Comparative efficacy of indigenous plant extracts and a synthetic insecticide for the management of tomato fruit worm ( Helicoverpa armigera Hub . ) and their effect on natural enemies in tomato crop

Efficacy of five botanical extracts (eucalyptus, bakayan, chilli, thyme and onion extract) and synthetic insecticide (Steward 150 EC) was evaluated against H. armigera and its associated natural enemies under field conditions during 2014, followed Randomize Complete Block Design with three replications. Results revealed that all the tested botanicals and insecticide were found effective in controlling the tomato fruit worm infestation as compared to control. Among all the tested spray materials, Steward 150 EC was found the most effective in reducing H. armigera larval infestation (61.01%) followed by bakayan extract (44.49%). However, the steward 150 EC was comparatively more toxic to the natural enemies than botanicals. Fruit infestation was minimum in Steward tested plots and maximum in control on weight basis and on number basis 10.53% and 10.29% and 30.88% and 29.11% respectively. Similarly, Steward treated plot yielded the highest (9564 kg ha) and control yielded the lowest (5487 kg ha). It was concluded that Steward 150 EC was the most effective in managing fruit worm infestation and hence resulting the minimum fruit damage and consequently enhanced the yield of tomato. However, the synthetic insecticide was extremely toxic to the natural enemies. Furthermore, eucalyptus, chilli, onion and thyme extract also showed better results than control in term of pest reduction and were comparatively safe to the natural enemies, Hence these botanicals should be included in IPM program for the suitable management of H. armigera associated with tomato crop.


Introduction
Tomato fruit worm (H.armigera Hub.) is one of the devastating pest of tomato resulting in considerable yield losses i.e. 32-53 % annually [1].Initially pest starts feeding on leaves, flowers and finally bore into tomato fruits, making them unfit for human consumption and also reduce its market value [2].Being a polyphagous pest, annual loss of approximately 5 billion US dollars has been attributed to H. armigera worldwide [3].To deal with this potential and notorious pest, 85% of the word insecticide is used to manage this pest [4].This incredible use of synthetic insecticide has led to the problem of pest resurgence, insecticidal resistance in insects, environmental pollution, health problems, decimation of useful fauna and the increased cost of pest controls as well [5].In order to address all these issues, it has become imperative to explore the substitutes of these toxic insecticides to keep the H. armigera population below injury level and have no harmful effect on biocontrol agents [6].One such alternate is the use of plant extracts.The use of plant extracts has been given major emphasis in IPM Programme.Compared to other commonly used synthetic insecticides, plant extracts are safe for both the pesticide user and consumer of the treated crop as well as to non-target animals and humans.Mostly the farmers rely on conventional synthetic chemicals to control insect pest and little attention has been made to explore the indigenous fauna having insecticidal properties that is ecofriendly and safe for nature enemies.The concept of botanicals extracts is not particularly new and some important practical progress has been made in other crops/ insects.Hence, an attempt has made to evaluate the efficacy of indigenous plant extracts i-e.Melia azedarach, Thymus volgaris, Eucalyptus tereticornis, Allium cepa and Capsicum annum on H. armigera and its associated natural enemies as alternative to synthetic insecticide for the sustainable management of tomato fruit.

Materials and methods
The current experiment was carried out at New Developmental Farm (NDF) of The University of Agriculture, Peshawar during spring 2014, to evaluate the efficacy of various indigenous plant against tomato fruit worm (H.armigera) and its associated natural enemies in tomato crop.

Field layout and experimental design
Seedlings of tomato variety (Riogrande) were transplanted in 2 nd week of March followed randomized complete block design (RCBD) with three replications.Plot size was 1.5 x 3 square meter.Plant to plant and row to row distance was maintained 45 cm and 90 cm respectively.Standard agronomic and cultural practices were applied uniformly to all experimental plots.

Treatments and its application
All the plant extracts and insecticide (steward) were sprayed twice by Knap Sack sprayer at 15 days interval.At the time of spray, polythene sheet was hanged around each plot to protect the adjacent plots from the drift effect of spray application (Table 1).

Yield
Yield in different treatments was recorded at each picking from net plot area.Total yield was calculated by adding the yield from all picking for each treatment and then converted in to yield per hectares with the following formula: Yield (kg ha -1 ) = Yield plot -1 x 10000 Plot size

Statistical analysis
All the above parameters were subjected to the analysis of variance and means were separated using LSD test at 5% level of significance.

H. armigera larval infestation
Results on efficacy of different botanicals and a synthetic insecticide against H. armigera larval infestation showed that all the tested treatments were significantly superior in reducing the larval population (Table 2).However, two sprays application of Steward was found to be the most effective after 24 hr, 48 hr, 48 hr and 7 days with maximum mean reduction (61.01%) in the larval population of H. armigera followed by Bakayan extract with a total larval reduction of 44.49%.

Natural enemies population
In the present study, two natural enemies (Green lacewing and ladybird beetle) were found to be associated with tomato crop.The presences of these natural enemies in the field play an important role in the population fluctuation of the pest.Previous studies showed that steward is safe and selective insecticides [18].However, table 3 clearly indicated that both natural enemies were significantly affected by the tested treatment applications.In both spray application, insecticide steward found more toxic to both the natural enemies (ladybird beetle and green lacewing) with mean percent reduction of 58.87% and 44.61% respectively.Similar finding has also been reported by [19,20] that Steward found from slight to moderate toxic against the green lacewing (Chrysoperla carnea) (68.8-84.8%mortality).Similarly, [21,22] revealed that Steward significantly reduced number of predators in field and is slightly toxic to the egg parasitoid Trichogramma chilonis as well.However, all the tested botanicals were comparatively least toxic and found statistically at par with each other.However, based on mean percent reduction, Chilli extract found relatively safer than other tested botanicals with minimum reduction of 16.64% and 20.33% in ladybird beetle and green lace wing population respectively.Present finding showed that steward was very effective and gave maximum mortality of the target pest (Table 2).However, it was slightly toxic to the natural enemies as presented in (Table 3).The present study indicated that two spray application of insecticide steward significantly reduced both the predators' population in tomato crop as compared with botanicals.It is clear from this study that botanical extract reduce insect pest infestation and is comparatively safe to the natural enemies.The present findings are in agreement with [23] who found that botanicals (neem) significantly reduced insect pest infestation.Similarly, in the present study predators population was significantly higher in botanicals treated plots as compared to synthetic insecticide, indicating that neem insecticide was

Percent fruit infestation
Results on fruits infestation by H. armigera larvae showed significant variation in tomato (Table 4).Fruit damage was lowest (on weight as well as on number basis) in Steward treated plot 10.29 % and 10.53% respectively and highest in control with 30.88% and 29.11% respectively.Similarly among the botanicals, Bakayain extract was found the second best treatment with 14.58% fruit damage on weight basis and 15.38% on number basis followed eucalyptus and onion extract.While thyme extract proved least effective with high fruit damage as compared to the rest of botanicals.Steward was the most effective, resulting in significant decrease in fruit damage over control on weight basis (66.67%) and on number basis (63.82%) followed by Bakayan extract, while the thyme extract found to be the least effective in reducing the fruit damage 18.20% and 20.85 % on weight and number basis respectively (Table 4).Similar finding has also been reported by [10] that synthetic insecticide was found superior over botanicals when evaluated against tomato fruit worm.Present study also showed that plant with highest larval infestation had highest degree of fruit damage and vice versa.Our results are in agreement with [8] that high larval infestation resulting high fruit infestation.Similarly, [25] reported that fruit worm infestation could cause serious damage to tomato by boring into the fruits thereby reducing the fruit weight, yield and market value as a result of larval feeding within the fruit contents.Thus the reduction of H. armigera larval infestation subsequently led to a reduction in damaged fruit.Yield (kg ha -1 ) Table 5 shows that tomato yield was significantly affected by tested botanical extracts as well as synthetic insecticide.Highest (9564 kg ha -1 ) tomato yield was recorded in case of steward treated plots with maximum (74.30%) increase in tomato yield over control plots.It was followed eucalyptus extract (8359 kg hac - 1 ), bakayain extract (8076 kg ha -1 ), chilli extract (7512 kg ha -1 ), onion extract (7102 kg ha -1 ) and thyme extract (6410 kg ha -1 ) with 52.34%, 47.18% ,36.90 and 29.42 % increase in yield over control respectively.Similarly, the lowest yield (5487 kg ha -1 ) was recorded in control plots.This variation in yield may be due to the different level of larval infestation after the application of different spray application.It has also been observed that the pest initially fed on fresh tender leaves, flower and later on entered into tomato fruits which ultimately affected fruit yield.

Conclusion and recommendation
Based on current study, it was concluded that the new chemistry insecticide, Steward 150 EC proved the most effective in controlling the fruit worm infestation and consequently led to better fruit protection with significant increase in tomato production.However, it is more toxic to natural enemies.Hence, the use botanical extracts (bakayan, chilli and onion) is the better alternative to synthetic insecticide as they are cheap, easily available and relatively safe to the natural enemies and other non-target species.Therefore, it is recommended to use different plant based, indigenous botanical insecticides such as eucalyptus, chilli and onion etc. in IPM programs for the sustainable management of H. armigera in tomato and other crops.

Table 1 . Detail of different botanical extracts and a synthetic insecticide used in the experiment
% damaged fruits (number basis) = Number of damaged fruits x 100 Total number of tomato

Table 2 . Effect of plant extract and synthetic insecticide on H. armigera larvae infesting tomato crop during 2014
Means in columns with different letters are significantly different at p = 0.05 using LSD Test