Repellent Plants Research Articles

Combining Pest Repellent Plants and Biopesticides for Sustainable Pest Management in Chinese Kale

The objective of this investigation was to study the use of pest repellent plant (PRP) species and biopesticides for sustainable pest management in Chinesekale( Brassica oleracea L. var. alboglabra Bailey). Ten selected treatments composed of three PRP species namely citronella grass - (CG) [ Cymbopogon nardus L. (Rendle)], sweet basil - (SwB) ( Ocimum basilicum L.) and sacred basil - (SaB) ( Ocimum sanctum L.)] were intercropped with Chinese kale, integrated with two commonly used biopesticides, viz. Bacillus thuringiensis (Bt) and neem extract ( Azadirachta indica) and a control were tested in a randomized complete block design (RCBD) with 3 replicates. The insect pest species infested in Chinese kale and their populations, % pest damage, fresh weight and quality of yield were investigated. The results showed that diamondback moth - (DBM) [ Plutella xylostella (Linnaeus)] density was lowest in CG alone, CG+SaB, SwB+biopesticides and SaB+biopesticides, relatively low in SwB alone, CG+SaB+SwB, and CG+biopesticides, and moderate in biopesticides and sacred basil alone, and highest in the control. The densities of common cutworm - (CCW) [ Spodoptera litura (Fabricius)], cabbage webworm - (CWW) [ Hellula undalis (Fabricius)] and flea beetle - (FBT) ( Phyllotreta sinuata Steph.) were not significantly different among treatments. The overall pest damage was lowest in CG+biopesticides treated plots followed by SwB+ biopesticides, SaB+biopesticides and biopesticides alone, and CG+biopesticides gave the best quality of yield of Chinese kale, and hence such combinations could be integrated for managing crucial insect pests, i.e. DBM and to minimize/avoid the use of highly toxic synthetic pesticides in Chinese kale.

Oviposition deterrence of shoots and essential oils of Minthostachys spp. (Lamiaceae) against the potato tuber moth

Abstract: The potato tuber moth is a noxious pest of potato in stores, where the use of repellent plants is an environmentally sound alternative to the application of chemical pesticides. We evaluated the protective effect of native Minthostachys species (Lamiaceae) against tuber infestation by the potato tuber moth in a rustic store in Cusco, Perú. We covered potato tubers with dried shoots of Minthostachys spicata and Minthostachys glabrescens and compared tuber damage with a control treatment of maize straw. We also conducted a no‐choice oviposition bioassay in the laboratory, testing the oviposition deterrence of essential oils of M. spicata, M. glabrescens and Minthostachys mollis at natural concentrations. We recorded the number of eggs laid by mated moths on filter paper treated with essential oils of each of the three species and on two control treatments: hexane and untreated blank. Finally, we tested for differences in oviposition deterrence among five full‐sib families of potato tuber moth raised under identical conditions. We found that dried, chopped leaves and flowers of Minthostachys species reduced the percentage of tuber damage in stores in comparison with the control (5% vs. 12%), but no difference in protection was found between species. Essential oils at natural concentrations deterred moth oviposition, reducing the number of eggs laid by about 80% compared with the control treatments; again, there were no significant differences between Minthostachys species. Finally, whereas we detected among‐family variation in oviposition on filter papers treated with essential oils, no difference was found in the number of eggs laid on control substrates. Therefore, there was genetic variation for oviposition deterrence in the potato tuber moth and resistance to repellent plants might evolve thereafter.

The effect of repellents Ocimum forskolei and deet on the response of Anopheles stephensi to host odours

The behavioural response of Anopheles stephensi Liston (Diptera: Culicidae) to incubated host odours (from human and goat) and to human odour in combination with a repellent plant, Ocimum forskolei (Labiatae), or deet (N, N, diethyl-toluamide) (20%) was tested in a dual-port olfactometer. An. stephensi was significantly attracted to both host odours compared with air alone, but showed no preference when given a choice between both host odours simultaneously. In choice tests, the addition of deet to human odour did not significantly divert mosquitoes to human odour alone, but did divert them to goat odour. O. forskolei combined with human odour diverted mosquitoes to goat or human odour alone. Combinations of human odour and O. forskolei, and human odour and deet were both as unattractive as air alone, and attracted mosquitoes equally when offered simultaneously. The results indicate that use of O. forskolei as a repellent would be beneficial in reducing vector biting if used in communities in areas with partially zoophilic mosquito species such as An. stephensi, and where animals are present.

Management of plant species for controlling pests, by peasant farmers at Lagoa Seca, Paraíba state, Brazil: an ethnoecological approach

Ethnoecological knowledge may be understood as spontaneous knowledge, culturally referenced of any society's members, learned and transmitted through social interactions and that are targeted at resolution of daily routine situations. The traditional knowledge in small scale economy societies as well as the non-academic knowledge in urban-industrial societies might be included in this concept. An ethnoecological approach study was performed here on people living at the communities of Alvinho, Almeida, Chã do Marinho, Floriano, and Chã de Oiti, all located in the municipality of Lagoa Seca, Paraíba state, Northeast Brazil. The general objective pursued here was to study the knowledge that peasant farmers have on management of plant species utilized for pest control. For this, the methodological instruments employed here to investigate the ethnoecological knowledge were: direct observation, structured and semi-structured interviews, and tours conducted by local peasant farmers. We analyzed the data obtained under an emic/etic view and also by comparing the local knowledge with those obtained from the literature. The results showed that people in those communities utilize management alternatives for controlling pests, which are mainly: (i) fallowing; (ii) crop rotation; (iii) destruction of crop remains and fruits attacked by pests; (iv) alternations of crops with repellent plants; and/or (v) mixed cropping; (vi) insect's larvae covered with soil; (vii) crops irrigated abundantly; and (viii) soil preparation. The recovery and comprehension we get about this knowledge as well as the farmers' savoir faire, are extremely important to the revival of ancient agricultural practices, which have been forgotten due to advances in modern agriculture. The data obtained here showed that a huge body of knowledge the farmers have on many forms or strategies of management are generally compatible with scientific knowledge.

Pengaruh Jenis Tanaman Penolak Organisme Pengganggu Tanaman terhadap Pertumbuhan dan Produksi Tanaman Kedelai (Glycine max (L.) Merr) yang Diusahakan Secara Organik

The purpose of this research is to determine the influence of repellent plant on growth and productivity of organic vegetable soybean. This research was conducted at Leuwikopo Research Station, from September 2004 to February 2005. Randomized Complete Block Design with one factor (type of repellent plant) and four replications was used. The type of repellent plant were Marigold (Tagetes erecta), Ocimum gratissimum, andropogon (Cymbopogon nardus), and leeks (Allium fistulosum).This research showed organic soybean with repellent plant had higher productivity than conventional soybean. Organic soybean with repellent plants had higher number of branches in 5 Weeks After Plant (WAP), the pod weight/plot, and 100 seeds dry weight. Growth and production of soybean were better under organic farming system than that under conventional farming. Soybean with repellent plant had lower total disease intensity than conventional treatment. Soybean with Tagetes erecta as repellent plant had lower total disease intensity than other repellent treatment. Key words: Organic vegetable soybean, repellent plant, pest and bulk disease intencity.

Evaluation of Extracts and Oils of Mosquito (Diptera: Culicidae) Repellent Plants from Sweden and Guinea-Bissau

In laboratory tests, ethyl acetate extracts of Hyptis suaveolens Poit. from Guinea-Bissau and Rhododendon tomentosum (Stokes) H. Harmaja (formerly Ledum palustre L.) and Myrica gale L. significantly reduced probing activity of Aedes aegypti (L.). In the field in southern Sweden, extracts of leaves of R. tomentosum, M. gale, and Achillea millefolium L. significantly reduced biting by Aedes mosquitoes. Volatile compounds from M. gale, R. tomentosum, A. millefolium, and H. suaveolens were collected by solid phase microextraction (SPME). Alternatively, compounds in the plants were subjected to extraction by organic solvents of different polarities or by steam distillation and collection by SPME. Compounds collected were identified by gas chromatography-mass spectrometry. Leaves of H. suaveolens contained mainly beta-caryophyllene, bergamotene, and terpinolene. The volatile fraction of an ethyl acetate extract of H. suaveolens was collected by SPME and included beta-caryophyllene, (-) -sabinene, beta-pinene, limonene, alpha-pinene, and bergamotene. The main volatiles detected were alpha-pinene, alpha-phellandrene, myrcene, and limonene from M. gale leaves or inflorescences; pcymene, sabinene, and terpinyl acetate from leaves of R. tomentosum; and (-)-germacrene D, beta-pinene, sabinene, and alpha-pinene from A. millefolium leaves or inflorescences. The selected plant species contained numerous volatiles known to have insecticidal, acaricidal, "pesticidal," and/ or insect repellent properties.

Evaluation of Extracts and Oils of Mosquito (Diptera: Culicidae) Repellent Plants from Sweden and Guinea-Bissau

Evaluation of Extracts and Oils of Mosquito (Diptera: Culicidae) Repellent Plants from Sweden and Guinea-Bissau

Feeding patterns by roe deer and rabbits on pine, willow and birch in relation to spatial arrangement

The location of a plant and its association with the surrounding vegetation may be a strong determinant of herbivore foraging decisions. The attractiveness of a food plant may be reduced if associated with a less preferred one (repellent–plant hypothesis) or, conversely, it may escape herbivory via association with a more preferred species (attractant–decoy hypothesis). In this study we tested the hypothesis that selection of the same food plants by two herbivore species with different body mass, i.e. roe deer and rabbits, is affected by the spatial disposition of preferred plants in relation to less preferred ones. We planted willows, birches and pines, representing food species of higher, intermediate and lower preference, respectively, in different spatial arrangements, to manipulate patch quality and accessibility to herbivores. Contrasting patches were constructed by planting willows or pines in the midst of birches and single‐species arrays of all three species, in a blocked design, replicated six times in an area occupied by both roe deer and rabbits. Preference patterns were studied by recording browsing on current years’ shoots and older plant parts. Across all trees in the experiment, we confirmed that roe deer clearly preferred willow over birch, pine was not browsed at all. There was greater herbivory by roe deer on birches occurring peripherally in an array, when the associated central species was willow or pine, as compared to birches in a single‐species birch patch. Therefore food choices by roe deer appear to be determined by both patch and individual level selection. The rabbits only showed preference at a species level and did not respond to spatial arrangement of trees. The results from this study indicate that the location and association of trees can strongly affect foraging patterns of roe deer, but not in a manner wholly consistent with the repellent–plant or the attractant–decoy hypotheses.

Field efficacy of thermally expelled or live potted repellent plants against African malaria vectors in western Kenya.

To estimate the effectiveness of live potted plants and thermal expulsion of plant materials in repelling African malaria vectors in traditional houses in western Kenya. Ocimum americanum, Lantana camara and Lippia ukambensis were tested in live, intact potted form whereas leaves of Corymbia citriodora, leaves and seeds of O. kilimandscharicum and O. suave were tested by thermal expulsion from modified traditional stoves. A latin square design was applied for randomly assigning the treatment and control plants to experimental houses over different nights. All plant species showed significant repellency against Anopheles gambiae sensu lato Giles (Diptera: Culicidae) (81.5%An. arabiensis Patton and 18.5%An. gambiae sensu stricto Giles), the main vectors of malaria in Africa, with the highest repellency by C. citriodora (48.71%, P < 0.0001) followed by an equal level of repellency of O. kilimandscharicum and O. suave (44.54%, P = 0.001) during application of plant material by thermal expulsion. All three plant species also showed a residual effect against An. gambiae s.l. with 36-44% repellency post-application period (22.30-06.30 hours) after a period of thermal expulsion. Similarly, intact potted plants of O. americanum and L. camara repelled An. gambiae s.l. significantly (37.91%, P = 0.004; and 27.22%, P = 0.05, respectively). Thermal expulsion of leaves and seeds of O. kilimandscharicum significantly repelled An. funestus Giles, although none of the potted plants repelled this species. Both methods of application may offer cost-effective alternatives as additional means of household protection, and a useful complement to bed nets, particularly for the early part of the evening before bedtime.

Evaluating companion planting and non-host masking odors for protecting roses from the Japanese beetle (Coleoptera: Scarabaeidae).

Effectiveness of companion planting, and use of nonhost masking odors were evaluated under field conditions for protecting roses against the Japanese beetle, Popillia japonica Newman. Three reputedly effective companion species, rue (Ruta graveolens L.), zonal geranium (Pelargonium x hortorum Bailey), and garlic chives (Allium scheonparum L.) were interplanted with roses in replicated garden plots. Numbers of beetles on these roses were compared with rose-only control plots on 6 d during beetle flight. The masking odor hypothesis was tested by hanging mesh bags of aromatic herbs or other sources of reputedly repellent nonhost volatiles around potted roses in the field. Treatments included crushed red pepper (Capsicum frutescens L.), fennel seeds (Foeniculm vulgare Miller), crushed spearmint (Mentha picata L.), cedar shavings (Juniperus sp.), osage orange fruits (Maclura pomifera (Raif) Schneid.), and fleshy gingko seeds (Gingko biloba L.). No treatment significantly reduced numbers of beetles relative to the controls. Interplanting with geraniums significantly increased numbers of Japanese beetles on roses. Similarly, roses surrounded by sachets with fennel seeds, cedar shavings, crushed red pepper, or osage orange fruits had significantly more beetles than the control plants on two or more sample dates. Our results suggest that the use of companion or reputedly repellent plants or plant odors probably will be ineffective for protecting roses or other highly-susceptible ornamentals from P. japonica. Use of such tactics in an effort to discourage other garden pests might even increase Japanese beetle damage in those plantings.

Traditional use of mosquito-repellent plants in western Kenya and their evaluation in semi-field experimental huts against Anopheles gambiae: ethnobotanical studies and application by thermal expulsion and direct burning

Ethnobotanical survey in 2 communities in western Kenya revealed that the most commonly known repellent plants were Ocimum americanum L. (64·1%), Lantana camara L. (17·9%), Tagetes minuta L. (11·3%) and Azadirachta indica A. Juss (8·7%) on Rusinga Island, and Hyptis suaveolens Poit. (49·2%), L. camara (30·9%) and O. basilicum L. (30·4%) in Rambira. Direct burning of plants is the most common method of application for O. americanum (68·8%), L. camara (100%) and O. basilicum (58·8%). Placing branches or whole plants inside houses is most common for H. suaveolens (33.3 and 57·8% for the respective locations), A. indica (66·7 and 100%), and T. minuta (54·8 and 56·0%). The repellency of plants suggested by the ethnobotanical survey and other empirical information was evaluated against the malaria vector Anopheles gambiae s.s. Giles in experimental huts within a screenwalled greenhouse. Thermal expulsion and direct burning were tested as alternative application methods for the selected plants O. americanum, O. kilimandscharicum Guerke, O. suave Willd., L. camara, A. indica, H. suaveolens, Lippia uckambensis Spreng and Corymbia citriodora Hook. When thermally expelled, only H. suaveolens failed to repel mosquitoes, whereas the leaves of C. citriodora (74·5%, P < 0·0001), leaves and seeds of O. suave (53·.1%, P < 0·0001) and O. kilimandscharicum (52·0%, P < 0·0001) were the most effective. Leaves of C. citriodora also exhibited the highest repellency (51·3%, P < 0·0001) by direct burning, followed by leaves of L. uckambensis (33·4%, P = 0·0004) and leaves and seeds of O. suave (28·0%, P = 0·0255). The combination of O. kilimandscharicum with L. uckambensis repelled 54·8% of mosquitoes ( P < 0·0001) by thermal expulsion. No combination of plants increased repellency by either method. The semi-field system described appears a promising alternative to full-field trials for screening large numbers of candidate repellents without risk of malaria exposure.

Control of witchweed Striga hermonthica by intercropping with Desmodium spp., and the mechanism defined as allelopathic.

During investigations into the control of insect damage to maize crops in subsistence farming in Kenya, which involved intercropping with repellent plants, the fodder legumes silverleaf (Desmodium uncinatum) and greenleaf (D. intortum) were also found to reduce dramatically the infestation of maize by parasitic witchweeds such as Striga hermonthica. This effect was confirmed by further field testing and shown to be significantly greater than that observed with other legumes, e.g., cowpea, as were the concomitant yield increases. The mechanism was investigated, and although soil shading and addition of nitrogen fertilizer showed some benefits against S. hermonthica infestation, a putative allelopathic mechanism for D. uncinatum was observed. In screenhouse studies, a highly significant reduction in S. hermonthica infestation was obtained when an aqueous solution, eluting from pots in which D. uncinatum plants were growing, was used to irrigate pots of maize planted in soil seeded with high levels of S. hermonthica. Growth of the parasitic weed was almost completely suppressed. whereas extensive infestation occurred with the control eluate. Laboratory investigations into the allelopathic effect of D. uncinatum, using samples of water-soluble chemical components exuded from cleaned roots, demonstrated that this involved a germination stimulant for S. hermonthica and also an inhibitor for haustorial development.

The influence of herbivores and neighboring plants on risk of browsing: a case study using arctic lupine (Lupinus arcticus) and arctic ground squirrels (Spermophilus parryii plesius)

We examined how herbivore distribution and density, neighboring plant density and species composition, and individual plant morphology all influence the risk that individual arctic lupines (Lupinus arcticus) will be browsed by arctic ground squirrels (Spermophilus parryii plesius). Risk of being browsed was significantly influenced by the number of resident ground squirrels but not by overall squirrel density at a site. As the leaf density of neighboring conspecifics increased, risk of browsing to an individual lupine decreased except when palatable neighbors were also present. The presence of other palatable species increased the risk of browsing. Risk was highest when both lupine and other palatable neighbors were present. The presence of unpalatable neighbors reduced the risk of browsing of individual lupines. We discuss these results in the context of three hypotheses: (1) attractant decoy, (2) resource concentration, and (3) repellent plant. No single hypothesis accounts for our observations, but an interaction between herbivores, neighbors, and individual lupine morphology determined risk of browsing.

People's perceptions about malaria transmission and control using mosquito repellent plants in a locality in Zimbabwe.

To assess peoples' perceptions and knowledge about malaria transmission and control with special reference to the use of plants as mosquito repellents. Cross sectional study. Mandeya ward "A" (33 degrees E and 18 degrees 30' S), Honde Valley, Zimbabwe. 226 household heads present when interview was conducted. Mosquito control methods, spraying coverage, plants used to repel mosquitoes and reasons for using them. 215 (95.0%) of the respondents' homes had been sprayed and their understanding of malaria transmission was not related to compliance with the National Malaria Control Programme (NMCP). Taking mosquito control measures was related to knowledge of malaria transmission, with 24 (75.0%) of those who did not know, taking no measures of their own. The use of plants was mentioned by 50 (23.5%) of the respondents and the reasons given were that they were cheap 43 (86.0%), effective five (10.0%) and locally available two (4.0%). The plant which was mentioned as being used by all age groups was L. javanica 25 (50.0%) and the other plants were used to a lesser extent. Forty six (92.0%) of the people said that they had used plants for mosquito control. The leafy part of the plant was used by 43 (86.0%) and a fresh preparation 43 (86.2%) gave better protection than a dry one. The plants were crushed and applied on the skin by eight people (14.6%), burnt by 36 people (72.8%) and used in their original form by six people (12.6%) and used once per by day 42 people (84.0%). One of the important points to emerge from this study is that, despite widespread knowledge about the morbidity of malaria, understanding about its prevention was generally low and this has negative implications on an integrated control programme.

Behavioural responses of Blattella germanica L. (Orthopt., Blattellidae) induced by repellent plant extracts

Abstract350 plant extracts were studied regarding to their characteristic repellency to Blattella germanica by means of a preference method. The repellency value reveals strong dispersion variation within plant families and, in some cases, also within genera. The individual developmental stages and sexes of B. germanica reveal differing behavioural patterns concerning test extracts. In the case of the strongly repellent extracts from Citrus sinensis and Allium sativum, there are indications for habituation processes regarding the repelling stimuli during long‐term tests.ZusammenfassungVerhaltensreaktionen von Blattella germanica L. (Orthopt., Blattellidae) auf abweisende PflanzenextrakteEs wurden Extrakte von 350 Pflanzenarten hinsichtlich ihrer abweisenden Wirkung auf die Deutsche Schabe Blattella germanica untersucht. Der Abweisungswert der Extrakte erwies sich als deutlich nach Pflanzenfamilien und in einigen Fällen auch nach Gattungen verschieden. Die Entwicklungsstadien und Geschlechter von B. germanica zeigten unterschiedliche Verhaltensmuster den getesteten Extrakten gegenüber. Im Fall der stark abweisenden Extrakte von Citrus sinensis und Allium sativum deuteten Hinweise auf eine Gewöhnung der Schabe an Abweisreize im Langzeittest.

Biological Methods of Bruchid Control in the Tropics: a Review

Bruchid beetles cause high losses of stored legumes in the tropics. Chemical control is inappropriate for the small scale farmer and the use of alternative measures should be encouraged. Different biological methods of control such as cultural, physical, varietal, biological, biorational and genetic control are reviewed. Cultural control techniques such as timely and frequent harvesting, legumes planted away from granaries, crop hygiene and storage in pods, are within the technical and financial means of the small scale farmer. The use of inert substances, vegetable oils and repellent plants may be cheap and effective if properly managed. The use of controlled atmosphere, vacuum, heating, cooling and sterilizing, requires relatively advanced techniques. Growth regulators and pheromones are currently not available for control. Varieties resistant to bruchids have been identified, but incorporation of resistance into suitable varieties has proven to be difficult. Biological control of bruchids should receive more attention in particular research on the introduction and conservation of natural enemies. To effectively implement control measures at farmer’s level socio-economic and cultural aspects should be taken into account. Proven appropriate techniques should be combined in an overall integrated pest management strategy.

Influence of Surrounding Plants on Densities of Pieris rapae (L.) Eggs and Larvae (Lepidoptera: Pieridae) on Collards

In three sets of field experiments, collards, Brassica oleracea var. acephala Decandolle, were surrounded by (1) other collards; (2) broccoli, Brassica oleracea var. botrytis (L.) deC., a closely related host; (3) collards treated with a systemic insecticide to make “decoy” plants; or (4) tomatoes, Lycopersicon esculentum Mill., an unrelated and perhaps repellent plant. Population densities of Pieris rapae (L.) eggs and larvae were the same for collards surrounded by other collards and for collards surrounded by broccoli. Nor were there differences in P. rapae densities on collards surrounded by collards that had been treated with aldicarb to make them toxic. Unexpectedly, however, P. rapae eggs and larvae were significantly more abundant on collards surrounded by tomatoes than on collards surrounded by other collards.

THE EFFECT OF COMPANIONATE PLANTING ON LEPIDOPTERAN PESTS OF CABBAGE

Companionate planting is one of many insect control strategies propounded by organic growers. A variety of herbs are purported to possess repellent properties to many insect pests of vegetables (Rodale 1975; Yepsen 1976; Hill 1976; Anonymous 1977a). According to Atsatt and O'Dowd (1976), repellent plants are members of plant defense guilds which prevent herbivores from locating their hosts. Perrin and Phillips (1978) reviewed the elements of natural pest control characteristic of mixed cropping systems and outlined suggestions for transferring these elements to “agronomically acceptable” monocultures. However, very little work has been done to substantiate these claims and field evidence of the protective properties of companionate plants is, therefore, warranted. This becomes all the more important because of the dramatic increase in home gardening recently in North America. It is estimated that 33 million home and community gardens were grown in the United States during 1976 and 1977 (Anonymous 1977b). Here we describe the results of field experiments in which we sought to quantify the effect of companionate plants against major lepidopteran pests of cabbage in southside Virginia.

Plant Defense Guilds

Optimal plant defense should incorporate any mechanisms that influence the feeding behavior of potential pests. From a diverse collection of examples suggesting that the defense of a plant may be improved in the company of specific neighbors, we discuss a framework of operational mechanisms that begin to clarify some aspects of the recognized influence of species diversity on herbivory. Neighbors serve as insectary plants for herbivore predators and parasites, and influence herbivore feeding behavior by repelling, masking, attracting, and decoying. Insectary plants lower the numerical response of herbivores by increasing the efficiency of their predators and parasites. Repellent plants primarily lower functional response by causing the predator to fail to locate or reject its normal prey. Attractant-decoy plants dilute herbivore impact by drawing off herbivores, either increasing or decreasing their numerical and functional response (or either). The concept of gene conservation guilds adds diversionary and delaying tactics to the adaptation-counteradaptation view of plant-herbivore coevolution. The useful life of a given gene for resistance may best be extended by mechanisms that disrupt genetic tracking (specialization) by herbivores. Some plants may remain inedible not because their chemistry or morphology represents an evolutionary impasse, but because they live in an environment that provides acceptable options of variable quality. Feeding environments that provide little or no choice promote specialization by forcing physiological adaptation. Conversely, the evolutionary momentum of specializing herbivores may be lowered by enhancing their susceptibility, either by selection against virulent individuals, or by decreasing the exposure frequency of susceptible genotypes. The latter mechanism of conserving susceptible individuals takes advantage of herbivore behavioral sensitivity to variable plant quality. Direct selection against virulent genotypes requires temporal cycling of the herbivore population between resistant and nonresistant hosts. Both events may occur within defense guilds that provide acceptable feeding options of similar but distinctive quality.

ChemInform Abstract: STRUCTURE OF NIC‐2, A MAJOR STEROIDAL CONSTITUENT OF THE INSECT REPELLENT PLANT NICANDRA PHYSALOIDES

Chemischer InformationsdienstVolume 5, Issue 22 Natural Products ChemInform Abstract: STRUCTURE OF NIC-2, A MAJOR STEROIDAL CONSTITUENT OF THE INSECT REPELLENT PLANT NICANDRA PHYSALOIDES R. B. BATES, R. B. BATESSearch for more papers by this authorS. R. MOREHEAD, S. R. MOREHEADSearch for more papers by this author R. B. BATES, R. B. BATESSearch for more papers by this authorS. R. MOREHEAD, S. R. MOREHEADSearch for more papers by this author First published: June 4, 1974 https://doi.org/10.1002/chin.197422425Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume5, Issue22June 4, 1974 RelatedInformation