Phytophagous insects

Landolt, P.J. and Phillips, T.W. 1997. Host plant influences on sex pheromone behavior of phytophagous insects. Annu. Rev. Entomol. 42, 371-391. 

Arnold TM, TargettNM, Tanner CE, Hatch WI, Ferrari KE (2001) Evidence for methyl jasmonate-induced phlorotannin production in Fucus vesiculosus (Phaeophyceae). J Phycol 37 1026-1029 Bemays EA, Chapman RF (1994) Host-plant selection by phytophagous insects. Chapman Hall, New York... 

Systemic insecticides are superior to contact insecticides in many ways. On account of their absorption and transfer in the plant they can deal with insects which might normally remain hidden or protected from the direct spray of a contact insecticide. Many systemic insecticides are specific to certain pests. For example, owing to the insecticide being contained within the plant, parasitic non-phytophagous insects are less likely than the pests to absorb the insecticide. And so ecological selectivity1 comes into play. 

Ananthakrishnan TN, Raman A (1993) Chemical ecology of phytophagous insects. International Science Publisher, New York... 

Although dealkylation is restricted to arthropods, not all insects possess this ability, nor do all insects employ the same steroid nucleus. In general, phytophagous insects are capable of dealkylation while zoophagous insects lack this ability. 

Physiological Interactions Between Phytophagous Insects and Their Hosts... 

Water. Although often omitted from lists of essential nutrients, water is the universal biological solvent in which the biochemical reactions of each cell occur. Most living organisms contain far more water than any other compound or group of compounds. Although most insects are 70-80% water, their food may vary from 1 to over 90% water. Stored-product Insects have remarkable abilities to conserve water, whereas phytophagous insects may suffer deleterious effects from low dietary moisture. 

Bernays, E. A. and Chapman, R. F. 1994. Host-Plant Selection by Phytophagous Insects. London Chapman Hall. 

Brues, C. T. 1924. The specifity of food plants in the evolution of phytophagous insects. American Naturalist, 58 127-144. 

The young leaves constitute an abundant food resource for phytophagous Insects and they are especially vulnerable to herbivores due to a high nitrogen content and lack of sclerophylly. These characteristics appear to be universal In new leaves of deciduous forest species, and this period of... 

This same scenario has not been observed with plant allelochemlcs. Phytophagous insects and plants have coexisted for eons. In general, plants, through their allelochemlcs have exacted their toll on Insects, while falling prey to these same insects. The reasons for these differences deserve comment. 

In conclusion it is evident that many research opportunities exist In the identification and characterization of new substances and evaluation of their ecological evolutionary and physiological significance. In a practical sense it can be hoped that some of these new compounds because of their novel mode of action may be useful for the control of phytophagous Insects as part of Integrated pest management programs. 

Immunization of Plants by Attenuated Forms of Pathogens. As has been argued by Kuc and Caruso (47), plants can be immunized to achieve higher levels of resistance to pathogens. Similar mechanisms may conceivably provide a line of defense against phytophagous insects without the challenge-independent accumulation of defensive compounds. 

The selection or avoidance of potential host plants by phytophagous Insects Is guided by a complex combination of physical and chemical stimuli. Color, shape and olfactory cues may play a role In the Initial orientation, whereas acceptance or rejection of a plant depends on texture as well as chemical stimulants or deterrents. Initiation of feeding Is stimulated or deterred by the presence or absence of specific chemicals or groups of chemicals, many of which have been Identified. The selection of a suitable plant for ovlposltlon Is also crucial for survival of the progeny of most herbivorous Insects, but the chemical factors Involved are known In relatively few cases. Ovlposltlon stimulants and deterrents often appear to be quite different from the chemicals that elicit or Inhibit feeding responses of larvae. 

Feeding. The feeding behavior of phytophagous Insects has been studied much more widely than other aspects of the Insect/plant relationship. The reason for this probably lies In the relative ease with which bloassays can be performed and the results Interpreted. Many Insects can be reared on artificial diets, and the effects of added plant constituents can readily be determined. Some early studies by Dethler (29) demonstrated a correlation between larval food choice and the presence of specific chemicals In the umbelliferous host plants of Paplllo polyxenes. However, many of the compounds typically found In the Umbelliferae are also present in other... 

Most phytophagous insects exhibit specialized feeding habits they feed on a restricted range of taxonomically related plant species, and are even specialized to feed on particular parts of these plants like leaves, stems, flowers, fruits or roots (J ). 

The diversity in insect-plant interactions is overwhelming as each insect species shows a series of adaptations to its host plants. These adaptations involve morphological features like the insect s mouthparts, as well as behavioural and metabolic changes in order to cope with the physical and chemical characteristics of the plants to which phytophagous insects became adapted in evolutionary time. It is beyond the scope of the present paper to list all the adaptations of insects to plants, or even all the counter-adaptations of plants to insects. At the risk to generalize to an extent which over-simplifies the diversity in... 

The nutritional requirements of insect species exhibiting different feeding habits like scavengers, parasites, predators and phytophagous insects, are similar in a qualitative sense (O. Each insect species needs, however, a particular quantitative composition of nutrients in its diet to complete development ( ). The presence of toxic substances in plants, secondary plant substances as they were formerly called by phytochemists, forms a barrier which phytophagous insects have overcome by specialization. Thus, an insect can tolerate or detoxify the secondary plant substances present in its host plants, while the majority of these substances being present in other plants still acts as toxins (J ). In this way phytophagous insects are adapted to the metabolic qualities of their host plants, i.e. a particular chemical composition of nutrients and secondary plant substances. 

Different insect species posses different gustatory receptor cells, their response spectra being adapted to the perception of chemical components distributed in their host plant species (9 ). Taste perception in P. brassicae larvae forms a representative example for phytophagous insects, which are able to discriminate a number of compounds like sugars, amino acids, salts, and secondary plant substances acting as feeding inhibitors or feeding incitants (3,6,, 10). 

Differential sensory sensitivity. The insect s perception of plant odours differs essentially from their discrimination of non-volatile taste substances, as phytophagous insects may already perceive the odour at some distance from the plant. In adult phytophagous insects the antennae bear a large number of olfactory sensilla in order to detect the minute concentrations of the leaf odour components in the air downwind from a plant. The overall sensitivity of the antennal olfactory receptor system can be measured by making use of the electroantennogram technique (17). An electroantennogram (EAG) is the change in potential between the tip of an antenna and its base, in response to stimulation by an odour component. Such an EAG reflects the receptor potentials of the olfactory receptor cell population in the antenna. 

The antennal olfactory receptor system in several phytophagous insects is very sensitive in the detection of the green odour components. In the Colorado beetle Leptinotarsa decemlineata, the threshold of response for trans-2-hexen-1-ol is circa 10b molecules per ml of air (17). In comparison, at 760 mm Hg and 20 C, 1 ml of air contains about 1019 molecules. The insects tested i.e., the migratory locust Locusta migratoria, the carrot fly Psila rosae (18), the cereal aphid Sitobion avenae (19), the Colorado beetle L. decemlineata (17), Leptinotarsa... 

Figure 4. Sensitivity spectrum of the antennal olfactory receptor system in several phytophagous insect species to the green odor components. BAG amplitudes in response to the iruiividual components are visualized in the areas of circles. Data were derived from Refs. 18 (a), 19 (b), 17 (c), and 20 (d).

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