Effect of ethylene degreening on the development of postharvest penicillium molds and fruit quality of early season citrus fruit

The effect of commercial degreening with ethylene gas on fruit susceptibility and quality and development of postharvest green (GM) and blue (BM) molds on early season citrus fruit was investigated. Each cultivar was harvested with different peel color indexes (CI). Fruit were exposed for 3 d to 2 μL L−1 ethylene at 21 °C and 95–100% RH before or after artificial inoculation with Penicillium digitatum or Penicillium italicum. Control fruit were kept at the same environmental conditions without ethylene. Fruit were stored at either 20 °C for 7 d or 5 °C for 14 d and disease incidence (%) and severity (lesion diameter) were assessed. No significant effect of commercial degreening was observed on fruit susceptibility to both GM and BM on citrus cultivars inoculated after degreening. Likewise, no significant effect was observed on disease incidence on citrus cultivars inoculated before degreening and stored at either 20 °C for 7 d or 5 °C for 14 d. In contrast, in cultivars like ‘Clemenules’ mandarins and ‘Navelina’ oranges, degreening significantly increased the severity on fruit with higher initial CI (−3.6 and 1.7, respectively). GM and BM severity on degreened and control ‘Clemenules’ mandarins incubated at 20 °C for 7 d was 146 and 118 mm and 56 and 46 mm, respectively. In general, commercial degreening did not significantly affect external and internal quality attributes of citrus cultivars. Commercial degreening after inoculation of less green (more mature) fruit showed a trend to increase mold severity, presumably through an aging effect (acceleration of peel senescence)

Preventive and curative activity of postharvest potassium silicate treatments to control green and blue molds on orange fruit

Preventive and curative antifungal activities of postharvest treatments with potassium silicate (PSi) against green (GM) and blue (BM) molds were evaluated on oranges (cvs. ‘Valencia’ or ‘Lanelate’) artificially inoculated in rind wounds with Penicillium digitatum and P. italicum, respectively. The most effective PSi concentration, the effect of fungal inoculum concentration, and the influence of temporal and spatial factors on antifungal activity were assessed in in vivo primary screenings. After 6 days of incubation at 20 °C, significant preventive (treatment before fungal inoculation) and curative (treatment after inoculation) activities against GM and BM were observed with PSi at 90 mM (GM and BM incidence reductions of 23 and 52 %, and 23 and 40 %, respectively). In preventive tests, the effectiveness of PSi was influenced by inoculum concentration (103, 104, 105, or 106 spores ml-1), but not by the distance between treatment and inoculation sites (10, 20 or 30 mm). PSi applied about 2 h before inoculation showed higher preventive activity than applied before 24, 48 or 96 h. In order to determine the best dip treatment conditions, PSi at 90 mM was tested at 20 or 50 °C for 60 or 150 s in small-scale trials with ‘Lanelate’ oranges artificially inoculated before or after the treatment and incubated for 7 days at 20 °C. Dips at 20 °C for 60 s were selected and subsequently applied on inoculated ‘Valencia’ oranges stored at 5 °C and 90 % RH for up to 6 weeks. Curative postharvest dips effectively reduced the incidence and severity of both GM and BM during cold storage, while preventive dips significantly reduced the severity but not the incidence. Overall, postharvest PSi treatments showed potential as a new tool to be part of non-polluting strategies to control penicillium decay of citrus fruit

Evaluation of sodium benzoate and other food additives for the control of citrus postharvest green and blue molds

The curative activity of the food additives dehydroacetic acid, dimethyl dicarbonate, ethylene diamine tetracetic acid, sodium acetate, and sodium benzoate (SB) was tested in in vivo preliminary screenings against green and blue molds on citrus fruit artificially inoculated 24 h before with Penicillium digitatum and Penicillium italicum, respectively. SB was the most effective compound and it was further tested in trials simulating postharvest industrial applications. Dip treatments for 60 s with 3% (w/v) SB heated above 50 °C resulted in about 90% reduction of green and blue mold incidence on ‘Valencia’ oranges inoculated, treated, and incubated at 20 °C and 90% RH for 7 days. This treatment was also effective on ‘Lanelate’ oranges, ‘Fino’ lemons and ‘Ortanique’ mandarins, but not on ‘Clemenules’ mandarins. Heated solutions combining SB with low doses (25 or 50 μL L−1) of the fungicide imazalil (IMZ) were synergistic and greatly improved the efficacy of stand-alone treatments. On ‘Valencia’ oranges stored for 8 weeks at 5 °C followed by 7 days of shelf-life at 20 °C, this combination reduced the incidence of green and blue molds almost by 100%. It was found in additional trials to test the preventive activity that 3% SB dips at 50 °C for 60 s did not reduce green mold on ‘Valencia’ oranges treated, inoculated with P. digitatum 24 h later, and incubated at 20 °C for 7 days. It can be concluded from this work that heated SB aqueous solutions might be in the future an interesting nonpolluting disease control alternative for the commercialization of citrus in markets with zero tolerance to fungicide residues

Antifungal activity of sodium propylparaben alone or in combination with low doses of imazalil against Penicillium decay on citrus fruit

The performance of postharvest treatments with sodium propylparaben (SPP), alone or combined with low doses of the fungicide imazalil (IMZ), against citrus green (GM) and blue (BM) molds was evaluated on several citrus species and cultivars artificially inoculated with Penicillium digitatum and P. italicum, respectively, and incubated at 20 °C or cold-stored at 5 °C. Effectiveness of 100 mM SPP dips at 20 °C for 60 s was higher on oranges than on mandarins, with GM and BM incidence reductions of up to 60–90 % after 7 days at 20 °C. Irrespective of citrus cultivar and storage condition, SPP generally improved the curative action of 25 μl l−1 IMZ to control Penicillium molds. In additional tests, 100 mM SPP dips at 20 °C for 60 s only prevented GM on ‘Valencia’ oranges inoculated 24 h after treatment when combined with IMZ. It can be concluded that postharvest SPP treatments show promise as an effective alternative to be considered in citrus postharvest disease control programs

Population Fluctuation of Disonycha teapensis Blake (Coleoptera: Chrysomelidae) in Crotalaria longirostrata Hook. & Arn. (Fabales: Fabaceae) in Huimanguillo, Tabasco, Mexico

Objective: To know the population fluctuation of adults and larvae of D. teapensis, and to determine its relationship with the amount of damaged foliage, temperature and precipitation Methodology: The study was carried out in a culture of C. longirostrata of 48 plants. Weekly data were recorded on the number of adults and larvae, percentage of damaged leaflets, phenology of the plants, temperature and precipitation. With these data, monthly averages were calculated, and correlation analyzes were performed between the population fluctuation of D. teapensis and the fluctuation of the percentage of damaged foliage, temperature and precipitation. Results: The pest occurred in all phenological stages of C. longirostrata, with constant population growth. The population fluctuation was similar to the fluctuation of the percentage of damaged foliage, with a significant positive correlation between both variables. Respect to temperature and precipitation, the correlation was negative but not significant, so the relationship between population fluctuation and that of these climatic factors is not clear. Limitations on study: It was not possible to conduct the study for a full year. Conclusions: The population development of Disonycha teapensis is dependent on the increase in the amount of foliage of its host plant. This insect attacks plants in all their phenological stages and the amount of damaged foliage is considerable. Keywords: Chrysomeloidea, population, chipilin.Objective: To establish the population fluctuation of Disonycha teapensis adults and larvae and to determine its relationship with the amount of damaged foliage, temperature, and precipitation. Methodology: The study was carried out in a n=48 Crotalaria longirostrata plant crop. The following data was recorded every week: number of adults and larvae, damaged leaflets percentage, plant phenology, temperature, and precipitation. Based on these data, monthly averages were calculated, and correlation analysis were performed between the population fluctuation of D. teapensis and the fluctuation of the damaged foliage percentage, temperature, and precipitation. Results: All the phenological stages of C. longirostrata were affected by the pest, which showed a constant population growth. The population fluctuation resembled the fluctuation of the damaged foliage percentage, with a significant positive correlation between both variables. Regarding temperature and precipitation, the correlation was negative but not significant; therefore, the relationship between population fluctuation and these climatic factors is not clear. Study Limitations: It was not possible to conduct the study for a full year. Conclusions: The population development of D. teapensis depends on the increase in the amount of foliage of its host plant. This insect attacks plants in all their phenological stages and the amount of damaged foliage is considerable

Evaluation of chemical resistance inducers in maradol papaya against Phytophthora nicotianae var. parasitica

Objective: To test the efficiency of four chemical resistance inducers in Maradol papaya, to reduce the infections of Phytophthora nicotianae var. parasitica in rainfed crops. Design / methodology / approach: Three doses of each of four resistance inducers were tested in 60-day-old papaya plants in a greenhouse, in a completely randomized design, with four replications and 10 plants as experimental plot. The inoculations with mycelium discs were made three days after the application of the treatments with the inducers, including negative and positive control treatments to evaluate the efficiency applying the Abbott formula. Results: The four chemical inducers (sodium silicate (SS), potassium silicate (SP), potassium phosphite (FP) and acibenzolar-s-methyl (ASM)) presented statistically differences to the negative control (P <0.0001 **). The inductors SS at 1%, SP 1%, FP 0.35% and ASM 0.1 mM showed greater effectiveness (81.2, 75.9, 74.7 and 74.0%, respectively). Study limitations/implications: The effective concentrations retained were tested in a single application, and their durability is not known, so it should be expanded on this point, but it can be an alternative for repeated use after transplantation. Findings/conclusions: the optimal concentrations of PS, SS, PF and ASM which respond against Phytopthora, which must to reduce damage in rainfed planting.Objective: To test the efficiency of four chemical resistance inducers on Maradol papaya to reduce Phytopthora nicotianae var. parasitica infections in rainfed crops at Chontalpa, Tabasco, Mexico. Design/methodology/approach: Three doses of four resistance inducers were tested on 60-day-old papaya plants in a greenhouse with a randomized design, with four replications and 10 plants as experimental plots.  Three days after the inducers' application inoculations with mycelium discs were made, there were negative and positive control treatments to evaluating their efficiency by applying Abbott's formula. Results: The four chemical inducers for resistance (sodium silicate (SS), potassium silicate (PS), potassium phosphite (PF) and acibenzolar-s-methyl (ASM)) were statistically different from the control (P < 0.0001**). The inducers SS 1 %, PS 1 %, FP 0.35 % and ASM 0.1 mM showed higher effectiveness (81.2, 75.9, 74.7 and 74.0 %). Study limitations/implications: The retained effective concentrations were tested in a single application, and their durability is unknown, so this point should be broadened. however, it may be an alternative for repeated use after transplanting. Findings/conclusions: Optimal concentrations of SS, PS, FP, and AMS, that respond against P. nicotianae var. parasitica infections can reduce damages in rainfed crops

The number of tree species on Earth.

One of the most fundamental questions in ecology is how many species inhabit the Earth. However, due to massive logistical and financial challenges and taxonomic difficulties connected to the species concept definition, the global numbers of species, including those of important and well-studied life forms such as trees, still remain largely unknown. Here, based on global ground-sourced data, we estimate the total tree species richness at global, continental, and biome levels. Our results indicate that there are ∼73,000 tree species globally, among which ∼9,000 tree species are yet to be discovered. Roughly 40% of undiscovered tree species are in South America. Moreover, almost one-third of all tree species to be discovered may be rare, with very low populations and limited spatial distribution (likely in remote tropical lowlands and mountains). These findings highlight the vulnerability of global forest biodiversity to anthropogenic changes in land use and climate, which disproportionately threaten rare species and thus, global tree richness