Toxicity of Some Insecticides to Control Mango Mealy Bug, Drosicha mangiferae, a Serious Pest of Mango in Pakistan.
Mango mealy bug, Drosicha mangiferae, is one of the most serious insect pests of mango because it reduces the plant vigor by sucking the sap from inflorescence, tender leaves, shoots and fruit peduncles. To control this pest, insecticides of different groups were evaluated in both the laboratory and field conditions. In laboratory conditions profenofos showed maximum percent mortality of 93.3% and 86.67% of the 1st and 2nd instar mango mealy bug. While triazophos proved to be an effective insecticide for the control of the 4th instar by showing 64.0 and 100% mortality in leaf dip method and foliar application. Out of seven insecticidal band applications tested in the field conditions, the combination of cotton + buprofezin proved effective by manifesting 99.10% control of mango mealy bug. The present study has shown that the insecticides tested, especially profenofos, methomyl and triazophos, and cotton + buprofezin band application provided effective control of the mango mealy bug.
The control of this insect pest throughout the orchards predominantly depends on judicious use of chemicals like profenofos, triazophos, methomyl, acetamiprid, buprofezin and deltamethrin, for the development of an integrated pest management strategy.
Key words: Insecticides, mango mealy bug, leaf dip method, new chemistry insecticides, carbamates.
Mango, Mangifera indica L, a member of the family Anacardiaceae, is one of the most important nutritionally rich in carbohydrates and vitamins and foreign exchange earning fruit crop of Pakistan. Nature has endowed Pakistan with wide range of agro-climatic conditions, which permit quality production of both tropical and temperate fruits. The climate of Pakistan is favorable to all types of fruits.
Mango is the second major fruit crop of Pakistan after citrus. Pakistan is standing at 5th place in world's total mango production (FAO,2001; MINFAL, 2002). The output during the current year (2010) has substantially decreased to 9-10 tons per hectare. It is about 50% of the potential yield, which is 20 tones per hectare (Shahid, 2006), that shows a significant difference between averageand potential yields. The main reason for the yield reduction is the pest pressure and diseases attacking the mango orchards.
A number of insect pests are known to attack the mango trees, which have been studied in detail (Sen, 1955; Giani, 1968; Herren, 1981; Tandon and Verghese, 1985). Some of these are certainly responsible for causing considerable damage and become a limiting factor in many mango-growing areas. To effectively monitor a mango orchard for insect pest outbreaks, growers must be first aware of the types of insect pests they are likely to encounter and should conduct the surveys on a regular basis. (Patriquin et al., 1995).
Mango mealy bug, Drosicha mangiferae is one of the most serious insect pests of mango in Pakistan due to its polyphagous nature (Green,1908). It lays egg in loose soil within radius of 2-3 meter around the infested trees. Hatching of the eggs starts with rise in temperature and the nymphs crawl to the succulent shoots and base of fruiting parts (Birat, 1964; Atwal, 1976). The nymphs and female bugs suck sap from inflorescence, tender leaves, shoots and fruit peduncles. As a result, the affected inflorescences are shriveled and get dried. Rigorous infestation affects the fruit set and causes fruit drop. They exude honey dew over the leaves, on which sooty mould is developed (Tandon and Lal, 1978). Mango mealy bug is difficult to control by insecticides and the use of chemicals has been inefficient (Yousuf and Ashraf, 1987; Khan and Ahsan, 2008).
The sticky bands along with burning and burying treatments significantly reduced the frequency of infestation of mango mealy bug by frequency of infestation of mango mealy bug by 0.00-15.79%. Burlap bands reduced population of mango mealy bug nymphs by 78.98%. Stem injection can achieve a very high level of mortality of sucking insects (98%). The mortality rates achieved with insecticide sprays were up to 55% (Ishaq et al., 2004).
Keeping in view all the problems associated with management of D. mangiferae, a study was planned with the objective to develop a propermanagement technique against mango mealy bugs by using different insecticides and band applications.
MATERIALS AND METHODS
The mango mealy bugs were collected early in the morning in a jar with the help of an aspirator and then brought to the laboratory. Fresh mango leaves as food were provided in the jars for the crawlers.
Effect of different insecticides Against 1st and 2nd instar
To examine the toxicity of insecticides viz.,thiodicarb, methomyl, profenofos, chlorpyrifos, bifenthrin, emamectin benzoate, methamidophos chlorfenpyr, flufenoxuron, imidacloprid, acetamiprid, buprofezin, l-cyhalothrin, deltamethrin and carbaryl against the 1st and 2nd instar of D. mangiferae, leaf dip bioassay method was used.
Insecticidal solution (30ml) of each insecticide was prepared at their field recommended doses (Table I). Fresh mango leaves equal to the size of Petri dish (5cm) were dipped into the insecticide solution for about 1 min and then air dried at room temperature.
After drying, these treated leaves were placed in the Petri dishes containing moistened filter paper to avoid desiccation of the leaves. Thereafter ten active crawlers of the 1st and 2nd instar were placed in the Petri dishes containing treated leaves with the help of fine camel hair brush. Each Petri dish was then placed under controlled conditions (25 +- 2degC, 60 +- 5 % RH). Experiment was laid under Completely Randomized Design (CRD) with sixteen treatments including control while all the treatments were replicated thrice. Mortality data was taken up to seven days of post treatment.
Table I.- Insecticides used at their field recommended doses against ft and 2nd instar mango mealy bug.
Common###Dose in###Dose in
name###Trade name###100 L###30 ml
Thiodicarb###Larvin(r) 80 DF###375 g###0.12 g
Methomyl###Lannate(r) 40 SP###250 g###0.075 g
Profenofos###Curacron(r) 50 EC###800 ml###240 ul
Chlorpyrifos###Larsban(r) 40 EC###750 ml###225 ul
Bifenthrin###Taistar(r) 10 EC###200 ml###60 ul
Chiorfenpyr###Pirate(r) 360 SC###330 ml###125 ul
Imidacloprid###Confidor(r) 205L###250 ml###100 ul
Acetamiprid###Acetamiprid(r) 20###150 ml###0.125 ul
Buprofezin###Buprofezin(r)###600 g###0.25 g
A-cyhalothrin###Karate(r) 2.5 EC###330 ml###125 ul
Deltamethrin###Decis(r) 10 EC###250 ml###60 ul
Carbaryl###Sevin(r) 85 SP###1.5 kg###0.1 g
Table II: Insecticides used at their field recommended doses against 4th instar mango mealy bug.
Common###Dose in 100###Dose in 30
###L water###ml water
Against 4th instar
In order to determine toxicity of insecticides at their recommended field doses (Table II) viz., triazophos, methomyl, emamectin benzoate, spinosad, imidacloprid, bifenthrin and kerosene oil, against the 4th instar mango mealy bug, two methods were applied i.e. leaf dip method and foliar method.
Leaf dip method
For the leaf dip bioassay, leaves were cut as the size of Petri dish. These leaves were dipped in insecticide solution containing 50 ml water + insecticide. There were five replications in each treatment and eighth treatment was labeled as control, in which leaf discs were dipped in tap water only. In each replication five, 4th instars mealy bug were placed. The data was recorded up to 7 days after insecticidal treatment.
Lady hand sprayer was used in this method. The insecticide solutions were prepared in the lady hand sprayer. Under spraying method, two different solutions were made i.e., one containing 200 ml water + insecticide and other containing 200 ml water + insecticide + 2000 ml vegetable oil. These solutions were then sprayed (one time) on dorsal side of mealy bug. Fresh mango leaves were provided to the treated mealy bugs. There were five replications in each treatment. One treatment was of control in which mealy bugs were sprayed with tapwater only. In each replication five 4th instar mealy bugs were placed. The data was recorded up to seven days.
Effect of different insecticidal bands against mango mealy bug under field conditions
Insecticides with powder formulations viz., carbaryl, acetamiprid, methomyl, trichlorophos, thiodicarb, buprofezin and cotton + buprofezin were used for band trial against the 1st instar mango mealy bug for their susceptibility against insecticides at their recommended field doses. The insecticide bands (2 inch diameter) were applied 3 feet above ground level around the trunks. The band was made in the way that first, the trunk (two inches width) was covered with moist soil and then, insecticide was gently applied on the moist soil.
Data collection and statistics
Data was recorded after every three days by adopting the following procedure: A square of 6 x 6 inches dimension above and below the band was made with the help of a pointed needle to record the number of mealy bugs present in that marked square only.
All the data recorded was subjected to statistical analysis by using SAS (2002).
Toxicity of different insecticides against 1st instar under lab. conditions
The results revealed that profenofos gave highest percentage mortality (93.3%) one day post treatment, followed by methomyl, thiodicarb and chlorpyrifos with 90.0, 83.3 and 80.0 % mortality of the 1st instar mango mealy bug, respectively (Fig.1A). The results exhibited that 100% mortality was achieved by using profenofos, methomyl, thiodicarb, methamidophos and chlorpyrifos after three days of treatment. In contrast to this, emamectin benzoate and bifenthrin proved to be least effective by showing 30.0 and 70.0% mortality after seven days of treatment.
Toxicity of different insecticides against 2nd instar under lab. conditions
The data showed that profenofos was the best insecticide after one day of treatment, which gave 86.67% mortality of the 2nd instar, followed by chlorpyrifos (80%) and buprofezin (73.33%).
Profenofos and buprofezin achieved 100% mortality after three days of the treatment, while chlorpyrifos produced 100% mortality four days post treatment. Methamidophos and carbaryl exhibited 100% mortality after five days of the treatment respectively. Conversely deltamethrin provided 100 % mortality after seven days of the treatment (Fig.1B).
Toxicity of different insecticides against 4th instar under lab. conditions Percent mortality of mealy bugs against different insecticides through leaf dip method is shown in Figure 2A. The results in turn revealed that triazophos gave the maximum mortality i.e. 64 % (after 7 days of treatment) followed by methomyl (40.0%), imidacloprid (28.0%), bifenthrin (24.0%), emamectin benzoate (12.0%) and kerosene oil (12.0%). Percent mortality of mealy bugs against different insecticides through foliar method is given in Figure 2B. The results revealed that triazophos provided the maximum mortality of 100%, followed by methomyl, spinosad, imidacloprid, emamectin benzoate, bifenthrin and kerosene oil which gave 96.0, 72.0, 52.0, 36.0, 16.0 and 4.0%, respectively. Percentage mortality of mealy bugs against different insecticides mixed with vegetable oil through foliar application method is displayed in Figures 3.
The results manifested that triazophos and spinosad gave the maximum mortality (100 and 96.0%) of mealy respectively while the band of methomyl gave least control (8.89%). After nine days of insecticidal bands application (Fig. 4) the efficacy of bands decreased and the percentage control by the bands was in the order of cotton + buprofezin greater than acetamiprid greater than carbaryl greater than buprofezin greater than thiodicarb greater than trichlorophos greater than methomyl showing that cotton + buprofezin band was the most effective while methomyl band was the least effective against mango mealy bugs.
The study was conducted to check the efficacy of different insecticides at their field doses as recommended by different insecticidal companies against various instars of D. mangiferae. The results revealed that profenofos, methomyl and triazophos provided effective results for the control of D. mangiferae under lab. conditions. The results are in confirmation with that of Saeed et al. (2007). It indicated that profenofos, chlorpyrifos and methomyl manifested better control of mealy bugs in field experiments. According to Agrello et al. (1992), chlorpyrifos and methomyl manifested good control against the Comstock mealybug, Pseudococcus comstocki (Kuwana) in both the laboratory and field conditions. The results showed that profenofos was the best insecticide for the control of the 1st and 2nd instar D. mangiferae (Fig. 1). Jia et al. (2001) found significant reduction of mango mealy bug through integration of dusting of 25% parathion in micro capsules formulation.
Effective control for the ymphs of mealy bug was reported by the application of 5% phoxim on the ground or painting mixture of 1 kg 40% omethoate + 5 kg mineral oil and spraying 300 times solution of Bt or 2000 times solution of 20% fenpropathrin. However the results of present experimentation revealed that maximum mortality percentage was obtained by using methomyl, imidacloprid, acetamiprid, buprofezin and deltamethrin (Fig. 1).
Different bioassay methods were used to check their efficacy, whether these can contribute in the efficiency of insecticides. The results revealed that triazophos was effective in both methods i.e. leaf dip bioassay and foliar application (Fig. 3). Our results are contrary to that of Ishaq et al. (2004) whose work on the integrated management of mango mealy bug reports that this pest is difficult to control by water based insecticides. So far its management by using sticky bands along with burning and burying treatments significantly reduces the incidence of infestation by mango mealy bug (0.00-15.79%).
In another trial, insecticidal bands were applied in the field conditions on the mango tree, to check the efficiency of different combination of insecticides. The results revealed that the insecticidal band i.e. cotton + buprofezin and acetamiprid showed effective control (92.57- 99.10%) of mealy bug (Fig. 4). The results are in accordance with that of Gul et al. (1997) who worked on D. stebbingi and reported that integration of banding of tree trunks, destruction of eggs by soil working and application of insecticides was the most effective control strategy. Another study related to the application of bands showed that for the control of Drosicha spp. and Rastrococcus iceryoides, exposure of eggs during summer, removal of weeds, conservation of natural enemies, application of alkathane bands and spray of 4% neem seed extract or garlic oil on trunk below band reduced the population (Tandon and Verghese,1985).
Our findings agree with the findings of Bajwa and Gul (2000) who reported similar results on Paulownia spp. attacked by mango mealy bug. They managed this pest through destruction of eggs, banding of trees and application of insecticides together. The studies by Karar et al. (2009) suggested that maximum reduction i.e., 98.46% of mango mealy bug was observed in the application where cultural methods were combined with mechanical and chemical methods. From these results it was concluded that combination of cultural, mechanical and chemical methods of control provided effective control of mango mealy bug. Moreover insecticidal profenofos, methomyl, triazophos and cotton + buprofezin band application are necessary for the effective control of mango mealy bug.
This research was funded by the Higher Education Commission (HEC), Islamabad, Pakistan under the research project "Diagnostic and Research Centers for the Mango Orchards".
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(Received 1 December 2010, revised 14 March 2011)
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|Author:||Hussain, Syed Ismat; Saleem, Mushtaq A.; Freed, Shoaib|
|Publication:||Pakistan Journal of Zoology|
|Date:||Apr 30, 2012|
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