Morphological and molecular characterization of Castniidae (Lepidoptera) associated to sugarcane in Colombia.

The giant sugarcane borer, Telchin licus, has been reported as an economically important sugarcane pest in Colombia; however, its taxonomic status has been scarcely investigated and previous reports offer an ambiguous characterization of both the immature and adult stages. The objective of this work is to identify Telchin species affecting sugarcane and alternative hosts in different departments of the country by integrating molecular analysis and conventional morphology. To date, T. licus has been found in the departments of Caquetá, Casanare, and Meta, while T. atymnius has been found in Antioquia, Caldas, Nariño, and Valle del Cauca. Sugarcane, Musaceae, and Heliconiaceae have been found to be hosts to both species. Additionally, the species T. cacica has also been registered in the department of Nariño, affecting heliconias and plantains. Genetic variation within the species allowed differentiation at the molecular level of subspecies of T. licus and T. atymnius, confirming that the subspecies present in Colombia are T. licus magdalena, T. atymnius humboldti, and T. atymnius atymnius. The haplotype diversity of populations is closely related to their geographical distribution, indicating low gene flow between populations and possible speciation inside the country. Analysis of genetic variance showed significant differences among and within T. atymnius populations, which may suggest a high genetic structure along the regions where it is found and the possible presence of additional subspecies to those previously reported. To understand the geographical and environmental conditions that determine the pest's distribution in Colombia, this information needs to be complemented with ecological considerations of possible geographical isolation and association of alternative hosts.

Response of resistant and susceptible Brachiaria spp. genotypes to simultaneous infestation with multiple species of spittlebugs (Hemiptera: Cercopidae).

The response of one susceptible and three resistant Brachiaria spp. (Hemiptera: Cercopidae) genotypes to individual or combined attacks by nymphs of Aeneolamia varia (F.), Aeneolamia reducta (Lallemand), Zulia carbonaria (Lallemand), and Zulia pubescens (F.) was studied. We assessed the effect of infesting plants of the susceptible check BRX 44-02 and of the A. varia-resistant genotypes CIAT 6294 and CIAT 36062 with A. varia, Z. carbonaria, or Z. pubescens either alone or in two-species combinations. In a second trial, we studied the performance of BRX 44-02, CIAT 6294, and the multiple resistant clone SX01NO/0102 exposed to individual or combined attack by A. reducta and Z. carbonaria. In a third trial, we compared the response of BRX 44-02, CIAT 6294, and CIAT 36062 to individual A. varia, Z. carbonaria, or Z. pubescens attack as opposed to a combined three-species attack. Plant damage scores and percentage of nymphal survival were recorded in all three trials. Data on percentage of survival indicated that competition between and among spittlebug species occurs. However, we found no evidence of interaction between species competition and different levels of resistance to spittlebug. Rather, host genotype reactions conformed to previously known categories of resistance regardless of the presence of more than one spittlebug species. Resistance rather than competition seems to have been the overriding factor determining nymph survival and resistance expression (damage scores) in these experiments. Our results corroborate the need to develop brachiariagrass genotypes with multiple resistance to spittlebugs.

Antibiosis and tolerance to five species of spittlebug (Homoptera: Cercopidae) in Brachiaria spp.: implications for breeding for resistance.

Several genera and species of spittlebugs (Homoptera: Cercopidae) are economic pests of Brachiaria spp. grasses in tropical America. To support current breeding programs aimed at obtaining multiple spittlebug resistance, we undertook a series of studies on antibiosis and tolerance as possible mechanisms of resistance to five major spittlebug species affecting Brachiaria spp. in Colombia: Aeneolamia varia (F.), Aeneolamia reducta (Lallemand), Zulia carbonaria (Lallemand), Zulia pubescens (F.), and Mahanarva trifissa (Jacobi). Four host genotypes, well known for their reaction to A. varia attack, were used to compare their resistance to other spittlebug species: CIAT 0654 and CIAT 0606 (susceptible) and CIAT 6294 and CIAT 36062 (resistant). CIAT 0654 and CIAT 36062 were used in antibiosis studies. Tolerance studies were conducted with CIAT 0654, CIAT 6294, and CIAT 36062. Sixty-five hybrid-derived clones were used to identify levels of multiple resistance to three spittlebug species. The levels of antibiosis resistance in CIAT 36062 clearly differed by spittlebug species and were classified as follows: very high for M. trifissa, high for A. varia and A. reducta, moderate for Z. pubescens, and absent for Z. carbonaria. Our results suggest the presence of true tolerance to Z. carbonaria in CIAT 6294 and CIAT 36062, true tolerance to Z. pubescens in CIAT 6294 and a combination of tolerance and antibiosis as mechanisms of resistance to Z. pubescens in CIAT 36062. Of the 65 hybrid clones tested with A. varia, A. reducta, and Z. carbonaria, 15 combined resistance to two species and three showed antibiosis resistance to all three spittlebug species.