Huanglongbing (HLB) is the most destructive disease of citrus worldwide. Monitoring of health and detection of diseases in trees is critical for sustainable agriculture. HLB symptoms are virtually the same wherever the disease occurs. The disease is caused by Candidatus Liberibacter spp., vectored by the psyllids Diaphorina citri Kuwayama and Trioza erytreae. Electron microscopy was the first technique used for HLB detection. Nowadays, scientists are working on the development of new techniques for a rapid HLB detection, as there is no sensor commercially accessible for real-time assessment of health conditions in trees. Currently, the most widely used mechanism for monitoring HLB is exploration, which is an expensive, labor-intensive, and time-consuming process. Molecular techniques such as polymerase chain reaction are used for the identification of HLB disease, which requires detailed sampling and processing procedures. Furthermore, investigations are ongoing in spectroscopic and imaging techniques, profiling of plant volatile organic compounds, and isothermal amplification. This study recognizes the need for developing a rapid, cost-effective, and reliable health-monitoring sensor that would facilitate advancements in HLB disease detection. This paper compares the benefits and limitations of these potential methods for HLB detection.Key words: HLB, detection, trees, monitoring, health.Résumé : La maladie du dragon jaune (MDJ) est la maladie des agrumes la plus destructrice au monde. Pour assurer la durabilité agricole, il est essentiel de contrôler la santé et la présence de maladies chez les arbres. Les symptômes de la MDJ sont pratiquement les mêmes quel que soit le point d'origine de la maladie. Celle-ci est causée par Candidatus Liberibacter spp. et transmise par les psylles Diaphorina citri Kuwayama et Trioza erytreae. La technique de microscopie électronique fut le premier mode de détection de la MDJ. De nos jours, des scientifiques travaillent à l'élaboration de nouvelles techniques de détection de la MDJ puisqu'il n'existe aucun détecteur commercial permettant l'évaluation de l'état de santé des arbres en temps réel. Actuellement, on doit la plupart du temps recourir à l'exploration pour surveiller la MDJ, un processus laborieux, coûteux et pénible. On a recours à des techniques moléculaires comme la réaction de la polymérase en chaîne pour identifier la MDJ, ce qui exige un prélèvement et un traitement minutieux. Par ailleurs, on évalue présentement des techniques de spectroscopie et d'imagerie, le profilage de composés végétaux organiques volatils et l'amplification isothermique. La présente étude met en relief le besoin de mettre au point un dispositif d'analyse de l'état de santé qui serait à la fois rapide, rentable et fiable et qui permettrait de faire progresser la détection de la MDJ. Cet article compare les avantages et les limites de ces méthodes aspirant à la détection de la MDJ. [Traduit par la Rédaction]

Source: Florida Entomologist, 98 (3) : 950-953Published By: Florida Entomological Society

Mexico is the main producer, consumer and exporter of avocado in the world, being Michoacan the main producer state contributing more than 80% of the national production. There are phytopathogens that decimate the production causing the death of the tree. Root samples were collected in avocado trees that showed the characteristic symptomatology of the disease known as avocado sadness, the sampling was carried out in four of the main avocado producing towns, in the state of Michoacan, Mexico. The isolation consisted in sowing root tissue in Petri dishes with V8®-PARPH culture medium, subsequently they were identified morphologically and for species level it was determined by molecular biology, with the PCR-ITS technique. Pathogenicity tests were performed in triplicate with avocado seedlings with more than six leaves. After 24 hours, the inoculated plants expressed decay in the apical part, after 120 hours the leaves showed yellowing and after 15 days there was a generalized wilt on the stem and leaves, re-isolating the phytopathogen Phytopythium vexans. This study confirms the first report of the oomycete P. vexans affecting avocado trees in the most important producing region of the Mexican Republic.

El trabajo se desarrolló durante 2012 en el Laboratorio de Nematología de la Universidad Autónoma Agraria Antonio Narro, con el objetivo de evaluar extractos vegetales derivados del nogal Carya illinoinensis (Wangenh) K. Koch, para el control del nematodo agallador Meloidogyne sp. Göldi 1889. Los nematodos fueron obtenidos a partir de tubérculos de papa (Solanum tuberosum L.) Var. “Alpha”, que presentaban sintomatología. Se realizó la identificación de los nematodos y se determinó que correspondían a Meloidogyne incognita. Para el estudio de evaluació de efectividad biológica de los extractos se colocaron los extractos a diferentes concentraciones, (1.0, 1.5 y 2%) utilizando una población de 30 ±5 especímenes de Meloidogyne incognita activos, se estableció un experimento completamente al azar, con once tratamientos incluyendo al testigo y cinco repeticiones. Se observaron al microscopio estereoscópico a las 24, 48 y 72 h de exposición con los extractos, para determinar el porcentaje de mortalidad. De los extractos evaluados, los que presentaron mayor actividad nematicida fueron el FIM8 (ruezno acuoso) con 89.16%, FIM6 (Ruezno etanolítico) con 69.22%, y el FIM7 (Cáscara acuoso) con 60.77%, todos éstos en la concentración al 2% y en la observación a las 72 h de exposición con el extracto.

No abstract

The complications caused by the generation of resistance in the psyllid Bactericera cockerelli by chemical pesticides, raise the need for the alternative use of products that reduce resistance and ensure better control. The species Crotalaria longirostrata is a source of secondary metabolites, which show possible activity against insect pests. The objective of the research was to identify the compounds of the crude methanolic extract of C. longirostrata leaves, as well as to evaluate their biological activity on B. cockerelli nymphs. Twenty-five compounds were identified by Gas Chromatography coupled to Mass Spectrometry (GC-MS) analysis; the most abundant was 1β,2β-epoxy-1α-methoxymethyl-8α-pyrrolizidine; an alkaloid of the iminosugar group, reported for the first time in C. longirostrata, of which concentrations from 2 to 30 mg/mL of the methanolic extract had to be prepared to evaluate on B. cockerelli nymphs. It showed that at 48 h, there was a mortality of 73.2%-100% in the treatments of 8, 12, 16, 20, and 30 mg/mL. The mean lethal concentration (LC50) was 4.78 mg/mL and LC95 14,52 mg/mL. The results obtained with the methanolic extract of C. longirostrata leaves for controlling the insect B. cockerelli suggest that it can potentially be used as an alternative insecticide of botanical origin to manage the insect.

No abstract

No abstract