Common name of each fungicide tested, their corresponding trade names, active ingredient percentages, manufacturers, and preharvest application rates.
Green mold, caused by Penicillium digitatum, is the leading cause of citrus decay in Japan. Due to a ban on the post-harvest fungicide application in Japan, the preharvest application of benzimidazoles has been used and demonstrated good efficacy since 1971. A benzimidazole resistant P. digitatum strain was first isolated from a packinghouse in 1974, and more cases were reported in subsequent years. On the other hand, very few cases were reported from the grove for two decades. However, by the mid-1990s, when the field incidences of benzimidazole resistant strain started to increase, the effect of benzuimidazoles became unstaible. An alternative to a benzimidazoles, iminoctadine triacetate, exhibited good antifungal activity against P. digitatum in vitro, but its efficacy was inconsistent in the field. We examined the efficacy of a mixed application of iminoctadine triacetate and benzimidazoles against each fungicide by itself based on five years of data from multiple locations. The results indicated a synergistic suppression on green mold, where the efficacy of the mixture was consistently greater than treatments with either fungicide alone. The improved efficacy was considered acceptable for a practical use by the industry, and lead to a development of a pre-mixed commercial product, Beftopsin flowable in 2006.
- citrus green mold
- iminoctadine triacetate
- preharvest control
- synergistic effect
Postharvest diseases of citrus, particularly on the Satsuma mandarin orange (
In this chapter, the problem of fungicide-resistant strains associated with the occurrence of citrus green mold (caused by
2. Postharvest diseases in citrus cultivated in Japan
Several postharvest diseases affect citrus fruits (Figure 1). Among these diseases, green mold (caused by
Excluding anthracnose and brown rot, each of these pathogens infects plants through wounds on rind tissues, causing the fruit to rot. Development of anthracnose can be promoted by a damage on rind tissues, but wounds were not necessary to cause infection. The increase in problems associated with postharvest diseases of citrus in recent years is partially due to a strong consumer preference for high sugar and low acid contents. This demand has driven the production of ripe fruits with a thinner, bruise-prone rind. Because many postharvest citrus diseases take advantage of damages on rind tissues, the prevention of postharvest diseases on ripe fruits becomes more difficult.
3. Factors influencing the occurrence of postharvest diseases and prevention
The occurrence of postharvest diseases, such as green mold, is related to three major factors: (i) ripe fruit that rots easily, (ii) the presence of pathogens and its infection condition, and (iii) insufficient efficacy of fungicides. Several environmental and cultivation conditions affect these factors (Figure 2). The market demand for riper fruit results in more green mold susceptible fruits; furthermore, these fruits are more susceptible to damage to the surface of fruits, which can be caused by rough handling, contaminations in a harvest container such as dead twigs, cut peduncles, and very small pebbles  or by peduncles attached to fruits that were cut too long .
It is safe to assume
Presence of all three of these major factors is required for fruit rot development. For example, even if the surface of a fruit is damaged by rough handling, the fruit would not rot in the absence of a pathogen. Even if a damaged fruit is exposed to a pathogen, an effective fungicide would prevent rot. Therefore, if the effect of one of these three factors can be eliminated, postharvest diseases can be prevented. However, it is difficult to completely eliminate any of these factors because not only these three factors are influencing each other, but also each is highly depended on so many other external factors to form complex relationships (Figure 2). Therefore, rather than aiming for the elimination, it is important to aim for sufficient reduction of these three factors so that incidences of rotten fruits can be suppressed.
4. Basis for the implementation of cultural measures against postharvest diseases
4.1. Relationship between precipitation and postharvest diseases
Precipitation during harvest sharply increases the number of rotten fruits both at harvest and postharvest . Precipitations not only make fruits more susceptible to rot , but it also washes fungicides off plants  to limit their function. In addition, many plant pathogens require water for their dissemination and penetration into plant tissues. However, when plants are grown outdoors, precipitation cannot be artificially controlled; thus, other than site selection and cultural practices to increase airflow in groves, our options against the precipitation are very limited.
4.2. Relationship between fruit cultivar, tree age, and postharvest diseases
Based on an analysis of fruits shipped from approximately 3200 groves, postharvest diseases tend to occur more frequently with fruits harvested from older trees than relatively young trees, irrespective of cultivar. The rate of rotten fruits did not differ between seedlings and top-grafted trees younger than 30 years but was higher with top-grafted trees 30 years or older . These findings indicate the influence of age and type of grafting, and stricter countermeasures are probably necessary for top-grafted grove of 30 years or older. The other potential tools for green mold management may be derived from understandings of tree properties and soil conditions that promote the occurrence of rotten fruits, but further researches are needed.
4.3. Importance of the source of infection and the control of disease via the removal of the source
The quantity of spores from green mold fungus scattered in groves can be substantially reduced by removing fruits affected by green mold prior to the harvest. By thinning fruits and removing all fruits with sign of spore formation prior to the harvest, the occurrence of rotten fruits can be reduced . For example, following the final thinning of fruits, some growers completely remove debris from their groves. This is a cultural measure that needs to be actively promoted in the future.
5. Importance of fungicide control
Damage to the surface of fruits, which often happen during the processes of harvest, transportation, and sorting, is the only means of infection for
6. Fungicide use to prevent postharvest diseases and the development of resistant strains
The fungicide with a superior effect against the green mold and the blue mold has not existed until the latter half of 1960s. Thus, by 1971, soon after the introduction of benzimidazoles, it became common to apply a benzimidazole (benomyl or thiophanate-methyl) immediately prior to harvest in Japan. In Japan, the use of fungicide to harvested fruits is prohibited by the Agricultural Chemicals Control Act. Therefore, unlike countries in which harvested fruits are drenched or dipped in fungicides in packinghouses in order to prevent the rotting of fruits during storage or transportation [3,18–20], the only chemical control measure available in Japan is fungicides that are sprayed in groves prior to harvest. The preharvest spray of benzimidazoles was shown to have a favorable suppressive effect on many postharvest diseases, particularly green mold [21–30]. Furthermore, iminoctadine triacetate [31, 32], which has a different mode of action from that of benzimidazoles, became available in 1985. Presently, seven preharvest fungicides have been registered to prevent postharvest diseases in Japan, but these two fungicides (i.e., iminoctadine triacetate and benzimidazoles) are the only ones in use. Compared to other mode of action groups, their effects are consistent, and costs are relatively low. However, compared to many other diseases of citrus or other crops that are typically managed using four or five modes of action, the use of just two fungicides for citrus postharvest disease increases the risk of resistant strain development.
Benomyl, (methyl 1-(butylcarbamoyl) benzimidazol-2-yl-carbamate, is a systemic benzimidazole fungicide discovered by DuPont in the early 1960s (rates and other information are summarized in Table 1). It prevents cell division in sensitive fungi by binding to tubulin and inhibiting the formation of spindle fibers at metaphase and is highly active at low concentrations against spore germination and mycelial growth. Further, locally systemic properties enable the fungicides to penetrate the host tissue and provide post-infection curative action. It was first registered under the brand name Benlate (50% wettable powder) by DuPont in Japan in 1971 and Sumitomo Chemical Co., Ltd. (Tokyo, Japan) acquired the business in 2002. Benomyl is a very broad-spectrum fungicide with low phytotoxicity and controls many fungi in the classes Ascomycetes, Deuteromycetes, and Basidiomycetes. It has long been used for wide range of crop groups, notably for citrus as a postharvest diseases control agent with its strong rainfastness and residual activity.
Thiophanate-methyl, dimethyl 4,4′-(
Iminoctadine triacetate, 1,1′-iminodi (octamethylene) diguanidinium triacetate, is a bis-guanidine with preventive effects (rates and other information are summarized in Table 1). It is classified as a multi-site contact activity fungicide and is generally considered to have a low resistance risk according to the FRAC (group M7). Its mode of action involves cell membrane transport and sterol biosynthesis at different sites via C14-demethylase in sterol biosynthesis inhibitors. Owing to these unique mechanisms of action, it is a good tool to manage resistance to fungicides with various modes of action, e.g., benzimidazoles, dicarboximides, C14-demethylase inhibitors, Qo inhibitors, and succinate dehydrogenase inhibitors. Its spectrum includes Ascomycota and imperfect fungi, and it inhibits spore germination, germ tube elongation, and appressorium and infectious hypha formation in the life cycle of pathogens. It was first registered in Japan in 1983 under the brand name Befran (25% liquid; Nippon Soda Co., Ltd.) as a preharvest spray targeting blue mold, green mold, Alternaria rot, and sour rot on citrus. However, the efficacy of this chemical on stem-end rot is lower than benzimidazoles, which shows a superior effect. Since it is a contact fungicide, spraying just before harvest is optimal.
6.1. Occurrence and spread of green mold fungus resistant to benzimidazoles
The extensive usages of benzimidazoles have led to the development of benzimidazole-resistant strains (BRS) of
6.2. Despite BRS incidences, the reduction of benzimidazoles’ efficacy was not reported prior to 1990s
These studies found that the incidence of BRS in groves sampled immediately after spraying with was either very low or nondetectable [37, 38]. Among early maturing Satsuma mandarin orange, which is shipped immediately after harvest or after a short period of storage, there was no decrease in control efficacy even after the development of BRS [37, 38]. In some varieties, such as mid-maturing Satsuma mandarin orange and mid-to-late-maturing citrus that are shipped after storage, the incidence of BRS tends to gradually increase during storage . However, if the damages on the fruit surface are limited, the disease incidence does not increase quickly . Moreover, there were reports of BRS in producing areas nationwide , but these occurrences were not severe enough to cause actual damage. Thus, despite reported cases of BRS, the efficacy of benzimidazoles was considered to be maintained at the acceptable level . Therefore, it was concluded that the efficacy of benzimidazole-based chemical management was not decreased by BRS .
6.3. BRS is already present in groves prior to harvest
High numbers of BRS isolates were observed after an outbreak of green mold in harvested greenhouse Satsuma mandarin orange fruits in Saga prefecture in late August of 1993. Subsequently, a survey of fruits from packinghouses in Saga was conducted  and resulted in a large number of thiophanate-methyl–resistant strains (Table 2). Without the host,
|Generic name||Trade name||FRAC code||Active ingredient (%)||Company, city, country||Rate applied (μg/mL)|
|Benomyl||Benlate wettable powder||1||50.0||Sumitomo Chemical Co., Ltd., Tokyo, Japan||125|
|Thiophanate-methyl||Topsin-M wettable powder||1||70.0||Nippon Soda Co., Ltd., Tokyo, Japan||350|
|Iminoctadine triacetate||Befran 25 liquid||M7||25.0||Nippon Soda Co., Ltd., Tokyo, Japan||125|
|Location of packinghouse||Source of isolate2||Rate of resistant strains3||Number of strains for each MIC range (μg/mL)|
|Total||48/59 (100)4||11 (19)||2 (3)||46 (78)|
6.4. Confirming cases of decreased control effects by resistant strains
In order to determine the presence of BRS, a series of experiments were conducted from 1993 to 1995 . Fruits were artificially damaged just before harvest to promote development of green mold. Throughout the experiment, benzimidazoles were not sprayed.
|Year investigated||Location of grove sampled||Rate of resistant strains1||Number of strains for each MIC range (μg/mL)|
|Total||38/41 (93)||3 (7)||0 (0)||38 (93)|
|Total||30/54 (56)||24 (44)||0 (0)||30 (56)|
|Total||29/84 (35)||55 (66)||0 (0)||29 (34)|
|Year investigated||Location of grove sampled||Rate of resistant strains1||Number of strains for each MIC range (μg/mL)|
|Total||151/184 (82.1)||33 (17.9)||48 (26.1)||103 (56.0)|
|Total||31/83 (37.3)||52 (62.7)||6 (7.2)||25 (30.1)|
|Total||54/181 (29.8)||127 (70.2)||8 (4.4)||46 (25.4)|
|Treatment||Fungicide and rate||Number of rotted fruit/number of fruit investigated|
|Thiophanate-methyl 350 μg/mL||0/50||3/50||1/50||1/50||0/50||0/50|
|Iminoctadine triacetate 125 μg/mL||0/50||1/50||0/50||0/50||1/50||0/50|
|Thiophanate-methyl 350 μg/mL||15/50||15/50||6/50||40/50||38/50||5/50|
|Iminoctadine triacetate 125 μg/mL||5/50||4/50||3/50||30/50||7/50||0/50|
|Number of resistant strains|
Furthermore, another experiment was conducted in a total of six groves to examine the effect of wounding and fungicide treatments . Three groves, each consisted of the one cultivar, were examined in 1994 and 1995. The experimental design was a split-plot design where the main block consisted of two wound treatments (artificial wounding or not) and the subplots consisted of three fungicide treatments (thiophanate-methyl, iminoctadine triacetate, and non-treated control). The experimental unit was a fruit, and 50 fruits per subplot were examined. Based on the data from this study , a generalized linear mixed model (GLMM)  (PROC GLIMMIX, SAS ver 9.4, SAS Institute, Cary, NC, USA) was utilized to reexamine the effects of grove, wounding, and fungicide treatments on the probability of green mold disease incidence per fruit. Grove, wounding, and fungicide were considered as a fixed effect, and a logit was used as a link function.
The number of rotted fruit ranged from 0 to 40 out of 50 fruits examined per subplot (Table 5). The results from a GLMM showed significant grove (
|Wound||Fungicide and rate||Mean probability of rotted fruit1||Standard error|
|Thiophanate-methyl 350 μg/mL||0.010 D||0.004|
|Iminoctadine triacetate 125 μg/mL||0.004 D||0.003|
|Thiophanate-methyl 350 μg/mL||0.380 A||0.033|
|Iminoctadine triacetate 125 μg/mL||0.118 B||0.019|
These findings differed from previous results indicating that the incidence of BRS is extremely low in groves prior to the harvest [37, 38]. When harvesting greenhouse Satsuma mandarin orange, very early maturing Satsuma mandarin orange, and early maturing Satsuma mandarin orange, BRS were present at a high rate and thus many cases of postharvest disease were observed.
The high rate of BRS during the harvest of greenhouse Satsuma mandarin orange and very early maturing Satsuma mandarin orange may be explained by the continuous use of fungicides over 20 years. BRS and benzimidazole-sensitive strains of
6.5. Increasing of BRS after benzimidazole spraying in groves
Another experiment was conducted in 1995 using three groves where detection frequencies of BRS were examined before and after application of fungicide treatments . Prior to the experiment, the detection frequencies of resistant strains were low (12–33%, Table 7) and not significantly different among groves (
|Grove2||Fungicide||Rate applied||Detection ratio of resistant strains3|
|Before spraying4||After spraying|
|Kyuragi||Thiophanate-methyl 70% wettable powder||350 μg/mL||–||10/12|
|Iminoctadine triacetate 25% soluble concentrate||125 μg/mL||–||1/16|
|No fungicide||–||2/17 A||0/10|
|Tara||Thiophanate-methyl 70% wettable powder||350 μg/mL||–||31/31|
|Iminoctadine triacetate 25% soluble concentrate||125 μg/mL||–||2/11|
|No fungicide||–||5/15 A||4/10|
|Ogi-2||Thiophanate-methyl 70% wettable powder||350 μg/mL||–||8/8|
|Iminoctadine triacetate 25% soluble concentrate||125 μg/mL||–||0/1|
|No fungicide||–||8/29 A||1/4|
|Fungicide and rate||Mean probability of BRS1||Standard error|
|Thiophanate-methyl 350 μg/mL||0.961 A||0.031|
|Iminoctadine triacetate 125 μg/mL||0.105 B||0.067|
Results from these series of experiment consistently show the lack of efficacy provided by thiophanate-methyl (Tables 5 and 6), as well as the high probability of detecting BRS from thiophanate-methyl–treated fruits (Tables 7 and 8). These results triggered growers to use iminoctadine triacetate, which also shown to be effective against green mold in our study (Tables 5 and 6).
6.6. Problems with iminoctadine triacetate
Although the use of iminoctadine triacetate shows strong antifungal activity
7. Tank-mix combination of fungicides for resistant strains
As discussed above, there are loss of efficacy provided by benzimidazoles, and the efficacy of iminoctadine triacetate, are found to be relatively inconsistent. Alternative fungicides to replace these materials are in need; however, there is no such alternative available in Japan at 1990s.
Combining fungicides with different modes of action can be more effective compared to the separate use of a single fungicide [44–51]. There are four main reasons for considering the use of fungicide mixtures [52, 53]. (1) Broadening the target spectrum: If the aim is to control two target pathogens that differ in sensitivity to fungicide modes of action with one application, it can be useful to spray mixtures of fungicides. (2) Improved disease control: if the target pathogen is susceptible to two modes of action, a use of two effective modes of action should increase the efficacy. (3) As an insurance against resistance: if a certain population of the target pathogen develops resistance to one of the mixture components, the other mode of action in the mix can act against the resistant population. (4) Resistance management: with a combination of reasons #2 and #3, the rate of resistance development among pathogen populations can be delayed, thus, the effective life of a fungicide can be extended. For our situation, the mix of a benzimidazole and iminoctadine triacetate is considered because both are still somewhat effective against green mold. For example, benzimidazoles sometimes show preventative effects even when resistant strains are detected at a high frequency, as shown in one of our experiments (Table 5; Ogi-1). In addition, antifungal activity of iminoctadine triacetate
7.1. Improved effects using a tank-mix combination of benzimidazole and iminoctadine triacetate
Table 9 shows the results of the effects of the combined use of 125-ppm benomyl and 125-ppm iminoctadine triacetate on incidence of green mold from different studies . The preventive effect of treatments was compared based on relative risk reduction (RRR). RRR is the percent reduction in risk in the treated group (e.g., benomyl application) compared to the control group (e.g., no application). RRR = (1 − risk ratio: RR) × 100. RRR values showed that a tank-mix combination of benzimidazole and iminoctadine triacetate improved the preventive effect substantially in 11 of 12 studies. Using a meta-analysis, the total relative risk ratio was 0.23 (95% confidence interval, 0.15−0.33), as shown in Figure 4. Including the error range, the risk ratio was 1.0 or less; thus, the onset of disease is significantly less than that in unsprayed plants (by approximately 15−33%).
|Year||Study||Spray timing (days to harvest)||Rate of BRS1||Fungicide and rate||Incidence of control (%)3|
|Benomyl 125 μg/mL||Iminoctadine triacetate 125 μg/mL||Iminoctadine triacetate 125 μg/mL + benomyl 125 μg/mL|
|Incidence (%)||RRR (%)2||Incidence (%)||RRR (%)||Incidence (%)||RRR (%)|
Incidences of diseased fruits in unsprayed grove block was not associated with those in the block of the combined spray, as shown in Figure 5 (
In the comparison between the combined spray of benomyl and iminoctadine triacetate and the individual fungicides, the preventative effect increased greatly. Combined spraying with another benzimidazole, thiophanate-methyl, and iminoctadine triacetate, also substantially decreased the occurrence of rotten fruits (Figure 6 and Table 10).
|Fungicide and rate||The number of the tests||Combined risk ratio (95% CI)2|
|Benomyl 125 μg/mL||12||0.60||(0.41–0.89)|
|Iminoctadine triacetate 125 μg/mL||14||0.80||(0.62–1.04)|
|Benomyl 125 μg/mL + iminoctadine triacetate 125 μg/mL||14||0.23||(0.15–0.33)|
|Thiophanate-methyl 350 μg/mL + iminoctadine triacetate 125 μg/mL||11||0.43||(0.30–0.63)|
7.2. Synergistic effects of the tank-mix combination
The control effects of the combined spray were superior to the effects of each individual fungicide. Whether the effects were additive or synergistic was examined using the Colby method , which compared theoretical values based on an additive model and measured values. Effects are additive if the total efficacy of multiple fungicides is similar or equal to the sum of the efficacies of individual fungicide. Synergistic effects are inferred when a total efficacy of multiple fungicides is greater than the sum of the efficacies provided by two individual fungicides.
As shown in Table 11, eight out of 12 tests (excluding Taku-2 and Taku-3 (2003), Chinzei-1 (2004), and Ogi-1 (2005)) showed the (actual RRR/expected RRR) values larger than 1. Thus, the observed RRR value was greater than the theoretical RRR values, indicating the synergistic effect of the combined spray. In Taku-2 and Taku-3 (2003), good control was achieved in not only the combined treatment but also benomyl only and iminoctadine triacetate only treatment. Only exception is Ogi-1 (2005), where efficacies of all treatments, including the combined spray, were low. Given the lack of efficacy of benomyl treatment, further examination of the BRS population may need for this location.
|Year||Study1||Actual RRR (%) in green mold compared with the control||Expected RRR (%)2||Actual RRR (%)/expected RRR (%)3|
|Benomyl 125 μg/mL||Iminoctadine triacetate 125 μg/mL||Iminoctadine triacetate 125 μg/mL+ benomyl 125 μg/mL|
7.3. Tank-mix combination improves resistance to precipitation and aftereffects
If the growing area is large (i.e., several hectares or more), application of preharvest fungicide for postharvest rot control can be difficult. Maturity timing among outdoor Satsuma mandarin orange cultivars varies; thus, harvest can start from mid-September for very early maturing cultivars and continue to late November for the others. Therefore, a long residual effect is often a desired aspect of the preharvest fungicide. The combined spray of benomyl and iminoctadine triacetate applied 3 weeks prior to the harvest showed a sufficient level of green mold rot prevention (Figure 7). Also, it appeared that the effect of the combined treatment seemed not to be affected by rain. A sufficient level of efficacy was achieved even with the case where cumulative precipitation after spraying was high, e.g., about 150 mm (Figure 8). Thus, this combined spray has desirable a long residual activity and rain fastness. Further studies are needed to examine the residual effect under artificial precipitation to examine rain fastness of the combined spray.
7.4. Increased cost of fungicides using the tank-mix combination
As of 2016 in Saga prefecture, the costs of 500 L of benomyl is 1225 yen, and that of iminoctadine triacetate is 1662 yen, thus, the combined application costs 2887 yen. The cost increases for the combined application; however, as noted previously, the presence of rotten fruits will result in a substantial negative impact on the responsible grower as well as the related production area. Therefore, the benefits of risk mitigation far exceed the relatively small increase in the cost of fungicides. Moreover, the synergistic effect reported in this study should support growers' decision to apply these two fungicides in combination, even with the increased cost.
7.5. Tank-mix combination is effective against green mold in varieties other than Satsuma mandarin orange
Superior disease-control effects of combined agents on green mold have been confirmed not only in Satsuma mandarin orange but also in mid-to-late-maturing citruses, such as Shiranui ((
7.6. The tank-mix combination is also effective against other postharvest diseases
Presently, in addition to green mold (
7.7. Development and evaluation of a mixed iminoctadine triacetate/thiophanate-methyl agent
For some growers, properly mixing two fungicidal materials can be challenging; thus, the production of an easily administered premixed agent can be beneficial. In fact, the outcomes discussed in this chapter resulted in a development of a premixed product of iminoctadine triacetate and thiophanate-methyl (flowable), which was registered in December 2006.
A pre-mixed product of 15.7% iminoctadine triacetate and 26.2% thiophanate-methyl is available in Japan. It was first registered in 2006 under the brand name Beftopsin flowable (Nippon Soda Co., Ltd.). Even in conditions of resistance, and as shown in the previous studies, synergistic effect is observed. Citrus diseases covered on the label are green mold, blue mold, stem-end rot, Alternaria rot, Aspergillus rot, sour rot, and anthracnose.
Limited studies have compared this pre-mixed product with the combined use of benzimidazoles and iminoctadine triacetate, but representative cases are described in Table 12. This mixed product had a favorable effect on green mold and as well as on anthracnose. Based on the RRR value comparison, its effectiveness was higher compared to that of the combined spray of iminoctadine triacetate and thiophanate-methyl. This may be attributed, at least in part, to the miniaturization of component particles by creating a flowable agent as well as the impact of an added auxiliary agent. Irrespective of the cause, the mixed product was a case of successful integration of two modes of action, which resulted in better efficacy than a combination of two solo materials and exhibiting an expanded range of target diseases.
|Mixed agent/+other compound||Active ingredient (%)||Rate applied||Investigated fruits||Rotted fruit||Total rotted fruit (%)||Discoloration on the fruit surface|
|Tank-mix combination of iminoctadine triacetate and thiophanate-methyl||220||8||8||7.3||–|
|Mixed agent of iminoctadine triacetate and thiophanate-methyl (flowable)||113||1||0||0.9||–|
|+Milbemectin wettable powder (acaricide)||2||10 μg/mL||306||1||2||1.0||–|
|+Etoxazole flowable (acaricide)||10||50 μg/mL||232||1||2||1.3||–|
|+Spirodiclofen flowable (acaricide)||30||75 μg/mL||291||0||3||1.0||–|
|+Chlorfenapyr flowable (pesticide)||10||25 μg/mL||322||1||9||3.1||–|
|+Acetamiprid water soluble powder (pesticide)||20||100 μg/mL||301||3||4||2.3||–|
|+Acetamiprid liquid formulation (pesticide)||18||90 μg/mL||325||2||4||1.8||–|
|+Bifenthrin wettable powder (pesticide)||2||20 μg/mL||188||0||1||0.5||–|
|+Fosetyl wettable powder (fungicide)||80||2000 μg/mL||287||2||3||1.7||–|
|+Kresoxim-methyl wettable powder (fungicide)||50||10 μg/mL||234||0||4||1.7||–|
Since this mixed product has better penetration and locally systemic effects, addition of acaricides, pesticides, and even fungicides other than benzimidazoles as a tank mix partner raised a concern on a coloring disorder in Satsuma mandarin orange fruit. However, none of mixtures did not result in symptoms of phytotoxicity (Table 12). Although the sample size is small, the combined use with other chemicals did not decrease the control effects (Table 12). In the future, we will continue to evaluate the effectiveness of this combined product on a number of crop varieties, both outdoors and indoors. Additional work is needed to determine the most effective use of this agent, such as determination of the optimum timing of spraying.
In this chapter, current understandings on increased cases of BRS of
Because of superior effects on postharvest rot shown in various studies, the tank-mix of benzimidazole and iminoctadine triacetate is widely used in citrus-producing areas of Japan. Additionally, the usage of a newly developed iminoctadine triacetate + thiophanate-methyl wettable powder (flowable) has increased since its introduction. Although this chapter focused exclusively on the effectiveness of fungicides, the mechanism of observed synergistic effects is not clear and warrant further investigations. In addition, other factors that can influence the effectiveness of fungicide application, such as the spray volume and nozzle selection need to be evaluated. As shown in Figure 2, many factors are associated with postharvest diseases and the preharvest spray of a fungicide alone cannot control the onset of disease. Precise verification of causal factors for rot is necessary to develop comprehensive and appropriate countermeasures against these factors. The use of technology to maintain the freshness of harvested fruits is another future challenge .