Calculating the cabbage/mustard aphid population on rapeseed, from top 10 cm of plant by gentle beating with a stick, and later to note the population fallen on paper, is a reliable method? This has been mentioned in good journals. And please also tell, any other method which can be used to count them easily, as they are overlapped and hundreds in number per plant.
Look at Dewar, Alan M., Godfrey J. Dean, and Ray Cannon. "Assessment of methods for estimating the numbers of aphids (Hemiptera: Aphididae) in cereals." Bulletin of Entomological Research 72.4 (1982): 675-685.
First take some twigs of rapeseed plants and count number of aphids per cm. on mean basis. Then take reading of twigs only cm. basis. This is the easy way of reading of aphids on rapeseed plant.
Dear Md. Wajid Javed, I advise you to work at the field level and follow my suggestion to take reading of aphids. If you face any problem again ask me I will try to help you.
Thanks Sunil Kumar Ghosh ,. Your advice was exactly in concurrence with my methodology. Thanks again.
The results isexpressed as mite population suppression (%) compared to densities recorded on the control treatment.
Percent reduction of mite population over control is calculated by the following formula (Abbott, 1925):
Po − Pc
Pt = ----------------------- ×100
100 − Pc
Where, Pt = Corrected mortality, Po = Observed mortality and Pc = Control mortality. Data were analyzed by using INDO-STAT- software for analysis of variance following randomized block design (RBD) treatment means were separated by applying CD Test (critical difference) at 5 % level of significance.
Abbott, W.S. 1925. A method of computing the effectiveness of an insecticide. J. Econ. Ent. 18: 265-267.
Dr. Sunil Kumar Ghosh I am doing an in vivo but not at field level. I used cages (5 replicates/treatment) using Aphis gossypii and Cucumis sativus as host plant and treated with various biopesticides. I used Abbotte (1925).Article A Method for Computing the Effectiveness of an Insecticide
). However my scoring for pest infestation is; 0=0 aphids, 1=11~50, 3=51~100, 4=101~200 and 5=more than 200. I stopped at 5 because that's the maximum score I have seen (even in disease severity). Would you recommend the same method (Po − Pc
Pt = ----------------------- ×100.
100 − Pc)? why 100-PC?
or is it technical problem, maybe you wrote Pt=(100-Po-Pc/Pc)*100?
thank you so much for your response.
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