Guia de identificação e controle das principais pragas e doenças do algodoeiro.

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Resistência de genótipos de amendoim às cercosporioses sob condições naturais de infecção.

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Comment On The Gd Crystalline Field And The Gd-pr Exchange In The Van Vleck Monopnictides

We report on the observation of resolved fine structure in the ESR of Gd in PrSb, TmSb, and PrBi single crystals. The fourth-order crystalline-field parameter b4 was found to increase with the lattice constant upon going from the antimonides to the bismuthides, consistent with the variation of b4 in the analogous nonmagnetic pnictides. A correlation between b4 and the Korringa rate in the analogous nonmagnetic compounds suggests that the variation of b4 is associated with conduction-electron effects. Also the variation of the Gd-Pr exchange parameter, JGd-Pr across the pnictides is attributed to variation of the conduction-electron d-d overlap. The data enable us to estimate the pressure derivative of b4 and JGd-Pr. © 1979 The American Physical Society.1942385238

Fungitoxicidade de grupos químicos sobre Myrothecium roridum in vitro e sobre a mancha-de-mirotécio em algodoeiro.

O objetivo deste trabalho foi avaliar a fungitoxicidade de produtos pertencentes aos grupos dos benzimidazóis, triazóis, estrobilurinas, isoftalonitrilas e ditiocarbamatos sobre a germinação conidial e o crescimento micelial in vitro de isolados de Myrothecium roridum e, in vivo, sobre a severidade da mancha-de-mirotécio em plantas de algodoeiro. Nos testes in vitro os fungicidas foram solubilizados em meio BDA, utilizando-se as concentrações de 0,1, 1, 10 e 100 mg L-1 de ingrediente ativo. A fungitoxidade dos produtos foi avaliada por meio da ED50 (dose necessária para inibir 50% da germinação conidial ou crescimento micelial). Em casa de vegetação, estimou-se a severidade da mancha-de-mirotécio pela porcentagem de área foliar lesionada nas plantas de algodoeiro tratadas antes (preventivo) e depois (curativo) da inoculação do patógeno. Os fungicidas tiofanato metílico, carbendazim, metconazol, tiofanato metílico + clorotalonil, piraclostrobina + epoxiconazol, piraclostrobina + metiram, triflostrobina + propiconazol e tebuconazol inibiram com alta eficácia (ED50<1 mg L-1), ou com eficácia (ED50 entre 1 e 10 mg L-1), a germinação conidial e o crescimento micelial in vitro de M. roridum. Os fungicidas piraclostrobina + epoxiconazol, tebuconazol, metconazol e azoxistrobina + ciproconazol são os mais eficazes em testes in vivo. O tratamento preventivo é mais eficaz que o curativo

Electron Spin Resonance Of Nd3+ And Gd3+ In D-band Intermetallic Compounds

We report on the ESR of the rare-earth ions Nd3+, Gd3+, Er3+, and Yb3+ on powdered samples of various intermetallic compounds of AB2 cubic structure where B is a transition-metal ion belonging to the group VIII of the Periodic Table, and A is a nonmagnetic ion (La, Ce, Y). The resonance of the Nd3+ in these compounds originates within a Γ6 crystal-field ground level and exhibits resolved hyperfine satellites for the Nd143 and Nd145 isotopes. The Gd3+ spectra show a single isotropic line. Using our data for Gd3+ and Nd3+ together with results previously published for the AB2 cubic compounds, we were able to show a correlation between the observed g shifts and the position of the B ion in the Periodic Table. This variation is explained qualitatively using a simple multiband model, as well as band-structure arguments. The hyperfine constants for the Nd143 and Nd145 isotopes were found smaller in magnitude with respect to the values in insulators; this effect is attributed to s-electron self-polarization due to the Nd localized-moment-s-electron exchange coupling. The ESR linewidths of LaIr2: Nd and LaRh2: Nd exhibit an exponential thermal dependence at high temperatures which is attributed to the presence of a Γ8 excited level at Δ=90±20 K. © 1979 The American Physical Society.19115495550