Abstract: To determine the pest status of Callosobruchus chinensis Linnaeus (CCL) (Coleoptera:Bruchidae) on chickpea, samples of chickpea were collected from different sources (the farmers, the villagers and general public homes). From each area/location three points were selected to collect the samples with the help of probe. From each collected sample 100 grains were examined. While collecting the samples, the temperature and humidity of the site from where the samples were collected were recorded with the help of portable thermohygrometer. Based on the samples collected, the percent infestation to the chickpea by this pest recorded was 12.18 with standard deviation of 05.42. Based upon the percent infestation, the insect was declared as major pest of chickpea, as it caused more than 10% damage to chickpea. Moreover, it was also concluded from the discussion that the damaged grains did not remain fit for human as well as animal consumption due to the bad smell created by the attack of the pest.
INTRODUCTION
Pulses contain 20-30% of protein, which is almost three times higher than that found in cereals[1]. Among the pulses, chickpea (Cicer arietinum L.) belonging to family Leguminosae is the fifth most important legume crop in the world and it ranks third among the world’s pulse crops after dry bean and dry pea[2]. Chickpea is cultivated over one million hectares in Pakistan and alone contributes about three forth of the pulses grown in the country[3]. Chickpea is the third largest food grain legume of the world and on an average the production of chick pea in Pakistan is 0.37 million tones per annum[4].
In Pakistan among the pulses chickpea occupies 75% (1.75 million ha) of the total area under cultivation of pulses[5]. Chickpea is also a major and cheap source of protein (20%), which meets the protein requirement of the majority of rural people in Pakistan[4]. The total area under cultivation for chickpea during 1986-1987 was 1.08 million ha with a total production of 0.583 million tones[6]. While during 2002-2003 in Pakistan the total area under chickpea cultivation was 0.96 million ha with a total production of 0.582 million tones. CCL is a destructive pest of chickpea in storage[7]. The pulse seeds suffer a great damage during storage due to insect attack[8]. Among the insect pests attacking stored products, pulse beetle is a serious one[9]. CCL has been reported to cause serious damage to pulses in Bangladesh, India and many countries of the world[10-14]. As it is evident that Callosobruchus spp. cause heavy losses every year and affect the economy of the country, suitable control measures should be taken against them.
Das[15] carried out a research to study the infestation of bruchid beetle (CCL) on different pulse seed treated with neem (Azadirachta indica) and til (Sesanum indicum) oils. After five months of storage, the infeststion by pulse beetle under free choice test in neem and til oil treated seeds of Khesari, lentil and chickpea @10 mL oil kg-1 of seeds was 9.30, 36.67, 22.50, 31.53, 27.03 and 36.37%, respectively, while it was 69.13, 64.97 and 67.13%, respectively in control. Neem oil was found to be superior to til oil for its surface protectant activity. The weight loss in neem and til oil treated seeds of khesari, lentil and chickpea due to CCL was 1.63%, respectively while it was 12.73, 34.36 and 2.85% in control. No adverse effect on the germination of the oil treated seeds was observed. Chickpea in the world is grown over an area of 12009 thousand ha, having the average yield of 742 kg ha-1 and total production of 8908 thousand metric tons[16]. In Pakistan gram alone contributes about three fourth of the pulses grown and as a result determines the production of pulses[3]. It is a conventional pulse crop of Pakistan. It is grown over an area of 1090 thousand ha, with an average yield of 586 kg ha-1 and total production 638 metric tons[16]. It plays a vital role in cropping system of subsistence growers of barani regions. Chickpea grains are stored in godowns and warehouses and are attacked by various insect pests. CCL is a destructive pest of chickpea in storage[7]. It is cosmopolitan in distribution, found in the countries where tropical and subtropical conditions prevail[17]. Beetle infestation usually originates from the farm stores[18]. Damage caused to stored chickpea by CCL is of utmost importance in terms of economic loss. A single larva of CCL can destroy several mature seeds[19,20].
In case of heavy infestation of grains by CCL, the grains lose their germination capacity and become unfit for human consumption. Severe infestation leads to 100% damage thus leaving the seed coat. In addition to quantitative losses, the CCL also causes qualitative losses[21]. In grub stage, the beetle lives inside the grain and fills the burrows with their excrement and dead bodies[22].
Millers are of the view that grains with more than 0.5% of insects infested kernels are unfit for milling[23]. Pingale et al.[24] found that chickpea when infested with CCL, total quantity of thiamine was reduced roughly proportional to the amount of pest damaged seeds.
In Syria infestation ranged from 0-79%, screening did not reveal any acceptable degree of resistance but some wild accessions were resistant[25]. The pulses are susceptible to the attack of insects before and after harvest, the extent of infestation has been reported as high as 70%[26]. The damage caused to such an extent renders the grains totally unfit for human and animal consumption.
Qayyum and Zafar[27] calculated 90% losses in gram. Storage facilities in Pakistan are inadequate and pulses are kept in gunny bags, earthen structures (pitchers), old sacks, or store bins, which are not safe and are easily deplorable by stored insect pests. These stores and bins are neither built properly nor they can be fumigated or sprayed against the insect pests concealed. The losses due to the insect pests often become enormous and cannot be neglected.
The heavy infestation of grains by CCL, loses their germination capacity and grains become unfit for human consumption. Both quantitative as well as qualitative losses occur due to CCL infestations. Since the last several years, a dire need was being felt by the entomologists that a current figure be available which could indicate the percent damage by CCL to chickpea. To meet that need a simple study of farmers’ houses, stores of Sukhu, Sohan, Pind Gondal, Dhoke Wajjan, Chakwal and Attock during February, March 2002 concluded that it caused about 13.83% damage to the stored chickpea. This simple study could not authenticate the results. Therefore more information on the extent of damage of this pest to stored chickpea was got during the project work during 2003-2004 to find out the pest status of CCL on chickpea. Hence in the present investigations, attempts was being made to study the extent of damage of CCL to stored chickpea more comprehensively so as to find out the current pest status of CCL on chickpea.
MATERIALS AND METHODS
Samples of chickpea were collected from different sources (the farmers, the villagers and general public homes). From each area/location three points were selected to collect the samples of chickpea with the help of probe. While collecting the samples, the temperature and humidity of the site from where the samples were collected were recorded with the help of portable thermohygrometer. From each collected sample 100 grains were examined. Based on the samples examined, the percent infestation to the chickpea by this pest was recorded so as to determine the status of this pest on chickpea.
The samples collected were stored in the incubator with maintenance of temperature at 30±2°C. The culture of the insect pest was maintained in the Laboratory of the Department of Entomology, University of Arid Agriculture, Rawalpindi to perform the other tests.
RESULTS AND DISCUSSION
The % damage to chickpea by CCL was 12.18 with standard deviation of 5.42 (Table 1). A simple study of farmers’ houses, stores of Sukhu, Sohan, Pind Gondal, Dhoke Wajjan, Chakwal and Attock during February, March 2002 concluded that it caused about 13.83% damage to the stored chickpea. A single larva of CCL can destroy several mature seeds[19,20]. In case of heavy infestation of grains by CCL, the grains lose their germination capacity and become unfit for human consumption. Severe infestation leads to 100% damage thus leaving the seed coat. In addition to quantitative losses, the CCL also causes qualitative losses[21]. In grub stage, the beetle lives inside the grain and fills the burrows with their excrement and dead bodies[22]. The dead bodies of insects and their excrement within the kernels are ground into flour or meal. Millers are of the view that grains with more than 0.5% of insects infested kernels are unfit for milling[23]. Chickpea when infested with CCL, total quantity of thiamine was reduced roughly proportional to the amount of pest damaged seeds[24]. In Syria infestation ranged from 0-79%, screening did not reveal any acceptable degree of resistance but some wild accessions were resistant[25]. The pulses are susceptible to the attack of insects before and after harvest, the extent of infestation has been reported as high as 70%[26].
| Table 1: | Showing percentage of chickpea grains damaged by Callosobruchus chinensis Linnaeus during 2003-2004 |
The damage caused to such an extent renders the grains totally unfit for human and animal consumption. Khare and Johari[21] calculated 90% losses in gram. The correlation between % damage and temperature and % damage and humidity was negative but was not significant (Table 2). The correlation between temperature and humidity was positive but was not significant.
| Table 2: | Correlation between % damage, temperature and humidity collected from different locations during 2003-2004 |
In the light of the above discussion, the pest status of CCL on chickpea could easily be identified/declared. It can be concluded safely that CCL is a major pest of chickpea as it does more than 10% damage to chickpea and renders the grains unfit for human consumption due the bad odour of insect excrements in the grains.
ACKNOWLEDGMENT
These studies were carried out under the financial assistance by Pakistan Science Foundation, Islamabad, Pakistan, under project No. PSF/R&D/P-UAAR/AGR (70).