J. Appl. Environ. Biol. Sci.,8(7)77-86, 2018 | ISSN: 2090-4274 |
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DepartmentofCrop Production andPlantBreeding, College ofAgriculture andNaturalResources, RaziUniversity, Kermanshah, Iran
Received:January28, 2018 Accepted: March24, 2018
In order to compare the efficiency of chemical and biological methods, used to reduce the damage caused by chickpea pod borer, an experiment was conducted as a randomized complete block design with three replications, at the college of Agriculture and Natural Resources, Razi University, Kermanshah, Iran, during March to June, 2013. Treatments consisted ofBacillus thuringiensis (Bt) insecticide, release ofBracon hebetor wasps at large larval stage of the pest, release of the wasps at medium larval stage of the pest, spraying Sevin (chemical control), and control (no control method). Results showed that, control treatment had the highest harvest index and seed protein content. Also, the highest amounts of traits including seed yield, number of pods per plant, number of seeds per pod, biological yield, plant height, leaf chlorophyll and hundred-seeds weight, were obtained for the treatments chemical control, and release of Bracon wasps at large and medium larval stages of chickpea pod borer, respectively. Chemical control treatment had the highest inhibitory effect, on controlling the chickpea pod borer pest population, although the use of Bracon wasps can be considered as an effective and ecological friendly method to reduce pod borerinfestationin chickpea. KEYWORDS: Braconwasp;Podborer;Biologicalcontrol
Chickpea (Cicer arietinum L.) is an importantgrain legume crop, belonging to the familyFabaceae. Because ofhigh nutritive value, chickpea is well considered, and is modified for some traits including protein, carbohydrate, and cholesterol lowering fiber, oil, ash, calcium and phosphorus. Chickpea cultivation raises the growers' income and contributes to soil fertility(Younis, Iqbal, Farooq, Jamil, & Khan, 2015). The crop grows generallyunder moderate to cold and semi-arid climates of the country, with a highly variable precipitation(Soltani, Ghassemi-Golezani, Khooie, & Moghaddam, 1999). The pod borer, Helicoverpa armigera Heubn is the most economically important pest of chickpea(Abbasi et al., 2007), which causes a significant damage to many farms, vegetables and crops. It feeds generally on flower buds, flowers and bolls. Females place eggs on the flowering and fruiting structures of these crops,wherehungrylarvalfeeding leads tohuge economic loss(Cunninghametal., 1999). Biologicalcontrol is the use ofliving organisms to keep pestpopulations at lower damaging levels. Natural enemies of arthropods fall into three main classes: predators, parasitoids, and pathogens. Biological control is often more effective, when it is joined with other pest control strategies, in an integrated pest management (IPM) program. Bacillus thuringiensis (BT) is a Gram-positive, soil-dwelling bacterium, usuallyused as a biological insecticide. BT is mostly used in agriculture, especially in organic farming. Bt is safe for humans and is used in urban aerial spraying programs, and in transgenic crops(Ibrahim, Griko, Junker, & Bulla, 2010). The microbial (Bt based) insecticides can be used as component ofintegrated pest management(IPM) approach to provide an environmentally safe and suitable alternative to generallyhazardous, broad spectrum chemical insecticides used against H. armigera. As far as environmental protection is concerned, there is need for complimentary use of microbial (Bt based) and botanical insecticides in support of IPM. Biologically derived insecticides, such as Bt-basedbio-pesticide have provided a commercial alternative to broad-spectrum chemical insecticide because of their specificity in killing target pest(Khalique Ahmed, Khalique, Durrani, & Pitafi, 2012). Bracon hebetor is a public gregarious ecto-larval parasitoid, which belongs to the familyBraconidae (Super familyIchneumonoidea). There appears to be two strains ofparasitoid, one attacking field pests, and the other predates the pests ofstored products. B. hebetor larvae growby rasping a cavity through the host’s integumentand feeding on pest tissues. Parasitismoccurs during the year Aim of
*Corresponding author: H. Miri, Department of Crop Production and Plant Breeding, College of Agriculture and Natural Resources, RaziUniversity, Kermanshah, Iran.E-mail: hamze_miri@yahoo.com
presentexperimentis tocomparetheperformance ofchemicalandbiologicalmethods,used to reduce damage ofthe chickpeapodborer(Helicoverpaarmigera), in Kermanshah west Iran.
The experiment was conducted as a randomized complete block design with three replications, at Agriculture and Neutral Resources College of Razi University, Kermanshah (Latitude: 34°18′51″N, 47°03′54″E; altitude: 4557 ft.), Iran, during March to June, 2013. Treatments consisted of BT insecticide, release of the wasps at large larval stage, release of the wasps at medium larval stage, spraying (chemical control), and control plot. The treatments chemical control by Sevin (250ml acre-1), and BT insecticide (1 kg/ha), were applied simultaneously (before flowering), medium larvae were released at the 50% flowering, and release of large larvae was performed at the beginning of pod formation. In order to measure the traits, fortnightly sampling was begun on early May. Leaf SPAD value was measured on three randomly selected plants in each plot (Japan, Minolta, and SPAD-502). Plant height was determined on three randomly selected plants in each plot. Final harvesting was conducted on two middle rows at each plot (1m2). Harvested plants were weighted after drying, to measure the biological yield. In order to obtain the seed yield, five plants were randomly harvested from each plot, and the number of pods and seeds per plant were counted. To determine the weight of100 seeds, four samples of100 seeds were counted, weighted, and their means were calculated. Seeds belong to the harvested plants from each plot were separated and weighted. Measuring seed protein contentwas performed usingvolumetricballoon.
Plantgrowth andpestconditions from germination until completelypod maturitystage, were monitored ona regular weekly basis, and data were collected. To determine the Bracon hebator flight peak on April 25, a pheromone trap was installed in the field, and data from trapped wasps were gathered once every two days. Then, according to the flight peak, while the maximum number of small larvae were observed, farm was sprayed at a rate of 2 to 3 kg per hectare, using BT microbial toxins (Strain in use: Bacillus thuringiensis serotype H-3a3b), and after 12 days spraying, once everytwo days, data were collected from the experimentalplots. Also, at the medium and large larval stages, 2000 Bracon wasps consisting of 80% female and 20% male, were released on the predetermined experimental plots, and data were collected for 12 days once every two days on the experimental plots after releasing the wasps. In order to avoid the flight ofwasps on other treatmentplots, the plots were bordered using thin meshes, with no inhibition for normal functioning of the wasps. Samples were also collected from chemical control (with Sevin pesticide at a rate of 3 kg per hectare) and control plots. To determine the number of infected and non-infected capsules, three plants ofeach plot were selected randomly, and marked, before applying the treatments, and then the number ofpods was counted. To studythe parasite damage, 12 days after the application of the treatments, the number of infected and non-infected capsules was counted again. Data analyses were carried out using SAS software (SAS Institute 2003).TheMeanswere separatedusing LSD testatthe probabilitylevelof5 percent.
Analysis of variance indicated that, the treatments had significant effects on biological yield, 100-seeds weight, plant height, and seed protein content at5% probabilitylevel, seed yield, leafchlorophyll, number ofpodsper plant, numberofseeds per pod, andharvestindex at1%probabilitylevel(Table1).
Table1.VarianceAnalysisofthe Impact ofPod BorerLarvaeon Chickpea Traits Table2. Effect ofApplying Different Treatmentson Number andSituation of thePodsper Plant
SOURC D E S OF F VARIAN CE | BIOMASS | NUMBER OF PODS PER PLANT | NUMBE R OF SEEDS PER POD | SEED WEIGH T | LEAF CHLORO PHYLL | PLANT HEIGH T | PROTEI N CONTE NT | SEED YIELD | HI | |
---|---|---|---|---|---|---|---|---|---|---|
BLOCK | 2 | 1998.296NS | 17.532* | 0.030NS | 20.220NS | 38.438NS | 7.108NS | 13.471NS | 66.445NS | 0.002NS |
TREAT MENT | 4 | 9005.729* | 55.699** | 0.408** | 103.335* | 129.280** | 83.852* | 24.410* | 1220.892** | 0.013** |
ERROR | 8 | 16263.034 | 24.621 | 0.157 | 232.078 | 124.797 | 122.856 | 42.348 | 449.285 | 0.009 |
CV (%) | 16.571 | 11.382 | 9.071 | 15.930 | 10.527 | 15.243 | 10.906 | 6.139 | 7.214 |
The highest and the lowest chickpea biological yield were related to the chemical control, and control treatments, respectively. No significant difference was found between the treatments release of bracon wasps at large and medium larval stages with chemical control. Results also indicated that, the treatments release of bracon wasp showeda higherbiological yield compared withBT treatment(Figure 1).
Figure1.Biological yield ofchickpea at differentcontrolmethods.t1:Chemicalcontrol, t2:release ofbraconwasp parasitoid at large larvalstage, t3:Release ofbraconwasp parasitoid at medium larvalstage, t4:BTinsecticide, t5: Control(nocontrolmethod)
According to the results, the highest number ofpods perplantwas observed at the chemical control treatment. Also, there was no significant difference between the treatments chemical control and release of bracon wasps on large larvae, in terms of this trait. Release ofwasp’s at large larval stage had ahigher number ofpods perplant, compared to BT treatment. The difference between the treatments of BT insecticide and releasing the wasps at medium larval stagewasnot significant for this trait(Figure 2).
Figure2.Numberofpodsperchickpea’splant atdifferentcontrolmethods. t1:Chemical control, t2:releaseofbracon wasp parasitoid atlarge larvalstage, t3:Release ofbraconwasp parasitoid atmedium larvalstage, t4:BT insecticide, t5:Control(no controlmethod)
Based on the results, the minimum and the maximum number of seeds per pod were related to the treatments of control and chemical control treatments, respectively. Considering the number of seeds per pod, there was no significant difference between control and BT insecticide, and also between chemical control and release of bracon wasp parasitoid at large larvalstage treatments(Figure3).
Figure3.Numberofseedsperpodatdifferentcontrol methods.t1:Chemical control, t2:releaseofbraconwasp parasitoid at large larvalstage, t3:Release ofbraconwasp parasitoid at medium larvalstage, t4:BTinsecticide, t5: Control(nocontrolmethod)
The control treatment, showed the highest hundred seeds weight, followed by chemical control and BT treatments. There was no significant difference between the treatments of BT insecticide and release of wasps at large and medium larvalstages, in terms oftheir impacton chickpea hundredseed weight(Figure 4).
Figure4.100-seed weightofchickpeaatdifferent controlmethods. t1:Chemicalcontrol, t2:releaseofbraconwasp parasitoid at large larvalstage, t3:Release ofbraconwasp parasitoid at medium larvalstage, t4:BTinsecticide, t5: Control(nocontrolmethod)
The impact ofBT insecticide on leafSPAD value was not different when compared with the impact of releasing the wasps at large and medium larval stage treatments. Moreover, control and chemicalcontrol led to the lowestand the highestvalueof leafSPAD,respectively(Figure5).
Figure5. LeafSPAD valueofchickpeaatdifferentcontrolmethods.t1:Chemicalcontrol, t2:releaseofbraconwaspparasitoidat largelarvalstage,t3:Release ofbraconwaspparasitoidatmedium larvalstage,t4:BT insecticide, t5:Control(nocontrolmethod)
Mean comparisons showed no significant difference between the treatments of chemical control and release of bracon wasp’s at large larval stage, as well as between the treatments of release of bracon wasps at medium larval stage, BT insecticide, and control, in terms of their impact on chickpea plant height. However, the highest plant height was recorded for chemical control and release of bracon wasp parasitoid at large larval stage treatments, respectively(Figure 6).
Figure6.Chickpea’s plantheightat different controlmethods. t1:Chemicalcontrol, t2:releaseof bracon wasp parasitoidat large larvalstage, t3:Releaseofbracon wasp parasitoid at medium larvalstage, t4:BT insecticide, t5:Control(nocontrolmethod)
Results indicated that, control treatment had the highest amount of seed protein content with no significant difference between this treatment and Bt. There were no significant differences between the treatments of chemical control andreleaseofBracon wasps at medium and large larvalstages, for seedproteincontent(Figure 7).
Figure7. Seedprotein contentofchickpeaatdifferentcontrolmethods.t1:Chemicalcontrol, t2:releaseofbraconwaspparasitoid atlarge larvalstage, t3:Releaseofbraconwaspparasitoidatmediumlarvalstage, t4:BTinsecticide,t5:Control(nocontrolmethod)
Based on the results, maximum chickpea seed yield was obtained from the treatment of chemical control, followed by the releasing Bracon wasp at medium and large larval stages. No control treatment led to the lowest chickpea seed yield. Moreover, BT could notsignificantlyincrease thistraitas comparedwithno controltreatment (Figure 8).
Figure8.Chickpea seed yieldatdifferentcontrolmethods. t1:Chemicalcontrol,t2:release of bracon wasp parasitoidatlarge larvalstage, t3:Releaseofbracon wasp parasitoid at medium larvalstage, t4:BT insecticide, t5:Control(nocontrolmethod)
Maximum chickpea harvest index was recorded in the plots in which podborer was not controlled with a significant difference with other treatments. Other treatments including chemical control, BT insecticide, and release ofBracon wasps at large and medium larval stages, didn’tshow significant differences in terms ofthe impact on harvest index ofchickpea (Figure 9).
Figure9.Chickpeaharvest indexatdifferent controlmethods. t1:Chemicalcontrol, t2:release ofbraconwasp parasitoid at large larvalstage, t3:Release ofbraconwasp parasitoid at medium larvalstage, t4:BTinsecticide, t5: Control(nocontrolmethod)
The results showed that, chemical control, and release of Bracon wasps at medium and large larval stages, had notable positive impacts on most of the traits including seed yield, the number ofpods per plant, and the number of seeds per pod, biological yield, plant height, and leaf SPAD value in chickpea. More effectiveness of chemical control compared with other treatments can be due to high durability and effectiveness of spraying, at all growth stages of pod borer. The frequencyof parasitoid releases will impact parasitism of H. armigera and the incidence of plant damage (Li et al., 2006) .However, less effectiveness of BT insecticide can be attributed to low durability of this biological agent during pest growth period (3 to 7 days).The efficacy of Bt, which can be enhanced by incorporation of suitable quantities of acids, salts, oils, adjutants, thuringiensin (exotoxin of Bt) and chemical insecticides, against lepidopteron pests including H. armigera has been demonstrated (Salama, 1984).Application of DiPel 2X and DiPel ES @ 1.6 kg ha-1 and 1.5 l ha-1, respectively, at early stages of crop infestation (1st, 2nd and 3rdinstars larvalinfestation)with at least2 applications at7 days interval resulted insignificant increases in yield of chickpea as compared to controls (KhaliqueAhmed &Khalique, 2012;KAhmed, Khalique,Malik,&Riley, 1994). Compared with medium larval stage, release of Bracon wasp’s at large larvalstage, had a higher suppressing impact on pod borer population, likely because of more existing food resources for Bracon wasps in this stage. Maximum hundred seeds weight of chickpea was related to the control treatment; same finding was reported by(kahraryan) based on his investigation on pesticide effect for chickpea pod borer control, who stated that, plots in which Bt insecticide, and Carbonyl and Diflubenzuron pesticides were applied, showed a lower 1000-seeds weight compared to the control, due to lose more flowers and buds. In this respect, the seeds remained on the plant, may use more photo-assimilate, and their weight can increase as a result. He also reported that, Diflubenzuron treatment had a
higher 1000-seed weight, compared to BT insecticide. Control treatment showed the highest harvest index. Although, both seed and biological yields were lower in this treatment compared to others, but the reduction for biological yield was higher, resulted in a higher harvest index. Control treatment also showed the highest protein content. Regarding the role of growth condition after seed filling, we believe that, before seed filling, most of assimilates are consumed for vegetationor flowering, while duringseed filling, mostofassimilates are designated to this stage. Therefore, a decrease in produced dry matter after pollination, because of pesticide application followed by lose flowers and buds, is likely to play a role in prediction of harvest index. Since, the highest damage of chickpea pod borer was observed for control treatment, we concluded that, the treatment has experienced stress condition caused bythe pest, through which the protein contenthas been increased (Mozaffarian & Sanborn, 2013), in a bio-Ecological study on chickpea pod borer, suggested that the pest has two generations per year, which the damage caused by the first generation is highly important. Damage of the first generation on pods has been estimated to be at least 15 percent. In this study, dominant wasp species was Bracon hebetor, which influenced at least 30 percent of large larvae of the pest. This researcher, in his parallel study on the effect of microbial poisons derived from strainsof the bacterium Bacillus thuringiensis onHeliothis larvae, concluded that Bactospinand Delfin are capable to decrease the damage ofthepestby4 percent.
Based on the results shown for all the treatments, despite the increase in the number of pods per plant, number of infected pods was significantlydecreased, after applying treatments. In addition, chemical control treatment had the highest impacton chickpea pod borerpopulation, compared with other treatments, which can be caused byapplying chemical control at tinylarval stage of the pest and durability of poison effect during pest growth. Due to high cost of chemical control and the problems caused by the use of chemical poisons for environment and human beings, it can be said that, biological control of pests might be the best alternative way to reduce costs and avoid the dangers ofusingchemical poisons.
This studywas supported and granted byRazi universityof Kermanshah under grant number 6715685438. I would also like tothankDr.BahramNourouzian for his extraordinarysupport.
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