M. A. Uddin
Department of Entomology, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh
M. Jahan
Department of Entomology, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh
M. M. Uddin
Department of Entomology, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh
Helicoverpa zea, Nature, Extent, Damage, Maize
Entomology Field Laboratory, BAU, Mymenisngh
Pest Management
The experiments were conducted in the Entomology Field Laboratory, BAU, Mymenisngh during November 2008 to May 2009 to study the nature and extent of damage of corn earworm, H. zea using two maize varieties viz. BARI Hybrid Bhutta-5 and BARI Bhutta-7. The experiments were laid out in a randomized complete block design (RCBD) with three replications. The crop was grown following the usual recommended practices. The fertilizers viz. Urea, TSP, MoP, Gypsum and Cowdung were applied @ 300, 200, 125, 150 and 5000 kg/ha, respectively. The cultural practices like gap filling, weeding, thinning, earthing up, irrigation etc. were done properly. The nature of damage of corn earworm, H. zea was observed regularly from egg hatching to pre-pupal stage. The total and mean numbers of infested cobs were counted from each plot at 3, 7, 12, 17, 21, 25 days after first occurrence of H. zea. The percentage of damage was determined by counting the number of total cob and infested cobs per plot. The percentage of cob damage was calculated using the following formula :
% cob damage = (P0/Pr) × 100
Where,
P0 = Number of infested cob/plot
Pr = Total number of cob/plot
The individual plots were selected randomly when the cobs become matured. From each plot three infested cobs were selected randomly. The total length and infested part of the same cob was measured and percent length of cob infestation was calculated. From each cob total kernel and infested kernel were counted. The percent length of cob infestation was calculated using the following formula :
% length of cob infestation = (I0/Ir) × 100
Where,
I0 = Length of infested part /cob
Ir = Total length /cob
The recorded data were compiled and tabulated for statistical analysis. The analysis of variance was done with the help of computer package MSTAT-C. The mean differences among the treatments were analyzed as per test with Duncan’s Multiple Range Test (DMRT)
Progress. Agric. 20(1 & 2) : 49 – 55, 2009 ISSN 1017-8139
Journal