Abstract. Hutasoit RT, Kalqutny SH, Widiarta IN. 2020. Spatial distribution pattern, bionomic, and demographic parameters of a new invasive species of armyworm Spodoptera frugiperda (Lepidoptera; Noctuidae) in maize of South Sumatra, Indonesia. Biodiversitas 21: 3576-3582. The fall armyworm, Spodoptera frugiperda, has reportedly been found in Indonesia since 2019. The main hosts of this new invading insect are food crops and several other crops. This study aimed to examine the spatial distribution pattern, bionomic, and demographic parameters for developing a sampling plan and strategy to control the pest. The study was conducted by observing the total population of S. frugiperda on nine plots of maize plants weekly. The development of S. frugiperda from egg to adult was also observed in plastic containers (diameter of 4 cm x height of 8 cm) fed with maize in controlled room conditions (temperature = 29 ± 2.1°C, 74 ± 10.1% RH). Observations were made on several bionomic and demographic parameters. The results of the study showed that the S. frugiperda distributes in groups, and each group spreads with a low grouping rate. The life cycle of S. frugiperda occurs for an average of 25.11 days with a range of 24-26 days. The net reproduction rate (Ro) of S. frugiperda was 422.46 individuals/parent/generation. S. frugiperda‘s intrinsic rate of increase was 0.22 individuals/parent/day. The length of generation (T) and S. frugiperda doubling time (DT) were 26.59 and 3.04 days, respectively. This species has survived well on the maize in the new habitat, so it will threaten the food crops, especially the maize. A sampling plan can be developed based on spatial distribution parameters to monitor population density to implement a control threshold and control measures from the early stage of maize during adult pre-emergence.

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SummaryThe population dynamics of Nephotettix virescens, a vector of rice tungro virus disease was investigated in a synchronized transplanting area at Jatisari (1984–1986), West Java and in a staggered transplanting area at Sidan (1986–1988), Bali, Indonesia. The FARMCOP suction sampler was employed for population censuses of N. virescens and its natural enemies. The population growth pattern was affected by transplanting pattern: In the staggered transplanting area, the population density increased from the immigrant generation to the first generation, and sharply decrease thereafter, while in the synchronized transplanting area the population density often reached the highest peak in the second generation. The degree of contageousness in the spatial distribution of N. virescens was negatively correlated with population density of the immigrant generation.

Green leafhopper (GLH), Nephotettix virescens, is the most efficient vector of rice tungro virus disease. The disease is endemic in some provinces of Indonesia and commonly con-trolled using resistant varieties. Resistance of rice varieties to tungro could be classified into resistance to a virus and a vector. The history of GLH resistant varieties adoption affected the GLH adaptation in an area. The study was conducted in the period of 2009-2011 to evaluate the resistance status of five GLH resistant rice variety groups (T0-T4) using survival and transmission test. The GLH populations were collected from 15 tungro endemic provinces in Indonesia. The GLH was then reared in the greenhouse before used for the test. The degree of resistance to tungro viruses was calculated by adding the value of survival (weight x score of survival rate) and virus transmission rate (weight x score of transmission rate). The weights for survival and transmission rate were set to 40 and 60, respectively. The results showed that the rank of resistant variety groups in decreasing order of resistance were T4, T1, T2 and T3. Five variations in GLH transmission efficiency were identified, i.e. 170, 070, 050, 030 and 010. GLH populations from Bali and West Nusa Tenggara were the most efficient vector for rice tungro virus. We concluded that there were diversities in the degree of resistance among GLH resistant varieties. Variation in virus transmission efficiency (biotype) among GLH populations collected from various tungro endemic areas closely related to the history of adoption of rice varieties.

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