Abstract
With a view to assessing the effect of temperature (ºC) and locations on species richness of thrips and whiteflies and their natural enemies (NEs), predatory Geocoris bug and Asian lady bug beetle (LBB) in mustard field of BARI Sarisha 16, the experiment was carried out at the farmers fields in two specific locations of Southern Bangladesh, Rupsha, Khulna and Abhaynagar, Jessore during November, 2015 to March, 2016. The studies were laid out with randomized complete block deign (RCBD) maintaining four replicates. The results depicted that there was a significant variation in mean population abundance of thrips, whitefly and their predators across the observation dates, which principally resulted from the variation of temperature along the various observation dates in each location and between locations along with phenological characters of host plants. Initially, population of thrips and whitefly, and their predators were very low in both locations at first observation date of 20 November, 2015 which gradually colonized and reached the peak in 19 March, 2016 with temperature of 27.8°C and 71% RH in Khulna and 26.1ºC and 61% RH in Jessore. Notably, temperature ranging from 2227°C during mid-February to March, 2016 considerably favors the species richness of both insect pests, thrips and whiteflies, and their predators, Geocoris bug and Asian lady bug beetle in both places. By contrast relative low temperature of 1620°C from December 20, 2015 to January 29, 2016 affected the species richness of predators and pest as well. The yield of mustard, BARI Sarisha 16 was significantly higher in Jessore (1365.75 kgha1) due to lower pest population and higher predator population relative to Khulna region (1277.25 kgha1). Ecological factors especially temperature appeared as major striking factor of species richness and played crucial role in getting up and down of mustard insect pests and NEs population across various date of observations and between places.J. Bangladesh Agril. Univ. 15(1): 7-14, January 2017
Highlights
Mustard (Brassica sp.) is one of the most dominant edible oilseed crops and positioned 2nd after soybean across the globe
The results revealed that mean species richness of thrips and whitefly, and their predators on mustard varied significantly with different dates and phenology of plant in the demonstration field of Rupsha, Khulna
The population abundance of thrips and whitefly (Bemisia spp.), and their predators, Asian lady bug beetle and Geocoris bugon Brassica crops as well as Brassica yield were estimated in two separate locations of Bangladesh, Rupsha, Khulna and Abhaynagar, Jessore
Summary
Mustard (Brassica sp.) is one of the most dominant edible oilseed crops and positioned 2nd after soybean across the globe. Mustard is a cold season oilseed crop whose yields considerably varies with variation in temperature. In winter season mustard crops used to confront a lot of insect prevalence, especially piecing sucking insects named whitefly, thrips and aphid reducing the crop vigor and yield potential. To control those pests, the growers principally depends on synthetic chemicals which are most often overused or misused resulting in death of both harmful insects and their natural enemies, predatory insects such as Asian lady bug beetle, Geocris bugs, and spiders. In uninterrupted agroecosystem with no insecticides usage, the natural enemies feed on the soft bodied harmful insect pests and prevent the pest richness from reaching the economic injury level and offer a solid foundation of ecofriendly management system of mustard pests for mustard growers (Furlong et al, 2008; Syed et al, 2016)
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