Development of a pest management system for table grapes in the Hex River Valley

[摘要] A study was performed to develop a generic pest monitoring system for sampling themain table grape pests in vineyards in the Hex River Valley, Western Cape Provinceof South Africa. The presence of phytophagous and predatory mites on cover cropplants was also investigated as this may contribute to biological control of thephytophagous mites in vines. Life table studies for Epichoristodes acerbella(Walker), an important phytosanitary pest, were conducted to determine whether ornot this pest was sensitive to high temperatures. Information gained from the lattercan also be used for breeding purposes in the possible future development of a sterileinsect technique (SIT) programme to control this pest.The sampling system consisted of inspecting 20 plots of five vines per plot per one totwo hectares. The top fork of each of the five vines per plot was examined forPlanococcus ficus (Signoret) to a distance of within 30 cm of the stem, as well as thedistal 15 cm of one cane per vine for the presence of P. ficus and damage caused byPhlyctinus callosus Boh. One bunch per vine was examined for insect damage orpresence, and one leaf per vine for the presence of leaf infesting arthropods, such asTetranychus urticae Koch, P. ficus and Frankliniella occidentalis (Pergande).Corrugated cardboard bands, tied around the stem of one vine per plot, were used tomonitor activity of P. callosus. Blue sticky traps, at a density of four to five traps perone to two hectares, were used to monitor activity of F. occidentalis. Pheromonetraps, at a density of one trap per one to two hectares, were used to monitor activity ofP. ficus, E. acerbella and Helicoverpa armigera (Hübner). All the above-mentionedinspections were done at two-weekly intervals, except traps for E. acerbella and H.armigera, which were inspected weekly. In each of the rows in which the sampleplots were situated, one leaf of each of the cover crop plant species was examined forthe presence of phytophagous mites and their predators. The abundance anddistribution of cover crop plants were determined using a co-ordinate samplingsystem. Cover crop sampling was done at monthly intervals.The current threshold for P. ficus is 2% stem infestation, which is reached when morethan 65 males per pheromone trap are recorded. Counting mealybugs on the stickypads in the pheromone traps is time consuming. However, the number of grid blockson the sticky pad with males present can be counted. When P. ficus males are found in 27 blocks on the sticky pad, stem inspections should commence. Due to the spatialassociation between P. ficus bunch and stem infestation, stem infestation could givean indication of where bunch infestation could be expected.The use of blue sticky traps for predicting halo spot damage, caused by F.occidentalis, is not recommended. The presence of thrips on the vine leaves could notgive an indication of where to expect bunch damage, since thrips on the leaves andhalo spot damage were not spatially associated. A suitable sampling method for F.occidentalis still needs to be developed. The monitoring system described here canonly provide information on the infestation status of the vineyard.For E. acerbella, H. armigera and P. callosus, the traps and cardboard bands could beused to identify vineyards where these pests are present and therefore, wherephytosanitary problems may arise. The presence of P. callosus under the bands wasspatially associated with P. callosus damage and could be used as an indicator of thelatter. The presence of drosophilid flies in the bunches could not be used as anindicator of the presence of E. acerbella in the bunches. If 5% bunch damage is usedas an economic threshold for E. acerbella and P. callosus, there will be a good chanceof not under spraying if control measures are applied at 1% bunch damage.Epichoristodes acerbella favoured more moderate constant temperatures, withconstant temperatures of 28°C and above being unfavourable for development.The economic threshold for Tetranychus urticae Koch is six mites per leaf, or ifpresence-absence sampling is used, 11 to 29% leaf infestation. Three importantpredatory mites, that kept T. urticae under control, were found in the Hex RiverValley, namely Euseius addoensis (Van der Merwe & Ryke), Neoseiulus californicus(McGregor) and an undescribed phytoseiid in the genus Typhlodromus. Variouscover crop plants served as hosts for T. urticae and predatory mites. The presence ofthese plants created suitable conditions for the survival of these mites and may haveinfluenced their presence on the vine leaves.In the case of phytosanitary pests, both field and pack shed inspections can be used toconclude with a 99% degree of certainty that infestation levels in the pack shed willbe 10% or less, since similar results for both methods were obtained. However, morethan 20 plots will have to be inspected.

[发布机构] Stellenbosch University