Changed host plant volatile emissions induced by chemical interaction between unattacked plants reduce aphid plant acceptance with intermorph variation

Olfactory orientation by aphids is guided by specific volatile blends released from their hosts. Host plants that co-exist with other plants may be less attractive for aphids due to volatile interactions between neighboring plants which can lead to changes in their volatile emissions. These changes in host plant volatile profiles induced by interactions between undamaged plants could be used to manage aphid populations in crops. When potato plants are exposed to volatiles from onion plants, the volatile profile of potato changes in relation to that of unexposed plants with consistently greater quantities of two terpenoids released. We examined the host plant searching behavior of aphids and showed that induced changes in plant volatile emissions affect aphid behavior. We assessed olfactory responses of winged and wingless aphids, Myzus persicae Sulzer (Hemiptera: Aphididae) to the changed volatile emissions. Both morphs were significantly less attracted to odors of potato plants that had been exposed to volatiles from onion than to odors of unexposed potato plants. Further, both morphs were significantly less attracted to synthetic blends mimicking volatiles emitted by onion-exposed potato plants than to blends mimicking non-exposed controls, and to single compounds emitted in greater quantities by exposed potato. Aphid morphs were repelled differently depending on the concentration of odor sources; winged aphids responded to higher doses than did wingless aphids. The aphid responses to changes in plant volatile profiles induced by neighboring plants may facilitate refinement of habitat manipulation strategies (e.g., intercropping) for integrated pest management to reduce aphid occurrence in crops

Parazitoidi i predatori štitastih vašiju iz familije Diaspididae u nekim voćnjacima u Srbiji

Five parasitoid and five predator species were registered on four armored scale species in apple, pear, peach and plum orchards at 16 sites in Serbia. The armored scales found were: Diaspidiotus perniciosus (Comstock), Pseudaulacaspis pentagona (Targioni-Tozzetti), Epidiaspis leperii (Signoret) and Lepidosaphes ulmi (L.). The parasitoid species detected were: Encarsia (=Prospaltella) perniciosi (Tow.), Encarsia (=Prospaltella) berlesei (How.), Aphytis proclia (Wal.), Aphytis mytilaspidis (Le Baron) and Coccobius testaceus (Masi), all of the Aphelinidae family. The most important endoparasitoids were: Encarsia perniciosi on D. perniciosus, Encarsia berlesei on P. pentagona and Coccobius testaceus on L. ulmi. Only one ectoparasitoid species, Aphytis mytilaspidis, was found on E. leperii, while Aphytis proclia was found as an ectoparasitoid on D. perniciosus, P. pentagona and L. ulmi. The predator species detected were: Chilocorus renipustulatus (Scriba), Chilocorus bipustulatus (L.), Cybocephalus fodori Endrody – Younga, Chrysoperla carnea (Stephens) and Deraeocoris ruber (L.). Cybocephalus fodori was for the first time found as a predator on E. leperii in Serbia.U periodu od 2007. do 2009. godine, u zasadima jabuke, kruške, breskve i šljive, u 16 lokaliteta na teritoriji Srbije, utvrđene su četiri vrste štitastih vašiju iz familije Diaspididae, i 10 vrsta njihovih prirodnih neprijatelja, među kojima je pet parazitoida i pet predatora. Vrste štitastih vašiju su: Diaspidiotus perniciosus (Comstock), Pseudaulacaspis pentagona (Targioni-Tozzetti), Epidiaspis leperii (Signoret) i Lepidosaphes ulmi (L.). Od parazitoida, odgajeno je pet vrsta iz familije Aphelinidae: Encarsia (=Prospaltella) perniciosi (Tow.), Encarsia (=Prospaltella) berlesei (How.), Aphytis proclia (Wal.), Aphytis mytilaspidis (Le Baron) i Coccobius testaceus (Masi). Najznačajniji endoparazitoidi su Encarsia perniciosi na D. perniciosus, zatim Encarsia berlesei na P. pentagona, i Coccobius testaceus na L. ulmi. Aphytis mytilaspidis je ektoparazitoid na E. leperii, a Aphytis proclia ektoparazitoid na D. perniciosus, P. pentagona i L. ulmi. Tri vrste predatora su iz reda Coleoptera, od kojih su Chilocorus renipustulatus (Scriba) i Chilocorus bipustulatus (L.) iz familije Coccinellidae, a Cybocephalus fodori Endrody – Younga iz familije Cybocephalidae. Iz reda Neuroptera utvrđena je Chrysoperla carnea (Stephens) (fam. Chrysopidae), a iz reda Hemiptera, Deraeocoris ruber (L.) iz familije Miridae. Cybocephalus fodori je prvi put registrovan u Srbiji kao predator E. leperii

Utvđivanje nivoa rezistentnosti Myzus persicae (Sulzer) biohemijskim metodama

Peach/potato aphid Myzus persicae (Sulzer) has developed three mechanisms of resistance: overproduction of one or two closely related carboxylesterases (E4 and FE4), production of modified acetylcholinesterase (MACE and knockdown resistance). Biochemical diagnostic methods can be used to identify levels of carboxylesterase production and sensitivity of modified acetylcholinesterase and, based on the values acquired we can classify aphids into one of the resistance cathegories. We used two tests: the total esterase activity test and test for checking sensitivity of acetylcholinesterase (MACE). Myzus periscae persicae from peach and Myzus persicae nicotianae from tobacco were tested. The total esterase activity test showed that 65% of the aphids tested were moderately resistant and 35% were highly resistant. Resistance based on the production of modified acetylcholinesterase is less represented because 80% of the aphids tested were susceptible to pirimicarb, which was used in the experiment. Also, both tests showed that aphids from tobacco were more susceptible than aphids from peach.Kod Myzus persicae (Sulzer) do sada su utvrđena tri tipa rezistentosti: povećana produkcija karboksilesteraza E4 i FE4, stvaranje modifikovane acetilholinesteraze i „knock-down” rezistentnost. Biohemijskim metodama moguće je izmeriti količinu karboksilesteraza, kao i aktivnosti modifikovane acetilholinesteraze i na osnovu dobijenih vrednosti, vaši svrstati u neku od kategorija rezistentnosti. Korišćena su dva testa, test totalne esterazne aktivnosti i test za proveru aktivnosti modifikovane acetilholinesteraze (MACE). Testirane su Myzus persicae persicae sa breskve i Myzus persicae nicotianae sa duvana. Test totalne esterazne aktivnosti pokazao je da 65% testiranih jedinki pripada kategoriji umereno rezistentnih vašiju, dok je 35% veoma rezistentno. Rezistentnost koja se zasniva na stvaranju modifikovane acetilholinesteraze manje je zastupljena, jer je čak 80% testiranih vašiju osetljivo na dejstvo pirimikarba, koji je korišćen u testu. Takođe, oba testa su pokazala da su vaši sa duvana osetljivije na dejstvo insekticida od vašiju sa breskve

The pressure of Aphids (Aphididae, Hemiptera), vectors of potato viruses

Plant viruses and aphids as their vectors, are limiting factors in the production of healthy seed potato. Potato Virus Y (PVY) and Potato Leafroll Virus (PLRV) are the two most significant potato viruses in Europe, and seed quality depends directly on the infection level. In order to determine the possibilities for healthy seed potato production in Serbia, aphid flight activities have been monitored for four years in four localities. Over 6400 specimens of aphids have been collected. The number of aphids and vector pressure index varies depending on the localities' altitude. In localities at altitudes under 1000 m, they were high. The highest index was in locality Kotraža in 2007, when the PVY index exceeded the value of 180, while for PLRV it was 60. At high altitudes, above 1100 m, the number of aphids was low, as was the vector pressure index. The lowest index values were recorded in localities on Mt. Golija at 1300 m a.s.l. where the indexes for both viruses never exceeded value 6

Aphid olfactory responses to synthetic blends of volatile organic compounds of exposed and unexposed potato.

<p>Responses of winged <i>Myzus persicae</i> in olfactometer experiments when presented with synthetic blends based on headspace collections of onion-exposed (treatment) and unexposed potato (control). Synthetic blends were at 1/100, 1/10, 1x, 10x or 100x the original concentration of volatiles identified in potato headspace. Error bars indicate ± SEM. * P≤0.05 Wilcoxon test.</p

Volatile emissions of onion exposed and unexposed potato plants.

<p>Mean quantities (+/− SE) of compounds identified from the headspace of onion-exposed and unexposed potato plants. Compound numbers: 1. (<i>E</i>)-2-hexenal; 2. (<i>Z</i>)-3-hexen-1-ol; 3. myrcene; 4. limonene; 5. linalool; 6. (<i>Z</i>)- 4,8-dimethyl-1,3,7-nonatriene; 7. (<i>E</i>)- 4,8-dimethyl-1,3,7-nonatriene; 8. α-copaene; 9. α-cedrene; 10. (<i>E</i>)-caryophyllene; 11. (<i>E</i>)-β-farnesene; 12. (<i>E</i>)-nerolidol; 13. (3<i>E,7E</i>)-4,8,12-trimethyl-1,3,7,11-tridecatetraene; 14. 6,10,14-Trimethyl-2-pentadecanone. * P≤0.05 Least Squares Means.</p

Aphid olfactory responses to volatiles from living plants.

<p>Behavioural responses of winged <i>Myzus persicae</i> in olfactometer experiments when offered choice between (A) volatiles of onion tested and volatiles of potato, (B) volatile mix of onion and potato and volatile mix of two potato plants, and (C) volatiles of onion-exposed potato and volatiles of unexposed potato plants. Asterisks indicate significant preferences * P≤0. 05, Wilcoxon matched pairs test.</p

Aphid olfactory responses to two terpenoids realised in greater quantities from potato exposed to onion.

<p>Responses of winged <i>Myzus persicae</i> in olfactometer experiments when presented with test solutions containing different doses of (A) (E)-nerolidol, and (B) (3E, 7E) 4, 8, 12-trimethyl-1, 3, 7, 11-tridecatetraene (TMTT), alongside hexane control. Error bars indicate ± SEM. *P≤0.05 Wilcoxon test.</p

Volatile exchange between undamaged plants - a new mechanism affecting insect orientation in intercropping

Changes in plant volatile emission can be induced by exposure to volatiles from neighbouring insect-attacked plants.However, plants are also exposed to volatiles from unattacked neighbours, and the consequences of this have not beenexplored. We investigated whether volatile exchange between undamaged plants affects volatile emission and plant-insectinteraction. Consistently greater quantities of two terpenoids were found in the headspace of potato previously exposed tovolatiles from undamaged onion plants identified by mass spectrometry. Using live plants and synthetic blends mimickingexposed and unexposed potato, we tested the olfactory response of winged aphids, Myzus persicae. The altered potatovolatile profile deterred aphids in laboratory experiments. Further, we show that growing potato together with onion in thefield reduces the abundance of winged, host-seeking aphids. Our study broadens the ecological significance of thephenomenon; volatiles carry not only information on whether or not neighbouring plants are under attack, but alsoinformation on the emitter plants themselves. In this way responding plants could obtain information on whether theneighbouring plant is a competitive threat and can accordingly adjust their growth towards it. We interpret this as aresponse in the process of adaptation towards neighbouring plants. Furthermore, these physiological changes in theresponding plants have significant ecological impact, as behaviour of aphids was affected. Since herbivore host plants arepotentially under constant exposure to these volatiles, our study has major implications for the understanding of howmechanisms within plant communities affect insects. This knowledge could be used to improve plant protection andincrease scientific understanding of communication between plants and its impact on other organisms