The objective of this study was to evaluate the physical interaction between simulated tank mixturesof different classes of pesticides. The treatments consisted of mixtures of six insecticides (methomyl,chlorpyrifos, teflubenzuron, triflumuron, cypermethrin and cyhalothrin + thiamethoxam) with sixfungicides (pyraclostrobin/epoxiconazole, trifloxystrobin/tebuconazole, carbendazin, flutriafol,azoxystrobin/cyproconazole, flutriafol/tiofanato- methyl) in the absence and presence of two pHreducers (Pyroligneous acid and boric acid) with four replications. We used a scale from 1 to 5to evaluate the degree of mismatch, where 1 is the immediate separation of the mixture and it isrecommended not to apply is 5 and the homogeneity of the mixtures without restrictions apply.The major physical incompatibilities in mixtures of insecticides and fungicides were observed inthe presence of the insecticides chlorpyrifos, cypermethrin, thiamethoxam/lambda-cyhalothrinand the insecticides physiological teflubenzuron, triflumuron and the fungicide pyraclostrobin/epoxiconazole, azoxystrobin/cyproconazole and flutriafol/thiophanate-methyl. Pyroligneous acidand boric acid showed to be good alternatives such as reducing the pH in the preparation of spraymixtures spraying of insecticides with fungicides. Should be avoided tank mixtures of chlorpyrifos,and teflubenzuron triflumuron with all fungicides tested.Objetivou-se com este trabalho avaliar a interação física entre misturas simuladas em tanque dediferentes classes de defensivos agrícolas. Os tratamentos foram constituídos pelas misturas de seisinseticidas (methomyl, clorpirifós, teflubenzuron, triflumuron, cipermetrina e tiametoxam + lambdacialotrina)com seis fungicidas (piraclostrobina/epoxiconazole, trifloxistrobina/tebuconazole,carbendazin, flutriafol, azoxystrobina/ciproconazol, flutriafol/tiofanato-metilico) na ausência epresença de dois redutores de pH (ácido pirolenhoso e ácido bórico) com quatro repetições.Utilizou-se uma escala de 1 a 5 visando avaliar o grau de incompatibilidade, onde 1 é a separaçãoimediata da mistura e recomenda-se não aplicar e 5 é a homogeneidade das misturas semrestrições de aplicação. As maiores incompatibilidades físicas nas misturas de inseticidas e fungicidasforam observadas na presença dos inseticidas clorpirifós, cipermetrina, tiametoxam/lambdacialotrinae os inseticidas fisiológicos teflubenzuron e triflumuron com os fungicidas piraclostrobina/epoxiconazole, azoxystrobina/ciproconazol e flutriafol/tiofanato-metílico. O ácido pirolenhoso eácido bórico demonstraram ser boas alternativas como redutores de pH, no preparo de calda depulverização com misturas de inseticidas com fungicidas. Deve se evitar misturas em tanque declorpirifós, teflubenzuron e triflumuron com todos os fungicidas testados. Physical incompatibility of mixing of insecticides and fungicidesAbstractThe objective of this study was to evaluate the physical interaction between simulated tank mixturesof different classes of pesticides. The treatments consisted of mixtures of six insecticides (methomyl,chlorpyrifos, teflubenzuron, triflumuron, cypermethrin and cyhalothrin + thiamethoxam) with sixfungicides (pyraclostrobin/epoxiconazole, trifloxystrobin/tebuconazole, carbendazin, flutriafol,azoxystrobin/cyproconazole, flutriafol/tiofanato- methyl) in the absence and presence of two pHreducers (Pyroligneous acid and boric acid) with four replications. We used a scale from 1 to 5to evaluate the degree of mismatch, where 1 is the immediate separation of the mixture and it isrecommended not to apply is 5 and the homogeneity of the mixtures without restrictions apply.The major physical incompatibilities in mixtures of insecticides and fungicides were observed inthe presence of the insecticides chlorpyrifos, cypermethrin, thiamethoxam/lambda-cyhalothrinand the insecticides physiological teflubenzuron, triflumuron and the fungicide pyraclostrobin/epoxiconazole, azoxystrobin/cyproconazole and flutriafol/thiophanate-methyl. Pyroligneous acidand boric acid showed to be good alternatives such as reducing the pH in the preparation of spraymixtures spraying of insecticides with fungicides. Should be avoided tank mixtures of chlorpyrifos,and teflubenzuron triflumuron with all fungicides tested.