Evaluation of the fungicide PENBOTEC 40 SC in postharvest of cherries 

A. Colodner; A.P. Candan and G. Calvo – Post-harvest Area – EEA Alto Valle, Year 2019.

Introduction 

The Alto Valle region of Río Negro and Neuquén offers excellent agro-ecological conditions for cherry cultivation, as well as the possibility of having markets in the off-season. Because of this, cherry production is a very interesting diversification alternative and the surface area planted with this species has increased significantly in recent years.  

Cherry is a highly perishable fruit with a limited marketing period, so it is necessary to have effective technologies that allow preserving the quality of the harvested product. The development of rot is one of the main causes of losses during the post-harvest of cherries. To prevent them, an integrated management program must be implemented that includes carrying out different practices during the field production phase, as well as during and after the harvest (Candan et al., 2017). Among prevention practices, the application of fungicide products in post-harvest is very effective when done at the right time and in the right way.  

On the packaging line, fungicides can be in contact with different sanitizing products, either accidentally, for example through the water used to wash or transport the fruit, or intentionally, when they are mixed. ad hoc in application systems that require recirculation, such as showers on the line or immersion trays. In these cases, it is important to know the compatibility between the sanitizing product and the fungicide, in order to maintain the microbiological quality of the mixture without compromising the biocidal activity, as well as to avoid possible phytotoxicity problems on the fruits.  

The fungicide pyrimethanil has been shown to be very effective in controlling postharvest diseases in pome fruit (Di Masi and Colodner, 2010), but information for its use in cherries is scarce. The aim of this work was to evaluate the compatibility of the fungicide Penbotec 40SC (i.e. pyrimethanil, Janssen) with peracetic acid and its efficacy at different concentrations in cherries. 

Two (2) tests were performed separately, using the following general procedure: 

-Cultivation: Cherry (Prunus avium) 

-Variety and harvest date: Bing 7/12/2018 

-Products evaluated: Penbotec 40 SC (ia pyrimethanil, Janssen) and BioFruit HF15 (mixture of peroxyacetic acid 15% and hydrogen peroxide 22%, Enviro Tech) 

-Maturity: a maturity assessment was carried out to characterize the batch of fruit at the time of the test. 

-N° of repetitions: 6; Sample size: 20 fruits 

-After harvesting, the fruit was cooled in hydrocooling to eliminate field heat and stored in a cold chamber until the next day when treatments were carried out with the fruit cold at 4-5 °C, simulating the usual practice in commercial establishments.  

-Application Method: Fruit was immersed for 1 minute. Sufficient volume of application was prepared to achieve proper immersion. The pH of the water was adjusted to between 6 and 8. All repetitions of the same treatment were treated at once.  

-After treatment, the fruits were packed in alveolar trays and boxes with folded 25μ LDPE bags. All treatments were stored in a chamber at -0.5 °C for 40 days.  

-After the 40-day cold storage period, the boxes were removed from the chamber and placed at room temperature (20ºC). Assessments were carried out at 0, 3 and 7 days after the boxes were removed from the chamber. 

–Reviews:  

a) Incidence and severity of fungal rots Alternaria spp., Penicillium spp., others. Incidence expressed as a percentage (%) of rotted units per treatment. Severity expressed in diameter (cm) of the rots. 

b) Symptoms of phytotoxicity on the fruit or on the peduncle 

c) Other effects, positive or negative, observed on the fruits. ∙ Statistical analysis: Statistical analysis of variances with separation of means was performed using the Scott & Knott test (0.05) using the InfoStat 2018 software.

Results and discussion

The maturity indices of the fruits at the time of the test (Table l) were within the harvest parameters recommended for this variety in the Alto Valle region (Raffo et al., 2009).

ESSAY 1: Effectiveness

The fungicide Penbotec 40SC was effective in controlling rot in Bing cherries after 40 days of storage plus 3 and 7 days at room temperature, depending on the concentration used.

At the time of removal from the chamber, no differences were observed between the evaluated treatments. After 3 days at room temperature, all the fruits treated with fungicide reduced the incidence of rot compared to the Control fruits. Seven days after the fruit was removed from the chamber, a very significant effect (p<0.0001) of the concentration of Penbotec 40SC was observed, obtaining 16.7% and 11.7% less rot with Penbo-200 compared to Penbo-50 and Penbo-100, respectively (Table 2). In previous studies carried out at the EEA Alto Valle of INTA, the same concentrations of this active ingredient were evaluated on Bing cherries and a significant reduction in the incidence of rot was observed with the concentration of 200 cc/hl, compared to the lowest concentrations evaluated, after 45 days at 0 °C plus 7 days at room temperature (Colodner and Candan, 2016).

ESSAY 2: Phytotoxicity
According to the results obtained in this study, the combination of Penbotec 40SC with PAA does not produce phytotoxic damage to the fruits or peduncles, in any of the concentrations or combinations evaluated.

After 40 days of cold storage plus 7 days at room temperature, the Penbo-200 treatment significantly reduced the amount of rotten fruit compared to Penbo-100, which in turn reduced the amount of rotten fruit compared to the Control, demonstrating the additive effect of the increase in concentration (Table 4). These results coincide with those obtained in the efficacy test presented above (Table 2), as well as with other previous work carried out at the EEA Alto Valle of INTA (Colodner and Candan, 2016).

The PAA-160 treatment significantly reduced the incidence of rot compared to the Control, while the lower concentrations of PAA-40 and PAA-80 did not achieve significant differences compared to the Control (Table 4). It is important to note that the main objective of adding a sanitizer to water is to reduce the amount of microorganisms present in the liquid to avoid cross contamination, but the effect on the surface of the fruits is limited (Vero, et al., 2010).

The mixture of Penbo-100 with PAA was effective, even at the lowest concentrations of the sanitizer evaluated. Penbo-100+PAA-40 reduced the percentage of rotten fruit by 60.51 TP3T compared to the control and had no significant differences compared to Penbo-200. In the case of Penbo-200, the combination with PAA did not provide an additional benefit compared to the use of the fungicide alone, which could be explained because the fungicide at this concentration reached the maximum possible control levels, according to the conditions in which this study was carried out (Table 4). In previous works carried out under similar conditions, the treatment with the concentration of 200 cc/hl of the fungicide significantly reduced the incidence of rot compared to the Control, obtaining 28.1 TP3T of rotten fruit after 45 days of cold storage plus 7 days at room temperature (Colodner and Candan, 2016).

In no case did the combination of Penbotec 40SC with the PAA sanitizer reduce the effectiveness of the treatment compared to the fungicide used alone, which shows that both products are compatible for use in a mixture. This coincides with the results presented by Adaskaveg (2015), who also demonstrated the incompatibility between pyrimethanil and chlorine, which is the most widely used sanitizer in the region. The possibility of mixing Penbotec 40SC with PAA is very interesting in treatment systems that foresee the recirculation of the broth, since the sanitizer reduces the microbial load of the broth while maintaining its quality and allowing a more efficient use of the fungicide (Table 4).

Regarding the severity of the rot, after the conservation period plus 7 days at room temperature, it is observed that all the fruits treated with Penbotec 40SC, either alone or combined with PAA, presented a smaller lesion size than the Control fruits or those treated only with PAA (Table 5).

Similar to the results obtained in the efficacy trial presented above and in previous studies carried out in the region (Colodner and Candan, 2016), Alternaria spp. was the main pathogen identified with more than 60% of the total rotten fruit in all treatments. The presence of Penicillium spp. was lower and was significantly reduced in the fruits treated with Penbotec 40 SC (Figures 3 and 4).