Artificial diets

A similar approach has been used to identify insect feeding deterrents (Escoubas et al. 1992). Here, chemical separations of plant extracts are carried out on silica thin-layer chromatography plates. After the separation is complete and solvent is allowed to evaporate from the plates, a thin layer of agar-based artificial diet is poured over the plate. Chemical compounds from the plate then diffuse into the artificial diet. Test subjects then are allowed to feed on the diet-coated plates. Presumably, the areas that are not eaten contain antifeedants, which can later be identified chemically. 

Although elegant, this approach also has particular limitations. First, because the test insects (Spodoptera litura) refused to consume any of the silica gel beneath the diet, the method can only identify antifeedants sufficiently polar to diffuse into the artificial diet in biologically effective concentrations. Second, heat-sensitive compounds may be broken down as the agar is poured over the plate. Thus, while positive results may provide dramatic and useful information, negative results are ambiguous. Finally, this technique is useful only for species for which an artificial diet has been developed (see following section). 

In cases when herbivores refuse to accept nonnutritious substrates regardless of the concentration of candidate semiochemicals, then a ubiquitous background feeding stimulant can be added. This is routinely done to test for deterrent activity on neutral or unpalatable artificial substrates. A number of sugars have been used, with sucrose (2.5-5% solutions by weight) being used most widely (e.g., Cottee et al. 1988 Navon et al. 1993). 

If nonnutritive neutral substrates are not acceptable, the next most uniform substrate is a completely defined artificial diet. Following completely defined diets in uniformity are semidefined diets (e.g., those that include some plant material) and plant tissues to which test chemicals are added. 

Artificial feeding substrates offer uniformity, evenness of application, and ease 

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Mahar AN, Jan ND, Mahar AQ, Mahar GM, Hullio MH, Lajar AG. Efficacy of entomopathogenic bacterium Photorhabdus luminescens and its metabolites against diamondback moth Plutella xylostella larvae on Chinese cabbage and artificial diet. Pak J Nematol. 2008 26 69-82. 

In the laboratory, we succeeded in raising Utetheisa on two alternative artificial diets, one made up with Crotalaria seeds and containing the PA monocrotaline (CS diet), the other based on pinto beans and devoid of PA (PB diet). On the assumption that the PB diet-raised moths, which we proved to be PA-free, would be vulnerable to predation, we took moths... 

Although Osborne and Mendel were coming to terms with the probability that some essential substance was present in milk, they had already that year (1912) published two articles which led readers to believe that Osborne and Mendel had developed a totally synthetic and successful diet. In early 1913> Hopkins and Neville questioned the validity of some of the experimental results obtained by Osborne and Mendel. They said that the Americans results seemed to indicate that young rats could grow on purely artificial diets and, therefore, that accessory factors or vita-mines were dispensable. "But...they contradict what is now a considerable body of experience, and the experiments which yielded them seem to call for repetition." (29)... 

In late February of 1913 Osborne and Mendel responded to the note in the Biochemical Journal in a letter to Hopkins in which they stated that they had been surprised by the outcomes of the experiments on purely arificial diets and that newer experiments demonstrated either poor growth or none at all on fat-free artificial diets. They also said in this letter that they believed they had a clue as to the cause of the differences in results. Furthermore ... 

All of us are dealing with problems which involve extremely complicated conditions, and we must be prepared to be confronted with unexpected results for some time to come. For example, our experience in studying the effect of small additions of milk to various artificial diets has rarely been that which we expected from your report.We have no intention of intruding on your field in making these experiments, nor do we expect to publish our results as evidence that your experiments involve error, or that your published conclusions are incorrect.. ..We are convinced that the pursuit of the growth substance involves some of the most important problems of biochemistry, and that it will not be long before the combined efforts of those who engage in it will solve at least some of them. (31)... 

Unlike their relatives, senita flies are unaffected by these toxins. They flourish on an artificial diet containing even ten times as much toxin as the cactus produces. The plant s toxins fail to deter... 

Interaction with cell membranes is also supported by recent experimental data from Barbeta et al In feeding trials using artificial diets and larvae from Helicoverpa armigera it was shown that kalata B1 has a... 

Glendinning, J. F., Brower, L. P., and Montgomery, C. A. (1990). Responses of three mouse species to deterrent chemicals in the Monarch butterfly. I. Taste and toxicity tests using artificial diets laced with digitoxin or monocrotaline. Chemoecology 1,114-123. 

Cuts from the silica gel column were incorporated into artificial diets optimized for several economically-important agricultural pest insects, the pink bollworm Pectinophora gossypiella> the tobacco budworm Heliothis virescens> the corn earworm H. zea and the fall armyworm Spodoptera frugiperda. > Monitoring with this artificial diet bioassay, further column chromatography and preparative TLC on silica gel in diethylether-petrol yielded five... 

The artificial diet feeding assay mentioned above was employed to monitor the chromatographic separation of the 5 bioactive principles. Once separated, purified, and spectrally identified, the active principles were synthesized and tested in the same artificial diet feeding assay in order to obtain ED5Q-values, the effective doses for 50% growth inhibition. 

The lethal activity of the isobutylamides on C. pipiens is shown in Table II. The amides were dissolved in 0.1% acetone in distilled water to give concentrations of 1-20 ppm. Third-instar C. pipiens were transferred (5 larvae/10 ml test solution) into 1 oz. plastic cups using a 1 x 1-inch circle of ordinary window screen. Each treatment was replicated 4 times and the minimum concentration of each compound which caused 100% mortality (LDioo) within 48 h at 25 C and 16L/8D photoperiod was determined. In a result similar to that found with the artificial diet bioassay with lepidopterous larvae, pellitorine proved to be the most toxic of the assayed amides (LDjqq = 5 ppm). 

Apoplastic transport, achieving, 197 Apparent partition coefficient, 227 Area, relationships, 260 Artificial diet feeding assay, 163-64 2-Ary1-1-cycloalkanediones biological properties, optimization, 321 structure-activity... 

To test if some stress compounds had beneficial effects on aphids proline, choline and glycine-betaine were incorporated into artificial diets. Proline and choline appeared to decrease survival of aphids, while glycine-betaine did not (Table V). Moreover, glycine-betaine caused a drastic increase in aphid reproduction. Thus, the increased susceptibility to aphids of water stressed plants may be partially due to the higher content of glycine-betaine. 

Effects of Gramine, DIMBOA and DIMBOA-Glucoside on ScfUzaph-Ci gAxmcnum feeding on artificial diets... 

Table V. Effects of Proline, Choline and Glycine-Betaine on SchizapluA gtutminum Feeding on Artificial Diets...

A variety of compounds may accumulate in plants under water stress (18, 19). One of these compounds, glycine-betaine, increased reproduction rates of aphids in artificial diets. It is likely that the observed increased susceptibility of barley to aphids may be due to glycine-betaine accumulation in barley leaves. It is... 

Figure 7. Electron Micrograph Illustrating Ecdysls Inhibition of a Larva of the Pink Bollworm, Pectlnophora gossyplella after Ingestion of 2 ppm Ponasterone A In an Artificial Diet (Magnification x 100)...

Table IV. Growth-Inhibitory Activity of Some Bioactive Constituents Derived from Geranium viscosissimum var. viscosissimum Fed in an Artificial Diet to First-Instar Larvae of Heliothis virescens...

The growth-inhibitory activity of azadirachtin fed in artificial diet to three species of agricultural pests, gossypiella, H. zea, and frugiperda, was compared to the activity of a number of limonoids isolated from plants in the Meliaceae and the Rutaceae (Table VI). After azadirachtin, the most active limonoid was cedrelone (Figure 13). Cedrelone was unique among the compounds tested in Table VI since it was the only limonoid, besides azadirachtin, to cause an inhibition in ecdysis (LC50 = 150 ppm) when fed to pink bollworm larvae (54). 

Oil Limonoids Fed in an Artificial Diet to Flrst-Instar Larvae of Heliothis virescens... 

Another limonoid isolated from neem seeds and determined to be as potent as azadirachtin as an ecdysis inhibitor has been identified as 3-deacetylazadirachtinol (Figure 15) (57). Both compounds were lethal to 50% of the treated H. virescens larvae (EI5Q) at 0.8 ppm in artificial diet (Table VII). Structurally, there are two differences between the compounds. In 3-deacetylazadirachtinol, the C-ll-O-C-13 ether linkage of azadirachtin is reductively cleaved at the 11 position and the acetoxyl group at C-3 is hydrolyzed to a hydroxyl group. 

Artificial Diet to First-Instar Larvae of Three Species of Agricultural Insect Pests... 

Table II. Mortality (%) of Flrst-lnstar Hellothls zea on Artificial Diets (28) Modified with Additives.

Mortality (%) of Heliothis with Carbaryl and zea on Artificial Diet Modified Piperonyl Butoxide (35) ... 

On an artificial diet, biotype C greenbugs (3) responded to pH like the beet leafhopper. Biotype E greenbugs also preferred a slightly alkaline diet (Figure 2). 

In another experiment, chinch bugs were initially placed into sealed J-cups containing a Parafilm-covered diet (greenbug diet) cap identical to those used for aphids. Chinch bugs readily located and fed upon the liquid through the membrane. This is the first example of chinch bug subsistence in the laboratory on an artificial diet. 

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). 

In our experiments, black cutworm (Agrotls Ipsllon) (BCT7) larvae were fed corn seedlings and artificial diet. While there appear to be species of plants that are even more susceptible to BCTJ larvae than com, corn was not statistically different from the most susceptible species tested by Buschlng and Turpin (52), and certainly BCW can occasionally be extremely damaging to corn. Further, Wilson et al. (53), Tseng et al. (54), and Jarvis et al. (55) have screened thousands of maize introductions, inbred lines, and hybrids, and have found only a very few sources of even moderate resistance. 

Figure 3. Mean weights of black cutworm larvae fed Funk s G4507A corn seedlings and given a 48-h "boost" on artificial diet at various times during the experiment. Control larvae were fed artificial diet for the entire experiment. Each bar represents the mean of 20 larvae.

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