Antifeedant Potential of Geranylacetone and Nerylacetone and Their Epoxy-Derivatives against Myzus persicae (Sulz.).

Geranylacetone and nerylacetone are natural sesquiterpenoids, which play various roles in plant-insect interactions, including the deterrent and repellent effects on herbivores. The structural modifications of natural compounds often change their biological activities. The aim of the study was to evaluate the effect of geranylacetone, nerylacetone and their epoxy-derivatives on the probing and settling behavior of Myzus persicae (Sulz.) (Hemiptera: Aphididae). The no-choice test using the Electrical Penetration Graph (EPG) technique showed that the probes before the first phloem phase were usually shorter than 3 min, which means that they were terminated within the epidermis and/or outer layers of mesophyll. This resulted in a tendency to delay the initiation of the phloem phase in aphids, which reflects a weak preingestive deterrent activity of the studied compounds at the level of non-vascular tissues. Most M. persicae showed bouts of sustained phloem sap ingestion. However, the 24-h free-choice test demonstrated that aphids did not settle on the leaves treated with geranylacetone, nerylacetone, and their epoxy-derivatives. The refusal to settle after the consumption of phloem sap on treated plants indicated that the studied compounds had postingestive deterrent activity. The epoxidation of geranylacetone and nerylacetone did not evoke significant changes in their activity profiles.

New insight into the behaviour modifying activity of two natural sesquiterpenoids farnesol and nerolidol towards Myzus persicae (Sulzer) (Homoptera: Aphididae).

The effect of structurally related sesquiterpenoids (E,E)-farnesol and cis-nerolidol on the host-plant selection behaviour of the peach potato aphid Myzus persicae (Sulz.) was evaluated using electrical penetration graph (EPG) technique. No repellent effects of (E,E)-farnesol and (Z)-nerolidol to M. persicae were found but aphid probing activities on (E,E)-farnesol- and cis-nerolidol-treated plants were restrained. During non-phloem phases of probing, neither (E,E)-farnesol nor (Z)-nerolidol affected the cell puncture activity. On (E,E)-farnesol-treated plants, the total duration of phloem phase, the mean duration of individual sustained ingestion periods were significantly lower, and the proportion of phloem salivation was higher than on control plants. On (Z)-nerolidol-treated plants, the occurrence of the first phloem phase was delayed, and the frequency of the phloem phase was lower than on control plants. The freely moving aphids were reluctant to remain on (E,E)-farnesol- and (Z)-nerolidol-treated leaves for at least 24 h after exposure. (E,E)-Farnesol and (Z)-nerolidol show complementary deterrent properties, (E,E)-farnesol showing ingestive and post-ingestive activities and nerolidol showing pre-ingestive, ingestive, and post-ingestive deterrent activities.

Effect of Naringenin and Its Derivatives on the Probing Behavior of Myzus persicae (Sulz.).

Substances that alter insect behavior have attracted a lot of attention as potential crop protection agents. Naringenin (5,7,4'-trihydroxyflavanone) is a naturally occurring bioactive flavanone. We evaluated the influence of naringenin on aphid activities during individual phases of probing and feeding and the effect of structural modifications of naringenin on its activity towards aphids. We monitored the probing behavior of Myzus persicae (Sulz.) (Hemiptera: Aphididae) using the Electrical Penetration Graph (EPG) technique. The chemical modifications were the substitution of hydrogen atoms with methyl, ethyl or pentyl groups and the replacement of the carbonyl group in naringenin and its derivatives with an oxime moiety. Depending on the substituents, the activity of naringenin-derived compounds varied in potency and mode of action. Naringenin was an attractant of moderate activity, which enhanced sap ingestion. The naringenin derivative with two methyl groups-7,4'-di-O-methylnaringenin-was a deterrent, which hindered aphid probing in non-phloem tissues. Naringenin oxime derivatives with methyl substituents-7,4'-di-O-methylnaringenin oxime, 7-O-methylnaringenin oxime, and 5,7,4'-tri-O-methylnaringenin oxime-and the derivative with a pentyl substituent-7-O-pentylnaringenin oxime-were strong attractants which stimulated aphid probing in non-phloem tissues and the ingestion of phloem sap.

ß-Thujone and Its Derivatives Modify the Probing Behavior of the Peach Potato Aphid.

Thujone is a natural biologically active monoterpene ketone component of essential oils of numerous plants. The aim of the study was to evaluate the effect of ß-thujone and ß-thujone derivatives bisulfite adduct, lactone, oxime, and lactam application on behavior of Myzus persicae (Sulz.) (Hemiptera: Aphididae) during probing and settling. The choice and no-choice tests (aphid settling and Electrical Penetration Graph (EPG), respectively) revealed that stereochemistry of thujone was important for biological activity (ß-thujone caused changes in aphid behavior while α-thujone did not) and that cyclopentane ring modifications and functional groups addition gave derivatives that possessed stronger and more durable deterrent effects. The most effective modification was the incorporation of a lactam moiety into the ß-thujone molecule. Application of ß-thujone lactam limited aphid settling for at least 24 h, caused restlessness in aphids and a delay or failure in reaching phloem phase by M. persicae. ß-Thujone lactam can be considered a deterrent of medium potency with activity expressed at preingestive phase of aphid probing. Other compounds did not restrain aphid stylet penetration in non-phloem tissues but slightly limited sap ingestion (lactone, oxime), and restrained aphid settling for a period of less than 24 h (ß-Thujone, bisulphite adduct, lactone).

Antixenosis Potential in Pulses Against the Pea Aphid (Hemiptera: Aphididae).

The aim of the study was to explore the acceptability of 14 species, varieties, and cultivars of grain legumes (Fabales: Fabaceae) to the pea aphid, by investigating the aphid probing behavior using the electrical penetration graph (EPG) technique. Phaseolus coccineus L. 'Felicia', Pisum sativum L. 'Medal', P. sativum arvense (L.) Poir. 'Fidelia' and 'Hubal', and Vicia faba L. 'Dragon' are highly susceptible, with no antixenosis potential against Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae): aphid probing and feeding activities were not impeded. Lathyrus sativus L. 'Derek', Lupinus luteus L.'Perkoz', Vicia faba minor Beck. 'Sonet' are moderately susceptible to A. pisum infestation, with minor antixenosis potential and with antixenosis factors in non-phloem tissues. Aphids on these plants had difficulty to attain the phloem phase and phloem sap ingestion phase. During phloem phase, ingestion lasted for long periods of time. Lens culinaris Medik. 'Green' and Phaseolus vulgaris L. 'Boruta' are moderately susceptible to A. pisum infestation, with minor antixenosis potential and with antixenosis factors in the phloem. Behavior of aphids during pre-phloem phase was similar to that on highly susceptible plants but individual phloem phases and sap ingestion phases were short and contained a high proportion of watery salivation. Glycine max (L.) Merr. 'Aldana', L. angustifolius L. 'Boruta', P. coccineus 'Rothbluende', and P. vulgaris 'Mamut' are highly resistant to A. pisum infestation, with high antixenosis potential and with strong antixenosis factors in non-phloem tissues: aphid probing time was shortened, non-probing intervals between probes were long, and the success rate in reaching phloem phase was very low or none.