Risk Assessment for Tomato Fruitworm in Processing Tomato Crop-Egg Location and Sequential Sampling
Linking Landscape, Environment, Agriculture and Food (LEAF), Instituto Superior de Agronomia, Universidade de Lisboa, 1349-017 Lisboa, Portugal
RAIZ—Instituto de Investigação da Floresta e Papel, Quinta de São Francisco, Apartado 15, 3801-501 Eixo-Aveiro, Portugal
Escola Superior Agrária de Santarém, Instituto Politécnico de Santarém, Quinta do Galinheiro, S. Pedro, 2001-904 Santarém, Portugal
CITAB-Centre for the Research and Technology of Agro-Environmental and Biological Sciences, Universidade de Trás-os-Montes e Alto Douro, Quinta de Prados, 5000-801 Vila Real, Portugal
Author to whom correspondence should be addressed.
Received: 2 December 2020
Revised: 23 December 2020
Accepted: 23 December 2020
Published: 28 December 2020
The tomato fruitworm, Helicoverpa armigera, is a key pest of several crops. It can cause particularly extensive damage in crops of processing tomatoes. Risk assessment can be a tedious and costly task if sampling protocols require a large number of plants. Sequential sampling allows sampling of a reduced number of plants when population densities are much lower or much higher than the economic or control threshold. Additionally, for crop protection purposes, sampling for classification (to assess if population density is lower or higher than the economic threshold) is adequate and requires much less effort. We studied the preferred location of eggs found on plants and then described the spatial pattern of oviposition in processing tomatoes using Taylor’s power law. Eggs were found more frequently in the exposed canopy in the upper and middle-upper strata, directly below open flower clusters, with an aggregated spatial pattern. A sequential plan was developed for 20 and 80 plants, as minimum and maximum sample sizes, respectively. This reduces sampling efforts and costs when compared to the fixed number sampling plan, and provides acceptable precision in decision-making for this pest in a processing tomato crop.