The population changes in waterbirds are recognised as a global issue. Many waterbird species, especially migratory ones, are undergoing population changes. Monitoring these changes is crucial for waterbird conservation. However, the lack of data to quantify these populations hinders comprehension of the factors responsible for these changes. Although a few studies have investigated the long-term trends of waterbirds in the Republic of Korea (ROK), most have concentrated on a limited number of species and groups. Understanding these changes enables us to identify which species are vulnerable and develop more effective conservation measures accordingly. This study aimed to investigate the population dynamics of waterbirds in the ROK from 2000 to 2024. Data from the Winter Waterbird Census of Korea were used to analyse trends across various waterbird groups and species. The results showed diverse population trajectories, with some species experiencing notable increases while others underwent severe declines. Among the observed trends, several globally threatened species, such as the White-naped Crane Grus vipio and Oriental Stork Ciconia boyciana, exhibited significant population growth. This is largely a testament to the effectiveness of conservation interventions aimed at these species. However, the study also identified population declines of some species, such as the Tundra Swan Cygnus columbianus and Common Pochard Aythya ferina, indicating pervasive threats due to habitat loss and degradation. Lastly, several recommendations are made regarding the identified population trends that should be used to guide future conservation efforts in the East Asian–Australasian Flyway. This study, with its comprehensive and detailed findings, reiterates the importance of long-term monitoring data for developing effective conservation measures.

Indian siris, Albizia lebbeck (L.) Benth., is a useful tree that is being widely planted for shade in the Ahwaz region of southwest Iran. The tree is, however, severely attacked by the citrus red mite Eutetranychus orientalis Klein. Seasonal population dynamics of the mite were investigated on A. lebbeck in Ahwaz during 2010–2011. Eutetranychus orientalis had two population peaks on A. lebbeck. The first and second activity periods were observed from 10 August to 28 October 2010 and 24 February to 20 June 2011, respectively. The highest density and activity of E. orientalis was observed during September to November and April to May. During these months, the average temperature and relative humidity were 20–35 °C and 21–40%, respectively. The spatial distribution of the mite was evaluated using the parameters of Taylor's power law, which revealed an aggregated spatial distribution of E. orientalis on A. lebbeck. The results of the study could be applied to develop an integrated pest management programme against the pest.

A survey was conducted in Ibadan, Nigeria, between 1 November and 30 December 2000 to examine the mango mealybug Rastrococcus invadens Williams infestation. Results obtained prompted another study in which the population of R. invadens and its parasitism were monitored from January 2001 to December 2005 on smoke-polluted infested mango trees after relocation of smoke sources. A third study was conducted between January and April 2007 in Ibadan, Nigeria, where mealybug-infested mango trees were searched for and the levels of pollution around them characterized using a derived rating scale. The survey results showed that only 7.5% of a total of 489 mango trees examined in 2001 were infested with mango mealybug and were located in exhaust, car park, motorway or converging environments. In study 2, the mango mealybug population significantly (P < 0.05) declined, and parasitism significantly increased on trees from where pollution sources were relocated. All the 86 mango mealybug-infested trees scouted for in study 3 were located in smoke-polluted areas. Significantly higher numbers of infested trees and mealybug population, and significantly lower parasitism levels were found on mango trees in exhaust areas, compared with others. Pollution level was correlated with mealybug population (positively) and parasitism (negatively) in 2000 and 2007. Whereas mealybug population gradually built up on hitherto clean trees where pollution sources were relocated, parasitoid activity seemed to be enhanced by the relocation of smoke sources. The effectiveness and conservation of the parasitoids may therefore depend on the air quality around the infested trees.

An experiment to examine the effects of four agrometeorological factors on population fluctuations in legume pod borer, Monica testulalis (Geyer) in two cowpea varieties was carried out under field conditions in Ibadan, Nigeria. Plots, 5 x 10 m each, of cowpea varieties IT84S-2246–4 and Dan ilan were planted fortnightly between 5 May and 5 October 1988 (12 plantings in all for each variety). Three peaks of the pod borer populations were observed on the cowpeas. There were smaller peaks on crops planted between 5 May and 1 June and again between 29 June and 13 July and a larger one on those planted between 24 August and 7 September. These two peaks coincided with the peaks of the rainfall.

Significant relationships were obtained between pod borer counts and (a) cumulative rainfall (R2 = 0.41; P = 0.004) (b) number of rainy days (R2 = 0.17; P = 0.04) from plant emergence to 50% flowering. These results suggest though, the distribution of rainfall over time is more crucial than the total amount in determining the fluctuations of pod borer populations. Thus, the adjustment of planting dates is suggested as an IPM tactic to avoid the development of damaging levels of pod borer infestations.

Surveys were conducted in two different ecological zones (semi-arid and arid) of Kenya to monitor egg, larval and pupal populations of the sorghum shootfly, Atherigona seccata, on a wild host, Sorghum arundinaceum. Populations were found to be usually higher on wild sorghum than on local varieties of Sorghum bicolor, the cultivated host. During dry periods, shootfly eggs and larvae were still found on wild sorghum, especially in moist areas such as beds of temporary streams or river banks. Population levels seem to be related primarily with the availability of susceptible stems, which in itself is determined by rainfall, soil conditions, density of other vegetation and by the phenology and the distribution of the host plant, Sorghum arundinaceum, being a pioneer species which colonizes recently disturbed areas and is subsequently replaced by other grass species. Since no evidence of the existence of an aestivation diapause has been found, it is reasonable to assume that Sorghum arundinaceum is a major reservoir for A. seccata, especially during the dry season.