Evaluation role of three insecticides, acetamiprid, lambada-cyhalothrin, chlorpyrifos and two natural oils, clove, bitter orange and mixture of both (1:1) in depress infestation of tomato plant by Liriomyza trifolli, Bemisia argentifolii and Tuta absoluta were carried out under semi field conditions. According to general mean of mortality, clove oil was the highest (60.5%) effect against L. trifolli followed by mix oil (48.3%), while acetamiprid had the lowest toxic effect with 39.6% of reduction. Also, data clarified that lambada and mix oil (clove and bitter orange oils 1:1) were the highest effective against eggs of B. argentifolii, both caused 85.4 and 85.3% reduction in eggs count, respectively, while acetamiprid was the lowest (50.9%). Clove gave satisfactory results against L. trifolli, B. argentifolii and T. absoluta, respectively, thereby; it was concluded that the use them for control tested insects on tomato plants.
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The tomato Lycopersicon esculentum Mill (family, Solanaceae) is a major vegetable crop that has consummate huge popularity over the last century. It is planted in practically every country of the world, in outdoor fields and greenhouses. The tomato plant is very versatile and the crop can be divided into two categories; fresh market tomatoes, which we are concerned with and processing tomatoes, which are grown only outdoors for the canning industry and mechanically harvested. In cases, world production and consumption has grown quite rapidly over the past 25 years (FAO., 2000). Tomato is one the most important economic vegetables in Egypt so far as the area under vegetables and commercial value of the crop is concerned. The tomato is considered as one of the few cultures for which pests and diseases are equally important, being a host plant to about 200 species of arthropods (Anonymous, 2001). Insect pests destroy crops in the field through their biting, chewing, boring, sucking and defoliation (Shalaby et al., 2012). A chemical designed to keep pests and primarily insects, away from agricultural plants. The application of synthetic pesticides has caused threat to non-target organisms and the environment due to their overuse (Savary et al., 2006). Since the release of xenobiotic results in the increase of environmental risk, the goal should be to use such compounds carefully so that they cause least negative impact on the environment (Savary et al., 2012) into which they are released. In recent years, a move toward biopesticides has been observed due to concerns over health problems caused by the use of chemicals. To determine the effectiveness of pesticides, experts look at plants to see if holes have been bored in their leaves or bite-marks are found on the flowers. Some insects will leave a sticky residue on the leaves, as well, or the bugs might actually be seen on the plant. Pesticides are necessary to keep our agricultural plants safe from insect infestation (Mahmoud et al., 2014). Natural pesticides are increasingly preferred, as they reduce the number of chemicals that are released into the environment (Hanafy and El-Sayed, 2013). Therefore, the present work was carried out to compare the relative toxicity of some chemical insecticides with three natural oils against Liriomyza trifolli, Bemisia argentifolii and Tuta absoluta on tomato plants.
MATERIALS AND METHODS
The experiment was run to compare the efficiency three of recommended insecticides and two of natural oil toward some of tomato insects under semi-field condition as follows:
|•||Acetamiprid 20% SP (Mospilan), 15 g/100 mL/5 pots|
|•||Lambda-cyhalothrin 5% EC (Lambda), 250 mL/100 mL/5 pots|
|•||Chlorpyrifos 48% EC (Pestban), 0.5 L/100 mL/5 pots|
|•||Clove oil (Syzygium aromatic L.) 10 μL/100 L, was obtained from Sigma (Germany)|
|•||Bitter orange (Citrus aurantium amara) 10 μL/100 L, was obtained from Haraz (Saudia Arbia)|
|•||Mix (Clove: Bitter orange, 1:1) 10 mL/100 L|
Each concentration of tested oils was mixed with one drop of Tween (60%) and glycerin (99%) to emulsify them with water.
Design of experiment: The test was carried out under semi-field condition. The tomato plant was planted in plastic pots (50×50×20 cm3) and placed in isolated area at National Research Center and covered by plastic ceiling to protect plant from dewy fall (Fig. 1). Each pot was prepared by added usual fertile soil and planted with three saplings of tomato plants (two weeks old). After three weeks of plantation was started the test by spraying the plant shouts by the prepared materials. The experiment was divided into seven treatments, the 1st, 2nd and 3rd treatments were treated by the following insecticides; lambada-cyhalothrin, acetamiprid and chlorpyrifos. While, the 4th, 5th and 6th treatments were treated by clove, bitter orange and mix of both oils (1:1), using the same rate according to Moawad et al. (2015). Seventh treatment was left untreated to serve as control. Each test was replicated five times. The evaluations against white flies (Bemisia argentifolii) and leaf miner (Liriomyza trifolli) were conducted on 20 leaflets (Gonzalez-Cabrera et al., 2011) were randomly collected from each replicate before spraying as well as 3, 5, 7, 10 and 15 days after spraying. The outer plants were never sampled in order to avoid border effects. Alive and dead larvae of L. trifolli; eggs and nymph of B. argentifolii were counted using a binocular microscope. On other side, to evaluate the infestation percent tomato plants by Tuta absoluta was recorded after two month of treatment. Percent reduction in infestation was calculated by using study of Henderson and Tilton (1955).
|Fig. 1:||Design of semi-field experiment was covered by plastic ceiling barrier to protect test from dewy or rain drop out|
RESULTS AND DISCUSSION
Efficiency of tested compounds against Liriomyza trifolli: Data in Table 1 revealed that lambada-cyhalothrin give highest mortality of L. trifolli larvae (69.1%) after three days of the application, followed by chlorpyrifos (59.2%) then Clove oil (56.8%). While the lowest mortality was noticed in acetamiprid insecticide (21.4%) followed by Bitter orange oil (38.2%). After 5th day the mortality percent was increased in plants treated by acetamiprid, Clove and Bitter orange (43.7, 61.4 and 40.1%), but it decreased in case of lambada, chlorpyrifos and mix oils (60.0, 53.6 and 49.1%, respectively). This trend was happened after 7 days. Obtained data after 15 days, natural oils more effective against L. trifolli compared with other insecticides. According to mean of mortality, clove oil was the highest (60.5%) effect on study pest followed by mix oil (48.3%), while acetamiprid had the lowest toxic effect with 39.6% of reduction (Fig. 2). These results agreement with those obtained by Sabbour and Abd-El-Aziz (2010), they reported that mustard and clove oils revealed a strong repellent activity after 7 days (89 and 71%, respectively) against B. incarnatus beetles.
The damage caused by L. trifolli is by feeding puncture, oviposition puncture and larval mines (Tilden, 1950). Data in Table 2 revealed the reduction percent in tunnels counts after tested insecticides and natural oils. The microscopic examination of tomato leaflets revealed that the reduction percent of tunnels count after 3 days of application ranged from 28.2-49.8%. This percent was increased after 5 days and reached its peak at 7 days (ranged from 43.4-84.0%), then decreased gradually after 10 and 15 days. General mean of reduction percent indicate that chlorpyrifos more effective as compared with other compounds followed by Clove oil (52.5 and 48.7%, respectively), while mix oil (Clove and Bitter orange) had the lowest effect (39.5%) (Fig. 3).
Effect of tested compounds on bemisia argentifolii: Results concerning the efficiency of tested compounds against eggs and numphal stages of B. argentifolii infesting tomato plants are presented in Table 3 and 4. After 3 days of application tested compounds caused considerable reduction in the eggs number (Table 3) ranged from 62.3-88.7%. These percent were decreased in acetamiprid, lambada insecticides and clove oil treatments (68.9, 82.6 and 61.8%, respectively), while it was increased in other treatments. By prolonging time after application, the efficiency of acetamiprid was decreased to 15.6% after 15 days, but it was increased in other treatments, chlorpyrifos had the highest effect with 96.4% reduction, followed by clove oil with 93.2%, then lambada-cyhalothrin and mix oil with 92.4%. The obtained data clarified that lambada and mix oil (Clove and Bitter orange oils 1:1) were the highest effective against eggs of B. argentifolii, both caused 85.4 and 85.3% reduction in eggs count, respectively (Fig. 4), while acetamiprid was the lowest (50.9%).
Table 4 indicated that the mortality percent of B. argentifolii nymph was ranged from 26.5-78.0% after 3 days for application, the high toxic effect was noticed in mix oil treatment followed by lambda, while the lowest effect was happened in Bitter orange oil. The mortality percent was fluctuated during experiment period and its reached 42.7, 54.1, 75.1, 73.7, 42.8 and 34.3% after 15 days in tomato plants treated by acetamiprid, lambda, chlorpyrifos, clove, bitter orange and mix oil, respectively.
|Table 1:||Effect of some insecticides and natural volatile oils on Liromyza trifolli infested tomato plants|
|Table 2:||Effect of some insecticide and natural volatile oils on tunnels count/20 leaflets of infested tomato plants by L. trifolli|
|Table 3:||Effect of some insecticide and natural volatile oils on eggs count of B. argentifolii/ 20 leaflets of tomato plants|
|Table 4:||Effect of some insecticide and natural volatile oils on nymphal stage of B. argentifolii|
|Fig. 2:||General mean of mortality percent (%) of tested compounds on L. trifolli|
|Fig. 3:||General mean of reduction percent (%) of tunnels count/20 tomato leaflets infested by L. trifolli|
|Fig. 4:||General mean of reduction percent (%) in eggs count of B. argentifolii/ 20 tomato leaflets|
Also, obtained data revealed that use of Clove oil and Bitter orange oil alone gave 43.5 and 36.9% reduction of nymph count, while mixture of both (1:1) induced 60.6% average of percent reduction (Fig. 5). These results agree with those obtained by Mousa et al. (2013), who reported that, garlic oil was the best efficient in reducing the population of leafhoppers and planthoppers by a mean reduction percentage of 68.09%, followed by the two chemical insecticides dimethoate 67.90% and pestban 64.02% and Eucalyptus oil was the least in this category as 43.27%.
|Fig. 5:||General mean of mortality percent (%) of numphal stage of B. argentifolii/20 tomato leaflest|
However in controlling aphids, also garlic surpasses again by a mean overall reduction 90.96%, followed by pestban 89.44%, while eucalyptus oil came in the third rank as 80.66% before the dimethoate which achieved the least rank in controlling aphids as 76.14%.
In this context, the obtained data revealed that the toxicity of pyrithroid compound (lambada-cyhalothrin) and natural mix oil (clove and bitter orange, 1:1) was higher than that of other treatments. In this respect, one might suggest the use of both compounds as adequate treatments to achieve satisfactory control against B. argentifolii. Essential oils may have attractive or repellent effects and in some cases they showed insecticidal action against certain insect pests. Oils isolated from plants which consist of cyclic and monocyclic mono-terpens proved effective repellents against insects (Rodriguez and Levin, 1975). It was found that these bioactive compounds are potentially toxic to insects and mites but relatively safe to human and wildlife. Recently, there is a great need to find alternative pesticides instead the traditional chemical insecticides which proved to have toxic effect on human, animal and on the whole environment. Some essential oils are extracted from natural sources, such as eugenol which is extracted from clove fruits (Farag et al., 1991).
Effect on tuta absoluta: The results indicated that the infestation percentage of T. absoluta to tomato plant affected by all treatment; although the investigation was carried out after month of application (Table 5). There is no observed big variation between treatments by chemical insecticide and natural oils, i.e., the reduction% of infestation ranged between 60-50% and real mortality percentage ranged between 88-77%; except in case of spraying with mixture of oils and Lambada. The most of application able to protect tomato plant from early attack of tomato leafminer, especially treatment by clove oil which caused reduction in infestation reached to 62.5% and mortality 87.3%.
|Table 5:||Effect of some insecticide and natural volatile oils on Tuta absoluta|
|*Reduction(%) = T-C/C X100|
In the same respect, Moawad et al. (2015) reported that mixed clove, bitter orange and zinc sulfate together had ability to cause highest mortality to T. absoluta larvae reached 97.0%.
Pest management is facing economic and ecological challenge worldwide due to human and environmental hazards caused by majority of the synthetic pesticide chemicals. The obtained results were spot light about the ability of natural oils to relatively protect tomato plant and serving as an alternative to insecticide. There are many authors evaluated efficacy of essential oils and agree with the achieved of present results as (Dos Santos et al., 2010; Regnault-Roger et al., 2012; El-Wakeil, 2013; Ootani et al., 2013; Regnault-Roger, 2013; Cavalcanti et al., 2015). Moawad et al. (2013) recorded that Clove, eugenol and isoeugenol caused highly reduction percentage of penetration and accumulative mortality of larvae and caused ovipositional deterrence reaction towards adult stage of T. absoluta under lab. conditions.
Generally, the extensive and unwise use of synthetic pesticides in the control programmers against agricultural pests often creates in major deleterious side effects. Fortunately, natural oils (Clove) gave satisfactory results against L. trifolli B. argentifolii and T. absoluta, respectively, thereby; it was concluded that the use them for control mentioned tomato insect pests as alternatives to the classic pest control agents.
This study in the part of the project No. 10120614 (2013-2016) funded by National Research Centre (NRC), Cairo, Egypt.
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