Abstract
Aphids are major pests of wheat crop in Pakistan inflicting considerable economic losses. A better knowledge of landscape scale spatial distribution of aphids and their natural enemies could be used to improve integrated pest management programs. Therefore, the present study aimed to document spatio-temporal variations in populations of wheat aphids and their natural enemies in Pakistan. The 2-year survey study was carried out at ten experimental farms located in five districts of four contrasted agro-ecological zones of eastern Pakistan (Punjab area) i.e. District Chakwal in arid zone, Gujranwala in rice-cropped zone, Faisalabad in central mixed-cropped zone, and Khanewal and Multan in cotton-cropped zone. The dominant aphid species i.e. Schizaphis graminum, Rhopalosiphum padi, R. maidis and Sitobion avenae varied significantly among the five districts surveyed. The population of S. graminum was observed more abundant in arid, R. padi in rice, S. avenae in aird and rice, and R. maidis in cotton-I zones. Aphids ended their population dynamics on 25th March in central mixed-cropped zone and 12th April in other three zones. Various species of natural enemies, mainly Coccinella septumpunctata, C. undecimpunctata, Menochilus sexmaculata, Chrysoperla carnea, Syrphidae and parasitoid mummies were inconsistently observed in four agro-ecological zones. The population of C. septumpunctata, was observed more abundant in rice zone, C. undecimpunctata and C. carnea in cotton-I and arid zones, M. sexmaculata in cotton-I and II zones, Syrphidae in cotton-I zone and parasitoid mummies in rice and arid zones. There were no clear relationships between aphid and the natural enemy populations. The present study may serve as a baseline regarding distribution of wheat aphids and their natural enemies and the results provided insights for further studies on the potential top-down (natural enemies) versus bottom-up (fertilization and irrigation regimes) forces in management of wheat aphids in eastern Pakistan.
Highlights
Wheat (Triticum aestivum L.) is Pakistan’s staple diet and accounts for 10 percent of value added in agriculture and contributes over two percent to the country’s GDP [1]
Several factors are responsible for the low yield of wheat in Pakistan like varieties [3], sowing time [4], improper inputs as water and fertilizers [5], weeds [6] rainfall and insect pests
The study was conducted at ten experimental farms without use of pesticides in four agro-ecological zones of Punjab, Pakistan during two consecutive wheat growing seasons in 2010 and
Summary
Wheat (Triticum aestivum L.) is Pakistan’s staple diet and accounts for 10 percent of value added in agriculture and contributes over two percent to the country’s GDP [1]. It has been cultivated on over nine million ha with production of 26.3 million tons of grains with an average yield of 2,893 kg per ha in 2017–18 [2]. Several factors are responsible for the low yield of wheat in Pakistan like varieties [3], sowing time [4], improper inputs as water and fertilizers [5], weeds [6] rainfall and insect pests. The direct wheat yield losses may reach up to 35–40% and indirect losses up to 20–80% due to aphids [12]
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