ISHS Acta Horticulturae 821: International Symposium on Tomato in the Tropics
NEW APPROACHES IN THE CONTROL OF INSECT PESTS IN TOMATO |
| Authors: | C. Ulrichs, T. Mucha-Pelzer, C. Büttner, I. Mewis, E. Scobel, E. Bauer |
| Keywords: | nano-silica, Trialeurodes vaporariorum, biotechnology, pest management, Encarsia formosa, FossilShield |
| Abstract:
Integrated pest management is recognized as a key element of sustainable horticultural production systems. The present paper reviews effective methods for prevention and control of pests, including the use of novel plant protection products for tomato production, and secondly, reports the results of some trials using amorphous silica (AS) for white fly control in tomato. The tomato variety Vitella F1 has been grown under glass at 25/18°C day/night temperatures with a relative humidity of 80-90% and the white fly Trialeurodes vaporarium Westwood has been identified as a major pest. Five treatments have been tested for control: 1) the AS products FossilShied® 100, 2) FossilShied®90s, 3) the parasitoid Encarsia formosa, and combinations of both, 4) FossilShied®100 + E. formosa, and FossilShied®90s + E. formosa, as well as a combination of NeemAzal-T/S® and FossilShied® 90s. All treatments have been conducted in separate greenhouse compartments simultaneously. AS have been applied electrostatically of about 1 g m-2 to ensure good leaf coverage and was removed 24 h after application by washing off. Efficacy of the treatments has been controlled by monitoring white fly populations with sticky yellow cards. NeemAzal-T/S® has been sprayed topically as 0.5% solution at a dose of 100 ml m-2. E. formosa was released at 100 wasp pupae/100 m2 with plant emergence. Regular parasitoid releases at a low rate (50 wasp pupae/100 m2) have been conducted until parasitized white fly nymphs were found in the crop. Starting from the first week after plant emergence, adult T. vaporariorum could be found and the numbers increased gradually over 14 weeks. AS treatments resulted in a good control of T. vaporariorum. The treatment was repeated every 3-4 weeks in order to keep the population below threshold (5 adults/yellow trap). The topical application of neem oil after silica treatment reduced necessary number of AS applications over a period of 14 weeks from three to two applications. Initial releases of the parasitoid Encarsia formosa have been able to keep T. vaporariorum population six to seven weeks below threshold. Seven weeks after release the white fly population recovered and was above threshold levels until the 10th week. The combination of initial E. formosa releases together with one application of hydrophilic AS (short shelf life) reduced white fly population over the whole period below threshold. In contrast, hydrophobe AS (long time insecticidal active) killed all wasps, and therefore, AS treatments had to be repeated. We concluded that certain silica products are feasible additions to biological control of white fly under the frame of an IPM program. Further research is needed for adjusted release rates and timings to compensate for differences in foliage and pest density and changes in levels of parasitism over the growing season. | |
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