Host plant preference

Host plant preferences of insect pests are often Influenced by environmental conditions. The effects of plant stress on susceptibility to Insect attack have been obseirved in many crop plants. Stress factors affecting the physiological state of the plant Include drought, disease, chemical pollutants, and high salt concentrations. Profound... 

Matsuo T, Sugaya S, Yasukawa J, Aigaki T, Fuyama Y (2007) Odorant-binding proteins OBP57d and OBP57e affect taste perception and host-plant preference in Drosophila sechellia. PLoS Biol 5 ell8... 

Svensson, PA, Malm, T, Engkvist, R, 2004, Distribution and host plant preference of Idotea baltica (Pallas) (Cmstacea Isopoda) on shallow rocky shores in the central Baltic Sea. Sarsia, 89(7), 1-7. 

Gerrits-Heybroek, E. M., Herrebout, W. M., Ulenberg, S. A. and Wiebes, J. T. (1978). Host plant preference of five species of small ermine moths (Lepidoptera Ypono-meutidae). Ent. exp. appl., 24, 160-8. 

Rovenska, G.Z., R. Zemek, J.E.U. Schmidt, and A. Hilbeck. 2005. Altered host plant preference of Tetranychus urticae and prey preference of its predator Phytoseiulus persimilis (Acari Tetranychidae, Phytoseidae) on transgenic Cry3Bb-eggplants. Biol. Control 33 293-300. 

Enzyme preparations of three Pieris species each contained B-thioglucosidase activity, a fact previously reported (36), and each inhibited hydrolysis in one or more combinations with a plant enzyme-substrate system. These data are being quantified and extended to include insect/preferred host-plant pairs. 

We have tested the hypothesis that even susceptible host plants have defenses against insect attack In contrast to an artificial diet containing low concentrations of defensive allelochemlcals and having no morphological means of defense. A few species of Insects have been observed to have Increased fecundity and growth on artificial diets compared to preferred plants (, 51). 

An insect host s exposure to parasites and predators may be increased by variable plant defenses in three ways. First, by restricting feeding activity to certain tissue types or portions of the host plant, the position of insect hosts becomes more predictable. Parasites (24,46,42) or predators (48) able to recognize physical plant traits such as tissue color or form, or those capable of employing the unique chemistry of the preferred tissues as cues (47,49) would be able to locate their hosts more readily by focusing their search on these traits. 

Most researchers probably accept this concept, and yet the preferred host plant of an insect species, or a crop that is decimated by a pest, is usually thought of as being quite susceptible and rather poorly defended against insect attack. 

The host range of the tobacco hornworm (Manduca sexta) is limited to selected members of the family Solanaceae. In an effort to better understand the chemical basis for the host plant selection process, we have undertaken an examination of both hornworm preferred and non-preferred members of the Solanaceae. Our investigations have shown this tc be a complex system involving the subtle interaction between such behavioral modulators as (1) Ovipositional stimulants (2) Feeding stimulants and imprinters (3) Anti-feedants (A) Repel-lants (5) Insecticides. The results of these investigations will be discussed. 

Although the ovipositional stimulant and the phagostlmulant are necessary to illicit their respective responses, they may not be sufficient to account for host-plant selection. In the case of Nicandra physaloldes, a member of the Solanaceae not preferred as a host plant by M. sexta, we have shown that aqueous extracts... 

Jermy (15) has emphasized the Importance of allomones in the host plant selection process. Although the ovlpositional and phagostimulative kalromones do not appear to be sufficient to account for host specificity by M. sexta in the host plant selection process, the mere avoidance of allomones does not appear to be sufficient either. Rather, the presence of a detectable allomone is sufficient to account for non-selection of a potential host plant. For example, given a choice between esculentum and any other suitable host plant M. sexta moths select 1. excu-lentum (16). No allomones are Involved To account for this preference, the presence of volatile orientation factor(s) may be Involved. In fact, Morgan and Lyon ( ) Isolated amyl salicylate from the host plant Datura stromonlum as an orientation factor for gravid female moths. We have also shown that an orientation factor is present in the steam distillate of esculentum leaves. 

Eben, A., Benrey, B Sivinski, J. and Aluja, M. (2000). Host species and host plant effects on preference and performance of Diachasmimorpha longicaudata (Hymenoptera Braconidae). Environmental Entomology 29 87-94. 

Poore, A.G.B. and Steinberg, P.D., Preference-performance relationships and effects of host plant choice in an herbivorous marine amphipod, Ecol. Monogr., 69, 443, 1999. 

Leaf surface compounds provide important information about host-plant acceptability to coleopteran insects. Although the tortoise beetle, Cassida canaliculata, is only weakly attracted to odors from host plants, it shows strong preferences for host plants when additional contact cues are provided.64 The cottonwood leaf beetle, Chrysomela scripta, which is a pest of cottonwood, poplar, and willow, is stimulated to feed by leaf surface chemicals produced by a beetle-preferred poplar clone 65 The feeding stimulants have been isolated and identified as 1-docosanol, 1-tetracosanol, 1-hexacosanol, 1-octacosanol, 1-triacontanol, and... 

On the other hand, microorganisms and herbivores rely on plants as a food source. Since both have survived, there must be mechanisms of adaptations toward the defensive chemistry of plants. Many herbivores have evolved strategies to avoid the extremely toxic plants and prefer the less toxic ones. In addition, many herbivores have potent mechanisms to detoxify xenobiotics, which allows the exploitation of at least the less toxic plants. In insects, many specialists evolved that are adapted to the defense chemicals of their host plant, in that they accumulate these compounds and exploit them for their own defense. Alkaloids obviously function as defense molecules against insect predators in the examples studied, and this is further support for the hypothesis that the same compound also serves for chemical defense in the host plant. 

Companion planting—planting two or more types of plants in close proximity—is a popular gardening technique that can reduce pest problems in a variety of ways. Some good companion plants, such as dill, fennel, and Queen Anne s lace, will attract beneficial insects. Other types of companion plants repel pests or confuse and confound insects or disease organisms in search of their preferred host plants. To learn more about how diversity helps reduce pest problems, see Encourage Diversity on page 6. 

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