Assessment of avoidable losses and economic injury levels for the sorghum head bug, Calocoris angustatus Leth. (Hemiptera:Miridae) in India

Sharma, H C and Lopez, V F (1989) Assessment of avoidable losses and economic injury levels for the sorghum head bug, Calocoris angustatus Leth. (Hemiptera:Miridae) in India. Crop Protection, 8 (6). pp. 429-435. ISSN 0261-2194

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Abstract

Avoidable losses and economic injury levels (EILs) were computed for the sorghum head bug, Calocoris angustatus Leth., on three cultivars during three rainy seasons (1985–1987) at ICRISAT. Grain yield in plots protected with 2–5 insecticide sprays (carbaryl at 500 g a.i./ha) between the half-anthesis and the dough stage was significantly higher than in untreated plots, with cost-benefit ratios > 1. Plots that were not protected at half-anthesis and/or complete-anthesis, and at milk and dough stages, suffered a significant loss in yield. Bug damage spoiled the grain quality in terms of germination, 1000-grain mass, grain hardness and percentage floaters. Three to four sprays between complete-anthesis and the dough stage prevented a significant reduction in grain quality. Head bug density at half-anthesis, complete-anthesis, milk and dough stages was significantly and negatively associated with grain yield. Bug density at different stages explained 43–94% of the variance in yield. Direct effects of bug numbers at the milk stage and the indirect effects of head bug density at other stages through the milk stage contributed towards maximum reduction in yield. Maximum avoidable losses were recorded in cultivar ICSV 1 (88·6%), followed by CSH 1 (69·9%), and CSH 5 (53·9% in 1986 and 55·0% in 1987). Loss in grain yield/ha due to one insect/panicle at half-anthesis and that based on natural increase, were 548 and 232 kg in CSH 5 during 1986 and 1987, respectively, 251 kg in ICSV 1, and 77 kg in CSH 1. EILs based on a cost-benefit ratio of 1:1 ranged from 1·3–1·4 insects/panicle for CSH 1, 0·4 for ICSV 1, and 0·4–0·6 and 0·2–0·4 for CSH 5 during 1986 and 1987, respectively. Simple cost estimates for insecticide sprays and the resultant saving in grain yield are a useful tool for decision-making in pest management.

Item Type:	Article
Divisions:	UNSPECIFIED
CRP:	UNSPECIFIED
Uncontrolled Keywords:	Sorghum; Head bug; Calocoris augustatus; Avoidable losses; Economic injury level; India
Subjects:	Mandate crops > Sorghum Others > Plant Pathology
Depositing User:	Ms. Ishrath Durafsha
Date Deposited:	14 Feb 2014 09:22
Last Modified:	14 Feb 2014 09:22
URI:	http://oar.icrisat.org/id/eprint/7521
Official URL:	http://dx.doi.org/10.1016/0261-2194(89)90069-0
Projects:	UNSPECIFIED
Funders:	UNSPECIFIED
Acknowledgement:	The authors are grateful to the staff of cereals Entomology for assistance in carrying out this work, And to Dr. Murari singh for his help in statistical Analysis. Approved as J.A .No. 867 by the International Crops Research Institute for the Semi-Arid Tropics ( ICRISAT ) , patancheru , A.P. 502 324, INDIA.
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