WINETECH Technical Yearbook 2021

VITICULTURE RESEARCH | SEPTEMBER 2021

KWAKU ACHIANO: ARC Infruitec-Nietvoorbij, Stellenbosch KEYWORDS: Biological control, pathogenicity, Planococcus ficus . Entomopathogenic fungi mortality on grapevine mealybug

Soil samples were collected from wine production areas, namely Stellenbosch, Constantia, Franschhoek, Paarl and Mal­ mesbury (table 1). At each vineyard, three blocks of grapevine were randomly selected, 200 m apart. Soil samples were collected with a garden spade at a depth of 15-20 cm. Soil samples, 300 g and 1 kg in weight, were put into plastic containers and paper bags, respectively. The 1 kg bags of soil were sent to Bemlab (Pty) Ltd (Somerset West, Western Cape) for soil analyses and the 300 g soil samples were transported to the laboratory, air-dried and sieved using a 2-mm sieve, and then used in the process of fungal isolation within 24 hours of collection. Fungi were isolated from the soil samples by baiting with fifth instar larvae of Cydia pomonella (Lepidoptera: Tortricidae). Conidia from the cultures of each fungal isolate were harvested. Twenty-three fungal cultures were transferred to the Molecular Bio­ logy Laboratory in the Department of Microbiology, Stellenbosch University for a more precise identification. Prior to assessing pathogenicity of chosen EPF on the grapevine mealybug, Planococcus ficus , the viability of conidia was determined to be 90%. An immersion bioassay was used to assess the virulence of four species of EPF isolates on adult females of P. ficus. The fungal isolates were tested at

Grapevine mealybug

GLOBAL DEMAND FOR ENVIRONMEN- TALLY FRIENDLY grapevine cultivation and pest control has necessitated an improved understanding of naturally occurring antagonists such as entomopathogenic fungi (EPF). INTRODUCTION Conventional control of grapevine mealy- bug in agricultural production has depend- ed on synthetic chemicals, which causes negative effects such as environmental deg - radation, concerns over workers’ well-be- ing, declining biodiversity in agro-ecosys- tem, development of insecticide resistance, and resurgence of pests, among others. This has necessitated the quest for alter- native and more environmentally benign biological control agents such as entomo-

pathogenic fungi (EPF). EPF are pervasive, however, the type of farming and farming system could influence fungal species dis - tribution. More isolates of the entomoptho- genic fungus Beauveria bassiana (Hypo­ creales: Clavicipitaceae) occur organically than conventionally farmed soils. Farming activities such as grapevine cultivation dis- rupt natural biotic and abiotic conditions, causing ecological disequilibrium, which can affect insect pest occurrences and their natural enemies, including EPF. The objectives of this study were to: 1. survey the occurrence of EPF in vineyard soils in the Cape Winelands, and 2. ascertain their pathogenicity against the grapevine mealybug.

Serious infestation of vine mealybug on grapes showing large quantities of honeydew.

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