Assessing the chemical ecology and shelter-seaking behaviour of the grainchinch bug, Macchiademus diplopterus (hemiptera: lygaeidae) for optimisation of trapping during aestivation

Ngadze, Masimbaashe (2016-12)

Thesis (MScAgri)--Stellenbosch University, 2016.

Thesis

ENGLISH ABSTRACT: The grain chinch bug (GCB), Macchiademus diplopterus (Distant) (Hemiptera: Lygaeidae) is a key quarantine pest of South African export fruit and is endemic to the Western Cape Province. The pest is troublesome in the drier wheat growing areas where it disperses from wheat in summer to find sheltered sites in which to aestivate. Aestivating adults can end up contaminating export fruit. The aim of the study was to gather more knowledge on the chemical ecology and shelter-seeking behaviour of the GCB. The involvement of pheromones in the aggregation behaviour of GCBs is yet to be fully elucidated. Further investigating the chemical ecology of the GCB in order to optimize its pheromone trapping was the primary focus of the first research chapter in this study. Headspace volatile compounds were identified from active bugs through gas chromatography-mass spectrometry (GC-MS) analysis. A total of 14 volatile compounds were identified from males and females in varying concentrations. For both sexes pooled, tridecane, (E)-2-hexanal and (E)-2-octenal were the three main components; (E)-2-hexenol, (E)-2-octenol, decanal and pentadecane were in medium amounts, while decanoic acid, dodecane, hexadecanal, hexanal, icosane, nonanal and tetradecanoic acid were minor components. The efficacy of synthetic lures using previously identified aggregation pheromone components, and sex pheromone volatile components (identified in present study) was studied in combination with modified traps using rubber septa dispensers in a field trial. There was no significant difference (P > 0.05) between insects caught in the sex pheromone baited traps and the aggregation pheromone baited traps. Traps caught low numbers of GCBs compared to the level of orchard infestation indicated by the amount of bugs that were found sheltering in corrugated cardboard bands tied around tree trunks. The corrugated cardboard bands showed a significant difference in the number of bugs sheltering between bands placed at bottom and top positions (0.5m and 1.5m above ground respectively) on the trees, at site 1 (P = 0.0058), site 2 (P < 0.0169) and site 4 (P < 0.0496) with the exception of site 3 (P > 0.4115). Cardboard band position influenced catches, as more bugs were found in bottom bands. This can be used advantageously in optimising innovative trap placements in the future in order to improve catches. In the second research chapter investigations into the behavioural responses of GCBs to visual objects were conducted. This was done to increase knowledge on how this behaviour can lead to the development of control measures such as the use of coloured traps of different shapes. Behavioural responses of GCBs to different shapes presented in their visual space indicated that there was a significant difference (P = 0.0001) in the choice of shape. Vertical/upright rectangular shapes had the highest number of GCB visits. GCBs responded to upright rectangles of different colours.Black and red rectangles were not significantly different (P > 0.05) from each other but were both significantly different (P = 0.0001) from green and yellow rectangles, off-target and sedentary insects. Vertical rectangles of two different colour patterns (black & white) and (red & white) did not show any significant difference (P > 0.153) in the number of GCB visits. Both black & white and red & white vertical stripes were significantly different (P = 0.0001) from off-target and sedentary insects. This indicates that GCBs were equally responsive to both colour patterns. These results indicate that GCBs exhibit a positive scototactic reaction towards dark upright surfaces. Information generated from this study will facilitate the development of pre-harvest monitoring and management measures against GCBs, using pheromone traps and physical barriers that prevent GCBs from dispersing into fruit orchards at the wheat to fruit orchard interface. This can help to reduce fruit contaminations, ultimately lowering the rejection risk of export fruit from South Africa.

AFRIKAANS OPSOMMING: Die graanstinkluis, Macchiademus diplopterus (Distant) (Hemiptera: Lygaeidae), is ’n belangrike kwarantynplaag van Suid-Afrikaanse uitvoervrugte en is endemies aan die Wes-Kaapprovinsie. Die plaag is ’n probleem in die droër graanbougebiede waar dit in die somer van graan versprei om skuilplekke te vind om in ’n somerrusperiode in te gaan. Volwasse insekte in hierdie somerrusperiode kan uitvoervrugte besmet. Die doel van hierdie ondersoek was om meer kennis oor die chemiese ekologie en skuilpleksoekende gedrag van die graanstinkluis te versamel. Daar moet nog afdoende bewys van die betrokkenheid van feromone by die aggregasiegedrag van graanstinkluise gevind word. Verdere ondersoek van die chemiese ekologie van die graanstinkluis om die feromoonlokval te optimaliseer was die primêre fokus van die eerste navorsingshoofstuk van hierdie studie. Vlugtige organiese verbindings in die bodamp van saamgetrosde stinkluise is deur gaschromatografie-massaspektrometrie (GC-MS)-ontleding geïdentifiseer. Altesaam 14 vlugtige verbindings is van mannetjies en wyfies in wisselende relatiewe konsentrasies geïdentifiseer. Vir albei geslagte was tridekaan, (E)-2-heksanaal en (E)-2-oktenaal die drie hoofkomponente; (E)-2-heksenol, (E)-2-oktenol, dekanaal en pentadekaan was in mediumhoeveelhede teenwoordig terwyl dekanoësuur, dodekaan, heksadekanal, heksanaal, ikosaan, nonanal en tetradekanoësuur mindere komponente was. Die doeltreffendheid van sintetiese lokmiddels deur gebruik van voorheen geïdentifiseerde aggregasie-feromoonkomponente en seksferomoon vlugtige komponente (in die huidige studie geïdentifiseer) is in ’n praktiese toets bestudeer in kombinasie met gemodifiseerde lokvalle deur gebruik van rubberseptahouers. Daar was geen beduidende verskil (P > 0.05) tussen insekte wat in die lokvalle met seksferomoon-lokmiddels en lokvalle met aggregasieferomoon-lokmiddels gevang is nie. Lokvalle het klein getalle stinkluise gevang in vergelyking met die vlak van boordinfestering wat aangedui word deur die hoeveelheid luise wat gevind is in riffelkartonstroke wat om boomstamme gebind is. Daar was ’n beduidende verskil tussen die aantal luise wat in die riffelstroke onderom en bo-om die bome gebind is (0.5m en 1.5m bo die grond), in terrein 1 (P = 0.0058), terrein 2 (P < 0.0169) en terrein 4 (P < 0.0496), met die uitsondering van terrein 3 (P > 0.4115). Die posisie van die riffelkartonstroke het die vangste beïnvloed aangesien meer luise in die onderste stroke gevind is. Dit kan voordelig aangewend word deur in die toekoms innoverende lokvalplasings te optimaliseer ten einde vangste te verbeter. In die tweede navorsingshoofstuk is gedragsresponse van graanstinkluise op visuele voorwerpe ondersoek. Dit is gedoen om kennis uit te brei oor hoe hierdie gedrag tot die ontwikkeling van beheermaatreëls soos die gebruik van gekleurde lokvalle in verskillende vorms kan lei. Gedragsreaksies van stinkluise op verskillende vorms wat in hulle gesigsveld aangebied word het getoon dat daar ’n betekenisvolle verskil (P = 0.0001) in die keuse van vorm was. Vertikale/regop reghoekige vorms het die grootste aantal besoeke gehad. Stinkluise het teenoor regop reghoeke van verskillende kleure gereageer. Die reaksie op swart en rooi reghoeke was nie beduidend verskillend (P > 0.05) van mekaar nie, maar albei het aansienlik verskil (P = 0.0001) van dié van groen en geel reghoeke, buiteteiken- en sedentarye insekte. Vertikale reghoeke van twee verskillende kleurpatrone (swart & wit) en (rooi & wit) het geen beduidende verskil (P > 0.153) in die aantal besoeke getoon nie. Swart & wit sowel as rooi & wit vertikale strepe het aansienlik verskil (P = 0.0001) van buiteteiken- en sedentarye insekte. Dit dui daarop dat graanstinkluise ewe goed op albei kleurpatrone gereageer het. Hierdie resultate dui daarop dat graanstinkluise ’n positiewe skototaktiese reaksie teenoor donker, regop vlakke toon. Inligting uit hierdie studie sal die ontwikkeling van vooroes-monitering en -bestuursmaatreëls teen die graanstinkluis fasiliteer deur gebruik van feromoon-lokvalle en fisieke grense wat stinkluise verhinder om na vrugteboorde by die graan-tot-vrugteboord-koppelvlak te versprei. Dit kan help om vrugtebesmettings te verminder, wat uiteindelik die afkeuringsrisiko van uitvoervrugte uit Suid-Afrika sal verminder.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/100362
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