Strawberry Fruit Rot Research Articles

First report of the new Neopestalotiopsis species causing strawberry leaf spot and fruit rot in Georgia.

In April 2023, symptomatic strawberry (Fragaria × ananassa) plants (cv. 'Camarosa' and 'Florida Brilliance') were observed at a commercial farm in Worth County, GA (USA). Symptoms included foliar, irregularly distributed, and different-sized spots (dark brown with light brown centers) and dark brown V-shaped necrotic areas starting at the leaf edge. By the time of sample collection, ~50% incidence was reported in the field. Leaf samples were collected and shipped overnight to the laboratory. Black acervuli were observed readily on old necrotic foliar lesions. Conidial morphology was consistent with that observed with Neopestalotiopsis species (Maharachchikumbura et al. 2014). Conidia were ellipsoid to fusiform, five-celled, with three light brown median cells and one hyaline apical and basal cell. Apical cells had two-to-four flexuous appendages, and the basal cell had one non-flexuous appendage (Fig 1). The average (n = 20) conidia length, not including the appendages, was 26.6 µm (SD: 2.8), and width was 6.3 µm (SD: 0.94). Fungal isolation was conducted on acidified PDA and incubated at 25°C for 6 days. Dense, white mycelia were observed on the upper plate surface, while a pale pink/orange coloration was observed on the underside (Fig 1). Black acervuli formed on the surface of the white mycelial mat. Six isolates were purified and selected to confirm the species identity. DNA was extracted from 6-day-old cultures and PCR was conducted following Kaur et al. (2023). Amplified DNA was digested with the restriction enzyme BsaWI and two bands were clearly visualized (~130 and ~290 bp), along with a faint band of 20-bp (Fig 2). Four of the six isolates were selected for sequencing of the β-tubulin gene. BLAST queries using the consensus sequence showed that all isolates had 100% identity to strain N21002 from Florida (FL), characterized as Neopestalotiopsis sp. (Kaur et al. 2023). One representative isolate (AJ07-2023) was deposited in GenBank (accession No. PP316103). Pathogenicity tests were performed on 27-day-old transplants of Sensation 'Florida127' provided by Natalia Peres from the UF. Plants were grown in 10.5 cm pots in the greenhouse. Isolate AJ07-2023 was grown on PDA for 30 days at 25°C, and the spore suspension was adjusted at 106 spore/ml. Five strawberry plants were sprayed with 5 ml of inoculum using a Preval sprayer with a CO2 canister, and 5 plants were sprayed with sterile distilled water. Plants were placed in a growth chamber for 6 days and covered with plastic bags after the sixth day to maintain ~85% relative humidity and 25°C. Foliar symptoms, including dark-brown circular lesions occurring towards the edge of leaves with light-brown center and light-yellow halo, developed 13 days after inoculation. No symptoms were observed on control plants. Neopestalotiopsis sp. was reisolated from inoculated plants as described above. Colony, conidial morphology, and PCR results were consistent with the original isolates. Neopestalotiopsis disease has been reported on strawberry in FL (Baggio et al. 2021), OH (Rotondo et al. 2022) and IN (Guan et al. 2023). Although the disease has been observed sporadically in GA since 2020 (Brannen, personal communication), to our knowledge, this is the first official report of the new Neopestalotiopsis sp. in GA. It has been reported that this new strain is more aggressive on fruits and leaves than other Neopestalotiopsis spp. (Baggio et al. 2021), therefore, accurate identification is critical for proper management.

First Report of Lasiodiplodia pseudotheobromae Causing Postharvest Decay of Strawberries in Florida

Postharvest decay of strawberry (Fragaria × ananassa Duch.) is a major factor causing fruit losses. Strawberries were obtained from various harvests at cooling facilities located in Dover and Plant City, FL during the 2018-19 and 2019-20 seasons. After the fruits were incubated at 22ºC for up to 5 days (d) to promote disease development, Lasiodiplodia decay was observed at up to 3% from some harvests, exhibiting gray mycelia on small lesions that gradually covered the whole fruit. The fungus was isolated onto potato dextrose agar (PDA). Five isolates (SBD18-14, SBD18-277, SBD18-279, SBD19-02 and SBD19-57) were characterized. Fungal mycelia were initially grayish white and then gradually changed to gray to dark gray on PDA at 25oC, and later produced black pigments (Fig. S1). Pycnidia were observed from inoculated strawberries at 14 d. Isolates shared similar conidia morphology: aseptate, hyaline, ellipsoid to ovoid, measuring L × W: 24.0-34.0 (28.3) × 13.0-16.0 (14.3) μm (n =100). Mature conidia were brown, one septate, measuring L × W: 25.0-33.0 (28.8) × 13.0-16.0 (14.5) μm (n =100). The isolates were identified as Lasiodiplodia spp. morphologically (Alves et al. 2008). DNA was extracted from fungal mycelia using an OmniPrep DNA extraction kit, and PCR amplification of ITS and EF1-α genes was performed following the conditions described by White et al. (1990) with some modifications using primers ITS1F-F/ITS4-R (Gardes and Bruns, 1993; White et al., 1990) and EF1-668-F/EF1-1251-R (Alves et al., 2008), respectively. The BLASTn in GenBank showed that the sequences obtained had 99.61 to 100% homology with those of ITS (EF622077) and EF1-α (EF622057) from L. pseudotheobromae CBS116459 (an ex-type strain) (Alves et al., 2008). Sequences of the isolates have been deposited in GenBank with accessions OP326017 to OP326021 for ITS, and OP356202 to OP356206 for EF1-α. Phylogenetic analysis showed that these isolates clustered in the same clade (bootstrap value at 64) with L. pseudotheobromae (Fig. S2). Two fungal inoculum types (mycelia and conidia), two fruit inoculation methods (injury and non-injury) and five fungal isolates were used for pathogenicity tests. Fungal mycelia (2-day-old) on PDA plug (5 mm) or 10 µL of conidial suspension (106 spores/mL) was placed onto each injury (1 x 1 mm in size) or a non-injury area on the surfaces of five strawberry fruits (cv. Florida Brilliance). PDA plug alone or water drops placed on injury or non-injury areas on fruits served as respective controls. Inoculated and control fruits were incubated in a covered plastic container with 100% RH at 22ºC. The experiment was repeated twice. Decay initially appeared as soft and lightly discolored tissue at inoculation areas 2 d post-inoculation (dpi) that extended quickly thereafter. Brown to dark lesions on both injury- and non-injury fruits inoculated with conidia or mycelia were observed at 3 dpi. Decay and gray mycelia gradually developed over the whole fruit at 6 dpi, and pycnidia were observed after 14 dpi (Fig. S1). Disease incidence of 100% was observed on all tests. Control fruits did not develop decay. The results indicate that these isolates are pathogenic to strawberries and infect fruit via both non-injured and injured fruit surfaces. The inoculated fungal isolates were re-isolated, thus, fulfilling Koch’s postulates. L. theobromae, Neofusicoccum parvum/N. ribis species complex causing strawberry fruit rot in Florida fields was reported (Oliveira et al., 2019), but not L. pseudotheobromae. To our knowledge, this is the first report of postharvest decay caused by L. pseudotheobromae A.J.L. Phillips, A. Alves & Crous on strawberries in Florida and in the USA, and it should be considered in strawberry disease management.

Identification, Characterization, and Pathogenicity of Fungi Associated with Strawberry Fruit Rot in Shandong Province, China.

China is the largest strawberry producer and exporter worldwide and has been constantly challenged by fruit rot diseases in recent years. Symptoms of various diseases on strawberry fruits were observed in Huangqiyuan Base, an important strawberry-producing region in Shandong Province, and symptomatic samples were collected from January to April 2021 for follow-up studies. In the present study, 137 isolates were obtained and classified into nine species based on morphological characteristics and multilocus phylogenetic analysis (ITS, GAPDH, HIS3, RPB2, EF-1α, HSP60, G3PDH, and/or TUB2), namely, Botrytis cinerea, B. fabiopsis, Alternaria alternata, A. tenuissima, Fusarium proliferatum, F. graminearum, F. ipomoeae, F. incarnatum, and Colletotrichum siamense. Pathogenicity results suggested that all nine pathogenic species could induce fruits to exhibit symptoms similar to those naturally infected in fields. The symptoms around the inoculation points varied, including dense white mycelia caused by Botrytis spp., fading and depression caused by Fusarium spp., black-brown rot caused by Alternaria spp., and shrinkage and dehydration caused by Colletotrichum spp. Overall, B. cinerea was the dominant pathogen, accounting for 61.3% of the total isolates, and showed significantly higher virulence against strawberry fruits than other species. In addition, this is the first report to identify B. fabiopsis, A. alternata, A. tenuissima, F. proliferatum, F. graminearum, F. ipomoeae, and F. incarnatum as causal agents of strawberry fruit rot in Shandong Province, China.

New Insights in the Detection and Management of Anthracnose Diseases in Strawberries

Anthracnose diseases, caused by Colletotrichum spp., are considered to be among the most destructive diseases that have a significant impact on the global production of strawberries. These diseases alone can cause up to 70% yield loss in North America. Colletotrichum spp. causes several disease symptoms on strawberry plants, including root, fruit, and crown rot, lesions on petioles and runners, and irregular black spots on the leaf. In many cases, a lower level of infection on foliage remains non-symptomatic (quiescent), posing a challenge to growers as these plants can be a significant source of inoculum for the fruiting field. Reliable detection methods for quiescent infection should play an important role in preventing infected plants’ entry into the production system or guiding growers to take appropriate preventative measures to control the disease. This review aims to examine both conventional and emerging approaches for detecting anthracnose disease in the early stages of the disease cycle, with a focus on newly emerging techniques such as remote sensing, especially using unmanned aerial vehicles (UAV) equipped with multispectral sensors. Further, we focused on the acutatum species complex, including the latest taxonomy, the complex life cycle, and the epidemiology of the disease. Additionally, we highlighted the extensive spectrum of management techniques against anthracnose diseases on strawberries and their challenges, with a special focus on new emerging sustainable management techniques that can be utilized in organic strawberry systems.

Heat Treatment as a Possible Means to Reduce Botrytis Inoculum on Strawberry Transplants

Nursery transplants have been reported as one of the major sources of Botrytis cinerea primary inoculum causing Botrytis fruit rot of strawberry in Florida. In this study, we evaluated the efficacy of heat treatment to reduce Botrytis spp. on strawberry transplants. In laboratory experiments, conidia and sclerotia of four isolates with different fungicide resistance phenotypes were exposed to 44, 48, 52, and 56°C for 1, 5, 10, 30, 60 (1 h), 120 (2 h), and 240 (4 h) min. Conidial germination was completely inhibited after exposure for 5 min at 48°C or higher temperatures, or after 30 min at 44°C. Sclerotial germination varied for different isolates but in general required higher exposure times and temperature for inhibition. Based on a previous protocol developed to target Xanthomonas fragariae, strawberry transplants were treated at 44°C for 2 or 4 h with or without a preheat step of 37°C for 1 h and a cooling step of 1 h. After exposure to the heat treatments, detached leaf assays showed that the treatments significantly reduced pathogen incidence on leaves. Treatments at 44°C for 4 h, with or without preheat, significantly reduced Botrytis spp. incidence by 95.3 to 100% on noninoculated and 88.9 to 100% on inoculated transplants. In field trials, early fruit production was not affected by the heat treatments. Our results suggest that heat treatment could reduce the inoculum load of Botrytis spp. on strawberry transplants and potentially help improve the efficacy of fungicides to control the disease in production fields.

Effect of Treatment with Plant Lectins on Postharvest Strawberry Fruit-Rot

Effect of Treatment with Plant Lectins on Postharvest Strawberry Fruit-Rot

Meyerozyma guilliermondii SQUCC-33Y suppresses postharvest fruit rot of strawberry caused by Alternaria alternata

Strawberry fruits are vulnerable to infection by a broad range of fungal pathogens before and after harvest. In this study, Alternaria spp. strains associated with fruit rot of strawberry were isolated and characterized and the potential of the antagonistic yeast Meyerozyma guilliermondii strain SQUCC-33Y for the control of fruit rot of strawberry was evaluated. A total of seven isolates of Alternaria (STR2-STR8) were isolated from strawberry fruits showing symptoms of rot. On the basis of internal transcribed spacer (ITS) ribosomal RNA (rRNA) sequences, these fungal isolates were identified as Alternaria alternata. Pathogenicity tests revealed that most of the strains of A. alternata were pathogenic to strawberry. The measurement of disease severity on strawberry fruits revealed significant differences in the virulence between A. alternata strains. M. guilliermondii restricted the growth of all the strains of A. alternata in dual culture assay. Postharvest treatment of strawberry fruits with M. guilliermondii significantly reduced the fruit rot lesion size caused by A. alternata. This antagonistic yeast has the potential for use as a biofungicide for the control of A. alternata-induced postharvest fruit rot of strawberry.

Pestalotia Leaf Spot and Fruit Rot of Strawberry

Pestalotiopsis-like fungi cause diseases on many different species of plants worldwide, including strawberry. The pathogen is not necessarily new to strawberry and was first reported causing fruit rot in Florida and Israel in the 1970s. However, during the 2018–19 and 2019–20 strawberry seasons, severe and unprecedented outbreaks were reported in Florida, characterized by symptoms on nearly all plant parts including roots, crowns, petioles, fruit, and leaves. This new 4-page publication of the UF/IFAS Plant Pathology Department describes the disease and its causal agent and briefly covers what is known about disease development and control practices. This document will provide valuable information to strawberry nursery and fruit production growers. Written by Juliana S. Baggio and Natalia A. Peres.https://edis.ifas.ufl.edu/pp357

First Report of Preharvest Fruit Rot of Strawberry Caused by Botrytis cinerea in Kazakhstan.

Strawberry (Fragaria × ananassa Duch.) is an important soft fruit crop in Kazakhstan and is cultivated on more than 1.000 ha each year. Gray mold caused by the fungus Botrytis cinerea is one of the most important fruit rot diseases of cultivated strawberry worldwide. In July 2017, strawberry fruit with gray mold symptoms (approximately 40% incidence) were observed in strawberry fields of Semey province in Kazakhstan. Fruit had light brown lesions that enlarged quickly and were covered with a gray, fuzzy mass of spores and mycelium followed by a soft rot. To isolate the causal agent, sporulating lesions from symptomatic fruit were cut into 3- 5 mm diameter pieces, surface disinfested for 1 min in 2% NaOCI, and plated onto potato dextrose agar (PDA) and incubated at 25°C for 4 to 5 days. Fungal colonies that were consistently isolated were transferred to PDA using single spore isolation. Fungal colonies were colorless at first and became gray to brown when the conidiophores and conidia developed. Conidia measured 4.99 to 9.36 × 3.70 to 6.36 μm, and were colorless to pale-brown, one-celled, ellipsoidal, globose and borne on tree-like conidiophores. The fungus was tentatively identified as Botrytis cinerea (Ellis 1971). In total, 56 isolates of Botrytis cinerea were obtained. The internal transcribed spacer (ITS) region of the ribosomal RNA was amplified using primers ITS1/ITS4 (White et al. 1990) and sequenced (GenBank Accession No. MT150132). The sequence was compared to the GenBank database through nucleotide BLAST search and the isolate (KAB-14) showed 99.62% homology to B. cinerea (MH992149.1). On the basis of morphological data and nucleotide homology, the isolate was determined to be B. cinerea. One isolate (KAB-14) of B. cinerea and strawberry fruit cv. Sabrina were used for assessing pathogenicity. Pathogenicity tests were confirmed by inoculation of 20 healthy strawberry fruit with single PDA 7-mm-diameter plugs containing actively growing mycelium and incubated at 25 °C in airtight plastic bags. Strawberry fruit had been disinfested by spraying fruit with 2% NaOCl and then rinsed two times with sterile distilled water. Noncolonized PDA plugs were used for 20 control fruit. After 2 days of incubation, typical gray mold symptoms were observed on inoculated fruit except controls. The pathogenicity test was repeated twice with identical results. Koch's postulates were fulfilled by the reisolation of B. cinerea from symptomatic fruit. After reisolation on PDA, morphological characteristics were similar to the original isolate. To the best of our knowledge, this is the first report of B. cinerea causing preharvest fruit rot of strawberry in Kazakhstan. This disease could have a high economic impact as strawberry production increases in Kazakhstan.

First Report of Sclerotinia sclerotiorum Causing Strawberry Fruit Rot in Florida.

During the 2019-2020 Florida strawberry season (October to April), a strawberry (Fragaria × ananassa) fruit rot was observed in two fields (Plant City and Wimauma, FL) with up to 5% incidence on short-day cultivars SensationTM Florida127, and Florida Brilliance. Symptoms on pink and ripe fruit consisted of softening, discoloration, watery rot with white fuzzy mycelium, and initial sclerotium formation. Diseased tissue was placed on General Isolation (GI) medium (Amiri et al. 2018) and incubated at 25°C under a 12-h photoperiod. A fungus producing spreading cottony white colonies with dark sclerotia near the outer edges of the plates was consistently isolated. One isolate from each cultivar field (20-51 and 20-55) was selected for identification and pathogenicity tests. Apothecial production was induced following the protocol of Li and Rollins (2009), and apothecia (n=30) had an average diameter of 4.5 (3.5 to 7.2) mm. Sclerotia were 3.6 (2.5 to 6.2) mm by 4.5 (3.1 to 5.9) mm (n=30) in size. Dimensions of asci were 130.2 (115.1 to 160.5) μm by 8.5 (6.2 to 13.1) μm (n=30), and those of ascospores were 12.2 (10.8 to 14.6) μm by 6.8 (5.7 to 8.1) μm (n=30). Based on these morphological features, the pathogen was tentatively identified as Sclerotinia sclerotiorum (Lib.) de Bary (Maas 1998). DNA was extracted from the same two isolates using the FastDNA kit (MP Biomedicals, Solon, OH), and the ribosomal internal transcribed spacer (ITS) region was amplified using the primers ITS1 and ITS4 (White et al. 1990). Sequences were deposited in GenBank (accession nos. MT378215 and MT378216). BLASTn searches revealed that isolates 20-51 and 20-55 were 99.62% identical (526 / 528 bp) to S. sclerotiorum CBS 499.50 (MH856725.1). Immature pink fruit of SensationTM 'Florida127' were harvested, surface disinfested in bleach solution (0.08% NaClO) for 90 sec, rinsed twice with deionized water, then placed into styrofoam egg cartons inside clean plastic boxes (30x24x7 cm) containing 150 ml of sterile deionized water to maintain moisture, and kept at 25°C with a 12-h photoperiod. Ascospores and sclerotia were used for inoculation tests with three repetitions in an egg carton containing 12 fruit each per isolate and inoculation method. The experiment was repeated once. Fruit were inoculated by placing 20 μl of a 1 × 106 ascospores/mL suspension or a single sclerotium on the upper half of the fruit. Controls were included, by placing 20 μl of sterile DI water or fruit with no sclerotia. Evaluations were done 6, 10, and 15 days after inoculation (DAI). Control fruit remained healthy, while inoculated fruit developed symptoms of softening and discoloration. For ascospore inoculation, disease incidence was 55 (± 5) and 78% (± 4), for 6 and 15 DAI, respectively, whereas for sclerotia inoculation incidence was 100% 6 DAI. Morphologically identical fungi to the original isolates were re-isolated from the diseased fruit. No other fruit decay fungi were observed. S. sclerotiorum has been previously reported causing strawberry fruit rot in Washington state in the United States, England, Israel, and Scotland (Alcorn 1966; Maas 1998; McLean 1957). It has also been listed in the indices of plant diseases from Florida, North Carolina, and California as causing crown rot (Farr and Rossman 2020). To our knowledge, this is the first report of S. sclerotiorum causing strawberry fruit rot in Florida. The pathogen is an aggressive necrotroph with prolonged survival and affects several vegetable crops grown in Florida (Paret et al. 2018). Because only the strawberry beds are fumigated, sclerotia remaining in the alleys could serve as inoculum sources. Currently, the disease is rare and of minor significance to strawberry production. However, efforts should be implemented to monitor its occurrence and spread.

Mycelial Growth and Biological Control Measures of Botrytis cinerea Isolated from Strawberry Fruit Rot Disease in Bangladesh

Fruit rot disease of strawberry caused by fungus is most economically important disease in Bangladesh, which reduces the production and quality of strawberry at both pre and post-harvest period. Present study was conducted to identify the causal organism of the fruit rot disease of strawberry through classical and molecular techniques and its eco-friendly control measures. A fungal pathogen causing fruit rot was isolated and identified as Botrytis cinerea through classical fungal taxonomy and molecular characterization based on their internal transcribed spacer (ITS) region of ribosomal DNA (rDNA). Sequence analysis showed that 5.8S of rDNA sequences were identical. The reciprocal homologies of the ITS region sequences ranged from 98 to 100%. Experimental results suggested that studied fungus (MH371474.1) was genetically similar with MF521935.1 Botrytis cinerea. Isolated fungus was evaluated on six different culture media and at five different temperature conditions. The optimum mycelial growth of B. cinerea was found on Richard agar medium at 25 ℃ temperature at 7days post inoculation (dpi), while mycelial growth was drastically reduced the temperature 30 ℃ and above. Three Trichoderma species viz., T. ressei, T. harzianum and T. asperellum were used to assess the antagonistic effect on isolated pathogenic fungus in which the mycelial growth of it was inhibited mostly by T. ressei. Experimental results revealed that Trichoderma ressei was the effective antagonistic fungus against Botrytis cinerea for the biological control.

Sensitivity of Colletotrichum Isolates Collected from Strawberries in Georgia to Pyraclostrobin, a Quinone Outside Inhibitor (QoI) Fungicide

Anthracnose fruit rot disease, caused by Colletotrichum spp., is the most significant disease problem of commercial strawberry (Fragaria × ananassa) production in the southeastern United States. The hot, humid weather and continuous rainfall in Georgia make Colletotrichum-induced fruit rot a widespread problem in strawberry production. In order to control this disease, growers mainly rely on preventive fungicide applications from flower bud emergence to harvest. The most commonly used single-site fungicides are quinone outside inhibitors (QoIs); the QoI active ingredients azoxystrobin and pyraclostrobin are utilized to manage anthracnose fruit rot. In 2019, we collected 108 strawberry fruits with visible rot symptoms from seven different strawberry farms in Georgia. These farms had received multiple applications of QoI fungicides during the 2019 growing season, as well as in previous seasons. Sensitivities to pyraclostrobin were assessed on 1% malt extract agar using a mycelial growth inhibition assay. Our results demonstrated that a majority of Colletotrichum isolates collected in 2019 were not inhibited by pyraclostrobin, suggesting a growing resistance issue with the QoI fungicides. A PCR-restriction fragment length polymorphism assay showed the presence of the G143A mutation in all QoI “resistant” C. acutatum isolates and none for isolates labeled “reduced sensitivity” or “sensitive”. These results further prove that C. acutatum isolates with the G143A mutation are highly resistant to the QoI fungicide. These findings suggest that there is a high risk of resistance development associated with using pyraclostrobin (likely all QoIs) for controlling anthracnose fruit rot of strawberry in Georgia.

Characterization of Rhizoctonia solani causing Fruit rot of Strawberry (Fragaria x ananassa Duch.) in Wayanad and in vitro Evaluation of Fungicides, Organic preparations and Bioagents for its Management

Strawberry, one of the most delicate, sweet and refreshing temperate fruit has grabbed the minds of several farmers and consumers all over the world. Several fungal diseases affect it. As part of the study, surveys were carried out in major strawberry growing parts of Kerala viz., Wayanad, Idukki, Malappuram and Thrissur. However, rotten fruits with dark and hard encrustations were collected only from Wayanad district during 2015-16. Pathogen was isolated by following the standard protocol and Koch’s postulates were proved. Upon culturing, the fungal isolate produced white mycelia turning brown on maturation with rapid growth. The hyphae were branched at right angles and did not produce spores. The pathogen was identified as Rhizoctonia solani based on cultural and morphological characters. In vitro evaluation was carried out with 9 fungicides and carbendazim 12% + mancozeb 63% , cymoxanil 8% + mancozeb 64% , propineb and Bordeaux mixture at all concentrations showed cent per cent inhibition. Copper hydroxide and difenoconazole inhibited the pathogen from 54.44 to 75 per cent and 58.88 to 70.55 per cent at 0.1, 0.15 and 0.2 and 0.05, 0.1 and 0.15, respectively. Copper oxychloride recorded less than 45 per cent inhibition, whereas carbendazim and potassium phosphonate were found to be least effective. Comparing the efficacy of organic preparations against Rhizoctonia, calphomil recorded highest inhibition of 55.33 to 63.88 per cent at different concentrations. Panchagavya and baking powder + vegetable oil mixture could inhibit the mycelial growth only by 23.33 to 25.50 per cent and 22.22 to 26 per cent, respectively. Whereas, neem oil was found to be least effective. Biocontrol agents were evaluated against the pathogen and Trichoderma asperellum could restrict growth of the pathogen by 66.67 per cent and Pseudomonas fluorescens by 33.33 per cent.

Characterization of Rhizoctonia solani causing Fruit rot of Strawberry (Fragaria x ananassa Duch.) in Wayanad and in vitro Evaluation of Fungicides, Organic preparations and Bioagents for its Management

Strawberry, one of the most delicate, sweet and refreshing temperate fruit has grabbed the minds of several farmers and consumers all over the world. Several fungal diseases affect it. As part of the study, surveys were carried out in major strawberry growing parts of Kerala viz., Wayanad, Idukki, Malappuram and Thrissur. However, rotten fruits with dark and hard encrustations were collected only from Wayanad district during 2015-16. Pathogen was isolated by following the standard protocol and Koch’s postulates were proved. Upon culturing, the fungal isolate produced white mycelia turning brown on maturation with rapid growth. The hyphae were branched at right angles and did not produce spores. The pathogen was identified as Rhizoctonia solani based on cultural and morphological characters. In vitro evaluation was carried out with 9 fungicides and carbendazim 12% + mancozeb 63% , cymoxanil 8% + mancozeb 64% , propineb and Bordeaux mixture at all concentrations showed cent per cent inhibition. Copper hydroxide and difenoconazole inhibited the pathogen from 54.44 to 75 per cent and 58.88 to 70.55 per cent at 0.1, 0.15 and 0.2 and 0.05, 0.1 and 0.15, respectively. Copper oxychloride recorded less than 45 per cent inhibition, whereas carbendazim and potassium phosphonate were found to be least effective. Comparing the efficacy of organic preparations against Rhizoctonia, calphomil recorded highest inhibition of 55.33 to 63.88 per cent at different concentrations. Panchagavya and baking powder + vegetable oil mixture could inhibit the mycelial growth only by 23.33 to 25.50 per cent and 22.22 to 26 per cent, respectively. Whereas, neem oil was found to be least effective. Biocontrol agents were evaluated against the pathogen and Trichoderma asperellum could restrict growth of the pathogen by 66.67 per cent and Pseudomonas fluorescens by 33.33 per cent.

Competitive saprophytic ability of the hypovirulent isolate QT5-19 of Botrytis cinerea and its importance in biocontrol of necrotrophic fungal pathogens

This study determined the competitive saprophytic ability (CSA) of the hypovirulent isolate QT5-19 of Botrytis cinerea on potato dextrose agar (PDA) at 20 °C. Meanwhile, importance of the QT5-19 CSA in biocontrol against virulent isolates of B. cinerea and Sclerotinia sclerotiorum (a close relative of B. cinerea), and the mechanisms for the QT5-19 CSA were elucidated. The results showed that QT5-19 had higher CSA than the virulent isolates 08168 (B. cinerea) and EP-1PNA367 (S. sclerotiorum) on potato dextrose agar. The hyphal fragments of QT5-19 exhibited an effective suppression against infection of leaves of oilseed rape by the hyphae of the two virulent fungal pathogens through competition. QT5-19 was detected to be able to produce volatile organic compounds (VOCs) with antifungal activity against B. cinerea and S. sclerotiorum, whereas the VOCs from the virulent isolate RoseBc-3 of B. cinerea had no detectable antifungal activity. The QT5-19 VOCs effectively reduced disease severity of strawberry fruit rot caused by two virulent fungal pathogens. These results suggest that QT5-19 may achieve success of competition through extensive mycelial growth and production of antifungal volatiles. This study provided an example of using hypovirulent isolates to control virulent isolates of B. cinerea and S. sclerotiorum.

Suppressive effect of compost bacteria against grey mould and Rhizopus rot on strawberry fruit

ABSTRACTGrey mould and Rhizopus rot are diseases of numerous food crops such as strawberry. Composts are sources of beneficial microorganisms, including bacteria that may help control plant disease. The present study evaluated compost bacteria efficacy in inhibiting growth of Botrytis cinerea and Rhizopus stolonifer and in controlling strawberry fruit grey mould and Rhizopus rot. Bacterial antagonists inhibited mycelial growth of B. cinerea and R. stolonifer by as much as 44% and 43%, respectively. The culture filtrates of many bacterial antagonists showed similar inhibitory effects on the growth of the two moulds. Various bacteria showed suppression of grey mould, decreasing disease severity by up to 71%. Different bacteria also provided inhibition of Rhizopus rot, reducing disease incidence and severity by up to 67% and 91%, respectively. Bacillus spp. were particularly suppressive to grey mould, whereas Arthrobacter spp. only suppressed Rhizopus rot. Pseudomonas spp. suppressed both diseases. Antibiosis seemed to be an important component of the activity of the most suppressive bacterial isolates against strawberry grey mould. Results of this study indicate that compost bacteria could aid in the control of strawberry fruit rot.

First Report of Anthracnose Causing Both Crown and Fruit Rot of Strawberry by Colletotrichum siamense in North Carolina

First Report of Anthracnose Causing Both Crown and Fruit Rot of Strawberry by <i>Colletotrichum siamense</i> in North Carolina

Validation of a Florida Strawberry Anthracnose Fruit Rot (AFR) Warning System in Iowa.

Field validation of a disease-warning system for strawberry anthracnose fruit rot (AFR), caused by Colletotrichum acutatum sensu lato, that was originally developed for use in Florida was conducted in Iowa from 2012 to 2014. Day-neutral strawberry (cv. Tristar) was artificially inoculated with the pathogen at the start of the fruit maturation period. A factorial combination in replicated trials of two spray timing methods (the Florida warning system and prescheduled, calendar-based timing) and two fungicides (captan and pyraclostrobin) was compared, along with a nonsprayed control. The calendar-based and warning system-based treatments provided statistically equivalent control of AFR incidence compared with the nonsprayed control, and the warning system treatments required an average of 1.7 fewer fungicide sprays annually than the calendar-based treatments. Further analysis of the field data suggested that the warning system might underestimate AFR risk under high disease pressure; in these circumstances, a lower action threshold value may need to be adopted. Overall, these results indicated that the Florida warning system can be valuable for helping Midwest strawberry growers control AFR with less reliance on fungicide sprays, but it may require modification to account for periods of high inoculum pressure, subject to results of further field trials.

Leaf spot and fruit rot of strawberry caused by Neopestalotiopsis clavispora in Indo-Gangetic plains of India

A severe foliar disease was observed on leaves and fruits of strawberry (Fragaria × ananassa) for the first time from Indo-Gangetic plains of West Bengal in India during 2016–2017. Typical symptom appeared as a small necrotic lesion with a grey coloured centre and purplish brown margin. The spots were scattered on the leaves and gradually the spots coalesced to each other and covered large necrotic areas causing gradual conversion from green areas into black necrotic areas. As the spots were older and matured, black coloured acervuli developed from the necrotic portion. Morphologically the pathogen was very much similar with the genus Neopestalotiopsis previously reported from other countries. Through molecular characterization the pathogen in the present study was confirmed as Neopestalotiopsis clavispora (NCBI accession number MF377347). Further isolated pathogen was tested in some leading strawberry varieties of India. Although all the cultivars showed susceptibility under laboratory as well as field conditions, the variety “Sabrina” showed moderately resistance in leaves as well as fruits among the tested varieties.

First Report of Preharvest Fruit Rot of Strawberry Caused by Botrytis cinerea in Khyber Pakhtunkhwa Province and Islamabad (Pakistan)

Strawberry (Fragaria × ananassa Duch.) is an emerging fruit crop in Pakistan, cultivated on approximately 1500 hectares. A survey was conducted during each crop season viz. 2014-2015 and 2015-2016 in geographically important strawberry growing regions of Khyber Pakhtunkhwa and Islamabad . Fruit rot was observed in all surveyed fields that indicates 100 % prevalence of the disease in the study area . Affected tissue was covered with a thin layer of grayish white to dark gray mycelium, which later became fuzzy due to profusion of conidiophores, and rot enveloped the entire fruit. Rotted fruit gradually dried, becoming hard and mummified. Fruit tissue segments at the margins of lesions on infected fruit were cut into 3- to 5 mm2 pieces, surface disinfected with 2% sodium hypochlorite for 1 min, rinsed by washing three times in sterile distilled water, and blotted dry. Disinfected segments were placed on Czapek-Dox (CZ) agar and incubated at 25 ± 2°C. Grayish colonies were observed 3 to 5 days later. Colonies...