Host preference

The role that chemicals play in host preference has received little attention. Contamination of an unacceptable host by the odor of a preferred host may result in the attack of the unacceptable host (Spradberry, 1968). Cardrochiles nigriceps, for example, readily attacks and accepts Galleria mellonella and 

Spodoptera frugiperda if the searching stimulant from Heliothis virescens is applied to these unacceptable hosts (Vinson, 1975a). 

The diet of the host may play a significant role in host preference. Hendry et al. (1976) reported that corn contains tricosane, the kairomone for Tricho-gramma evanescens which was first isolated from Heliothis zea, a com feeder. Sauls et al. (1979) reported that the frass of H. zea reared on different diets differed significantly in its kairomonal activity for Microplitis croceipes. Thus, the preference for a given host may be influenced by the food consumed by the host, possibly, a particular host might be able to escape parasitoidism by feeding on certain plants or food resources. 

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Contrary to the structure similarity of the pheromones secreted by taxonomical related moths, some differences are necessary for their sexual communication systems to play an important role in their reproductive isolation. In addition to further modifications of the various structures, diversity of the lepidopteran sex pheromones is generated by blending multiple components. Innumerable pheromone blends are based not only on combinations of different components but also on variations in the mixing ratio. A pioneer study with Adoxophyes spp. (Tortricidae Tortricinae) had already proposed this concept in the early 1970s. While the smaller tea tortrix (A. honmai) and the Japanese summerfruit tortrix (A. oranafasciata) had been considered to be variant strains with different host preferences in the same species, Tamaki et al. found that females of the former pest insect in the tea garden secreted Z9-14 OAc and Zll-14 OAc in a ratio of 7 4 but females of the latter defoliator of apple trees secreted them in a ratio of 13 4 [127,128]. Furthermore, two other components (Ell-14 OAc and MelO-12 OAc) were subsequently identified from the former species [129]. 

Subtle differences In allelochemlcally based host preference and/or the ability to survive on various hosts may have very significant Implications for the population dynamics and geographical ecology of Insects (1-4). Differential adaptations... 

Monteith, L. G. (1955). Host preferences of Drino bohemica Messn. (Diptera Tachinidae) with particular reference to olfactory responses. Canadian Entomologist 87 ... 

Genetic manipulation of arthropod natural enemies Is an old concept (9-10), although field Implementation of genetically-improved natural enemies was not achieved until recently (8,11). Various biological and behavioral attributes have been discussed as amenable to genetic selection. Including sex ratio, temperature tolerance, developmental rate, fecundity, diapause, and host preference, as well as pesticide resistances (12). 

Stadler, E. and Hanson, F. E. (1976) Influence of induction of host preference on chemoreception of Manduca sexta Behavioral and electrophysiological studies. Symp, Biol, Hung, 16, 267-73. 

Singer, M. C. (1982) Quantification of host preference by manipulation of oviposition behavior in the butterfly Euphydryas editha. Oecologia, 52, 224-9. 

Other authors, however, came to different conclusions when they transferred ergot from Lolium sp. to rye (Bekesy, 1956) or to wheat (Bretag and Merriman, 1981). Kybal and Brejcha (1956) succeeded in infecting rye with ergot from Phragmites and Molinia, whereas Campbell (1957) found no host preferences at all in Canadian isolates. 

Marquis, R.J. H.E. Braker. 1987. Influence of method of presentation on results of plant-host preference tests with two species of grasshopper. Entomol. Exp. Appl. 44 59-63. 

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