Efficacy testing of dDifferent IPM methods against Thrips tabaci Lindeman (Thysanoptera: Thripidae) on cabbage and onion
Trdan S, Valic N, Znidarcic D
University of Ljubljana, Biotechnical Faculty, Dept. of Agronomy, Jamnikarjeva 101, SI-1111 Ljubljana, Slovenia.
Correspondence: stanislav.trdan@bf.uni-lj.si
In 2001¨C2002, the efficacy of light blue sticky boards for mass trapping of onion thrips in onion was investigated. In the drier year 2001, no differences in yield were determined between the treatments. In 2002, which was quite average regarding the weather conditions, the least damage on the leaves and the highest yield was in plants treated twice with deltamethrin. In the treatments with sticky boards the extent of damage on leaves was higher compared to the control treatment. It was concluded that adults from distant plants are attracted to the light blue color, but near the onion, the smell of plants prevails (Trdan S et al. 2005. Zeitschrift f¨¹r Pflanzenkrankheiten und Pflanzenschutz 112: 173¨C180). In 2004, the efficacy of four intercrops to reduce the damage caused by thrips feeding was tested on the same host. In onion grown with buckwheat or lacy phacelia, the extent of damage on leaves was lower. In both treatments the yield of onion was significantly lower too, compared to onion grown with white clover or orchard grass, which were less efficient in deterring the pest from onion. Growing onion with buckwheat or lacy phacelia seems appropriate when the priority is a production of healthier food. When we aim to produce a higher yield, white clover or orchard grass are recommended as intercrops. The efficacy of deltamethrin was tested for control of onion thrips in early white cabbage too. In 2002, when the thrips population was numerous, no significant differences were found in the index of damage (considering the lower threshold), yield loss and net mass of heads between the plants sprayed once and twice. The threshold in both treatments was exceeded up to seventh leaf of head, the same as in the control plants. Considering the higher threshold, we recommend to remove four exterior leaves on cabbage heads sprayed once and twice. In the Slovenian growing region, as well as in other regions with similar climatic conditions, we recommend one application of deltamethrin in the first decade of June. In 2004, the efficacy of different mulches against the pest on early white cabbage was tested. The most damage was established on the exterior leaves of heads grown on black PE mulch and on unmulched soil. The mass of heads and net mass of heads were the highest in the PE mulch, while both parameters were the lowest in the soil covered with hay and barley straw. In the parallel experiment the soil was mulched with PE mulch one month after transplanting and after this time the organic mulches were put on the soil. No significant differences in both weight parameters and extent of damage on leaves were determined between PE mulch, hay and unmulched soil. The highest yield loss was found in cabbage plants, grown on artificial mulch and straw. The efficacy of IPM methods for thrips control in onion and cabbage is different and depends on many factors. The expedience of these methods in vegetable production depends on the pest population level, susceptibility of varieties (Trdan S et al. 2005. African Entomology 13: 85¨C95), agrotechniques and weather conditions. As the latter are more and more unforeseen, such is also the efficacy of IPM methods.
