to be more effective, when the host was exposed to both parasitoids at the same time, reduced H. didymator population by 69070 to 24 h. It is, therefore, better to release these two parasitoids individually in different locations to avoid any possible competitive interaction between the two. No difference in developmental time was observed irrespective of parasitoid sequence.

Competitive interaction between two ichneumonid parasitoids of Spodoptera litura

“…Reitz (1996) reported with reference to tachinid parasitoids Eucelatoria bryani Sabrosky and E. rubentis (Coquillett), gregarious tachinid parasitoids of Helicoverpa zea (Boddie), that presence of similarly aged heterospecific competitors often resulted in prolonged developmental time for both competing species. However, Jalali et al (1988) observed no significant differences in the developmental times of C. kazak and H. didymator, larval parasitoids of H. armigera when they were parasitising alone in comparison to that in interaction treatments. In the present study, no significant differences were observed between the treatments where the parasitoids were allowed to parasitise singly and the interaction treatments, with respect to developmental time (from parasitism to cocoon formation) of C. chlorideae (8.4-10 days) (df=12,39; F=1.35; p=0.23) and of E. argenteopilosus (13.3-16.5 days) (df=10,33; F=0.66; p=0.76).…”

“…Jalali et al (1988) reported that when larvae of H. armigera were parasitised by the braconid Cotesia kazak (Telenga) and the ichneumonid Hyposoter didymator (Thunberg), C. kazak was more effective and reduced H. didymator population by 69% in 24 h time interval. Godwin and Odell (1984) reported that in the gypsy moth (Lymantria dispar L.) larvae, which were multiparasitised by tachinid parasitoids, Parasetigena silvestris (Robineau-Desvoidy) and Blepharipa pratensis (Meigen), the former suppressed the latter by 65%.…”

“…In the individual exposure experiment, the mated female parasitoid was released in a plastic container with feeding of 50% honey solution and water (on cotton swabs), a host larva was introduced into the container using a camel hair brush and was forcibly induced to be stung by the parasitoid. The methodology followed was as in Dijkerman and Koenders (1988) and Jalali et al (1988), where the host larvae were exposed to the parasitoids and checked for insertion of ovipositor, and not on whether the parasitoid egg was actually laid. Following this method, the host larvae were allowed to be stung by the two parasitoid species individually and also in two sequences -in one sequence the larva was allowed to be stung by C. chlorideae first followed by E. argenteopilosus, in the second sequence first by E. argenteopilosus followed by C. chlorideae.…”

“…In endemic host-enemy associations, inter-specific competition plays a crucial role in structuring the parasite guild (Force, 1974) and probably influences the entire natural enemy complex as well. Several researchers have demonstrated that there is no distinct advantage of releasing two or more species as one species could be more effective in reducing the pest population than the entire natural enemy guild (Diamond, 1973;May and Hassell, 1981;Ehler and Hall, 1982;Kakehashi et al, 1984;Spiller, 1986;Jalali et al, 1988). Other studies indicated that the total percentage of hosts attacked could increase with an increase in natural enemy species (Miller, 1977;Ehler, 1979;Ismail andLong, 1982, Hogarth andDiamond, 1984) or that the percent parasitism could remain constant irrespective of the number of natural enemy species involved (Ehler, 1977).…”

Efficiency, intrinsic competition and interspecific host discrimination ofCopidosomadesantisiandTrichogrammaevanescens, two parasitoids ofPhthorimaea operculella

“…This is mainly attributable to the inability of coexisting parasitoids to distinguish between unparasitized and previously parasitized hosts, which led to direct intrinsic competition (Fisher 1971;Force 1974;Jalali, Singh, Ballal, and Kumar 1988;Strand, Johnson, and Culin 1990). Competition among introduced natural enemies or between introduced and native natural enemies can be of great importance in ecological community dynamics and is particularly important for biological control (Yamamoto, Henderson, Corley, and Iwabuchi 2007).…”