Management of Green Peach Aphid, Myzus Persicae Sulzer Hemiptera: Aphididae , in Potato Crop

Research experiments were conducted in Khyber Pakhtunkhwa province of Pakistan during 2007-09 to develop an IPM package for green peach aphid, Myzus persicae (Sulzer), in potato crop, having minimum adverse/detrimental effects on its natural enemies including ladybird beetle, syrphidfly and green lacewing. Parasitized M. persicae mummies, percent parasitism of M. persicae by the Aphidius (PPAA), percent emergence rate of the Aphidius from M. persicae mummies (PERA), and fecundity rate of the Aphidius (FRA) were explored. Initially, impact of three different agro-climatic locations/zones, seasons and nine potato varieties were compared for abundance of M. persicae and its natural enemies. Varietal resistance to M. persicae was re-confirmed through antibiosis test. Later, two foliar [Provado 1.6F (imidacloprid) and Actara 25WG (thiamethoxam) and two soil routed insecticides [Admire 2F (imidacloprid) and Platinum 2SC (thiamethoxam)], in separate experiments, were tested at labeled and reduced doses (by 20%) on resistant Kuroda and susceptible Desiree varieties for their impact on the corresponding parameters and yield. Lastly, yellow water pan traps and reduced doses of Provado and Admire were compared alone and in combinations on Kuroda and Desiree with same objectives. The mean populations of M. persicae and its natural enemies during spring were much higher than fall, in all the locations. During spring, the mean population of M. persicae was highest at Mingora and lowest at Malakandair. During fall, it was highest at Malakandair while at Mingora and Abbottabad it was statistically equal. During spring, the ladybird beetle population at Abbottabad was higher than Malakandair while at Mingora it was statistically equal to both the locations. During fall, it was significantly higher at Malakandair than Abbottabad and Mingora that were statistically equal. Averaged over seasons, syrphidfly population was significantly high at Abbottabad and low at Malakandair; green lacewing population at Abbottabad was higher than Malakandair while at Mingora it was statistically equal to both the locations. Population of parasitized M. persicae mummies during each season was statistically equal at Abbottabad and Mingora but higher than Malakandair. In each location; the populations of M. persicae and its natural enemies were gradually building up till Day 60 during spring and Day 45 of the seeds germination during fall, thereafter they started decreasing up to Day 75 i.e. crop maturity. Among the potato varieties, in each location during spring, Kuroda and Desiree responded as the most resistant and susceptible to M. persicae population build up, respectively. During fall; the varieties did not differ for this parameter at Abbottabad and Mingora while at Malakandair both varieties responded similar to spring. Antibiosis test, during spring at Malakandair, gave similar results wherein the rm value for M. persicae was highest on Desiree and lowest on Kuroda. Taking into account all the experiments; the mean populations of M. persicae on Kuroda control plants was lesser than Desiree by 49.9-45.8% while the ladybird beetle, syrphidfly, green lacewing, parasitized M. persicae mummies, PPAA, PERA and FRA were higher 13-4.4, 61.6-35.4, 32.1-19.8, 46.9-39.6, 54.1-17.8, 9.0-4.3 and 27.9-13.2%, respectively. Considering the population difference as a parameter, in foliar experiments the imidacloprid reduced dose was less toxic to M. persicae than its labeled dose but significantly more toxic than both the doses of thiamethoxam. At the same time its reduced doses were significantly less toxic to natural enemies than its labeled dose and both the doses of thiamethoxam. Soil routed experiment gave similar results except that for M. persicae and FRA this interaction was not significant. Excluding the difference among control plants; the foliar and soil routed insecticides (at an average) reduced M. persicae on Kuroda more than Desiree by 0.5 and -7.3%, respectively, while the corresponding natural enemies were observed at reduced number by 4.9 and 9.3, 10.6 and 26.5, 12.6 and 29.0, - 0.4 and 3.3, 1.0 and -3.0, 5.8 and 5.8, 0.0 and -11-6%, respectively. The difference between labeled and reduced doses of foliar insecticides, to reduce M. persicae population, on Kuroda was 5.7% and for De it was 4.8%; while for soil routed insecticide this interaction was not significant. Kuroda vs Desiree comparison (on each formulation) showed that Kuroda treated with reduced doses was next to Kuroda treated with labeled doses; however, had smaller mean population of M. persicae than the Desiree treated with labeled doses. In foliar experiment; Kuroda treated with reduced doses was the least toxic, Kuroda treated with labeled and Desiree with reduced doses were nearly equally toxic whereas Desiree with labeled doses was the most toxic to natural enemies. In soil routed experiment; Kuroda treated with Admire reduced dose had significantly highest population of ladybird beetle than all other treatments except Kuroda and Desiree control plants. Kuroda treated with reduced dose of Admire and Control (being statistically equal) had significantly highest populations of syrphidfly and green lacewing than other treatments including Desiree control plants. Minimum numbers of ladybird beetle, syrphidfly and green lacewing were recorded on Desiree treated with labeled dose of Platinum. Population of parasitized M. persicae mummies on Kuroda treated with reduced doses was statistically smaller than Kuroda control but significantly highest than all other treatments including Desiree control. Kuroda control and Desiree treated with reduced doses (being statistically equal) had significantly higher PPAA and PERA than Kuroda and Desiree plants treated with labeled doses; however, maximum were recorded on Kuroda control followed by Desiree control plants. Highest yield in both the experiments was obtained from plant treated with labeled and reduced doses (being statistically equal) of imidacloprid than thiamethoxam and lowest from control plants. At an average; Kuroda delivered significantly higher yield than Desiree. The last experiment; as per significant interactions, showed that Kuroda treated jointly with Provado reduced dose and yellow water pan traps was the most effective to reduce M. persicae as compared to least effective treatment that was Desiree Control. Highest population means of ladybird beetle next to yellow water pan trap and Control (being statistically equal) was recorded on plants treated with Provado reduced dose + yellow water pan and reduced doses of Provado or Admire (being statistically equal). Yellow water pan traps, Control, and plants treated with reduced dose of Provado + yellow water pan traps (being statistically equal) had significantly highest populations of syrphidfly and green lacewing than other treatments. Highest means of parasitized M. persicae mummies, PERA and FRA were recorded on Kuroda treated with Provado reduced dose or jointly with yellow water pan traps (being statistically equal); except Kuroda control with or without yellow water pan trap. Kuroda plants treated with Provado reduced dose + yellow water pan, and Kuroda control had significantly highest PPAA than all other treatments except Kuroda plants treated with yellow water pan traps. Minimum numbers of the natural enemies were recorded on Desiree plants treated with Admire reduced dose or carrying yellow water pan traps. Maximum yield was obtained from Kuroda treated with Provado reduced dose + yellow water pan traps and minimum from Desiree control plants. These findings indicated that resistant potato variety ‘Kuroda’, treated with yellow water pan traps and Provado 1.6F reduced dose was the better IPM package to manage M. persicae with minimum adverse/detrimental impact on its associated natural and enhancing tuber yield significantly.