Research Article
Management of Aphid (Myzus persicae) on Autumn Sown Potato Crop
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Muhammad Idrees Khan
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Rashid Mahmood
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Muhammad Naeem
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Potato (Solanum tuberosum) is the worlds most important food crop with annual production of nearly 300 million tones on more than 12 million hectares (Martin et al., 1990). Three crops of potato are annually grown in Pakistan, i.e., autumn and spring crops in the plains and summer crop in the hills (Anonymous, 1991a). The total area under potato cultivation was 72900 hectares with an average production of 10 tones per hectare, where as in NWFP the crop was grown on 6900 hectares with an average yield of 13.4 tones per hectare (Anonymous, 1991b).
Aphids infest the foliage of potato crop (Panajotou and Katis, 1986) and is a vector of "PVY" (Potato Viral Yellows) (Turl and Mc-Donald, 1987) and leaf roll mosaic (Palgrave, 1972). On the crop planted on 1st Sept. the aphid population reached a peak number in the 1st week of Nov. and declined thereafter. The pest disappeared by the 3rd week of December (El-Saadany and Fattah, 1980). The pest M. persicae was also observed in the 1st week of December with 1.68 aphids per plants, which increased to 9.01 per plant in the 4th week of January (Anwar et al., 1987).
Among the management practices, vegetational diversity is a useful tactics in the control of insect pests in various agroecosystems. It might change herbivore population and interferes with visual host finding cues. Mix culturing also disrupts the olfactory cues of the pest in host finding and once the pests leave the polycuture, they have difficulty in locating and relocating their host plants (Shahjahan and Streams, 1973 and Andow, 1992). Similarly the subsequent removal of alfalfa in the dicultural agroecosystem reduced the herbivore population in the alfalfa-soybean mix cropping (Poston and Pedigo, 1975).
Organophosphorus sprays were used against M. persicae when population density reached 71500/100 leaves which increased the tuber yield of potato about 10 % (Southall and Sly, 1976). Carbofuran (Curater) used as granules and sprays against M. persicae showed good effects on potato yields (Koble, 1975).
For monitoring and control of aphids, large (150 x 100 cm2) medium (20 x 25 cm2) or (20 x 40 cm2) and small (12.5 x12.5 cm2) sticky plastic sheets in various directions were found equally effective (Shahid, 1986; Ali, 1986; Rehman and Shahid, 1988).
Keeping in view the importance of the crop and the damage caused by the aphid, a research project was initiated to determine the population density of aphids, to assess the effect of Potato- Berseem and Potato- Radish mix / Inter cropping over the relative effectiveness of four insecticides on the population density of aphids and to determine the effect of yellow sticky plastic sheet traps for monitoring and control of aphids.
Research project was under taken at the Agricultural Research Farm, NWFP Agricultural University, Peshawar. Commercial cultivar AAl-Thamash@ was sown on 10th September, 1994 on an area of 720 m2 in 32 sub plots (8 treatments x 4 replications) each measuring 5 x 4.5 m confined to Randomized Complete Block Design (RCB Design) with DMR Test at 5% level of significance (Walter, 1967). The distance between plots was ½ m, between the rows 75cm and between the plants 20cm was maintained. There were six rows each having 25 plants in every sub plot containing in all, 150 plants. At the sowing time, "DAP" fertilizer was applied at the rate of 2 bags ha-1. The data on insect pests was recorded at weekly interval from date of sowing to harvest. Treatments details are given as under:
Insecticidal trials
T1: | DDVP 80% | @200 mlacre-1 |
T2: | Anthio 25 EC | @250 mlacre-1 |
T3: | Monitor 600 EC | @500 mlacre-1 |
T4: | Laser 25 EC | @500 mlacre-1 |
T5: | Check | (Untreated plots for population density) |
Non insecticidal trials
PBM | Potato-Berseem mix cropping |
PRM | Potato-Radish mix cropping |
YPT | Yellow plastic sheet traps |
Sampling and analysis for aphids
Population dynamics: In each sub plot three plants were randomly selected. Aphids were counted on leaves of the top, middle and bottom branches of the plant.
Yellow plastic sheet trap flag (YPT): Aphids are attracted to yellow color which helps in monitoring and to some extent to control the winged form aphids (alate). A plastic sheet of 30x30 cm2 on wooden frame was fixed one meter above the ground level in T3 during the crop was emerged. Common mobile oil was used as adhesive material on the sheet for aphids and the sheet would cleaned and applied the material at fortnight interval as done by Shahid (1986). The aphids were counted on both plant leaves and plastic sheets.
Mix/inter cropping system: Berseem and radish were mix sown separately after thirty days of potato sowing. But before sowing, all the agronomic practices to potato crop like hoeing, soil raising and tilling were completed. Berseem was sown between the ridges with broadcast method while radish was sown on alternate edge of ridges as directed by the Department of Farm Management. Berseem was removed subsequently at fortnight intervals for fodder purposes whereas full grown leaves of radish were left as such and removed at the time when potato crop was harvested. The population of aphids were recorded only on the leaves of potato crop.
Insecticide application: The insecticides were used at the recommended doses in T1, T2, T3 and T4 respectively. These insecticides were sprayed once during second week of December. Besides routine data, data one day before the spray and three data at one day interval after spray was recorded to find the comparative efficacy of the insecticides.
Results and Discussion
Population dynamics: The population of both forms of the aphids (wingless aphids from the leaves and winged (alate) on the yellow sheets) were recorded. The pest was flowed out during September that gradually reached a peak in December and then decreased thereafter (Fig. 1 and 2). On the leaves, the pest emerged during October. Maximum population (43 aphids per leaf) was found during December with highest seasonal mean 15.55 per leaf. Previously the highest population of Myzus pesicae. on the crop planted on 1st Sept. was recorded in the 1st week of Nov. which declined thereafter and disappeared by the 3rd week of December (El-Saadany and Fattah, 1980). The pest was also observed in the 1st week of December with 1.68 aphids per plants which increased to 9.01 per plant in the 4th week of January (Anwar et al., 1987).
The emergence of the alate form of the aphids occurred during the third week of September that remained active till second week of January (Fig. 2). The pest was abundant from last week of November till third week of December. The peak (235 aphids/YPT) was found during the second week of December. In past, these sheets were used by Shahid (1986), Ali (1986) and Rehman and Shahid (1987) for the control of aphids.
Management tactics: All the management tactics were found better and effective against aphid. Among the mix cropping system, PBM (Potato-berseem mix grown) was far better than PRM (Radish-potato mix grown). Similarly in the plots reserved for yellow plastic sheet (YPT), the population of the wingless aphids was significantly lower. Among the four insecticides, Monitor was found significantly good against aphids and the other three insecticides were found similar in action.
Response of (Myzus persicae) to mix cropping: Seasonal means of aphid population was 4.62 in PBM, 8.05 in PRM with 70.3% reduction in PBM and 48.23% in PRM against 15.55, in control plots (Table 1). The reason for low population in PBM and PRM may be the effect of diverse habitat, as it is thought that in polyculture insect pest population is considerably lower than in monoculture. Tehvanainen and Root (1972) called the phenomenon as Associational; resistance which refers to reduced herbivore attack that a plant experience in association with genetically or taxonomically diverse plant habitat. Andow (1992) suggested herbivore were more likely to find and remain on host plants that occur in large, dense and pure stands. Plant species diversity, when interferes with visual host finding cues in locating and relocating host plants after leaving polyculture, alter the herbivore population.
PBM verses PRM: In PBM 42.6% more aphids were reduced than in PRM (Table 1). The reason for the lowest population in PBM was that berseem was cut at various intervals subsequently for fodder purpose while radish left undisturbed to grow uniformly. However both the crops were terminated along with potato crop. Subsequent removal of berseem at different interval disrupted the olfactory and visual cues of aphids due to which the pest could not relocate its host, was therefore, unable to re-establish its population in PBM and thus confirms the findings of Shahjahan and Streams (1973) and Andow (1991). Similarly it is also observed that radish is a broad leafed plant which is believed that aphids are more attracted to broad leaf as Andow (1992) studied many Empoasca spp. and E. fabae in particular are more attracted to broad leafed weeds in diverse plant habitat whereas population reduces when grassy weeds i.e., maize sugarcane etc are used in polyculture habitats.
Fig. 1: | Population of aphid in different months of year 1994-95 |
Fig. 2: | Monitoring of number of aphids through yellow sticky plastic sheets |
Table 1: | Pest population of insect pests of autumn potato crop in mix cropping system |
Table 2: | Percent reduction in aphid population after insecticide application |
Means followed by different letters are significantly different at 5 % level of significance. |
Table 3: | Comparison among the insecticide applications for percent reduction (%) in aphid population (%) |
Table 4: | Mean Population Density of Aphids per branch of Potato plant at Malakendher Farm of the NWFP Agricultural University Peshawar, Pakistan |
Relative efficacy of insecticides: Four insecticides DDVP, Anthio, Monitor and Laser were applied during second week of December. All the insecticides controlled more than 65% of the pest after one day of the spray which increased to more than 80% during second day after spray. Similarly on the third day of the spray more than 90% of the pest reduced (Table 2). On average, more than 80% of the population of aphids were reduced in three days after spray.
Among the insecticides, Monitor was found more efficient as 92% of aphids were reduced which was followed by Anthio which reduced 86% of aphids. Previously Organophosphorus sprays were used against M. persicae when population density reached 71500/100 leaves which increased the tuber yield of potato about 10 % (Southall and Sly, 1976). Carbofuran (Curator) used as granules and sprays against M. persicae showed good effects on potato yields (Koble, 1975).
Analogy among the treatments: Among the treatments YPT, PBM and Monitor were found most effective as lowest population of aphids were recorded during the entire growing season (Table 3). In YPT 72%, in PBM 70% and in the plot reserved for Monitor 52% of the aphid population remained lower than in control plots. In the remaining treatments less than 50% of the population was recorded during the intact growing season of the potato crop. However all the treatments were better than the control plot.
During September to November pest was gradually increased and then reached the peak during December (Table 4). Plots reserved for the insecticidal application and the control were almost similar till November because no insecticide was applied till 11th December in which the pest population was significantly dropped after the applications. Among the non insecticidal treatments, PRM was statistically less effective against aphids as compared to PBM and YPT. For aphid management, the three types of practices, (diverse culture, yellow plastic sheet trap and insecticides) were found most effective. Among the diverse culture practices, potato-berseem mix cropping was significantly better than potato-radish mix cropping. Similarly YPT was used efficiently to monitor and control the alate form of aphids. Although there were no apparent differences among the insecticides, monitor was however found slightly better against aphides.