The center of origin of peanut is located in South America, specifically in southeastern Bolivia and northwestern Argentina, where its parental species are found in wild habits. Even though Argentina is only the seventh largest producer of peanut in the world (2% of global production), it is the leading exporter of edible grain and crushed (e.g., flour, butter, and oil) peanut products worldwide. Peanut production was moved to more southern areas of Cordoba in the early 1990s to avoid the consequences of production issues in the northern region. During this migration process, a new disease emerged in commercial plots: peanut smut caused by Thecaphora frezii. Peanut smut was first detected in the northern peanut producing areas in Córdoba Province, and then established on the central region where the main grain processing industries are located. Currently, the prevalence is 100% in Argentinian peanut area. This finding showed evidence that pathogens could also migrate along with peanut production activities and contaminate soil of new production areas.

In Brazil, passion flower is grown across almost the entire country. The predominant disease of the passion flower crop is passion fruit woodiness, caused by the potyvirus cowpea aphid‐borne mosaic virus (CABMV), and transmitted by aphids in a nonpersistent manner. The disease reduces the useful life of the orchard from 36 months to approximately 18 months. Up to now, there has not been an efficient method for disease management. The aim of this work was to evaluate the efficiency of systematic roguing of diseased plants through weekly inspections, for disease management in the field. The latent and incubation periods of CABMV in passion flower vines were determined in order to optimize roguing efficiency. Passion fruit plants inoculated with CABMV started to act as sources of inoculum from 3 days after inoculation (DAI), and the symptoms were expressed, on average, at 8 DAI. Five field experiments, conducted in the states of São Paulo and Bahia, Brazil, demonstrated that systematic roguing of diseased plants was significantly efficient for managing passion fruit woodiness disease. In order to facilitate identification and subsequent removal of the infected plants, they need to be grown separately. This cultural practice can be recommended for managing passion fruit woodiness disease, provided it is applied on a regional scale by all passion fruit growers. The development of some pilot plantings for the application of roguing in a passion flower‐producing region is recommended to validate the use of this technique for managing passion fruit woodiness disease.

No abstract

Target spot of soybean has spread in Brazil, the southeastern United States and Argentina in the last decade. A collaborative network of field Uniform Fungicide Trials (UFT) in Brazil was created in 2011 to study the target spot control efficacy of fungicides, including azoxystrobin + benzovindiflupyr (AZ_BF), carbendazim (CZM), fluxapyroxad + pyraclostrobin (FLUX_PYRA), epoxiconazole + FLUX_PYRA (EPO_FLUX_PYRA), mancozeb (MZB) and prothioconazole + trifloxystrobin (PROT_TRIF). Network meta‐analysis was used to conduct a quantitative synthesis of UFT data collected from 2012 to 2016 and to evaluate the effects of disease pressure (DP, low ≤ 35% target spot severity in the nontreated control < high) and year of experiment on the overall mean efficacy and yield response to each of the tested fungicides. Based on mean percentage control of target spot severity, the tested fungicides fall into three efficacy groups (EG): high EG, FLUX_PYRA (76.2% control relative to the nontreated control) and EPO_FLUX_PYRA (75.7% control); intermediate EG, PROT_TRIF (66.5% control) and low EG, MZB (49.6% control), AZ_BF (46.7% control) and CZM (32.4% control). DP had a significant effect on yield response. At DPLow, the highest response was due to PROT_TRIF (+342 kg ha−1, +12.8%) and EPO_FLUX_PYRA (+295.5 kg ha−1, +11.2%), whereas at DPHigh, EPO_FLUX_PYRA and FLUX_PYRA outperformed the other treatments, with yield responses of 503 kg ha−1 (+20.2%) and 469 kg ha−1 (+19.1%), respectively. The probability of a positive return on fungicide investment ranged from 0.26 to 0.56 at DPLow and from 0.34 to 0.66 at DPHigh.

Tomato severe rugose virus (ToSRV) and tomato chlorosis virus (ToCV) are among the major viruses that affect tomato (Solanum lycopersicum) development and yield in Brazil. ToSRV and ToCV are transmitted in a persistent circulative and semi-persistent manner, respectively, by the whitefly Bemisia tabaci Middle East-Asia Minor 1 (MEAM1), considered the main vector of these viruses. In this study, the kinetics of systemic invasion and the latent and incubation periods of ToSRV and ToCV were evaluated in singly- and doubly-infected tomato plants. Both viruses moved systemically into tomato plants as early as one day after inoculation. The mean ToCV latent periods in single and co-infections with ToSRV were 13 and 11 days, respectively, while incubation periods in single and co-infections were, on average, 30 and 31 days, respectively. For ToSRV, the mean latent period was 7 days in single infections and 6 days in co-infections with ToCV. Incubation periods were, on average, 18 and 17 days in single and co-infections, respectively. As latent periods for both viruses were shorter than their respective incubation periods, field-infected tomato plants may act as sources of inocula soon after infection and before onset of symptoms.

No abstract

The American palm weevil, Rhynchophorus palmarum, is the main primary pest of palms in tropical America and the principal vector of the red ring disease, the major phytosanitary problem of coconut and oil palm in South America. The current management of the problem is based on the capture of adult weevils with aggregation pheromone and the elimination of diseased palms, a system difficult to implement for smallholder producers. Biocontrol agents of the weevil, the tachinid parasitoids Billaea spp., are known with limited distribution in Bahía State of Brazil. Their introduction and release in affected areas could greatly improve the natural control of the weevils. Furthermore, these parasitoids are known to attack palm-boring weevils in five different genera and could be a new control option for the red palm weevil, Rhynchophorus ferrugineus, the worst pest of palms worldwide. The collection, rearing and study of these parasitoids for introduction in new areas are the aim of this study. A detailed analysis of the necessary steps to comply with regulatory aspects and a research programme to ensure biosafety is described.

The lack of robust estimates of soybean yield losses due to target spot led to this study. The objective was to determine whether soybean yield at stage R8 (W, expressed as kg ha−1) was related to target spot severity at soybean stage R5–R6 (S, expressed as %) and to identify variables that could affect this relationship. Plot‐level estimates of mean disease severity and yield from 41 selected Uniform Fungicide Trials carried out in Brazil during 2012–2016 growing seasons were used to estimate linear regression coefficients for the relationship between yield and target spot severity through random‐coefficient mixed effects model analysis. The overall estimated mean regression intercept and slope were truenormalβ0^ = 3564 kg ha−1 (disease‐free yield) and truenormalβ1^ = −17.1 kg ha−1 %−1 (W decrease per percent increase in S), respectively. The model was then refitted with different covariates to determine their effects on model parameters. β0 was influenced by baseline yield (less than or greater than 3300 kg ha−1) and β1 was affected by yield response to fungicide treatments. Estimated yield loss at 50% target spot severity ranged from 8% to 42%. Cultivar also had a significant effect on the magnitude of yield reduction due to target spot, which ranged from 11% to 42%, depending on the cultivar.