Intercropping against onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae) in onion production: on the suitability of orchard grass, lacy phacelia, and buckwheat as alternatives for white clover

摘要

During 2004 and 2005, field experiments were done to compare the effectiveness of four different intercrops in reducing onion thrips (Thrips tabaci Lindeman) damage on onion plants, The four intercrops were lacy phacelia (Phacelia tanacetifolia Benth.), buckwheat (Fagopyrum esculentum Moench.), orchard grass (Dactylis glomerata L.) and white clover (Trifolium repens L.). The experiment was done in a fertile soil in 2004 and a relatively infertile soil in 2005. In both years, the thrips population waslower than expected due to two cold springs and wet summers. The amount of damage on the two onion varieties tested, 'Rdeci baron' and 'Holandska rumena', exceeded the 20% leaf damage threshold only on some onion plants. In both years, white clover wasthe least attractive intercrop for onion thrips, and orchard grass was only slightly more attractive. Although the damage to the onion leaves was the highest in these two intercrops, these plots still produced the highest yield of onions. In contrast, lacy phacelia and buckwheat were both highly attractive to onion thrips, but were not suitable as intercrops, as they competed too strongly with the onion crop. Hence, lacy phacelia, buckwheat and orchard grass should not be used in onion production to replace white clover, the intercrop used currently. In the current experiments, intercropping with white clover resulted in the highest yield of onions in both high and low fertility soils.