Practical experiences
MonitoringUse yellow sticky traps to detect whitefly, thrips and leaf miner; use one sticky trap per cultivar, more than one in sensitive cultivars.
WhiteflyIt is important to start from a situation that is as clean as possible, following a chemical clearing programme in the winter months. Start setting out slow-release bags of Amblyseius swirskii from mid February: 8,000 bags per hectare. Repeat after 4, 8 and 12 weeks, with 4,000 bags per hectare. Adapt the dosage and the intervals between introductions to suit the sensitivity of the cultivar to whitefly. Amblyseius swirskii is able to establish itself well in gerberas, and a good balance is possible at low infestation levels. In mid March, begin introducing parasitic wasps (a combination of Encarsia formosa and Eretmocerus eremicus). After five introductions, switch to 100% Eretmocerus eremicus. Act promptly to tackle hot-spots. Release extra A. swirskii onto hot-spots: 100-500 per m2, and/or spray these with Verticillium lecanii (MYCOTAL) + vegetable oil (ADDIT). Use 2,000 litres of spray solution per hectare and be sure to reach the underside of the crop. This strategy can be very effective in the summer period. In the winter period, the cultivation temperatures are too low for the predatory mite and parasitic wasps to work effectively, whereas whitefly continues to thrive.
ThripsThe ground-living predatory Hypoaspis aculeifer contributes to combating the problem by preying on thrips pupae. Introduce 100-200 predatory mites per m² onto or near to the pots. If A. swirskii is released on a regular basis to combat whitefly, or if a sizeable population of this predatory mite is present, this will be sufficient to effectively combat thrips. If no A. swirskii mites are being deployed, introduce A. cucumeris slow-release bags: one bag per 5 m2 every 6-7 weeks. In cases of greater thrips infestation, deploy Orius laevigatus too: 3-5 predatory bugs per m2, and repeat after one week.