The impact of vegetational diversity through intercrop and the application of antifeedants were assessed for their ability to reduce the infestation of shoot and fruit borer Leucinodes orbonalis Guen. on eggplant. Intercropping with coriander and fennel reduced the fruit damage to 12–15% compared with the plots with eggplant monoculture. Total yield of intercropped eggplant was significantly higher than the eggplant monoculture yield. Coriander and fennel were found to be equally effective in reducing infestation by L. orbonalis. Neem seed kernel extract (4%) and the neem-based product Neemarin® were found to be more effective in controlling L. orbonalis than ash dust and were lower than the untreated control. The fruit infestation level in the neem treatments (either of them) was 15–16% less than the untreated check. The interaction of intercrop and antifeedant showed that coriander-intercropped eggplant along with foliar spray of Neemarin® significantly reduced fruit damage. In a multiple choice chamber, orientation of female moths to eggplant was significantly reduced in the presence of fennel or coriander. With 38.9 and 37.1 per female, the extent of egg-laying by L. orbonalis on eggplant associated with fennel or coriander, respectively, was significantly less than on sole eggplant (48.4/female).

Two phenylpropanoid glucosides, namely acetylmartynoside A and 4”-O-acetylmartynoside, isolated from Aegiphila obducta (Verbenaceae) were studied for insect antifeedant activity against fourth-instar larvae of Chilo partellus (Lepidoptera: Pyralidae). Acetylmartynoside A showed weak antifeedant activity at all the concentrations tested while 4”-O-acetylmartynoside showed strong antifeedant activity, particularly at the higher concentrations of 400 and 500 μg/disk.

Bioactivity of Melia azedarach L. was tested against diamondback moth (DBM), Plutella xylostella L. in the laboratory. The adult of DBM laid significantly lesser number (upto 71%) of eggs on the surfaces treated with methanolic extracts of M. azedarach than on those treated with solvent only. When larvae derived from above eggs were reared on fresh food, the mortality in the larval stage was upto 22.8% and that in pupal stage was upto 29.6%. The methanolic extracts also reduced feeding among the larvae significantly, when methanolic extract-treated food was offered to second instar larvae in a different set of experiment, thus, indicating an antifeedant effect.

Six amide alkaloids of Piper guineense were tested for antifeedant activity against fifth instar larvae of Chilo partellus in choice assays. These amides include piperine, Δα, β-dihydropiperine, wisanine, Δα, β-dihydrowisanine, trichostachine and N-isobutyl-trans-2-trans-4-eicosadienamide. Piperine and its dihydrosaturated derivative exhibited the most potentantifeedant activity. Δα, β-dihydrowisanine and trichostachine were intermediate in activity followed by wisanine. The N-isobutyl derivative was the least active. These results suggest that the presence of a methylenedioxybenzene and an alicyclic amide group in the compound may be crucial for high antifeedant activity.

Earias vittella (Fabricius) feeds on some malvaceous plant species, but has never been reported to attack Thespesia populnea Cav., even though this plant belongs to the same family. The factors responsible for the failure of E. vittella to establish on T. populnea were, therefore, studied. When whole fruits or fruit pericarps of this plant were provided as larval food, larvae failed to develop and none of them pupated. However, on developing seeds of these fruits, larval growth and development were normal and comparable to those of larvae reared on developing seeds of the most favoured host plant, Abelmoschus esculentus Moench. Ether extracts from fruit pericarps exhibited antifeedant and antibiosis activity against this insect. Ether as well as ethanol extracts affected oviposition to some extent. In a choice situation, significantly less eggs were laid on treated than on untreated okra fruits. However, in a no-choice situation most of the eggs were laid on treated okra fruits.

Essential oil of sweetflag, Acorus calamus L. was fed (in artificial diet) to the variegated cutworm, Peridromo soucia Hubner, to assess its antifeedant and growth inhibitory effects. The oil decreased food consumption and larval growth in a dose-dependent manner in both neonate (first instar) and second instar larvae. Calamus oil applied to cabbage leaf discs significantly inhibited feeding by fourth and fifth instar larvae in a choice test. Nutritional experiments with fourth instar larvae using topical application or dietary exposure confirmed that sweetflag oil induces both antifeedant and growth inhibitory effects in Peridroma saucia, the latter possibly being independent of feeding behaviour.

Selected studies in chemical ecology are described that have led to the identification of semiochemicals playing key roles in pest behaviour. In some instances, these compounds can provide alternatives to insecticides, but novel integrated control programmes including use of semiochemicals are described which have greater potential for the future. Thus, semiochemicals can be used to increase the efficacy of entomophagous fungi and to manipulate populations of beneficial insects. New strategies are being developed which use both antifeedant and attractant semiochemicals to deter insects from crops and aggregate them in areas where they can be destroyed. For the long term, strategies are described that employ genetic manipulation of crop plants so that pests are controlled by semiochemicals produced directly in the plants.

Limonoids such as deoxylimonin, obacunone and pedoniti are known to have antifeedant effects against some lepidopteran pests. However, there is no electrophysiological data showing the effect these compounds have on taste receptor cells. This information gap is due to the fact that limonoids are insoluble in water and this makes it difficult to apply the tip-recording technique in an electrophysiological bioassay of limonoids. This problem was solved by dissolving the limonoids in a mixture of 50 % tetrahydrof uran and 50 % aqueous NaCl. Limonoids and sucrose so dissolved were used to investigate responses of Eldana saccharina maxillary styloconic sensilla. The solvent mixture did not appear to damage the taste receptor cells and the taste receptor responses to solutes dissolved in that solvent were reproducible. Sucrose stimulated a cell in the medial as well as in the lateral styloconic sensilla. Deoxylimonin alone stimulated a cell in the medial sensillum but not in the lateral sensillum. When presented with sucrose, deoxylimonin inhibited the sugar receptor cell and this was also true for obacunone.

Conessine, the steroidal alkaloid of Holarrhena antidysenterica Wall, possesses a wide range of activities against four insect species viz. Aedes aegypti, Dysdercus koenigii, Spodoptera litura and Pieris brassicae. In D. koenigii the compound inhibits the egg hatching of treated adults and nymphs. In Ae. aegypti the larval developmental periods are extended, resulting in a high mortality rate. Such effects are produced at very low dosages of 0.5 to lOppm. Antifeedant activity is observed against larvae of S. litura and P. brassicae at concentrations of 0.005 to 0.2 % of conessine.

Various neem products were compared with copra oil, palm oil and 0.25% diazinon dust for protection of stored maize against the grain weevil, Sitophilus zeamais Motsch. Maize kernels treated with neem oil or ash were damaged less than the control. Although copra and palm kernel oil reduced S. zeamais attack, these edible oils were not as effective as neem oil. Neem wood ash was however, less effective than 0.25% diazinon dust. Neem derivatives inhibited oviposition and/or deterred feeding.

The structure of hildecarpin, an insect antifeedant 6a-hydroxypterocarpan isolated from the roots of Tephrosia hildebrandtii has been confirmed by a combination of degradation reactions, NMR and mass spectra. Hildecarpin has been dehydrated to the corresponding pterocarpene 3-hydroxy-2-methoxy-8,9-methylenedioxypterocarpene. Hydrogenation and hydrogenolysis of the pterocarpene has afforded the isoflavan 2′, 7-dihydroxy-6-methoxy-4′,5′-methylenedioxyisoflavan, acetylation of which has led to 2′, 7-diacet6xy-6-methoxy-4′,5′-methylenedioxyisoflavan. The NMR and mass spectra of the degradation products confirm the structure previously assigned to hildecarpin.

A new 6a-hydroxylated pterocarpan, named hildecarpin, has been isolated from the healthy roots of Tephrosia hildebrandtii. It has been assigned the structure (−)-3, 6a-dihydroxy-2-methoxy-8, 9-methylenedioxypterocarpan on the basis of its spectroscopie data, optical rotation and chemical transformations. Hildecarpin has exhibited insect antifeedant activity against the legume pod-borer Maruca testulalis, an important pest of the cowpea (Vigna unguiculata), and antifungal activity against Cladosporium cucumerinum. This finding suggests that the pterocarpan phytoalexins formed as a result of microbial infection of the cowpea plant may constitute a basis for induced resistance in the plant against M. testulalis.

Three 9-acridone alkaloids, melicopicine, tecleanthine and 6-methoxy tecleanthine were isolated from the bark of Teclea trichocarpa. Melicopicine and tecleanthine exhibited mild antifeedant activity against the African armyworm, Spodoptera exempta. All the three alkaloids showed antimicrobial activity against the fungus, Cladosporium cucumerinum and the bacterium, Bacillus subtilis.