Development of a habitat management plan for improving the biological control of the vine mealybug planococccus ficus (signoret) in vineyards

Faure, Sariana (2015-03)

Thesis (MSc)--Stellenbosch University, 2015.

Thesis

ENGLISH SUMMARY: The vine mealybug, Planococcus ficus (Signoret) is a major, cosmopolitan pest in all regions where grapes are grown. Vine mealybug has a direct injurious effect on vines through feeding, produces honeydew, on which sooty mould develops and has been shown to be a vector of the grapevine leafroll virus and associated closteroviruses. This project entailed research on the parasitoids of P. ficus, mainly Coccidoxenoides perminutus (Timberlake). The aim of this work was to contribute basic biological information for the establishment of a habitat management plan in vineyards to improve biocontrol of P. ficus. Two surveys were conducted to determine, firstly, the occurrence of mealybug parasitoids in the vineyards and their associated natural habitats, and secondly the association between flowering plants and parasitoids close to vineyards. Olfactometer screenings were conducted to determine attractiveness of six plants as food sources for adult C. perminutus. A comprehensive life history experiment was initiated to be compared with previous findings. In the first survey, to assess the biodiversity of mealybug parasitoids in vineyards and their associated natural habitats, C. perminutus, Anagyrus sp. near pseudococci (Girault) and Leptomastix dactylopii (Howard) were the predominant parasitoids found between January and May, with a peak in abundance during February. Signficantly more parasitoids were found in vineyards compared to associated natural habitats (p=0.049). The survey further indicated that these parasitoids, being density-independent and therefore not in need of high pest populations to sustain numbers, could contribute to integrated pest management, and with effective habitat modifications, their numbers could be naturally boosted to lend a valuable eco-system service. In the second survey, to determine whether parasitoids occur in the field in flowering plants associated with vineyards, a total of 20 indivdual parasitoids from 16 species were found. This is a promising indication that, although their impact on P.ficus was not measured during this study, the correct flowering plants interplanted in vineyards or on the edges could have a positive effect on the necessary occurrence of mealybug parasitoids as well as other natural enemies and pests in vineyards. Attractiveness of plants for C. perminutus was determined through the screening of a variety of flowering plants with a four-armed Pettersson olfactometer. Of the six plants tested, only Euryops abrotanifolia (L.) DC had a significant attractant effect (p=0.003926) on C. perminutus. The population of the parasitoid could possibly be increased by planting this plant in or around vineyards to provide a food source, and it is recommended that this plant be further investigated as a parasitoid attractant in the field. Furthermore, more plants need to be tested for inclusion in habitat management, as it is likely that a combination of plants will be more effective for biological control. To determine life table parameters of C. perminutus, including adult fitness and larval host preferences, laboratory experiments were conducted at 25°C on Planococcus citri (Risso), as initial experiments utilizing P. ficus had failed. In constrast with previous studies where the second and third nymphal instars were parasitised, all nymphal instars were attacked in this study, with no significant difference between them (p=0.057). Cost of life when laying eggs or not also came to no significant difference (p=0.46252). Lifetable parameters (Ro=159.5; T=27.602; rm=0.511) were different to those determined by Walton (2003) (Ro=69.94; T=29.5; rm=0.149) except for T which was similar, although the latter study was conducted on P. ficus. These differences could also be attributed to the use of mummies instead of hatched parasitoids, when collecting progeny for the determination of the preferences and parameters. Information obtained through these above mentioned experiments should be of use to rearing facilities and contribute to the establishment of a habitat management plan in vineyards to improve the control of P. ficus.

AFRIKAANS OPSOMMING: Die wingerdwitluis, Planococcus ficus (Signoret) is ‘n ernstige, wêreldwye pes in alle areas waar druiwe verbou word. Wingerd witluis het ‘n direkte, skadelike effek op wingerd deur hul voeding, die produksie van heuningdou, waarop roetskimmel groei, en is ook ‘n vektor van wingerd rolblaarvirus. Navorsing vir hierdie projek het gefokus op die parasitoïede van P. ficus, hoofsaaklik Coccidoxenoides perminutus (Timberlake). Die doel van hierdie studie was om basiese biologiese inligting by te dra vir die vestiging van ‘n habitat bestuursplan in wingerde om die biologiese beheer van P. ficus te verbeter. Twee opnames is gedoen om, eerstens, die voorkoms van witluis parasitoïede in die wingerd en omliggende natuurlike habitat, en tweedens, die verbintenis tussen blomplante en parasitoïede naby wingerde te bepaal. Olfaktometer toetse is gedoen om aantreklikheid van ses inheemse plante vir C. perminutus te bepaal en ‘n volledige ontwikkelingstudie is gedoen wat met vorige bevindinge vergelyk is. In die eerste opname, om die biodiversiteit van witluis parasitoïede in wingerd en, meer belangrik, die nabyliggende natuurlike habitat, te evalueer, was C. perminutus, Anagyrus sp. near pseudococci (Girault) en Leptomastix dactylopii (Howard) die oorheersende parasitoïede tussen Januarie en Mei, met ‘n piek in getalle in Februarie. Daar is beduidend meer parasitoïede in wingerde gevind as die natuurlike habitatte (p=0.049). Die opname het ook aangedui dat hierdie parasitoïede, wat onafhanklik is van digtheid en dus nie hoë pes populasies nodig het om hul getalle te handhaaf nie, ‘n bydrae sal kan lewer tot geïntegreerde plaagbestuur, en met die regte habitat veranderinge, sal hul getalle natuurlik vermeerder kan word sodat hulle ‘n waardevolle diens aan die ekosisteem te kan lewer. In die tweede opname, om te bepaal of parasitoïede wat in die veld voorkom ‘n verbintenis met die blomme rondom wingerde het, is ‘n totaal van 20 individuele parasitoïede van 16 spesies gevind. Dit is ‘n belowende aanduiding dat, alhoewel hul impak op P. ficus nie in hierdie studie bepaal is nie, die regte blomplante tussen of om die wingerde geplant ‘n positiewe effek kan hê op die nodige voorkoms van witluis parasitoïede, asook ander natuurlike vyande en pests in wingerd. Die aantreklikheid van verskeie blomplante vir C. perminutus is getoets met ‘n vier-arm Petterson olfaktometer. Van die ses plante wat getoets is, het slegs Euryops abrotanifolia (L.) DC ‘n beduidende aantrekkende effek (p=0.003926) op C. perminutus gehad. Die populasie van die parasitoïed kan moontlik vermeerder word deur hierdie plant tussen of om wingerde te plant om te dien as ‘n voedselbron, en daar word voorgestel dat hierdie plant verder ondersoek word as ‘n lokmiddel vir parasitoïede in die veld. Meer plante moet ook getoets word vir insluiting in ‘n habitat bestuursplan aangesien ‘n kombinasie van plante meer effektief sal wees vir biologiese beheer. Om die parameters vir die lewenstabelle van C. perminutus te bepaal, insluitende fiksheid van volwassenes en voorkeure vir larwala stadia van gashere, is laboratorium eksperimente gedoen teen 25°C op Planococcus citri (Risso), aangesien aanvanklike eksperimente op P. ficus nie suksesvol was nie. In teenstelling met vorige eksperimente waar die tweede en derde nimfale instars geparasiteer is, is alle nimfale instars in hierdie eksperimente geparasiteer, met geen beduidende verskille (p=0.057) nie. Daar is ook geen beduidende verskille gekry vir lewenskoste wanneer die parasitoïed eiers lê of nie (p=0.46252). Parameters vir die lewenstabelle (Ro=159.5; T=27.602; rm=0.511) het verskil van dié bepaal deur Walton (2003) (Ro=69.94; T=29.5; rm=0.149), behalwe vir T wat eenders was, alhoewel Walton se studie op P. ficus was. Hierdie verskille kan toegeskryf word aan die gebruik van mummies in plaas van parasitoïede wat reeds uitgebroei is, met die insameling van nageslagte vir die bepaling van voorkeure en parameters. Inligting uit hierdie studie kan van nut wees vir telingsfasiliteite en kan help met die vestiging van ‘n habitat bestuursplan in wingerde om biologiese beheer van P. ficus te verbeter.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/96607
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