WINETECH Technical Yearbook 2019

Mealybug and scale insects are currently the only proven vectors of leafroll virus. All producers do not have the financial means to remove and replace leafroll infected grapevines. New grapevines from certified virus-free plant material are consequently being established amongst infected blocks. HANNES VAN RENSBURG 1 , PETRIE DE KOCK 2 AND PIETER LE ROUX 3 : 1 Private consultant, 2 BASF, 3 Villa Crop Protection KEYWORDS: Mealybug, scale insects, leafroll virus. FEBRUARY 2019 OF MEALYBUG IN SOUTH AFRICAN VINEYARDS AND WINE STRATEGY FOR THE CONTROL

HOW TO DETERMINE THE PRESENCE AND POPULATION OF MEALYBUG • Physical monitoring. • Pheromone traps. • Degree day model. The following control measures may be applied for mealybug: NB: Only active ingredients are listed – consult your agricultural chemical advisor. Read and follow the prescriptions and safety periods on the label. Spray judiciously – only sections where infection occurs. Withholding period is indicated in brackets. ANT CONTROL This is the first step in the control of mealybug. Ants and mealybug live in symbiosis with each other – ants eat the honeydew secreted by mealybugs. The following chemicals may be used: • Alpha-cypermethrin (28 days). • Chlorpyrifos (28 days). • Fipronil + Lambda Cyhalothrin (28 days). BIOLOGICAL CONTROL This entails the release of natural predators that parasitise the mealybug. Locally bred predators are available for this purpose: • Anagyrus pseudococci.

• Cryptolaemus montrouzieri. • Coccidoxenoides perminutus.