Future-proofing food : striving towards minimal insecticidal application in Western Cape pome fruit orchards

Thesis (MSc)--Stellenbosch University, 2015.

ENGLISH ABSTRACT: Increasing pressure on food production and the concern over maintenance of biodiversity and ecosystem services is creating an urgent need to future-proof food production, while maintaining the natural environment for future generations. Within the Cape Floristic Region (CFR) biodiversity hotspot in the Western Cape of South Africa, deciduous fruit is widely grown, contributing significantly to the local economy. To ensure access is maintained to important export markets, this study reviews the current available pest control options with focus on techniques able to preserve the biodiversity of the CFR, while simultaneously providing effective control over arthropod pests in pome fruit. A scenario planning technique is then used to depict potential future scenarios and the options we have in dealing with them. Emphasis here is placed on economically important arthropod species, particularly Mediterranean fruit fly Ceratitis capitata (Wiedemann) and codling moth Cydia pomonella (L.). Biological control (biocontrol) is discussed in detail, covering predators, parasitoids and pathogens. Biocontrol is an important, sustainable pest control measure. However, certain risks associated with releasing living organisms into the environment must not be ignored. Monitoring of release programmes is essential. The sterile insect technique (SIT) offers a species-specific approach to controlling pests. However, the technique is research and management intensive. Globally SIT has shown great success, but lack of financial support has limited SIT uptake locally. SIT has shown increased effectiveness as an integrated technique, particularly with parasitoid release and pheromone-based mating disruption. The management of orchards as agroecosystems shows that preservation of natural vegetation and beneficial plant species increases crop resilience, encourages conservation biological control and maintains crop health. The importance of area-wide control is discussed under each section, as a favourable strategy which deals with entire pest populations rather than isolated farm-by-farm approaches. Other techniques covered include pheromone-based mating disruption, attract-and-kill and physical barriers such as sticky tree-bands, which all show integration potential with biologically-based techniques while minimising insecticide application. The usefulness of insecticides as a curative approach is recognised, and ways of preserving insecticide life-spans by limiting insecticide resistance are discussed. Social, economic, political, environmental and technological driving forces are used to develop four realistic future scenarios for pome fruit production in the CFR. The scenarios are based on the extremes of two key uncertainties: development of resistance to chemical insecticides, and changes in legislation regulating insecticide usage. The options we face in dealing with each potential scenario, with the suite of arthropod pest control techniques currently developed, is discussed. It is hypothesised that a best-case scenario, in which environmentally-friendly techniques which support healthy, productive agroecosystems, can be reached. We should carefully assess our options, and begin to shift pest control from a predominantly chemical basis to one in which habitat management and biocontrol form the basis of control, with techniques such as SIT, mating disruption and physical barriers assisting in creating holistic arthropod pest control systems. In light of the uncertainty that the future holds, a scenario planning exercise such as this, can assist in decision making today that will best prepare us to deal with future threats such as climate change and new pest invasions.

AFRIKAANSE OPSOMMING: Toenemende druk op voedselproduksie en kommer oor die handhawing van biodiversiteit en ekosisteemdienste lei tot „n dringende behoefte om voedselproduksie toekoms-bestand te maak, asook om tegelykertyd die natuurlike omgewing vir toekomstige generasies te bewaar. Binne die Kaap Floristiese Streek (KFS) „biodiversiteitskern‟ in die Wes-Kaap van Suid-Afrika word sagte vrugte algemeen verbou en lewer „n aansienlike bydrae tot die plaaslike ekonomie. Om toegang tot belangrike uitvoermarkte te verseker ondersoek hierdie studie die plaagbeheer opsies tans beskikbaar, met die fokus op tegnieke wat die biodiversiteit van die KFS kan bewaar en tegelykertyd effektiewe beheer oor geleedpotige plae van kernvrugte kan verskaf. „n Scenario-beplannings-tegniek word dan gebruik om moontlike toekomstige scenario‟s en die opsies tot ons beskikking om hulle te hanteer, uit te beeld. Klem word hier geplaas op geleedpotige spesies van ekonomiese belang, veral die Mediterreense vrugtevlieg, Ceratitis capitata (Wiedemann) en die kodlingmot Cydia pomonella (L.). Biologiese-beheer (biobeheer) word in diepte bespreek, en dek predatore, parasiete en patogene. Biobeheer is „n belangrike, volhoubare plaagbeheer-middel; alhoewel sekere risiko‟s verbonde met die vrystelling van lewende organismes in die omgewing nie verontagsaam moet word nie. Dit is noodsaaklik dat vrystellingsprogramme gemoniteer word. Die steriele-insek-tegniek (SIT) bied „n spesies-spesifieke benadering tot die beheer van plae, alhoewel dit navorsings- en bestuursintensief is. SIT het wêreldwyd al groot suksesbehaal, maar „n tekort aan finansiële ondersteuning het die plaaslike toepassing van SIT beperk. SIT het verhoogde effektiwiteit as „n geïntegreerde tegniek vertoon, veral met die verlies van parasiete en feromoon gebaseerde parings-ontwrigting. Die bestuur van boorde as agro-ekosisteme wys dat die bewaring van natuurlike plantegroei en voordelige plant spesies oes-herstelvermoë verhoog, bewaring-biologiese-beheer aanmoedig en oes-welstand handhaaf. Die belang van streekswye beheer word bespreek onder elke afdeling as „n gunstige strategie wat te doen het met algehele plaagbevolkings, eerder as afsonderlike plaas-tot-plaas benaderings. Ander tegnieke wat gedek word sluit in feromoon gebaseerde parings-ontwrigting, lok-en-doodmaak en fisiese versperrings soos taai boom-bande, wat alles integrasie-potensiaal wys met biologies gebaseerde tegnieke en tegelykertyd insekdoder aanwending verminder. Die nuttigheid van insekdoders as „n herstel benadering word erken en maniere om die leffektiwiteit van insekdoders te behou deur insekdoder-weerstand te beperk, word bespreek. Sosiaal-, ekonomies-, polities-, omgewings- en tegnologies-gedrewe kragte word gebruik om vier realistiese toekomstige scenario‟s vir kernvrug-produksie in die KFS te ontwikkel. Die scenario‟s is baseer op die ekstreme van twee belangrike onsekerhede: ontwikkeling van weerstand teen chemiese insekdoders, en veranderinge in wetgewing wat die gebruik van insekdoders reguleer. Die opsies wat ons in die gesig staar om elke potensiële scenario te hanteer met die verskeidenheid van geleedpotige plaagbeheer-tegnieke tans ontwikkel is, word bespreek. Dit word veronderstel dat „n beste scenario, waar omgewings-vriendelike tegnieke wat gesonde, produktiewe agro-ekosisteme onderhou, bereik kan word. Ons moet ons opsies versigtig assesseer, en begin om plaagbeheer vanaf „n oorwegend chemiese basis te skuif na een waar habitat-bestuur en biobeheer die basis van beheer vorm, en waar tegnieke soos SIT, parings-ontwrigting en fisiese versperrings help om holistiese geleedpotige-plaagbeheer sisteme te vorm. In die lig van die onsekerheid wat die toekoms inhou, kan „n scenario-beplannings oefening soos hierdie besluitneming vandag aanhelp wat ons die beste sal voorberei vir die hantering van toekomstige bedreigings soos klimaats-verandering en nuwe en vreemde plaag-indringing.