New Compound catches more thrips

An odour to attract western flower thrips, as well as onion thrips, has been tested successfully, resulting in a new patented product to improve the monitoring and application of integrated pest management. Thrips is an important pest that affects many different crops and causes direct feeding damage as well as damage through virus transmission. Effective and early monitoring is important for a successful control of this pest. Scientists from New Zealand’s Crop and Food Research and Plant Research International in the Netherlands have been searching for compounds that attract thrips for several years. This has led to the development of a new kairomone for several species, both males and females. Effective in open and protected crops, extensive field tests were run last year at growers with sweet peppers, eggplant, roses, gerberas and foliage plants. The test product introducing the new odour together with a blue (or yellow) sticky trap, developed by Koppert Biological Systems and Pherobank, which is part of Plant Research International. Season and efficacy In a sweet pepper crop, the blue sticky traps (with or without attractant) were refreshed twice a week from mid April to September 2006. The number of thrips caught per trap was counted weekly (Figure 1). On a number of occasions the exact species composition on the traps was determined by thrips taxonomists of the Plant Protection Service of the Netherlands. Figure 2 shows that onion thrips and western flower thrips were the dominant species. Comparing the control traps to those with the new attractant, the latter caught more thrips. In fact from April to June, the number of thrips trapped on the test traps was two to three times greater. By the end of June, this number was up to 20 times greater. The June increase is probably associated with a period of higher activity and migration of the thrips. It is also a period when there are increased chances of thrips flying into the greenhouse from outside. Monitoring major changes in the population in greenhouses during these flight periods are essential to support timed, control actions. The peak flights were hardly visible on sticky traps without the attractant; this suggests that an opportunity for effective control is missed. Taking action during this period may prevent many problems since the thrips have not yet become hidden in the crop and are therefore easier to control. Secondly, the alert signal leading to action may prevent peak infestations and thus damage. Still, however, the merit of combining these observations with extra control measures must be demonstrated in practice. A collapse of the population in the sweet pepper greenhouse from mid August onward was a further interesting observation. The extent to which the odours play a role is still unknown and is the subject of follow-up research. Notably, the odour traps did not catch any more natural enemies than the control sticky traps