The effect of glucosinolates on responses of young Phyllotreta nemorum larvae to non‐host plants

Abstract

All recorded host plants of Phyllotreta nemorum L. (Coleoptera: Chrysomelidae) contain glucosinolates and belong to the plant families Brassicaceae (Cruciferae), Resedaceae and Capparaceae. The acceptability of 56 plant species from 28 other plant families (non‐hosts) for young larvae has been studied in the laboratory. None of these species were fully acceptable for initiations of leaf mines when intact untreated leaves were presented, and only one species, Malva silvestris L. (Malvaceae), was partially acceptable. The acceptability of some species increased when leaf discs were presented instead of intact leaves; but the highest percentages of mine initiations occurred in leaf discs treated with the glucosinolate, sinigrin. A stimulatory effect of sinigrin could be demonstrated in experiments with 7 plant species: Papaver dubium L., Papayer rhoeas L., Fumaria officinalis L., Malva silvestris L., Pisum sativum L., Campanula latifolia L. and Lactuca sativa L. The majority of species remained unacceptable even after treatment with glucosinolates. The main causes for these differences between plant species are supposed to be differences in contents of deterrents and/or other stimulants for mine initiation. These possibilities are discussed in relation to the content of allelochemicals in acceptable plants and the position of these plants in botanical classifications. Zusammenfassung Die Wirkung von Glukosinolaten auf die Reaktionen der Junglarven von Phyllotreta nemorum an Nichtwirts‐Pflanzen. Phyllotreta nemorum L. ist ein oligophager Erdfloh, der an Cruciferen und anderen Glukosinolat‐haltigen Pflanzenarten gebunden ist. Die Imagines fressen Löcher in die Blätter und die Weibchen legen ihre Eier in den Boden. Die Larven sind Blattminierer. Nach dem Schlüpfen im Boden klettern sie an die Pflanzen hoch, und die Einbohrung und der Anfang der Minierung erfolgt in eines der unteren Blätter der Wirtspflanze. Die Wirkung von Glukosinolaten auf die Einbohrung von Junglarven in Pflanzenarten, die keine natürliche Inhalt von Glukosinolaten haben, ist in Laborexperimenten untersucht worden. 56 Pflanzenarten aus 28 Familien wurden präsentiert teils als unbehandelte Blätter und teils als Glukosinolatbehandelte Blattscheiben. Unbehandelte Blätter von nicht‐Glukosinolathaltigen Arten waren immer unbefriedigend für die Larven. Nur in eine Art, Malva silvestris L. war die Frequenz der Einbohrung ein bisschen höher als 10%. Eine signifikante Erhöherung der Anzahl eingebohrten Larven nach der Sinigrin‐behandlung erfolgte in 7 Pflanzenarten: Papaver dubium L., P. rhoeas L., Fumaria officinalis L., Malva silvestris L., Pisum sativum L., Campanula latifolia L. und Lactuca sativa L. Doch blieben die meisten Pflanzenarten (84%) auch nach der Sinigrin‐Behandlung unbesiedelt. Pflanzenarten, die nach der Sinigrin‐Behandlung nicht besiedelt werden enthalten vielleicht frasshemmende Stoffe, oder ihnen fehlen noch weitere Frass‐stimulierende Stoffe. Diese Möglichkeiten werden diskutiert in Zusammenhang mit den Inhalt von Allelochemik...

Trap Crops and Insectary Plants in the Order Brassicales

“…and Psylliodes chrysocephala (Nielsen 1989, Bartlet et al 1994, Giamoustaris and Mithen 1995, Nielsen et al 2001; the cabbage fly, D. radicum ; and the cabbage webworm, H. undalis (Mewis et al 2003). In these cases increasing glucosinolate content in trap crops could enhance their effectiveness.…”

Variation in defences of the plant Barbarea vulgaris and in counteradaptations by the flea beetle Phyllotreta nemorum

“…Renwick, pers. Some glucosinolates stimulate mine initiation in P. nemorum larvae (Nielsen 1989b), but the compounds present in Barbarea species have not yet been tested. The P-type of B. v. ssp.…”

“…It is still a possibility that different hydrolysis products may be formed from (2S)-glucobarbarin in B. vulgaris and B. stricta. Some glucosinolates stimulate mine initiation in P. nemorum larvae (Nielsen 1989b), but the compounds present in Barbarea species have not yet been tested. Most crucifer specialist insects are able to tolerate high levels of glucosinolates, and production of other allelochemicals may be a more effective defensive strategy against such adapted insects (Nielsen, 1978;Sachdev-Gupta et al, 1993a,b).…”

Microbial Symbiont-Based Detoxification of Different Phytotoxins and Synthetic Toxic Chemicals in Insect Pests and Pollinators

“…Glucosinolates are another common group of defense compounds, often occurring in plants in the Order Brassicales (sometimes referred to as Capparales), including oilseed rape [ 52 ]. They are sulfur- or nitrogen-containing compounds, and have been shown to decrease aphid fecundity [ 55 ], though like the cyanogenic glucosides, some insects show a preference for glucosinolate-producing plants [ 56 ]. Many well-known plant phytotoxins are alkaloids, which are subdivided into three major classes: the true alkaloids, which includes nicotine; the pseudoalkaloids, such as caffeine; and the protoalkaloids, like mescaline.…”