Control failures with several chemicals have prompted research into the resistance status of Tuta absoluta and the effectiveness of certain active ingredients against this pest. In this context, a comparison was made of the effectiveness of the most widely used chemicals against T. absoluta in Tunisia. The results show that the L1 larval stage of Tuta absoluta is very sensitive to all of the chemicals tested. Stage L2 is sensitive to Spinosad, indoxacarb and emactin, while Bacillus thuringiensis, martine do not cause 50% mortality. L3 stage mortality fluctuates between 20% and 80% mortality. The L4 stage is more affected by the treatment with Bacillus thuringiensis which can go to 100%. Based on these results, chemical treatments should be directed according to the dominant larval stage in the plants

Ali Bazmi

Ali Ben Belgacem

Besma Assadi

Faouzi Aoun

Mohamed Sadok Belkadhi

Refki Ettaib

Sabrine Chouikhi

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Journal of Oasis Agriculture and Sustainable Development, 2(1), 2020, 25-28 25   JOURNAL OF OASIS AGRICULTURE AND SUSTAINABLE DEVELOPMENT www.joasdjournal.org  Comparison of the effectiveness of the most used chemicals against Tuta absoluta in Tunisia Ettaib Refki1,2,3*, Aoun Faouzi1, Assadi Besma1,2,  Ben Belgacem Ali1 , Chouikhi Sabrine1, Bazmi Ali1 and BelKadhi Mohamed Sadok1,2 1 Arid and Oases Cropping Laboratory, Arid Area Institute Medenine 4119, Tunisia. 2 Department of Food Process Engineering, Higher Institute of Technological Studies, Kebili 4200, Tunisia. 3Technical Center for Protected and Geothermal Crops, El Manara, 6011, BP 65 Gabes (Tunisia)  Article info  Abstract Article history: Received 23 September 2020 Accepted 29 November 2020 Control failures with several chemicals have prompted research into the resistance status of Tuta absoluta and the effectiveness of certain active ingredients against this pest. In this context, a comparison was made of the effectiveness of the most widely used chemicals against T. absoluta in Tunisia. The results show that the L1 larval stage of Tuta absoluta is very sensitive to all of the chemicals tested. Stage L2 is sensitive to Spinosad, indoxacarb and emactin, while Bacillus thuringiensis, martine do not cause 50% mortality. L3 stage mortality fluctuates between 20% and 80% mortality. The L4 stage is more affected by the treatment with Bacillus thuringiensis which can go to 100%. Based on these results, chemical treatments should be directed according to the dominant larval stage in the plants. Keywords: Tuta absoluta, active ingredients, chemicals tested   Copyrightⓒ2020 JOASD  * Corresponding author refki.ettaib1985@gmail.com  Conflict of Interest : The authors declare no conflict of interest 1. INTRODUCTION  From the 2008-2009 agricultural season, geothermal crops and in particular tomato crops are in danger of a new leafminer; Tuta absoluta (Meyrick) which caused significant losses in tomato production (Desneux et al., 2010, 2011; Lebdi et al., 2011; Abbes et al., 2012). Damage is caused by larvae attacking leaves, stems and fruits and losses can reach up to 100% (Chermiti et al., 2009). Tomato plants can be attacked at any stage of development, from young seedlings to maturity. The damage of Tuta absoluta occurs mainly on the leaves, the attack is characterized by the presence of clearly visible discolored areas. The larvae only devour the parenchyma, leaving the epidermis intact. Subsequently, the attacked leaflets completely necrotize. On stem or peduncle, larval necrosis disrupts the development of the plant. On the other hand, on fruits, tomatoes show necrosis on the calyx and exit holes on the surface. Fruits are susceptible to be attacked from their formation until maturity. A larva can damage several fruits in the same bouquet (Ramel and Oudard, 2008). Historically, T. absoluta was controlled with organophosphates and pyrethroids which were used during the 1970s and 1980s until newer products introduced in the 1990s (such as abamectin, spinosad, tebufenozide and chlorofenapyr) became available (Lietti et al., 2005). At least 12 classes of insecticides control T. absoluta (IRAC, 2009a, b). Control failures with organophosphates and pyrethroids in South America have prompted research into the resistance state of Tuta absoluta (Lietti et al, 2005; Siqueira et al, 2000a, b); however, the newer classes of insecticides provide good control of this pest (IRAC, 2009a). The unstudied use of insecticides can lead to the development of resistance. In Bolivia and Chile, T. absoluta was reported to be resistant with organophosphates during the first half of the JOASD p-ISSN: 2724 – 699X e-ISSN: 2724-7007 Journal of Oasis Agriculture and Sustainable Development, 2(1), 2020, 25-28 26  1980s. More recently, resistance studies on strains of T. absoluta in Argentina revealed   the reduction of the efficiency of deltamethrin and abamectin (Lietti et al, 2005). Resistance to cartap, abamectin, permethrin and methamidophos (Siqueira et al, 2000a, b), acephate and deltamethrin (Branco et al, 2001) has been reported. In Brazil, classes of new insecticides have provided good activity against tomato leafminer (IRAC, 2009a). However, the modes of action must be maintained when implementing resistance management. In practice, alternation, or rotation of compounds with different modes of action, generally provides a sustainable and effective approach to the management of insecticide resistance (IRAC, 2009c).  2. MATERIAL AND METHODS  The aim of this experiment is to evaluate the effectiveness of some of the most widely used chemicals against Tuta absoluta in Tunisia. The test was carried out at the El khbayet geothermal site located 84 km from Kebili. Six tri-tunnel greenhouses on the southwest side of the site were monitored by comparing the effectiveness of certain chemicals. These greenhouses are isolated from other newly installed greenhouses and are comparable to traditional greenhouses. The variety of tomato grown in these greenhouses is Romana grown above ground on perlite.The chemicals tested are: Spinosad, Emactine, Martine, Emactine, indoxacarb and Bactospeine Bacillus thuringiensis, all products are spray tested (Table 1). Table 1. Ingredients used Treatment products and active Greenhouse product Active ingredient  Dose  2232 m2 application mode TT1 Tracer Spinosad 60  cc spray TT2 Proact Emactine 75 cc spray TT3 Baico Martine Emactine 75cc spray TT4 Avaunt indoxacarbe 30 cc spray  TT5 B .T Bacillus thuringiensis 150g/100L spray  TT6 without treatment ( W.T)     Three days after treatment, 60 samples per tri-tunnel were taken. The samples are tomato leaves showing galleries with different larval stages of Tuta absoluta. Each sample is placed in a plastic bag on which is written all the necessary information, in particular: the date of the sampling, the location, the greenhouse number and the nature of the treatment product. In the laboratory, samples are stored in a cool medium to be analyzed as quickly as possible. The analysis is done under a binocular magnifying glass to identify the larval stages present and to determine their state (dead or alive). Thus we can determine the mortality rate of the larvae according to the treatment, and know the most sensitive stages for each product. 3. RESULTS AND DISCUSSION Observation of the histogram (Figure 1) which represents the effect of chemical treatments on larval mortality shows that the L1 larval stage of Tuta absoluta is sensitive (100% mortality) to all chemicals tested. Stage L2 is sensitive to Spinosad, indoxacarb and emactin, while Bacillus thuringiensis, martine do not cause 50% mortality. L3 stage mortality fluctuates between 20% and 80% mortality. The L4 stage is more affected by the treatment with Bacillus thuringiensis which can go to 100%.  Figure 1.  The effect of treatment products on T. absoluta larval mortality Based on these results, chemical treatments should be directed according to the dominant larval stage in the plants. Indeed, the two larval stages, L1 and L2 of Tuta absoluta generally appear to be the most sensitive to the chemical tested. Thus, treatments should target these stages, to ensure their effectiveness. 020406080100L1L2L3L4Products% MortalityW.T Journal of Oasis Agriculture and Sustainable Development, 2(1), 2020, 25-28 27  Interventions based on indoxacarb alone or Bt + indoxacarb, carried out against Heliothisarmigera, and treatment with spiromesif against Aculopslycopersici did not affect the population of N. tenuis (Abbes et al 2012). This confirms the work of Alomar et al. (2002) and Arno et al. (2006). Indoxacarb or Bacillus-based products are classified as not very harmful against N. tenuis. Indeed, several natural enemies are able to limit the populations of T. absoluta, but the most important and the most used are limited to predatory bugs of eggs and larvae in particular: Nesidiocoris tenuis and Macrolophus caliginosus (Torres et al., 2002) and parasitoids of eggs of the genus Trichogramma spp. (Villas Boas & Franca, 1996; Torres et al. 2002). Given the risks of large-scale use of chemicals that are not very specific to the environment and auxiliary fauna, researchers have focused in recent years towards a rationalization of chemical control and the development of biological protection. The latter corresponds, mainly, to microbiological control by the use of antagonistic biological agents such as predatory entomophagous beneficial insects such as Nesidiocoris tenuis and other predators. 4. CONCLUSION Cultivation in heated greenhouses in southern Tunisia is a very important axis of agricultural development. Thanks to a great geothermal potential in the governorates of Kebili, Gabes and Tozeur, this sector has experienced great development since its start in 1986. Despite its importance, this sector is subject to several technical and phytosanitary constraints. Among the problems affecting tomato crops in greenhouses heated by geothermal water, the introduced insect Tuta absoluta. Indeed, the control failures have prompted research into the resistance state of Tuta absoluta and the effectiveness of several active ingredients against this pest. In this context, our study of the effect of chemical treatments on larval mortality shows that the L1 larval stage of Tuta absoluta is sensitive to all the chemicals tested. Stage L2 is sensitive to Spinosad, indoxacarb and emactin, while Bacillus thuringiensis, martine and it do not cause 50% mortality. L3 stage mortality fluctuates between 20% and 80% mortality. The L4 stage is more affected by the treatment with Bacillus thuringiensis which can go to 100%. Based on these results, chemical treatments should be directed according to the dominant larval stage in the plants. Indeed, the two larval stages, L1 and L2 of Tuta absoluta generally appear to be the most sensitive to the chemical tested.  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Chermiti B.,AbbesK.,AounM.,BenOuthmane S., Ouhibi M.,Gamoon W.,Kacems.,2009- First estimate of the damage of Tuta absoluta (Povolny) (Lepidoptera: Gelecheiidae) and evaluation of the efficiency of sex pheromone traps in greenhouses of tomato crops in the Bekalta region, Tunisia.- Afr. J. Plant Sci. Biotechnol. 3: 49-52. Desneux N, Wajnberg E, Wyckhuys K, Burgio G, Arpaia S, Narvaez- Vasquez C, Gonzalez-Cabrera J, Catalan Ruescas D, Tabone E, Frandon J, Pizzol J, Poncet C, Cabello T, Urbaneja A .2010.Biological invasion of European tomato crops by Tuta absoluta: ecology, geographic expansion and prospects for biological control. J Pest Sci 83:197–215  IRAC.2009a. Tuta absoluta on the move.IRAC (Insecticide Resistance Action Committee) newsletter, eConnection (20).Accessed January 4, 2010.http://www.iraconline.org/documents/eConnection_issue20a.pdf IRAC.2009b. Lepidoptera Insecticide Mode of Action Classification Poster.IRAC (Insecticide Resistance Action Committee). IRAC.2009c. 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Siqueira, H. A. A., R. N. C. Guedes, and M. C. Picanço. (2000b). Cartap resistance and synergism in populations of Tuta absoluta (Lep.,Gelechiidae). Journal of Applied Entomology 124:233-238. Torres JB, Evangelista WS, Barras R &Guedes RNC (2002) Dispersal of Podisusnigrispinus nymphs preying on tomato leafminer: effect of predator release time, density and satiation level. Journal of Applied Entomology 126, 326–332. Villas Boas GL & Franca FH (1996) [Use of the parasitoid Trichogramma Pretiosum for control of Brazilian tomato pinworm in tomato grown in the greenhouse.] HorticulturaBrasileira  14, 223–225 (in Portuguese)Journal of Oasis Agriculture and Sustainable Development, 2(1), 2020, 25-28 29   

Comparison of the effectiveness of the most used chemicals against Tuta absoluta in Tunisia

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Comparison of the effectiveness of the most used chemicals against Tuta absoluta in Tunisia

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