Cassava is attacked by a complex of arthropod pests across the tropical regions of the world where the crop is grown. Root yield losses have been recorded for several pests, including mites, mealybugs, whiteflies, hornworm, lacebugs, thrips and burrower bugs. Agronomic characteristics such as vegetative propagation, a long growth cycle, drought tolerance, staggered planting dates and intercropping contribute to the considerable diversity of pests that feed on the crop. The dynamics of cassava production are evolving as trends in the food, feed and industrial starch sector are leading to an increased demand for high quality starches. The resulting shift to larger scale production units, expansion of cultivated area and modifications in crop management combined with the effects of climate change, especially warmer temperatures and altered rainfall patterns, affect the occurrence and dynamics of arthropod pests in cassava agro ecosystems. Data is presented to describe the effects of temperature and dry seasons on key pest species. Whiteflies, mites and mealybugs register a suitability increase in the same areas in South America: Northeastern Brazil, Northern Argentina, South-Central Bolivia, and Southwest Peru. In Africa increases are projected in Southeast Africa and Madagascar. In Asia, regions with greater projected suitability for these pest species are Coastal India and Southeast Asia. Future trends and important criteria that will influence the severity and management of key pests are discussed.

El desarrollo del mapa genético de yuca ha facilitado las investigaciones en la búsqueda de genes asociados con resistencias a plagas que disminuyen producción y calidad. Las herramientas moleculares como los marcadores facilitan la identificación de los genes que dominan la resistencia a plagas como el caso del ácaro verde (AVY) Mononychellus tanajoa en yuca (Manihot esculenta). Inicialmente se identificaron los individuos de poblaciones retrocruces (BC1) progenie de las cuatro familias denominadas CW. De estos BC1 se seleccionaron individuos resistentes y susceptibles teniendo en cuenta la escala de daño reportada por el programa de Entomología del Centro Internacional de Agricultura Tropical. Se evaluaron 500 cebadores microsatélites mediante análisis de grupos segregantes (BSA), cinco de ellos expresaron polimorfismo y mostraron diferencias significativas entre los parentales, los grupos contrastantes y tres cebadores SSRY 11 SSRY 346 y NS 1099. Al realizar los análisis estadísticos correspondientes se encontró que los cebadores NS 1099 y NS 346 presentaron asociación entre estos y los individuos de las familias CW 67 CW 66 y CW 67 respectivamente. Las familias CW67 Y CW66 presentaron la mejor asociación con los marcadores y éstos presentaron mayor asociación con la característica de resistencia al daño causado por M. tanajoa en la población segregante (cebador NS1099 familias CW66 0.56 CW67 0.61 y NS346 familia CW67 0.61). Con base en estos resultados se puede sugerir la utilización de microsatélites en análisis posteriores en otras poblaciones para lograr la identificación de algunas regiones cromosómicas que confieren la resistencia al ácaro verde de la yuca.

The development of the cassava genetic map has promoted research such as the finding of genes associated with the resistance of pests that diminish the production and quality of the crop. Molecular tools, such as markers can facilitate the identification of the genes that dominate resistance to pests this is the specific case of the presence of resistance to the green mite Mononychellus tanajoa (CGM) in cassava (Manihot esculenta). Initially, at International Center for Tropical Agriculture CAT, individuals populations of backcrosses (BCl), lineage of four denominated families CW, were identified. These BCl were identified and categorized according to 1-5 scale of damage reported by the Entomology Program at International Center for Tropical Agriculture. Resistant and susceptible individuals were identified. A total of 500 microsatellite markers were evaluated using the bulk segregant analysis (BSA). Five of them expressed polymorphism and showed significant differences between parental and contrast groups and three markers, namely, SSRY 11, SSRY 346 and, NS 1099. Statistical analysis revealed that markers NS 1099 and NS 346 displayed the highest association between resistance and the individuals of families CW 67, CW 66 and CW 67, respectively. On the basis of these results we can recommend the use of microsatellite for further analysis in other populations in order to achieve the of some chromosomal regions conferring resistance to green mite cassava.

The cassava mealybug Phenacoccus herreni (Sternorryncha: Pseudococcidae) is a pest of cassava, Manihot esculenta Crantz (Euphorbiaceae), in South America. Proteins, representing direct gene products, are prime candidates in genetic engineering manipulations for host plant resistance. Jatropha gossypiifolia L. (Euphorbiaceae), a plant species known to contain proteins toxic to insects, exhibited insecticidal properties to P. herreni. The toxic compounds consisting of proteins around 101.02 kDa appeared to be mostly located in the mature leaves. Further studies are needed to identify the proteins and to ensure that they are not toxic to mammals.

Insect pests and plant diseases reduce cassava yields substantially, posing a threat to food security throughout the developing world. While agricultural scientists have recognized these threats, few assessments of the geographic distribution of cassava pests and diseases have been made at the global scale. The goal of this study is to make such an evaluation for four key biotic constraints to cassava production in developing countries: whiteflies, cassava green mites, cassava mosaic disease and cassava brown streak disease. Occurrence records were obtained from laboratory and biodiversity databases and from the scientific literature. These records were then used in ecological niche models to predict the potential distribution of cassava pests and diseases. The distribution maps were cross validated by holding back 20% of the occurrence records. Potential distribution maps were developed by combining the results of the best ecological niche models. Hotspots for potential cassava pest and disease outbreaks include the Mato Grosso in Brazil, northern South America, the African rift valley, the southern tip of India and much of Southeast Asia, where all four biotic constraints show high potential suitability. Our work highlights how potential geographical shifts in infestation hotspots for several cassava biotic constraints will require intensified monitoring, evaluation and research to prevent yield losses and ensure food security.

Scarab larvae (Coleoptera: Melolonthidae) are important pests in a diversity of crops and climates owing to their damage to the quality and yield of agricultural products. An alternative for their biological control are the entomopathogenic nematodes, generalist parasites and effective control agents in laboratory and field trials. Isolates of introduced and native entomopathogenic nematodes were evaluated against third instar larvae of Phyllophaga bicolor. We determined the infectivity and mortality of isolates of Steinernema (S. riobravis-Sr, S. carpocapsae Strain all-Sc, Steinernema sp.-SNI, S. arenarium-Sa and S. feltiae-Sf1 and Sf2) and Heterorhabditis (H. bacteriophora-Hb1, Hb2 and Hb3) at a concentration of 10,000 IJs/ml at 23°C and 70 ± 5% R.H. The evaluation was done on larvae that were one, two and three months old. The most ineffective isolates were those of Heterorhabditis (93.75%-Hb2; 89.58% and 64.58%-Hb1-Hb3), compared to those of Steinernema (10.42%-SIN; 12.50%-Sr; 16.67%-Sa, 22.92%-Sc; 33.34%- Sf2; 66.67%-Sf1). The lowest mortalities resulted from Steinernema isolates (0%-Sc and SNI; 2.08%-Sr, 6.25%-Sa; 6.25%-Sf2 and 47.92%-Sf1) while the highest were from Heterorhabditis (52.09%-Hb3; 72.92% and 91.67%-Hb1- Hb2). Differences were noted in infection (1 = 65.64%, 2 = 42.50%, 3 = 29.17%) and mortality (1 = 53.33%, 2 and 3 averaged 31.46%), depending on larval maturity, with a noticeable reduction in these variables when approaching the prepupa. The genus Heterorhabditis is the most promising for the white grub management, especially when applied to young larvae.

Las larvas de escarabajos (Coleoptera: Melolonthidae) son plagas muy importantes en diversidad de cultivos y climas debido a las pérdidas que producen en la calidad y rendimiento de los productos agrícolas. Una alternativa para su manejo biológico son los nematodos entomopatógenos, parásitos generalistas de éstas, y controladores efectivos en pruebas de laboratorio y campo. Se evaluaron aislamientos de nematodos entomopatógenos nativos e introducidos sobre larvas de tercer estadio de Phyllophaga bicolor. Se determinaron la infectividad y mortalidad de aislamientos de Steinernema (S. riobravis-Sr, S. carpocapsae all Strain-Sc, Steinernema sp.-SNI, S. arenarium -Sa y S. feltiae-Sf1 y Sf2) y Heterorhabditis (H. bacteriophora-Hb1, Hb2 y Hb3) con una concentración de 10.000 JIs/ml, a 23C y 70 ± 5% H.R. La evaluación se hizo en larvas de uno, dos y tres meses. Los aislamientos más infectivos fueron los de Heterorhabditis (93,75%-Hb2, 89,58%-Hb1 y 64,58%-Hb3), comparados con los de Steinernema (10,42%-SNI; 12,50%-Sr; 16,67%-Sa; 22,92%-Sc; 33,34%-Sf2; 66,67%-Sf1). Las menores mortalidades se produjeron con los aislamientos de Steinernema (0%-Sc y SNI; 2,08%-Sr; 6,25%-Sa; 6,25-Sf2 y 47,92%-Sf1) mientras que las mayores con los de Heterorhabditis (52,09%-Hb3; 72,92%-Hb1 y 91,67%-Hb2). Dependiendo de la madurez de la larva se presentaron diferencias en infección (1 = 65,64%; 2 = 42,50%; 3 = 29,17%) y mortalidad (1 = 53,33%; 2 y 3 promediaron 31,46%), notándose una disminución en la magnitud de estas variables al acercarse a prepupa. El género Heterorhabditis es el más promisorio para el manejo de chisas especialmente aplicado a las larvas jóvenes.

Aleurotrachelus socialis is one of the most important pests of cassava (Manihot esculenta Crantz) in the Neotropics. In Colombia, high whitefly populations can reduce crop yields by 79%: and although the farmers intensify the use of insecticides, this practice is highly contaminating, costly and leads to the development of resistance in the insect. An alternative for managing whitefly populations is to develop genetically resistant varieties. Wild parents of Manihot are a useful source of genes against pests for the cultivated species of cassava. Based on prior research that showed the existence of moderate-to-high levels of resistance to A. socialis in Manihot flabellifolia, a wild species of cassava, this study was proposed to characterize this new source of resistance, evaluating the biology and demographics of A. socialis on eight accessions of M. flabellifolia, a susceptible check (CMC-40) and a resistant (MEcu72) check. The averages of A. socialis longevity and fecundity on the accessions were not significantly different to MEcu72, but different from CMC-40 (P < 0.05). Development time was not significantly different, ranging from 35-40 days on accessions and MEcu72 and 33.5 days on CMC-40 (P < 0.05). In contrast, the population growth rate (r(m)) was significantly lower on the M. flabellifolia accessions, with Fla 61 standing out with a growth rate 98 and 99% less than that obtained on MEcu72 and CMC-40, respectively. Once the resistant levels have been identified to A. socialis on the M. flabellifolia accessions, interspecific crosses of M. esculenta subsp. M. flabellifolia and backcross programs could be developed to incorporate the desirable characteristics from the wild relatives into elite progenitors of M. esculenta. (C) 2009 Elsevier Ltd. All rights reserved.

Nematodos entomopatógenos (NEP‚s) de los grupos Heterorhabditidae y Steinernematidae son usados como agentes potenciales de control de numerosas plagas subterráneas, encontrándoselos según estudios de su distribución, en diversidad de hábitats a través del mundo. En el mismo interés de control de rizófagos, especialmente las plagas del complejo chisas (Coleoptera: Melolonthidae) y chinche de la viruela Cyrtomenus bergi (Hemiptera: Cydnidae), se realizó una búsqueda e identificación de cepas nativas de NEP‚s, tomando muestras de suelos en Quindío, Risaralda, Caldas y Cauca. Para la extracción de NEP‚s se emplearon larvas trampa de Galleria mellonella (Lepidoptera: Pyralidae); después de comprobar su patogenicidad siguiendo los postulados de Koch, se multiplicaron, almacenaron e identificaron. De las 284 muestras (300 g de suelo c/u) de 15 cultivos, en 23 sitios 17 resultaron positivas para nematodos entomopatógenos y saprófagos. Usando la técnica PCR dos muestras fueron identificadas como Steinernema kraussei Steiner (Rhabditida: Steinernematidae), procedentes de yuca (ex Manihot esculenta L.) de Cauca y Risaralda (ex Inga spp.), constituyéndose en el primer reporte para Colombia.

Entomopathogenic nematodes (EPN) of the groups Heterorhabditidae and Steinernematidae are used as potential control agents of soil pests, being found in many habitats worldwide according to studies of their distribution. We collected soil samples in four Colombian departments (Quindio, Risaralda, Caldas, and Cauca) in order to isolate and identify native EPN strains associated with whitegrub (Coleoptera: Melolonthidae) and burrower bug (Hemiptera: Cydnidae) Cyrtomenus bergi soil pests. EPN isolation was done through the Galleria mellonella (Lepidoptera: Pyralidae) bait method. After verifying the entomopathogenicity of the samples using Koch"rsquo;s postulates, we multiplied, stored and identified the EPN. We analyzed 284 samples (300 g of soil each) collected in 23 sites in 15 crops. Pathogenic and saprophytic nematodes were present in 17 samples. PCR technique lead to the identification of Steinernema kraussei Steiner (Rhabditida: Steinernematidae) coming from of two samples, one from Cassava (ex Manihot esculenta L.) in Cauca and the second one from Inga spp. in Risaralda, being these the first record of the species for the country.