Populational fluctuation of lace bug in cassava

ABSTRACT: Vatiga illudens is a pest of economic importance for the cultivation of cassava. Knowing the time of incidence of this insect in combination with environmental factors enables control strategies. The objective of this study was to determine the population dynamics of V. illudens in cassava cultivars and the correlation of these insects for climatic factors in Dourados, Mato Grosso do Sul. Four cultivars of cassava were evaluated: Kiriris, N-25, IAC 90 and Fécula Branca. Population assessment of the lace bug was conducted over 18 months observing 2 crop cycles. Fortnightly, they were randomly sampled four central plants of each plot and five leaves from the middle third of each plant, quantifying the number of nymphs and adults per leaf. Twenty months after planting cassava, two central rows of each plot were harvested and measured productivity in kg ha-1. The experimental design was randomized blocks with four treatments and two replications. The peak population of nymphs and adults for the first crop cycle occurred during the months from March to May. For the second cycle, these population indices happened in the months from January to April. Cultivar Kiriris showed the highest mean number of nymphs and adults per leaf cassava and cultivar IAC 90, the lowest number of insects. There was a negative correlation between the population of adult insects and root yield. The maximum, mean and minimum temperatures affected the population of nymphs V. illudens. These results are fundamental to define management strategies for control of lace bug.

摘要：木薯网蝽（Vatiga illudens）是木薯种植中的重要经济害虫。明确该昆虫的发生时段并结合环境因子，可为其防控策略的制定提供科学支撑。本研究旨在探究南马托格罗索州多拉杜斯市不同木薯品种上木薯网蝽的种群动态，及其与当地气候因子的相关性。本试验共评估4个木薯品种：基里里斯（Kiriris）、N-25、IAC 90以及费库拉·布兰卡（Fécula Branca）。种群监测时长为18个月，覆盖2个种植周期。每两周开展一次随机采样：选取每个小区中央的4株植株，采集每株中下部的5片叶片，统计单叶上的若虫与成虫数量。木薯定植20个月后，采收每个小区的中央2行植株，以kg·ha⁻¹为单位计测产量。试验采用随机区组设计，设置4个处理组与2次重复。首个种植周期内，若虫与成虫的种群峰值出现在3月至5月；第二个种植周期则为1月至4月。其中，基里里斯品种的单叶若虫与成虫平均数量最高，IAC 90品种的虫量最低。成虫种群与木薯块根产量呈负相关。最高气温、平均气温及最低气温均会影响木薯网蝽若虫的种群数量。本研究结果可为制定该网蝽的防控管理策略提供重要依据。