The nematodes are the important pests for watermelon and among them Meloidogyne incognita (Kofoid y White) Chitwood and Rotylenchullus reniformis Linford and Oliveira. The use of rootstock is a power tool to control soil borne diseases like nematodes, and this research had as main objective to evaluate the effect of several bionematocides and chemicals in a randomized block design with three replications. The watermelon hybrid Royal Charleston grafted on RS-841 (Cucurbita maxima x Cucurbita moshata), was planted. The dosages employed were the recommend by the fabricant and were applied to soil in two moments, at transplant and 20 days after. The galling index (AI), the reproduction factor (FR) and reproductive index (IR) were determined 45 days after transplantation and after the first harvest (65 d). The evaluation consisted in determine agronomicals parameters and fruit quality. The results showed that applied nematicides no controlling M. incognita nor R. reniformis before 45 days after transplantation, but the grafted plants with high gall levels because the important development and vigor of the plant, allow to obtain satisfactory commercial yield.

Los nematodos constituyen una importante plaga agrícola para la sandía y dentro de ellos las especies Meloidogyne incognita (Kofoid y White) Chitwood y Rotylenchulus reniformis Lindford y Oliveira. El empleo de portainjertos constituye una práctica muy eficaz para controlar patógenos del suelo incluyendo los nematodos, y esta investigación se realizó con el objetivo de evaluar el efecto de diferentes nematicidas de origen biológico y químico en un diseño de bloques al azar con tres réplicas. Se utilizó el híbrido de sandía Royal Charleston injertado sobre RS-841 (Cucurbita maxima x Cucurbita moschata). Las dosis empleadas fueron las recomendadas por el fabricante, aplicadas al suelo al trasplante y a los 20 días con suelo en capacidad de campo. A los 45 días después del trasplante y después de la primera cosecha (65 ddt), se determinó el Índice de Agallamiento (IA), el Factor de Reproducción (FR) e Índice de Reproducción (IR). Se evaluaron en cada variante las variables agronómicas y de calidad del fruto. Los resultados arrojaron que los nematicidas aplicados no controlaron el ataque de M. incognita ni de R. reniformis hasta los 45 días después del trasplante, pero el injerto sobre el patrón de calabaza RS 841, aun con niveles de agallamientos muy altos, debido al desarrollo y vigor de las plantas, permiten obtener producción comercial satisfactoria.

Four cytotypes of Simulium exiguum occur in Ecuador, where this morphospecies is the primary vector of onchocerciasis. In this paper, we give the first full description of the banding pattern of the larval polytene chromosomes of the Quevedo cytotypes differ from the chromosomal standard sequence (of the Cayapa cytotype) by the fixed inversions IIL-5 and IIL-6. The Quevedo cytotype additionally differs from the standard and Bucay cytotypes by processing a differentiated X chromosome, wich is indicated by the inversion IIS-A. As the degree of reproductive isolation between the Bucay and Quevedo cytotypes has not yet been estabilished, they must be regarded as intraspecific variants of the same species. In fact, isoenzyme characterizations showed that the Bucay and Quevedo cytotypes are differentiated only to the extent expected of incipient species or geographical populations. Moreover, the sibiling species status previously given to the Bucay cytotype needs be reassessed, there being inadequate analysis from areas in Ecuador where Bucay occurs in sympatry with the standard Cayapa cytotype. No isoenzyme electromorphs were discovered that identified all or mostadult females of any one (cytotype-pure) collection.