Multiple Parasitism and Advantages of Multiple Parasitism
Multiple Parasitisms:
It refers to that condition in which individuals of two or more species of parasitoids occur simultaneously or on the same single host at the same time. In most cases, only one of these species survives to maturity. In rare cases, (e.g. Trichogramma species) more than one species may complete their development.
The condition of multiparasitism generally results in the death of one of the individuals through one or other mortality factor, but not through hyperparasitism. Many of primary tachinid parasitoids of the spruce budworm compete with ichneumonid parasites. The multiparasitism results in direct competition for food between the parasite larvae so that usually one fails to mature.
Advantages of Multiple Parasitisms:
1. A series of parasites which live in the same habitat but attack a sequence of host stages is advantageous because environmental variations which adversely affect one species may favor another and total host mortality should be greater.
2. When several parasite species are established on a common host, these will usually be broader habitat coverage.
3. Past records indicated that multiple species introduction improved the results of parasitizing and pest population regulation and rarely occur detrimental effects.
4. Multiple introductions increase the chances of obtaining a gives species which will attack more than one host in the new environment. This enables the natural enemy to overcome difficulties of host scarcity which might occur if only one host were involved. Multiple introductions of new natural enemies is accepted as a policy and undertaken the effect of competition between the established and the newly imported natural enemy again assumes importance. This does not cause detrimental effect but the host population balance.