BIONOMICS OF TRIOXYS (BINODOXYS) INDICUS, AN APHIDIID PARASITOID OF APHIS CRACCIVORA. III. NUMERICAL ASPECTS OF THE INTERACTION OF THE PARASITOID AND ITS HOST

Abstract

Laboratory experiments on the numerical aspects of the interaction of Trioxys (Binodoxys) indicus Subba Rao & Sharma and its aphid host Aphis craccivora Koch are described. If 1, 2, 3, 4 or 5 parasitoids are released on 25, 50, 75 or 100 hosts, the number of parasitoids emerging is greatest when 4 or 5 are put on. However, the rate of multiplication (i.e. parasitoids emerging/parasitoids at start) is greatest with one parasitoid on 100 hosts; this rate of multiplication declines as more parasitoids or fewer hosts are put in. The fact that more parasitoids have a lower rate of multiplication shows the existence of interference processes. Various aspects of the parasitoids' behaviour which could give rise to interference effects are discussed, including the experimental study of the mortality of the hosts from repeated pricking by parasitoids' ovipositors. RÉSUMÉ BIOLOGIE DE TRIOXYS (BINODOXYS) INDICUS, PARASITOIDE APHIDAE DU PUCERON APHIS CRACCIVORA. III. ASPECTS QUANTITATIFS DES INTERACTIONS ENTRE LE PARASITOIDE ET SON HÔTE L'exposé décrit des expériences de laboratoire sur les aspects quantitatifs des interactions entre Trioxys (Binodoxys) indicus et son hôte, le puceron Aphis craccivora. Une exposition de 15 minutes suffit pour obtenir le nombre maximum de parasitoides. Quant 1, 2, 3, 4 ou 5 parasitoides sont libérés sur 25, 50, 75 ou 100 hôtes, le nombre de parasitoides le plus élevé est obtenu avec introduction de 4 ou 5 d'entre eux. Cependant, le taux de multiplication (parasitoides obtenus/parasitoides introduits) le plus important est atteint avec un parasitoide introduit pour 100 hôtes; ce taux diminue quand les nombres de T. indicus augmente et de A. craccivora diminue. L'abaissement du taux de multiplication du nombre de T. indicus montre l'existence d'interactions, dont certaines ont été observées: interactions directes dues à des contacts entre parasitoides, repulsion des hôtes contaminés, superparasitisme, perte d'œufs de parasitoides par suite de la mortalité de l'hôte par des perforations répétées par la tarière des parasitoides.

Bionomics ofTrioxys indicus [Hym.: Aphidiidae], a parasitoid ofAphis craccivora [Hem.: Aphididae]: 31. Effect of host haemolymph on the numerical response of the parasitoid

“…The reason for increase in the oviposition response was the stimulation and continuous reinforcement of an intensified searching behaviour of the parasitoid and not the direct attraction or guiding of the parasitoid to the host (Lewis & Nordlund, 1985). Singh (1980) andPandey et al (1982) have estimated 1 : 100 parasitoid to host ratio for better results. However, the present findings indicate that if kairomones are applied properly the ratio may increase in favour of the parasitoids to 1 : 200, thus fewer parasitoids would be needed to regulate an estimated number of hosts.…”

“…The influence of kairomones on the oviposition of parasitoids at varying densities has not yet been worked out. The numerical response (Solomon, 1949) of Trioxys indicus Subba Rao & Sharma, an aphidiid parasitoid of Aphis craccivora Koch, is strong enough for its establishment in the target area and the number of parasitoids needed to destroy a known population of hosts has alerady been establishment (Sinha & Singh, 1980). However, the number of kairomone stimulated parasitoids should also be estimated for the effective control of a known population of the hosts.…”

Effect of Food Plants on the Numerical Response ofDiaeretiella rapae(Mclntosh) (Hymenoptera: Braconidae), a Parasitoid ofLipaphis erysimiKalt. (Hemiptera: Aphididae)

“…Under field conditions such a response might result in the dispersal of the parasitoid (Sinha & Singh, 1980). Shorter attacks play an important role in reducing the probability of host contamination by the parasitoids, due to antennal encounters and host stabbing without laying eggs (Sinha & Singh, 1980;Shukla & Tripathi, 1993 The significant variance in the numerical response of D. rapae on aphids bred on different food plants may be due to differences in concentration and chemical nature of allomones (Vinson, 1984) and kairomones (Read et al, 1970) and in quality and quantity of the honeydew, which contains kairomones, excreted by the aphids (Cloutier, 1984). The differences in concentration of mustard oil (allyl-isothiocyanate) present in brassicaceous plants may cause variation in the parasitoid responses for the aphids.…”

“…The experiment was replicated ten times. After mummification, the mummies were collected and transferred singly to sterilised glass vials (2.5 x 10 cm) for adult emergence, which has been considered as a parameter of effective parasitisation (Sinha & Singh, 1980;Shukla & Tripathi, 1993). The data were subjected to statistical analysis (ANOV A).…”

“…Establishment of paras it is at ion efficiency values for different parasitoid ·Correspondence address: Department of Science, Tribhuvan University, Institute of Agriculture and Animal Sciences, Paklihawa Campus, Bhirahawa, Nepal. and host densities is a critical element in the study of their population interaction (Sinha & Singh, 1980). The parasitoids may respond to increased host densities by increasing their own number (numerical response), or they may respond by increasing the number of hosts that each individual destroys (functional response) (Solomon, 1949).…”