Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Dichloro-diphenyl-trichloroethane (DDT) was extensively used in agriculture pest control and is still used for indoor residual spraying to control malaria. The lipophylicity of DDT and its breakdown product dichloro-diphenyl-dichloroethylene (DDE) dictates that they associate with membranes, lipids and hydrophobic proteins in the biological environment. Their poor degradable nature causes DDT and DDE to persist for decades in the environment and in individuals who are or were in contact with the pesticide. In many countries the synchronised resistance of the mosquito vector to insecticides and the malaria parasite towards antimalarial drugs led to a drastic rise in malaria cases and to malaria epidemics. This study assesses the influence of low level exposure of DDT and DDE on chloroquine (CQ) resistance of the dire human malaria parasite, Plasmodium falciparum. The in vitro activity of p,p’-DDT and p,p’-DDE towards blood stages of chloroquine sensitive (CQS) P. falciparum D10 and chloroquine resistant (CQR) P. falciparum Dd2 was determined using two complementary in vitro assays (Malstat and SYBR Green 1). The 50% inhibition concentrations (IC50s) of p,p’-DDT and p,p’-DDE were found to be ±14 to 38 μM (5-12 μg/mL) and highly similar towards CQS and CQR P. falciparum strains. This result indicated that the proteins involved in CQ resistance have no effect on the activity of the insecticide DDT and it breakdown product DDE. In order to assess the influence of DDT and DDE on CQ activity, in vitro fixed ratio drug combination assays were performed, as well as isobologram analysis. We found that CQ works in synergy with p,p’-DDT and p,p’-DDE against CQS P. falciparum D10. However, both p,p’-DDT and p,p’-DDE were antagonistic toward CQ activity in CQR P. falciparum Dd2. This indicated that p,p’-DDT and p,p’-DDE do have an effect on CQ resistance or on the action of CQ via a target other than hemozoin polymerization. The observation of reciprocal synergism of p,p’-DDT and p,p’-DDE with CQ against CQS D10 and antagonism against CQR Dd2 strain is highly significant and strongly indicates selection of CQ resistant strains in the presence of p,p’-DDT and p,p’-DDE. People who have low levels of circulating DDE and/or DDT could be at a high risk of contracting CQR malaria. However, medium term (nine days) DDE exposure of CQS P. falciparum D10 did not induce resistance, as no significant change in activity of CQ, p,p’-DDT and p,p’-DDE towards blood stages the CQS strain was observed. This exposure was, however, shorter than expected for a malaria infection and would be addressed in future studies. From our results on the interaction of CQ with p,p’-DDT and p,p’-DDE, it was important to assess the residual DDT and DDE variable and how much of residual p,p’-DDT and/or p,p’- DDE would enter into or remain in the different compartments (the RPMI media, erythrocytes and infected erythrocytes) over time. In combination with liquid-liquid extraction, we developed a sensitive GC-MS analyses method and a novel HPLC-UV analysis method for measuring DDT and DDE levels in malaria culturing blood and media. Whilst the HPLC-UV method was relatively cheaper, faster, and effective in determining high DDT and DDE concentrations, the optimised GC-MS method proved to be effective in detecting levels as low as 78 pg/mL (ppt) DDE and 7.8 ng/mL (ppb) DDT in biological media. Using both the HPLC and GC-MS methods we observed that malaria parasites influence distribution of the compounds between the erythrocytic and media fractions. P. falciparum D10 infection at ±10% parasitemia lead to must faster equilibration (less than 8 hours) between compartments. Equimolar distribution of p,p’-DDE was observed, but the parasites lead to trapping of the largest fraction of p,p’-DDT in the erythrocyte compartment. These results indicate that a substantial amount would reach the intra-erythrocytic parasite and could influence the parasite directly, possibly leading to either synergistic or antagonistic drug interactions. This study is the first to illustrate the “good and bad” of the insecticide DDT in terms of CQ resistance and sensitivity toward the human malaria parasite P. falciparum. These results will hopefully have an important influence on how future policies on malaria control and treatment particularly in endemic areas will be addressed and could also have an impact on the anti-malarial drug discovery approach. / AFRIKAANSE OPSOMMING: Dichlorodifenieltrichloroetaan (DDT) is op groot skaal in landbouplaagbeheer gebruik en word nog steeds gebruik vir binnenshuise oppervlakbespuiting om malaria te beheer. Die lipofilisiteit van DDT en sy afbraakproduk dichlorodifenieldichloroetileen (DDE) dikteer dat hulle met membrane, lipiede en hidrofobiese proteïene in die biologiese omgewing assosieer. Stadige afbraak veroorsaak dat DDT en DDE vir dekades in die omgewing agterbly, asook in individue wat in kontak is, of was met die insekdoder. In baie lande het gesinkroniseerde weerstand van die muskietvektor teenoor insekdoders en die malariaparasiet teenoor antimalariamiddels gelei tot 'n drastiese styging in malariagevalle en tot malariaepidemies. In hierdie studie word die invloed van lae vlak blootstelling van DDT en DDE op chlorokien (CQ) weerstand van die mens malariaparasiet, Plasmodium falciparum, geëvalueer. Die in vitro aktiwiteit van p,p'-DDT en p,p'-DDE teenoor die bloedstadia van chlorokiensensitiewe (CQS) P. falciparum D10 en chlorokien-weerstandbiedende (CQW) P. falciparum Dd2 is bepaal deur gebruik te maak van twee komplementêre in vitro toetse (Malstat en SYBR Groen toetse). Die 50% inhibisie konsentrasies (IC50s) van p,p'-DDT en p,p'-DDE is bepaal as ±14 to 38 μM (5-12 μg/mL) en was hoogs vergelykbaar tussen CQS en CQW P. falciparum stamme. Hierdie resultaat het aangedui dat die proteïene betrokke by CQ weerstand geen effek op die aktiwiteit van die insekdoder DDT en die afbraakproduk DDE het nie. Om die invloed van DDT en DDE op CQ aktiwiteit te evalueer, is die aktiwiteit van kombinasies van die verbindings in vaste verhoudings getoets, tesame met isobologram ontleding. Ons het gevind dat CQ sinergisties saam met p, p'-DDT en p, p'-DDE teen CQS P. falciparum D10 werk. Daarteenoor het beide p, p'-DDT en p, p'-DDE antagonistiese werking getoon teenoor CQ aktiwiteit met CQW P. falciparum Dd2 as teiken. Dit het aangedui dat p,p'-DDT en p, p'-DDE wel 'n invloed op CQ weerstand het of ‘n aktiwiteit van CQ, anders as hemozoin polimerisasie, beïnvloed. Die waarneming van resiproke sinergisme en antagonisme van p, p'-DDT en p, p'-DDE in kombinasie met CQ teenoor die CQS D10 en CQW DD2 stamme respektiewelik, is hoogs betekenisvol en dui op seleksie van CQweerstandige stamme in die teenwoordigheid van p, p'- DDT en p, p'-DDE. Mense wat lae vlakke van sirkulerende DDE/DDT het, het dus 'n hoër risiko om CQW malaria te kry. Verder is gevind dat medium termyn (nege dae) DDE blootstelling van CQS P. falciparum D10 nie weerstand nie veroorsaak nie, want geen beduidende verandering in die aktiwiteit van CQ, p,p'-DDT en p,p'-DDE teenoor die bloed stadiums van die CQS stam is waargeneem nie. Hierdie blootstelling is egter korter as in 'n malaria-infeksie en sal verder bestudeer word in toekomstige studies. Vanuit die interaksie resultate van CQ met p, p'-DDT en p, p'-DDE was dit belangrik om die residuele DDT en DDE veranderlike te evalueer, asook die distribusie van p,p'-DDT en p,p'- DDE tussen die verskillende kompartemente (die kultuurmedium, eritrosiete en geïnfekteerde rooibloedselle) oor verloop van tyd. In kombinasie met vloeistof-vloeistof ekstraksie, het ons 'n sensitiewe GC-MS en nuwe HPLC-UV analisemetode ontwikkel vir die meet van DDT en DDE-vlakke in bloed (normale en geïnfekteerde eritrosiete) en die kultuurmedium. Terwyl die HPLC-UV metode relatief goedkoper, vinniger en effektief in die bepaling van hoë DDT en DDE-konsentrasies is, was die geoptimaliseerde GC-MS metode doeltreffend in die opsporing van vlakke so laag as 78 pg/mL (dpt) DDE en 7.8 ng/mL (dpb) DDT in biologiese media. Met behulp van beide die HPLC-UV en GC-MS metodes is waargeneem dat die malariaparasiet die ekwilibrasie van die verbindings tussen die eritrosiet- en media kompartemente beïnvloed. P. falciparum D10 infeksie met ± 10% parasitemia lei tot vinniger ekwilibrasie (minder as 8 uur) tussen die kompartemente. Ekwimolêre verspreiding van p,p'- DDE is waargeneem, maar die parasiete het die grooste fraksie van p,p'-DDT in die eritrosiet kompartement vasgevang. Hierdie resultate wys dat 'n aansienlike fraksie die intraeritrositiese parasiet kan bereik en sodoende die parasiet direk kan beïnvloed en moontlik kan lei tot sinergistiese of antagonistiese middel interaksies. Hierdie studie is die eerste om die "goed en sleg" van die insekdoder DDT in terme van CQ weerstand en sensitiwiteit teenoor die menslike malariaparasiet P. falciparum te illustreer. Hierdie resultate sal hopelik 'n belangrike invloed hê op die toekomstige beleid oor die beheer van malaria en behandeling, veral in endemiese gebiede, en mag ook 'n impak hê op die antimalariamiddel navorsing.

Thesis (MScAgric)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: Colonies of Planococcus ficus (Signoret) were reared from three different areas, Hex River Valley, Robertson and Stellenbosch. An insectary colony and a table grape colony from Nietvoorbij experimental farm were also included in the study. A range of concentrations of chlorpyrifos was applied topically to individuals from the different colonies. The Stellenbosch population had the lowest LDso, although it was not significantly different from that of the insectary and Robertson colonies. The Hex River Valley and table grape colonies had a significantly higher LDso than the Robertson, Stellenbosch and insectary colonies, although the relative tolerance was 1.5, which would probably not result in significant control failure in the field. However, this does indicate that there is potential for the development of resistance to chlorpyrifos in the vine mealybug in South Africa. / AFRIKAANSE OPSOMMING: Kolonies van Planococcus ficus (Signoret), is versamel en geteel uit drie verskillende areas, Hex.riviervallei, Robertson en Stellenbosch. 'n Bestaande insektarium kolonie van die Lanbou Navorsings Raad en 'n tafeldruif kolonie vanaf Nietvoorbij proefplaas is ook ingesluit in die studie. 'n Reeks konsentrasies van chlorpyrifos is topikaal aangewend aan individue van die verskillende kolonies. Die Stellenbosch populasie het die laagste LDso getoon alhoewel dit nie betekenisvol verskil het van die LDso van die insektarium - en Robertson kolonies nie. Die Hexriviervallei en tafeldruif kolonies se LDso was betekenisvol hoër as die Robertson, Stellenbosch and insektarium kolonies. Alhoewel die relatiewe weerstand 1.5 was, sal dit waarskynlik nie tot 'n aansienlike beheermislukking in die veld lei nie. Nogtans dui dit op die potensiaal vir moontlike ontwikkeling van weerstand teen chlorpyrifos in die wingerdwitluis.

Twelve lactating Holstein dairy cows were randomly divided into four groups of three animals each. Group A served as the control, group B was dosed at 0.05ppm/day of DDE (2,2-bis(P-chlorophenyl-1, 1-dichloroethylene), cows in group C were dosed at 0.1ppm DDE/day, while group D cows were dosed at 1.0ppm DDE/day. DDE was administered in a residue free peanut oil solution for 32-consecutive days. Milk samples were taken daily during the 32 day dosing period and for an additional 32 days after the dosing period. Quantitative analysis of DDE residue in milk fat was determined by using a Tracor MT-220 gas chromatograph with a Tritium electron capture detector. The average increase in DDE milk fat concentration during the dosing period was directly related to intake levels. DDE was the only organochlorine compound detected in the milk fat. The general slope and shape of the curves of milk fat DDE levels were similar for all treatments. The levels of DDE increased rapidly after the onset of dosing. After 15 days of dosing and throughout the remaining 17 days of the dosing period, milk fat DDE increased at a relatively slow rate. The level of milk fat DDE declined rapidly as soon as the DDE residue source was withdrawn. At the end of the 32-day post-dosing period, one cow from each group was slaughtered and samples were taken from muscles, brain, lung, lymph, spleen, kidney fat, heart, gonad, placenta, udder, and kidney for DDE analysis. Considerable DDE was found in the muscle, lymph, kidney fat, and udder tissues.

Objective: To look at the Red Cross and the Red Crescent societies integrated campaigns between 2002 and 2006 with free distribution of insecticide treated nets (ITN)that have taken place and its contribution to the Millennium Development Goals(MDG) and the Abuja target.  Method: Review of surveys, evaluations and reports from the International Federation of Red Cross and Red Crescent integrated campaigns. Published articles up to 2007 have been accessed from electronic databases Medline, PubMed, the Cochrane Library and website`s from WHO, UNICEF, GFATM , and related articles available from international organisations web sites in addition to informal discussions and meetings with key stakeholders. Results: The integrated vaccination and free distribution of long lasting insecticidal nets (LLINs) achieved a rapid, high and equal LLIN coverage among all wealth quintiles. The MDG and Abuja target for ITN coverage at household level were reached within a week giving a unique opportunity for a significant reduction in malaria incidences, morbidity and mortality. The ITN possession remained higher than utilisation, but utilisation increased if a follow up visit, ensuring nets being hung and properly used, had taken place at household level post campaign. Conclusion: Large scale free distribution of LLINs  bridge the equity gap between poor and rich and increased the use rate among children under five and pregnant women. The low utilisation versus possession remains a challenge and thus a “minimum standard” of a two phased strategy is recommend to reach maximum impact and the MDG; Phase one preparing for pre campaign data, logistical planning and distribution while phase two should focus on a post campaign Keep Up program providing health education at household level to ensure proper net hanging and use. / <p>ISBN 978-91-85721-42-9</p>

The whitefly Trialeurodes vaporariorum Westwood (Hemiptera: Aleyrodidae) is a serious pest of protected vegetable and ornamental crops in most temperate regions of the world. Neonicotinoids, pymetrozine (a feeding blocker), spiromesifen (a tetronic acid derivative), bifenthrin (a pyrethroid), and pyriproxyfen (a juvenile hormone mimic) are among the most important insecticides used to control this species. Bioassays were used to quantify responses of recently-collected strains of T. vaporariorum to three neonicotinoids (imidacloprid, thiamethoxam, and acetamiprid), pymetrozine, spiromesifen, bifenthrin, and pyriproxyfen. 454 pyrosequencing was exploited to generate the first transcriptome for this species. PCR-sequencing was used to identify mutations in the target proteins of spiromesifen and bifenthrin potentially associated with resistance to these compounds. Microarray sequencing technology was employed to investigate differences in gene expression associated with pyriproxyfen resistance. Resistance to neonicotinoids was age-specific in expression and consistently associated with resistance to pymetrozine, supporting a hypothesis of metabolic resistance analogous to that in the tobacco whitefly, Bemisia tabaci. Bioassays also showed moderate to high level resistance to spiromesifen, bifenthrin and pyriproxyfen in some strains. Analysis of the transcriptome identified genes encoding enzymes involved in the detoxification of xenobiotics (cytochrome P450s, carboxyl/cholinesterases, and glutathione-s transferases) and ones encoding insecticide targets: acetyl-coA carboxylase (ACCase), the target of spiromesifen and the voltage-gated sodium channel protein targeted by pyrethroids. PCR-sequencing revealed a single nucleotide polymorphism in the ACCase gene, which was consistently associated with spiromesifen resistance. Three amino-acid substitutions in the sodium channel of pyrethroid-resistant T. vaporariorum were found in positions previously implicated in pyrethroid resistance in B. tabaci. Microarray sequencing disclosed that a cytochrome P450 gene (CYP4G61) was overexpressed in a strain selected for increased pyriproxyfen resistance. The implications of these results and opportunities for further work are discussed.

The intensification of agricultural production in the Mekong Delta has faced serious challenges with respect to increased use of agrochemicals and especially pesticides. The indiscriminate use of pesticide could potentially impact on the long-term food production, environmental and human health in the delta. The aim of this thesis was to investigate the negative side effects of the current use of pesticides on climbing perch (Anabas testudineus) in rice fields using brain acetylcholinesterase (hereafter referred to as AChE) activity as a biomarker. The empirical work, on which this thesis is based, includes structured questionnaires, laboratory and field experiments. First, a field survey using questionnaires was carried out to gain a better understanding of the current state of rice farming systems, the use of pesticides and attitude to pest management strategies among rice and rice-fish farmers, as well as to provide basic information for the set-up of the laboratory and field experiments. Secondly, laboratory studies were conducted to clarify if the selected insecticides applied alone and in mixtures caused negative side effects on climbing perch fingerlings. Thirdly, further toxicity studies were carried out, under rice field conditions, to further investigate the toxicity effects of the insecticides, applied alone, in mixtures and under sequential applications, on climbing perch fingerlings. The results showed that although there were a more selective use of pesticides and an increased awareness among farmers of the negative side effects of pesticides in 2007 as compared to 1999, the current use of pesticide in the Mekong Delta still cause many problems to the environment and human health. Chlorpyrifos ethyl (hereafter referred to as CPF) was found to cause a significant and more prolonged inhibition on the brain AChE activity in climbing perch than fenobucarb (hereafter referred to as F). The inhibition by the mixture of CPF and F were significantly higher than the inhibition by only F, but less prolonged and significant lower than the inhibition by only CPF. The results suggest that the combined effect from a mixture of F and CPF can create both additive effects initially and later antagonistic effects. CPF and F applied at concentrations used by farmers, either as separate doses, in a mixture or in sequential doses, decreased the brain AChE activity, growth and survival rates in climbing perch. The results demonstrate that brain AChE activity in climbing perch is a relevant biomarker for monitoring of exposure to, and sub-lethal impacts from organophosphates and carbamates under tropical conditions. The result also shows that 2-PAM re-activate the brain AChE activity, and can be used as an alternative method to assess the AChE inhibition level in organisms recently exposed to OP’s, in situation where it may be difficult to find unexposed individuals as controls. In conclusion, this thesis shows that the current use of pesticides in the Mekong Delta has a negative effect on climbing perch living in rice fields. It indicates that a sustained long-term food production in the Mekong Delta must be based on ecological principles, taking advantages of ecosystem biodiversity and productivity, and not through intensified use of pesticides. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 5: Submitted.</p>

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Master of Science / Department of Plant Pathology / Harold Trick / The object of this study was to find a target sequence for the known Heterodera glycines Y25 sequence that contained no homology to any known Glycine max genes so homologous endogenous soybean gene expression will not be effected. In addition, in attempt to improve the accuracy of SCN bioassays performed in greenhouse settings, applications of a variety of insecticides with differing modes of action were applied to screen for any detectable effects on the SCN populations. The full-length sequence of the Y25 gene was blasted against the G. max genome using the National Center for Biotechnology Information blast database and a portion of the gene was found to contained no homology to the G. max genome. A rapid hairy root assay was used to screen for resistance to H. glycines. The sequence was transformed into Agrobacterium rhizogenes using a modified heat shock method. The transformed A. rhizogenes were used to inoculate soybean seedlings. The inoculated seedlings developed hairy roots expressing the target sequence. Upon finishing the hairy root assay it was discovered that there were no detectable differences across any of the treatments or the controls. It was neither proved nor disproved that the new target sequence containing no homology to the G. max genome was as effective as the original target. Further investigation will need to be conducted to show the level of control for the new target sequence.

O controle químico de pragas, para muitas culturas agrícolas é uma das principais táticas em programas de manejo integrado de pragas (MIP), trazendo benefícios reais e diminuindo as perdas por insetos-praga, além do aumento na produção de alimentos e fibras, proteção de produtos armazenados e proteção de pragas e doenças de seres humanos. O controle de pragas em soja e milho tem sido realizado, em sua maioria, utilizando-se plantas Bt e produtos químicos, este último, além das diversas vantagens citadas, pode ter desvantagens, principalmente quando utilizado de maneira inadequada, com potencial de causar diversos problemas no agroecossistema, além de desequilíbrios ambientais. Devido a importância da cultura da soja e do milho para o Brasil e para o mundo, como base da alimentação animal e humana, reconhecendo o grande uso e papel dos inseticidas como uma das principais táticas usadas para o controle de insetos-praga destas culturas, se faz necessário estudos que tratem da melhor forma de uso dos inseticidas e estudos que avaliem possíveis efeitos adversos destas moléculas em insetos benéficos, para que estejam de acordo com as premissas do MIP. Para viabilizar esta importante tática de controle, realizou-se estudos com os seguintes objetivos: 1) Estudar a toxicidade residual dos inseticidas indoxacarb (Avatar&reg;), chlorantraniliprole (Premio&reg;), spinosad (Tracer&reg;) e teflubenzuron (Nomolt 150&reg;) para C. includens em soja, em ensaio com e sem simulação de chuva; 2) Estudar a toxicidade residual dos inseticidas indoxacarb (Avatar&reg;), chlorantraniliprole (Premio&reg;), spinosad (Tracer&reg;) e teflubenzuron (Nomolt 150&reg;) para S. frugiperda em milho, em ensaio com e sem simulação de chuva; 3) Avaliar efeito letal e subletal de inseticidas recomendados para soja e milho sobre o predador Doru luteipes. Para o primeiro objetivo, teflubenzuron (15 g i. a. ha-1); spinosad (36 g i. a. ha-1); chlorantraniliprole (5, 10 e 20 g i. a. ha-1); indoxacarb (30, 60 e 90 g i. a. ha-1) não tiveram a eficácia afetada quando submetidos à simulação de chuva em todos os tempos avaliados. Quanto a toxicidade residual ao longo do tempo, teflubenzuron, chlorantraniliprole e indoxacarb, nas duas condições, com e sem simulação de chuva, tiveram redução da eficácia após o 5° dia. Diferentemente, os inseticidas spinosad (36 g i. a. ha-1) e indoxacarb (90 g i. a. ha-1), nas duas condições, não tiveram redução da eficácia até 15 dias após aplicação, e em todos os tempos avaliados foram mais eficazes do que os demais inseticidas. Para o segundo objetivo, spinosad (36 g i. a. ha-1) e chlorantraniliprole (10, 20 e 30 g i. a. ha-1) mantiveram a eficácia até o 15º dia após pulverização. Quanto aos efeito da simulação da chuva, spinosad (36 g i. a. ha-1), chlorantraniliprole (10, 20 e 30 g i. a. ha-1) e indoxacarb (90 g i. a. ha-1) mantiveram a eficácia. O inseticida chlorantraniliprole na maior dose utilizada e recomenda para o controle da praga na cultura foi o mais efetivo dentre todos, quanto a toxicidade residual e sob ação da simulação de chuva. Quanto ao terceiro objetivo, ensaio de efeito letal, Tracer, Premio e Avatar foram classificados como nocivos (classe 4), e somente Nomolt foi inócuo (classe 1). No ensaio de efeito subletal apenas o inseticida Nomolt teve parâmetros avaliados. Apesar disso, causou efeitos adversos ao predador, como: aumento do período de pré-oviposição; aumento do período embrionário e diminuição da fecundidade; não sendo, portanto, recomendado para utilização em programas de MIP, pois, altera a capacidade de desenvolvimento e reprodutiva da tesourinha predadora. Os resultados obtidos nesses estudos proveram importantes informações para o refinamento do uso de moléculas inseticidas e classificação desses quanto a seletividade ao predador generalista D. luteipes, agregando informações práticas para o manejo de pragas na cultura da soja e milho. / Chemical pest control for many agricultural crops is one of the main tactics in integrated pest management (IPM) programs, bringing real benefits and decreasing losses by pest insects, as well as increased food and fiber production, protection of stored products and protection of pests and diseases of humans. Pest control in soybean and corn has been mostly carried out using Bt plants and chemical products, for the latter, in addition to the several advantages cited, may have some disadvantages, especially when used improperly, with the potential to cause several problems in the agroecosystem, as well as environmental impacts. Owing to the importance of soybean and corn cultivation to Brazil and to the world, as a basis of animal and human feeding, recognizing the great use and role of insecticides as one of the main tactics used to control insect pests of these crops, it is necessary to study the best use of insecticides and studies that evaluate the possible adverse effects of these chemical molecules on beneficial insects, so that they are in accordance with the IPM premises. To enable this important control tactic, studies were carried out with the following objectives: 1) To study the residual toxicity of insecticides indoxacarb (Avatar&reg;), chlorantraniliprole (Premio&reg;), spinosad (Tracer&reg;) and teflubenzuron (Nomolt 150&reg;) for C. includens in soybeans, with and without rainfastness; 2) To study the residual toxicity of insecticides indoxacarb (Avatar&reg;), chlorantraniliprole (Premio&reg;), spinosad (Tracer&reg;) and teflubenzuron (Nomolt 150&reg;) for S. frugiperda in maize, with and without rainfastness; 3) To evaluate the lethal and sublethal effect of insecticides recommended for soybean and corn on the earwing predator Doru luteipes. For the first objective, teflubenzuron (15 g a. i. ha-1); spinosad (36 g a. i. ha-1); chlorantraniliprole (5, 10 and 20 g a. i. ha-1); indoxacarb (30, 60 and 90 g a. i. ha-1) were not affected when submitted to rainfastness at all evaluated times. Concerning for residual toxicity over time, teflubenzuron, chlorantraniliprole e indoxacarb, under both conditions, with and without rainfastness, had a reduction in efficacy after 5 day. In contrast, the insecticides spinosad (36 g a. i. ha-1) and indoxacarb (90 g a. i. ha-1), in both conditions had no efficacy reduction until 15 days after application and at all times evaluated were more effective than the other insecticides. For the second objective, spinosad (36 g a. i. ha-1) e chlorantraniliprole (10, 20 and 30 g a. i. ha-1) maintained efficacy until the 15th day after spraying. As for the effects of rainfastness, spinosad (36 g a. i. ha-1), chlorantraniliprole (10, 20 and 30 g a. i. ha-1) and indoxacarb (90 g a. i. ha-1) remained effective. The insecticide chlorantraniliprole at the highest dose used and recommended for the control of the pest in the crop was the most effective of all, regarding residual toxicity and under the action of the rainfastness. About the third objective, lethal effect bioassay, Tracer, Premio e Avatar were classified as harmful (class 4), and only Nomolt was innocuous (class 1). In the test of sublethal effect, just the insecticide Nomolt had parameters evaluated. Nevertheless, it caused adverse effects to the predator, such as: increased pre-oviposition period; increase in the embryonic period and decrease in fecundity; therefore, it is not recommended for use in IPM programs, because it modify the developmental and reproductive capacity of predatory earwings. The results obtained in these studies provided important information for the refinement of the use of insecticidal molecules and the classification of these as the selectivity to the generalist predator D. luteipes, adding practical information for pest management in soybean and corn crops.

Com a crescente expansão de cultivos agrícolas no Brasil, tem sido bastante comum o sistema de produção de algodão e milho em uma mesma região. Como uma possível conseqüência deste sistema de cultivo, os problemas com Spodoptera frugiperda (J. E. Smith) têm aumentado nestas duas culturas nos últimos anos. Assim, para o estabelecimento de um manejo mais efetivo desta praga, foi levantada a hipótese de que as mesmas populações de S. frugiperda atacam as culturas do algodão e milho em uma determinada região. Para testar esta hipótese, foram realizados os seguintes estudos: 1) a avaliação a suscetibilidade ao piretróide deltametrina em populações de S. frugiperda, e 2) a estimativa da similaridade e da estrutura genética em populações de S. frugiperda com o uso de marcadores moleculares RAPD e AFLP. A avaliação da suscetibilidade a deltametrina das populações de S. frugiperda foi realizada mediante bioensaio de aplicação tópica. Além disso, foi avaliada a resposta à seleção com deltametrina em uma população de S. frugiperda em condições de laboratório. As populações de S. frugiperda coletadas na cultura do algodão foram significativamente menos suscetíveis a deltametrina do que as populações coletadas no milho. Estes resultados poderiam ser entendidos como uma conseqüência da pré-seleção de indivíduos resistentes a deltametrina A população de S. frugiperda selecionada em laboratório apresentou uma razão de resistência a deltametrina de &#8776;14 vezes. Pela técnica de RAPD, os dendrogramas (Simple Matching e Jaccard) classificaram as populações da praga em grupos proximamente relacionados com a região geográfica de coleta dos insetos. Não foi identificado nenhum ramo capaz de separar e associar as populações de S. frugiperda a nenhuma das duas plantas hospedeiras avaliadas. Estes resultados sugeriram que as populações da praga em algodão e milho em uma determinada região do Brasil apresentam um nível significativo de fluxo gênico. Os resultados da técnica AFLP foram organizados em um dendrograma UPGMA (índice de Jaccard), o qual também não classificou as populações da praga em grupos relacionados às plantas nas quais os insetos foram coletados. Não foi detectada correlação significativa entre a dissimilaridade genética e distância geográfica nas populações testadas. Foi detectada variação molecular entre as populações da praga atribuída à origem geográfica dos insetos. A análise molecular de variância indicou que 7% da variação molecular total poderiam ser atribuídos à divisão das populações de S. frugiperda em grupos de insetos coletados no Brasil e na Argentina. Além disso, foi detectado 0% de variação genética, e um valor de fluxo gênico Nm=1,32 entre os grupos de populações da praga coletadas nas culturas do algodão e do milho. Assim, as infestações de S. frugiperda que ocorrem em campos de milho e algodão podem ser consideradas como subunidades potencialmente intercruzantes de uma mesma população. Portanto, conclui-se que há necessidade de um planejamento bastante estratégico nos plantios de algodão e de milho, no delineamento de programas de manejo de S. frugiperda no Brasil. / Due to the expansion of the cultivated areas in Brazil, it has been very common to find the cultivation of cotton and maize in the same region. As a potential consequence to this cultivation system, the problems with Spodoptera frugiperda (J.E. Smith) have increased for the last years at both crops. In order to provide elements to the establishment of a more effective management of this pest it was hypothesized that the same populations of S. frugiperda attack the cotton and maize crops in Brazil. To test this hypothesis the following studies were conducted: 1) the evaluation the susceptibility to the pyrethroid deltamethrin in S. frugiperda populations and 2) the assessment of the molecular variability and genetic structure in S. frugiperda populations by using RAPD and AFLP molecular markers. The evaluation of the susceptibility to deltamethrin in S. frugiperda populations was conducted by using topical application bioassays. Furthermore, the response of this pest to the selection pressure with the insecticide was evaluated under laboratory conditions. The insect populations collected in the cotton crop were significantly less susceptible to deltamethrin than the ones collected in the maize crop. These results might be consequence of a pre-selection of deltamethrin-resistant individuals. The deltamethrin-resistant population selected under laboratory conditions had the resistance ratio of &#8776;14 fold. The dendrograms obtained by using RAPD markers (Simple Matching and Jaccard) classified the populations into clusters related to the geographical origin of the samples. Any branch of the dendrograms underpinned a molecular association of S. frugiperda with neither of the two host plants. These results suggested the existence of considerable gene flow between cotton and maize populations of S. frugiperda collected at the same region in Brazil. The AFLP results were organized in a UPGMA dendrogram (Jaccard index) which also did not classify the populations of S. frugiperda into clusters related to the host plant in which the insects were collected. It was not found a significant correlation between genetic dissimilarity and geographical distances. It was detected genetic variation attributable to the geographical origin of the populations. The analysis of molecular variance highlighted 7% of the variation due to the division of the S. frugiperda populations into Brazilian and Argentine groups. Also, no molecular variation (0%) and a gene flow rate equal to Nm=1.32 were estimated between fall armyworm group of populations collected at maize and cotton fields in Brazil. The same populations of S. frugiperda infest cotton and maize crops in Brazil and could be considered as interbreeding subunits of the same population. Therefore, there is a need of strategic action plans to the planting of cotton and maize crops for designing of management programs of S. frugiperda in Brazil.