WINETECH Technical Yearbook 2020

Katydid ecology in vineyards

from February 2013 to March 2015. We monitored eggs, nymphs and adults, as well as damage (photo 1). POPULATION SURVEYS Three species were found in vineyards in the greater Stellenbosch region of the Western Cape, namely Plangia graminea , Eurycorypha lesnei and a Phaneroptera species (table 1). In a taxonomic review of the Plangia complex in 2015, the two species that were originally thought to occur in Western Cape vineyards, P. graminea and P. compressa , were found to be the same species and what we thought was P. compressa , is actually E. lesnei. A study of the seasonal cycle revealed that both species were found from February to June (figure 1), while the Phaneroptera species was only present from May/June, therefore not a significant economic threat. It was also found that katydids overwinter

as eggs during winter, which are laid on the bark of vines and eggs are present throughout the year. MONITORING Eggs were found to be a good early predictor for katydid abundance later in the season and are therefore recommended as a monitoring tool. The monitoring system of De Villiers and Pringle (2008) was adapted as follows: Five evenly spaced rows were selected in each vineyard block and in each row, four evenly spaced plots, consisting of five vines between two trellis posts, giving a total of 20 plots used. Eggs were sampled by searching the bark on the main stem (photo 2) and two main cordons, 15 cm on either side of the main stem. This was done on one vine/plot. Plangia eggs measure 2.3 x 4.3 mm and are therefore relatively easy to spot, whilst the adults and nymphs are cryptic and

JUNE 2020

PIA ADDISON, MARCE DOUBELL & CORINNA BAZELET: Department of Conservation Ecology and Entomology, Stellenbosch University, Stellenbosch KEYWORDS: Katydids, vineyard pests, biological control

The aim of this study was to contribute knowledge towards the formulation of an integrated pest management programme, as well as an appropriate monitoring system. INTRODUCTION Katydids (“krompokkels”) are considered minor pests in vineyards of the Western Cape province, but little is known about

their assemblage structure and biology due to their secretive and sporadic nature. We therefore set about investigating what species were involved in causing damage and adapting a generic monitoring system that could practically be used in vineyards as an early warning system before damage occurs. To do this, we surveyed four wine farms in the greater Stellenbosch area

A

B

C

D

PHOTO 1. Katydid adult (A), egg (B), nymph (C) and damaged berry (D).

WINETECH TECHNICAL YEARBOOK 2020 41