Monitoring whitefly, Bemisia tabaci (Genn.) on cotton
2001
Aslam, M. (Bahauddin Zakariya Univ., Multan (Pakistan). University Coll. of Agriculture) | Khan, A.H. | Rasheed, T. | Khan, I.A.
The study was conducted in two fields around Multan to develop an efficient and time saving method for monitoring of whitefly, Bemisia tabaci (Genn.), on cotton during 1999. Whitefly adults were counted weekly on 20 alternately upper (second fully expanded leaf from the top), middle and lower (second leaf from the bottom during June and third from July to September) leaves of CIM-446 cotton variety from June to September. Mean number of adults / leaf was non-significantly different among upper, middle and lower leaf. Regression analysis was performed between mean number of adults/upper (X1), middle (X2) and lower (X3) leaf, their combinations (X1 + X2, X1, + X3, X2 + X3) and per upper + middle + lower leaf (Y). Highest correlation was found between mean number of adults/upper + middle leaf (X4) and Y on pooled data of the two fields (r2 = 99.6%, P=0.00). Correlation was poor between X1 and Y (r2 = 62.4%, P=0.000), whereas correlation between X2 and Y (r2 = 97.7%, P=0.00) and X3 and Y (r2 = 94.7%, P=0.000) was high enough to be used for pest scouting. It is recommended that for saving time and cost involved in monitoring population of whitefly, number of adults/middle leaf could be used to make management decisions. Mean number of adults corresponding to economic injury level for each leaf and combination thereof is also given for use by the farmers.
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