RESEARCHES ON MONITORING AND EARLY WARNING OF BROWN ROT MONILIA LAXA ATTACK ON SOME VARIETIES OF CHERRY AND PLUM

Brown rot caused by Monilia laxa (Aderh. & Ruhland, Honey) is one of the most damaging fungal disease for stone fruit species, in all European countries and in Romania as well. A great deal effort is done to study its biology and ecology, for disease monitoring and containment. This paper presents the result obtained at RIFG Pitesti Romania during 2018-2020 in monitoring and early warning of the disease attack, using two different weather stations and forecast modules made in Europe and USA. A correlation was found (R 2 =0.0146, r=0.1208, n=585), which proves that the microclimate was favorable for stone fruits brown rot infections, for varieties evaluation and classification and to supply data to develop new early warning tools as well. The results obtained with the two forecast systems makes possible the early warning on the attack risk of brown rot, both cherry and plum orchards. In the same period 26 cherry and 22 plum varieties were studied regarding their behavior to the pathogen natural infections. Among the Romanian varieties the ones with the lowest damages degree were: 'George', 'Clasic', 'Daria', 'Negre de Bistriţa', 'Roşii de Bistriţa', 'Rubin', 'Severin' and 'Uriaşe de Bistriţa' (DD%=0.13-0.14) on cherry and 'Pescaruş' 'Record', 'Gras ameliorat', 'Romanţa', 'Roman, 'Ialomiţa' and 'Dâmboviţa' (DD%=0.03-0.14) on plum. Under long term study, the most sensitives to brown rot attack were 'Lapins' cherry variety (DD%=3.93) as well as 'Stanley' Centenar and 'd’Agen' plum varieties (DD%=4.68-4.72), which can be used as 'indicators', in order to triggers the phytoprotection programs. Cuvinte cheie: cireş, prun, avertizare timpurie monilioza.

temperature. Secondary spore production begins almost immediately after primary spore infection symptoms occur on the blossoms and stems. Blossoms do not progress into fruit and remain on the tree, brown and wilted (Cannon et al., 2017). Wilting and browning blossoms on twigs and cankers (necrotic areas) on invaded woody parts are typical symptoms of infection by M. laxa. A gummy substance usually exudes from the cankers. Under humid conditions, ash-grey-brown sporodochia bearing conidia form on the surface of diseased blossoms and twigs. Stem cankers can eventually girdle diseased stems being additional sources of inoculum. Few blighted blossoms may be enough to cause severe fruit rot if environmental conditions are optimal as fruits ripen. If spores are present during wet and warm conditions, infection of ripening fruits is highly susceptible (Cannon et al., 2017).
Fruit lesions are brown and circular, and eventually the whole fruit decays and turns brown. Tufts of mycelium and conidia (ash-grey-brown in color) sprout from the skin of the infected fruit and are scattered on its surface; later, rotten fruits become "mummies" ( Monilia fructigena fungus overwinters mainly in or on diseased mummified fruit either attached to the tree or on the ground. The fungus can survive long periods of adverse environmental conditions as mycelium within mummified fruits, twigs, cankers and other infected tissues and serve as sources of primary inoculum. In the spring or early summer, under favorable conditions, dense bunches of conidiophores (sporodochia) form on the surface of the mummified fruits and infected tissues, occurs and bear chains of conidia. The conidia are dispersed by wind and rain water or by insects to young fruits. Initial infection takes place via wounds caused by pests. Subsequent spread is done by contact between adjacent fruits may also cause infection. Any infected tissue in which the moisture content is sufficient for sporulation may serve as a source of secondary inoculum. Infections of fruitlets during, or shortly after flowering may result in latent infections on green fruits, and become active before or after harvest (Veteket et al., 2017). When continued heavy rainfall is occurring or other conditions are conducive to infection, shorten this interval to 10 days. Immature sweet cherries may show symptoms of small (4.8 mm to 19 mm in diameter), sunken brown spots with a red halo (Cannon et al., 2017). Infection of fruits can occur at any time during fruit development, but the disease is only severe in ripe or ripening fruits. Fruit lesions are brown and circular, and eventually the whole fruit decays and turns brown. Bunches of mycelium and conidia (2-3 mm in diameter) emerges from the skin of the infected fruit, often arranged in concentric rings on pome fruits (however, when the relative humidity is low and/or when the fruits are not ripe, very few or no tufts develop). On some sour cherry varieties, the fruits damages can reach 80-90% (Rădulescu and Răfăilă, 1972;Tomşa, 2003). Rotted fruits may either fall to the ground or dry out and remain attached to the tree, leaving a hard, shriveled "mummy" (Veteket et al., 2017).

Researches regarding brown rot monitoring and containment
Monitoring of the trees. At least 20 trees per block should be checked for fruit mummies and cankers during or after pruning early in the spring (before white bud stage). One to ten mummies and/or cankers per 20 trees is considered a moderate risk level for blossom infection. Greater than 10 mummies and/or cankers indicate a high risk level. During flowers shuck fall, scout ten shoots of 20 trees for blossom infections. A moderate risk level for fruit infection is reached when one to ten blossom infections per 20 trees is present. More than ten blossom infections indicate a high risk of fruit infection. As fruit ripens and becomes softer, the risk for infection increases. Two symptomatic fruit found per 4 ha during scouting before harvest is considered high risk for a brown rot outbreak (Cannon et al, 2016).
Monitoring of weather conditions and key fruit pests (plum curculio, fruit moths, fruit flies, aphids, various bugs), direct into the orchard are important because preventive control measures can be properly applied, agrotechnical ones, the adequate control of pests as well as fungicides can be applied according to weather conditions, and that can cause injuries to fruits may reduce the risk of infection of fruits by In order to prevent and contain the damages produced by the brown rots on stone fruits species, intensive researches were carried out in Europe and USA, which conducted to the screening and release on the market of more efficient active ingredients and mixtures such as: new formulations of copper and captan), as well as molecules with systemic action like: boscalid; myclobutanil, propiconazol, tebuconazol, fenhexamid, penthiopyrad, pyrimethanil, pyraclostrobin, fluopyram + trifloxystrobin, fluxapyroxad + pyraclostrobin, cyprodinil + difenoconazole; tebuconazole + trifloxystrobin, etc.), biological or biotechnical products were tested and included in integrated phytoprotection programs.
Also, intensive researches were carried out to improve the use of the weather station platforms (Adcon Telemetry, WatchDog, Pessl, Delta T, SysAgria, Enten, etc.) and forecasting software and modules (addVantage 6.4, Specware Pro 9, iMeteo Pro 6.4, DeltaLink 3.2, WD3 WinDIAS, SysWin, etc.), new models and long-term studies on the behavior of valuable stone fruits varieties to brown rots, in order to increase the efficacy of the treatments and reduce the impact of fruit production on the environment.

Material and methods
The studies were carried out during 2018-2020 at RIFG Pitesti-Maracineni Romania, and had as objectives the assessment of some valuable Romanian and foreign cherry and plum cultivars, to establish their behavior to brown rot (Monilia spp) attack, to classify them accordingly, and use the most sensitive ones as indicators. The assessments were done on 26 cherry varieties (13 from Romania and 13 from abroad) and 22 plum varieties (18 from Romania and 4 foreign ones), conducted in intensive and superintensive experimental orchards belonging to the Institute research platform. The cherries varieties were grafted on 'Gisela-5', 'Gisela-6', 'Gisela-12' and 'Weiroot 2' rootstocks planted at 4.0 x 1.5-2.0 m and trained as spindles or slender-spindles. The plum varieties were grafted on 'Adaptabil' and 'Saint Julien' rootstocks, planted at 4 x 2.25m and trained as slender spindles or 'goblet'. The row data were collected in 4 replicates per variety on at least 5 trees / replicate. After a general evaluation the researches were focused on the most sensitive varieties to highlight the most sensitives and the tolerant ones to brown rot infections. Another objective was to use two different weather station platforms and forecasting modules to collect data and predict the period of brown rot attack and its severity, aiming to better positioning of preventive chemical treatments diminish and the impact on the environment.
The annual average temperature (1969-2020): 10.0 °C; the absolute maximum temperature in July: 38.8 °C; the absolute minimum temperature in January: -24.0ºC; the average precipitation amount (1969-2020): 678 mm / year. First autumn frost occurs at the end of Octomber, and the latest spring frost in the second decade of the April and accidentally in the last decade of the month).
All the data related to the studied biological material were collected using the study methodology for collections and comparative trial (Cociu V. et al., 1989) and international standards as well.
The data related to local microclimate were collected using the semi-automate weather station WatchDog (Spectrum Technologies Inc.), and automate weather station Pessl (Pessl Instruments, Austria), which use the WatchDog and Pessl weather platforms, Specware Pro 9 and iMeteo Pro 6.4 forecasting software and modules. The results were stored, processed and analyzed using the facilities of MS Office Excel 2010, Specware Pro 9.0 and iMetos Pro 6.4 disease modules for early warning.
The experimental data were stored, processed and analyzed, using MS Office Excel 2010 facilities.

Results on about the infection risk brown rot on plum and cherry and infections early warning
The local microclimate data collected reveal that the years of the study (2018-2020) were very favorable for the brown rots on cherries and plums. Assessment of the figure 1 reveal that the monthly average temperatures ranged between 10. Based on collected and processed data, between the monthly average temperatures -higher than 5⁰C and the air relative humidity values, a correlation was found (R 2 =0.0146, r=0.1208, n=585), which proves that the microclimate was favorable for stone fruits brown rot infections and development, for varieties evaluation and as well. The collected data might serve also to improve the forecast done with used models (Figure 3).
Assessment of the figures 4-6, generated by Specware Pro 9.0 software on the data collected by WatchDog system, using Mills Rothwell model, confirmed that during the years of study the brown rot (moniliose) found good microclimate conditions for contamination and infections development, both on stone fruits flower clusters and young shoots, as well as on growing shoots and fruits.
According the data processed with the software, in 2018 the risk for brown rot attack was medium from the end of April and the month of May (note 4-5), while in 2019 the risk for brown rot attack in May was low (note 2) (Figure 4 and 5). In all three years of study, during June and early of July, the risk of infections on growing shoots and young fruits was medium to very high, (note 4-7) due the intense rains falling down, increased air humidity and leaf wetness (Figures 4-6).
In all years of study, from mid of July to September the risk of brown rot attack on growing up to full size fruits was medium-high to very high, (note 5-7).
Assessment of the figures 5-6, also reveal that in 2019 and 2020 the microclimate conditions were favorable for brown rot (attack risk note 4-6) and for early infection in the following springs.
Assessment of the figure 7 generated with MS Excel 2020 on the data collected by Pessl system in 2019 and 2020 reveal that, the risk for brown rot attack was medium from March to the end of dormant period of the trees. From the mid of April and the month of May, the attack risk on the growing shoots was medium (note 4-5), and from mid of May till to mid of August the attack risk on the growing and ripening fruits was almost constantly high (note 5-6). The most risky microclimate conditions were the ones from 2020. The results obtained with the two weather platforms and software systems in collecting storing and processing weather data, together with the assessment 'biological reserve from the previous years' established on sensitive varieties, makes possible the early warning on the attack risk of brown rot (Monilia spp.), both cherry and plum orchards.

Results regarding the behavior of valuable plum and cherry varieties on brown rot attack
The assessments done on 26 cherry varieties and 22 plum varieties carried out in the years previous to this study allowed their general classification taking into account their behavior to brown rot attack quantified by overall damages degree DD%. A

Results on brown rot attack on some appreciated plum and cherries varieties grown under superintensive system.
The study conducted during 2018-2020 aimed also to highlight the behavior of some appreciated cherry and plum varieties grown under superintensive system (1904 trees / ha or more) to the attack of brown rot on flower clusters and young shoots and on growing and ripening fruits as well.
Examination of the figures 10 and 11 highlights that during the study period, the year of 2018 was the most difficult (with spring late frost), and the medium attack of brown rot on shoots was registered at the cherry varieties: 'Ferovia', 'Skeena', 'Kordia' and 'Daria', (DD%=1.05-1.80), but the attack on fruits ranged between medium and high (DD%=1. 23-2.12).
Assessment of the figures 12 and 13 suggest that, in the year of 2018, the medium attack of brown rot on shoots was registered at the plum varieties 'Stanley', 'Centenar' and 'Piteştean', (DD%=0.82-1.40) but on the plum varieties 'Stanley', 'Cacanska Rodna', 'Centenar' and 'Pitestean', the attack on fruits ranged between (DD%=0.69-1.12). The data obtained suggest that brown rot attack on cherries and plums is rising up exponentially with the late frost occurrence, inoculum reserve from the previous years, rain falls and increased air humidity in first half of the summer and increase sugars content in the ripening period and short periods of yield cooling.

Conclusions
Based on collected and processed data, between the monthly average temperatures higher than 5⁰C and the air relative humidity values, a correlation was found (R proves that the microclimate was favorable for stone fruits brown rot infections and development and for varieties evaluation and classification as well.
Brown rot attack on cherries and plums is rising up exponentially with the late frost occurrence, inoculum reserve from the previous years, rain falls and increased air humidity in first half of the summer and increase sugars content in the ripening period and short periods of yield cooling.
The results obtained with the two weather platforms and software systems in collecting storing and processing weather data makes possible the early warning on the attack risk of brown rot (Monilia spp.), both cherry and plum orchards.
Under long term study, the most sensitives to brown rot attack was 'Lapins' cherry variety (DD%=3.93), as well as 'Stanley' and 'd'Agen' or 'Andreea' plum varieties (DD%=4.68-4.72), which can be used as indicators, in order to triggers the phytoprotection programs.