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Determination of Economic Injury Levels of Helicoverpa Armigera (hubner) in Chickpea

M.A. ZAHID
Scientific Officer
ARS, BARI, Burirhat, Rangpur

M.M. ISLAM
Scientific Officer,
ARS, BARI, Burirhat, Rangpur

M.H. REZA
Senior Scientific Officer
ARS, BARl, Burirhat, Rangpur

M.H.Z. PRODHAN
Senior Scientific Officer,
RARS, BARI, Ishurdi, Pabna

M. RUMANA BEGUM
Senior Monitoring Officer
RDRS, Rangpur, Bangladesh.

Abstract/ Executive Summary:

Chickpea pod borer Helicoverpa armigera (Hubner) is considered to be one of the major pests of chickpea. The damage potential and economic threshold level for Helicoverpa armigera larvae on chickpea crop were worked out. On an average, single larva per m row reduced the yield to the extent of 155 kg/ha and 157 kg/ha in 2004-05 and 2005-06 cropping season, respectively. The ratio of the value of yield saved to the cost of insecticide application at one larva per m row was 1.06 and 1.12 in 2004-05 and 2005-06, respectively. EILs for Helicoverpa armigera were determined as 12 and 0.95 per m row and ETLs was at 09 and 0 73 larvae per m row in 2004-05 and 2005 - 06, respectively.

Keywords: Economic injury, Chickpea, Pod borer

Location: ARS, BARI, Buiirhat, Rangpur

Start Date: 00-00-2004

End Date: 00-00-2006

Program Area: Pest Management

Commodity: Chickpea

Objectives:

The present investigation was aimed to determine the economic injury levels of H. armigera infesting chickpea.

Methodology:

The experiment was conducted at ARS, BARI, Buiirhat, Rangpur during rabi seasons of 2003-05 and 2005-06. The methods of artificial infestation by different levels of larval population were followed to establish the economic injury levels of H. armigera. The ETL was determined based on the benefit cost ratio as suggested by Farrington (1977). There were six treatments consisted of six different larval densities i.e., 0, 1, 2, 3, 4 and 5 larvae per m row length, released at flowering stage of the crop. Seeds were sown in row maintaining row to row distance of 30 cm. Spacing between plants was kept 30 cm. The experiment was laid out in RCBD. The second or third instars larvae were used for this purpose. The plants of one meter row length was covered with nylon mesh cages of 1.0 x 0.5 x 1.0m size before flowering to avoid natural infestation. The cages were designed in such a way that they did not interrupt ventilation and aeration to the growing plants inside. The bottom edges of the cages were inserted into the soil in all sides to check the escape or entry of larvae. These nylon net cages were erected on bamboo sticks fixed in four corners. The larvae were released once at the time of flowering and subsequently at 15 days interval to maintain constant population throughout. Pupae and prepupal stages of larvae from the previous release were collected at the time of next release. The population density was maintained till the pod maturation stage. The number of total and damaged pods and weight of grains from all the covered plants of each cage were recorded. Relationship between the larval density and the percentage of pod damaged were worked out by correlation co-efficient and regression equations. Yield data were converted into kg/ha. Yield losses due to different treatments were derived by deducting the yield of the respective treatment from the yield of control (where no larvae was released). The value of yield loss was determined according to the wholesale market price of chickpea grains prevailing at Rangpur just after harvest during the season. Eighty percent of the yield loss was considered to be avoided with insecticidal treatment, hence was taken as avoidable loss or yield saved. Benefit cost ratio (BCR) was worked out as the ratio of the value of yield saved to the cost of insecticidal application. Cypermethrin @ 0.02 percent was considered for calculating the cost of insecticidal application. Finally, the economic injury level for pod borer larvae was calculated by fitting regression equation Y= a+bx, between larval population levels and BCR. The larval density corresponding to unit benefit cost ratio was the economic injury level and economic threshold level was set at 75% of ETL (Pedigo, 1991).

Source of Information: Bangladesh J. Agril. Res. 33(3): 555-563, December 2008, ISSN 0258-7122

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Results of the present study showed that the control measures should be initiated when the Helicoverpa larval population reaches one larva per m row length in chickpea plants, in order to prevent the population in reaching economic injury levels.

Knowledge Management: Journal