Species composition and population dynamics of some arthropod pests in cotton fields of irrigated and semi-arid regions of Punjab, Pakistan

Abstract

The present study aimed to record seasonal dynamics and diversity of different insect pests in cotton agroecosystems. Two well-known cotton growing districts i.e. district Layyah and Vehari were selected for the study from the cotton belt of Punjab, Pakistan. Sampling was done bi-weekly for two consecutive years from July to October during 2018 and 2019. Sweep netting, visual counting, hand picking, wet finger method, beat sheets, aspirator and pitfall trapping methods were used for collection. Shannon-Wiener and Simpson indices were used to compute diversity while Menhinick and Margalef indices were used for the estimation of species richness. A total of 94,343 individuals representing 43 species, 40 genera, 28 families and 6 orders were recorded. Family Aleyrodidae dominated over other pest families. Bemisia tabaci (Gennadius, 1889) of family Aleyrodidae was the dominant species with 39.68% share among all pest species. Estimated species richness of all arthropod pest species belonging to both districts were about 94%. The densities of pests fluctuated with time. The peaks of sucking pest densities were observed in July and August while densities of chewing pests peaked in late September or early October each year. Population densities of jassids Amrasca biguttula (Ishida), armyworm Spodoptera litura (Fabricius), and pink bollworm Pectinophora gossypiella (Saunders), showed strong negative correlation with temperature, humidity and rainfall while thrips population density showed positive correlation with these parameters. Minor loss due to pests are acceptable everywhere, but it is only possible when their populations remain below their economic threshold levels. Present study will aid to design pest management strategies in cotton growing areas round the globe.

Keywords: Biodiversity; Chewing-pests; Cotton; Population-dynamics; Sucking-pests.

Graphical abstract

Fig. 1

Species accumulation curve for insect pests recorded from cotton fields of district Layyah (A) and district Vehari (B). Note: Each curved line in Fig. 1 is showing species accumulation curve and is obtained by using SPDIVERS.BAS program while each circular dot is showing actual number of species recovered from the collected specimen.

Fig. 2

Seasonal dynamics of sucking and chewing insects collected from cotton fields of district Layyah of Punjab, Pakistan.

Fig. 3

Seasonal dynamics of sucking and chewing insects collected from cotton fields of district Vehari of Punjab, Pakistan.

Fig. 4

Cluster analysis of different trapping sites showing percent similarity on the basis of abundance data of different Pests of district Layyah and Vehari. Note: (L-1, L-2 and L-3 were three selected sites of district Layyah while V-1, V-2 and V-3 were three selected sites of district Vehari).