Blue trap improves thrips monitoring in onions

The blue sticky trap demonstrated the best performance for monitoring thrips in commercial onion crops. The method recorded a relative variance of 5,27%, an economic precision of 135,50, and a cost of $3,64 per hectare. The result indicates greater operational efficiency for Integrated Pest Management programs.

Researchers from the Federal University of Viçosa compared four techniques in 30 fields of the Andromeda cultivar in the Alto Paranaíba region of Minas Gerais (doi 10.37486/2675-1305.ec08029). The study evaluated direct counting, beating of plants, bagging, and blue sticky traps. Direct counting served as a reference for absolute density.

The blue trap showed a coefficient of determination of 0,79 and a regression slope of 0,82. These values ​​indicated the highest correlation with the population present on the plants. The method required 0,10 samples per hectare and recorded an average time of 61,94 seconds per sample.

The bagging method had the lowest unit cost, at $0,08 per sample. However, it required 60,14 samples per hectare and did not show a significant correlation with absolute density. The technique also required 94,45 seconds per sample.

The plant beating method showed the shortest time, with 10,16 seconds per sample. The method achieved a moderate correlation with thrips density, but recorded a relative variance of 43,81%, above the 25% limit adopted in the study.

Direct counting identified a predominance of Thrips tabaci, responsible for 89,4% of the individuals. Frankliniella occidentalis and Frankliniella schultzei completed the observed composition.

The researchers concluded that blue traps offer the most reliable indicator of infestation pressure in the field and can support decisions about the timing of control measures.

The work was carried out by scientists Lara B. Ribeiro, Samuel R. França, Daniel C. Nogueira, Monique F. Malaquias, Mariana MF Oliveira, Carlos G. da Cruz, and Flávio L. Fernandes.