Vertical distribution of the greenhouse whitefly, Trialeurodes vaporariorum Westwood, within potato plant canopy

Abstract

The greenhouse whitefly, Trialeurodes vaporariorum Westwood (Hemiptera: Aleyrodidae) is one of the most important pests of horticultural crops worldwide. The presence of the insect in South Sulawesi was first reported in 2016 when it was seriously damaging field grown potato crops in Malino, causing a yield loss of up to 39%. As a new invasive pest in the region, its population and distribution must be continuously monitored. Effective monitoring can only be achieved if it is based on the knowledge of insect bio-ecology and behavior. Therefore, the purpose of this study was to determine the vertical distribution of T. vaporariorum within the plant canopy. A survey was conducted in a farmer’s potato plantation in Tinggi Moncong, Gowa Regency, South Sulawesi Province, Indonesia. The selected plantation was about 0.2 ha. Ninety plants were randomly selected throughout the field. Each plant canopy was divided into three parts: upper, middle, and lower parts. From each part of the canopy, two leaflets were randomly selected for egg, nymph, and adult counts. The adult number was determined in the field by slowly turning the leaves and all adults found on the lower leaf surface were counted and recorded. The leaves were then picked up and put inside of zip lock bags and brought to the lab for counting the eggs and nymphs under a dissecting microscope (200x). The results showed that about 81, 18, and 1% of the eggs were laid on the upper, middle, and lower parts of the canopy, respectively. Similarly, about 80, 17, and 3% of the adults were found on the upper, middle, and lower parts, respectively. In contrast, no nymphs were found in the upper part of the canopy but about 39 and 61% were found in the middle and lower parts, respectively. This information is very important in monitoring the pest on potato because we now know that for monitoring eggs and adults, the sample should be taken from the upper part of the canopy, whereas for monitoring the nymphs, samples should be taken from the middle and lower parts of the plant canopy.