🍎사과나무 화상병 (Apple Fire Blight)

병해 개요 📝: 사과나무 화상병은 사과, 배 등 장미과 과수에 발생하는 치명적인 세균병으로, 병에 걸린 부위가 불에 탄 것처럼 검게 마르는 것이 특징입니다. 병원균은 Erwinia amylovora로, 전 세계 50여 개국에 분포하며 한 번 발생하면 과원을 폐원해야 할 정도로 피해가 큰 검역병입니다​. 감염 초기에는 개화기에 꽃이 시들어 갈색으로 변하며 마르는 꽃썩음(화상) 증상이 나타납니다​. 이어서 새로 나온 어린 잎과 가지로 번지며, 어린 잎과 신초(새순)가 물에 담갔다 뺀 듯 축 처졌다가 점차 갈색~흑갈색으로 변색됩니다​. 특히 신초 끝이 고리 모양으로 굽어들어가는 “양치기 지팡이(쉐퍼드 크룩)” 형태를 보이는 것이 전형적입니다​. 병든 잎은 검게 말라 죽지만 가지에 붙어 떨어지지 않고 매달린 채로 남아, 나무 전체가 마치 화재 후 그슬린 듯한 초흑색으로 보입니다​. 과실이 감염되면 과일도 갈색~검정색으로 썩으며 말라붙어 **과일 미라(과건)**가 형성되고, 가지와 함께 검게 변해 남아 있습니다​. 줄기나 가지에는 약간 *함몰되고 검게 갈라진 궤양(칸커)*이 생기며, 습도가 높을 때 이 궤양에서 유백색 또는 황갈색의 세균 점액(삼출액)이 흘러나옵니다​. 이런 증상들 때문에 이 병을 *“화상병”(불에 탄 것 같은 병)*이라 부릅니다. 이 병에 걸린 나무는 수년 내 고사하거나, 생육이 약해져 과실 생산이 불가능해지기 때문에 조기 방제가 매우 중요합니다.

 

 

병 발생 환경 🌦️: 화상병균은 온난다습한 봄철에 가장 활발히 증식합니다. 일반적으로 개화기 전후 (5월경)에 평균 기온이 *18-25℃*이고 비가 내리거나 습도가 높은 기간에 꽃 감염이 일어나며, 이후 1-2주 잠복기를 거쳐 증상이 나타납니다​. 75-82℉(24-28℃) 범위와 60% 이상의 상대습도가 유지되면 세균의 번식과 전파가 급증합니다​. 반대로 개화기 기온이 낮고 건조하면 전염 위험이 줄어듭니다​. 우박, 강풍, 폭우 등으로 나무에 상처가 나는 기상 조건 후에도 가지를 통한 감염이 증가합니다​. 예를 들어 67월 장맛비나 우박이 맞은 후 며칠내 기온이 25℃ 이상 오르면 잠복해 있던 세균이 활성화되어 새 가지 감염 및 급격한 확산이 일어날 수 있습니다. 곤충 활동도 중요한 요인인데, 병원균은 꽃의 꿀이나 분비물에 섞여 나와 향기로 곤충(꿀벌 등)을 유인하고, 이들이 다른 꽃으로 옮겨가며 세균을 전파합니다​. 따라서 꽃이 피는 시기에 비가 자주 와서 꽃이 축축해지고 매개곤충이 출현하는 조건 – 이를 “화상병 적우조건” – 에서 1차 감염이 극대화됩니다. 감염된 나무에서는 밤낮의 온도차가 커지는 초가을(9~10월)에 줄기/가지 궤양에서 세균이 분비되어 근처 나무로 전염되는 2차 감염도 일어날 수 있어, 수확기 전후까지도 경계를 늦추면 안 됩니다.

 

 

감염 경로와 확산 🔄: 화상병의 병원균 E. amylovora는 꽃, 신초, 상처 부위를 통해 나무에 침입합니다. 꽃 감염이 가장 흔한 경로로, *매개곤충(벌 등)*이 감염된 나무의 꽃에서 흡밀할 때 꽃에 맺힌 세균을 묻혀 오고, 다른 건강한 꽃으로 옮겨가면서 세균을 떨어뜨려 전염시킵니다​. 또한 빗물도 중요한 매개체인데, 병든 꽃이나 가지에서 흘러나온 세균이 빗물에 섞여 흐르거나 튀어 인접 가지와 나무로 옮겨집니다. 비 오는 날 개화한 꽃이 있으면, 그 꽃가지에 묻은 세균이 빗물과 함께 흘러내려 꽃자루와 가지로 침투할 수 있습니다​. 신초 감염은 주로 우박이나 강풍 등 기상해로 잎과 가지에 생긴 미세한 상처로부터 이루어집니다​. 바람에 문질러진 잎, 날아온 물방울에 긁힌 잎, 곤충 흡즙에 난 상처 등으로 세균이 내부 조직에 들어가면 그 신초 전체가 시들며 병이 진전됩니다​. 줄기 및 가지 전파는, 봄철 1차 감염 후 여름철 병든 가지에서 분비되는 세균이 빗물에 의해 아래로 흘러 다른 가지 접합부로 들어가거나, 또는 전정가위 등의 작업도구에 의해 이루어집니다. 실제로 화상병은 전정 작업 후에 전염이 확산되는 사례가 많아, 환부 가지를 자르던 전정가위를 소독 없이 다른 나무 가지를 자르면 세균이 그대로 묻어들어가 감염을 일으킵니다. 이 때문에 화상병 의심 증상 발견 시 전정 등을 자제하도록 권고하고 있습니다. 병이 진전됨에 따라 줄기 궤양(canker)에서 세균이 분비되는데, 이 삼출액은 비 또는 곤충, 새 등에 의해 물리적으로 옮겨질 수 있습니다​. 심지어 병든 과실이 떨어져 땅에 닿으면 토양 표면에 세균이 퍼지고 이것이 빗물 튀음 등으로 동일 나무나 이웃 나무의 하부에 감염을 줄 수도 있습니다. 이렇게 꽃→가지→나무→과원으로 확산되며, 최종적으로는 과수원 전체가 초토화되는 경우도 있습니다. 장거리 확산은 주로 감염 묘목이나 접수의 이동으로 발생하므로, 묘목 반입 시 철저한 검역이 필요합니다.

 

 

병원체의 생활사 ♻️: Erwinia amylovora 세균은 숙주 없이 토양에서 오래 생존하지 못하고, 주로 감염된 나무 조직 내에서만 월동합니다. 병원균은 늦가을겨울에는 감염 가지의 *겉보기에 건강한 조직과 병든 조직 경계부(캔커 가장자리)*에서 월동하며, 이 부위에서 낮은 온도에도 살아남아 이듬해 봄 활력을 띱니다​. 이때 세균은 나무 조직 속에서 소수로 존재해 진전을 멈춘 상태로, 특별한 포자 형태로 변하는 것은 아닙니다. 겨울을 난 병원균은 *봄철(기온 약 18℃ 이상)*에 수액 이동과 함께 증식을 시작합니다​. 개화 직전 습도가 높아지면, 월동한 캔커 부위에서 유백색크림색의 점액(세균 덩어리)이 삼출되기 시작합니다. 이 삼출물이 1차 전염원이 되어 곤충이 흡밀하거나 비에 씻겨 꽃으로 가서 꽃 감염을 일으킵니다. 꽃 속에서 대량 증식한 세균은 꽃자루를 타고 가지로 내려간 뒤 그 가지를 따라 내려가며 잎, 과일을 감염시키고, 위로는 신초로 올라가 어린 잎과 가지를 썩게 만듭니다​. 여름철 고온건조기에는 병의 진행이 다소 둔화되지만, 세균은 숙주 내부에서 생존을 이어가다가 (이 시기 일부는 캔커로 자리잡음) 초가을에 비가 오거나 습도가 높아지면 다시 캔커에서 삼출액이 분비되며 2차 전염이 일어납니다​. 이런 사이클이 반복되면서 감염 범위가 점차 확대됩니다. 병이 든 나무는 시간이 지날수록 캔커 부위가 커지고 나무 전체가 쇠약해져 결국 고사에 이르게 됩니다. 병원균은 사과, 배나무 외에도 산사나무, 마가목, 피라칸타, 비파나무, 모과나무 등 130여 종의 장미과 식물에 감염될 수 있어​, 인근의 대목용 야생배나 조경용 나무에서도 잠복할 수 있습니다. 그러므로 주변 수목 관리도 화상병 방제의 일부가 됩니다.

 

 

방제 방법 🛡️: 예찰 및 격리: 화상병은 치료제가 없기 때문에, 예방과 초동 대처가 핵심입니다. 의심 증상이 보이면 곧바로 방제단계로 전환합니다. 병든 가지(시들거나 검게 변한 꽃, 잎, 가지)를 발견하면, 해당 나무 뿐만 아니라 주변 나무까지 반경 100m 내 과수 이동제한 및 방제 조치를 취합니다. 전정 및 제거: 감염부위를 정상부위보다 최소 30~60cm 아래에서 잘라 제거하며, 잘라낸 가지는 과원 밖으로 가져가 소각하거나 땅에 깊이 묻습니다​. 절단 도구는 매 절단 시마다 70% 알코올이나 락스(차아염소산나트륨 1:10 희석)로 소독하여, 도구를 통한 세균 전파를 막습니다​. 전정 작업은 비 오는 날이나 잎이 젖어 있는 상태에서 하지 않고, 가능하면 건조한 날에 신속히 실시합니다. 예방 약제 살포: 개화 시기에 *항생제 제제(스트렙토마이신 등)*를 살포하면 꽃 감염을 상당 부분 억제할 수 있습니다​. 실제로 미국 등에서는 개화기 3~4차례의 스트렙토마이신 살포로 화상병을 방제하는 것이 표준이지만, 한국에서는 항생제 사용이 불허되어 있어 *석회보르도액(1-2%)*이나 구리 수화제 같은 동제살균제를 개화 직전과 만개기에 살포하는 방식으로 예방을 시도합니다. 하지만 구리제는 세균 성장 억제 효과는 있으나 완전한 예방은 어려워, 개화기 일기예보(온도·강우)에 따라 화상병 발생 예측 시스템을 활용하여 가장 위험할 때 적기에 약제를 적용하는 것이 중요합니다​. 발생 지역 격리: 화상병이 한 번 발생한 지역의 과원들은 방제 기간(약 3년) 동안 지속적인 검사를 실시하고, 발생 시 신속히 격리·제거합니다. 신규 묘목 식재를 자제하고, 인근에 차량이나 작업자 출입을 제한하여 지역 간 전파를 막습니다. 정부 방제 지침에 따라 필요한 경우 과원을 폐원하고 매몰, 소독 등의 조치를 취해야 합니다. 위생 관리: 평소 과수원 바닥의 낙엽과 잔재물을 잘 치워주고, 질소질 비료를 과다하게 주어 가지와 잎의 연약한 신장을 유도하지 않습니다 (연한 조직이 감염에 취약함)​. 오히려 인산칼륨 비료를 충분히 주어 조직 강화를 돕습니다. 겨울철 병든 나무의 궤양 부위는 눈에 보이지 않더라도, Dormant 시즌에 구리 석회 유제(석회유황합제)나 구리 살균제를 도포하여 잠복 세균 밀도를 줄일 수 있습니다​. 또한 인접 야생 배나무, 산사나무 등 감염될 수 있는 식물도 주기적으로 살펴보고 제거하거나 가지치기합니다. 정부 방제: 국내에서는 법정 금지병해충으로 지정되어, 발견 시 즉시 방역당국에 신고(☎☎1588-8572)하도록 의무화되어 있습니다. 관계기관은 발생 과수원 및 인접 과수원에 소독제 살포, 이동제한, 예찰강화 등의 조치를 취합니다. 화상병 예측시스템 (예: K-Maryblyt 모델)을 활용해 기상 조건과 병 발생 위험을 예보받아 약제 살포 시기를 결정하는 것도 권장되고 있습니다​. 이러한 철저한 조치를 통해 화상병의 지역 확산을 막고자 하며, 일단 지역에 정착하면 완전 근절이 어려운 만큼 초기 차단이 최선입니다.

 

 

참고문헌 및 링크 📖 :

 

- 농림축산검역본부 식물검역 정보​ : https://www.qia.go.kr/plant/pest/plant_FireBlight.jsp#:~:text=Image%3A%20%EB%B3%91%EC%9B%90%EA%B7%A0%20%EC%82%AC%EC%A7%84%20%C2%A0%C2%A0%C2%A0%C2%A0%C2%A0%C2%A0,%EC%82%AC%EA%B3%BC%EB%82%98%EB%AC%B4%2C%20%EB%B0%B0%EB%82%98%EB%AC%B4%2C%20%EB%AA%A8%EA%B3%BC%EB%82%98%EB%AC%B4%2C%20%ED%94%BC%EB%9D%BC%EC%B9%B8%EB%8B%A4%20%EB%93%B1

과수화상병이란 - 병해충 정보 - 식물검역-농림축산검역본부

- 농림축산검역본부 발표 (2022년 과수화상병 발생지 정보) : https://www.qia.go.kr/viewwebQiaCom.do?id=63277&type=3_80FBepid

2022년 과수화상병 신규발생지역 역학조사분석 보고서 - 과수화상병 역학분석 보고서 - 병해충

 

- UMN Extension Fire blight​ : https://extension.umn.edu/plant-diseases/fire-blight#:~:text=Wilted%20shoot

Fire blight

 

- Morton Arboretum Plant Clinic​ : https://mortonarb.org/plant-and-protect/tree-plant-care/plant-care-resources/fire-blight/#:~:text=Fire%20blight%20can%20affect%20several,Bark

Fire blight | The Morton Arboretum

 

- 국내 과수화상병 예측 시스템 안내 : https://www.fireblight.org/mobile/index/#:~:text=%EA%B3%BC%EC%88%98%ED%99%94%EC%83%81%EB%B3%91%EC%9D%B4%20%EB%B0%9C%EC%83%9D%EB%90%9C%20%EC%A7%80%EC%97%AD%EC%9D%98%20%EC%97%B0%EA%B5%AC%EC%9E%90%EC%99%80%20%EC%A7%80%EB%8F%84%EA%B8%B0%EA%B4%80%EC%9D%84,%EB%8C%80%EC%83%81%EC%9C%BC%EB%A1%9C%20%ED%99%94%EC%83%81%EB%B3%91%20%EC%98%88%EC%B8%A1%EC%A0%95%EB%B3%B4%EB%A5%BC%20%EC%A0%9C%EA%B3%B5%ED%95%98%EB%8A%94%20%EC%8B%9C%EC%8A%A4%ED%85%9C

과수화상병 예측 서비스 V1.0

 

 

태그 🏷️: #사과 #배 #화상병 #Erwinia #세균병 #과수

 

 

Disease Overview 📋: Fire blight is a highly contagious bacterial disease affecting apple, pear, and other members of the rose family. It is caused by the bacterium Erwinia amylovora and is notorious for giving infected trees a scorched, fire-blasted appearance. Fire blight can kill blossoms, shoots, limbs, and even entire trees. In spring, one of the first signs is blossom blight: infected flowers and flower clusters become water-soaked, then wilt and shrivel, turning brown or black while remaining attached to the tree​. As the infection spreads, young twigs and shoots develop a characteristic “shepherd’s crook” shape – the tips wilt, bend downward, and turn blackish-brown​. Leaves on these shoots blacken along the midrib or veins and hang on the tree as if singed by fire (hence the name “fire blight”)​. By mid-summer, an affected apple or pear tree often has multiple blighted shoots, giving it a burnt, lifeless appearance with blackened foliage and twig tips that may cling well into winter​. Infected fruits (if any develop) turn brown, shrivel, and mummify, often exuding droplets of sticky bacterial ooze when weather is humid​. The bacteria can also invade larger branches via the shoots, leading to the formation of cankers – sunken, dark, necrotic lesions on the bark​. These cankers are typically found at the base of blighted twigs or on larger limbs and can girdle and kill limbs or the trunk. Fire blight is extremely destructive; in severe cases, an entire orchard can be devastated if the disease is not managed, as the infection can quickly move from blossoms into shoots and then into the rootstock. Because of this, fire blight is considered the most serious disease of apples and pears in many regions and is subject to strict quarantine regulations in countries like South Korea​.

 

 

Occurrence Environment 🌦️: Fire blight outbreaks are favored by warm, humid, and rainy weather during the spring (especially the bloom period). The bacterium becomes active when daytime temperatures are above about 18 °C (65 °F) and nights are warm (above 12–15 °C). In particular, the risk is highest when temperatures range between 24–28 °C (75–82 °F) with high humidity or intermittent rain during bloom​. Under these conditions, the bacteria can multiply rapidly on flower surfaces and infect via natural openings (nectaries, stomata) or wounds. Rain and insects are the primary vectors that deliver the bacteria to susceptible flower tissues​. Wet weather about 1–2 weeks after bloom, combined with average temperatures above ~18 °C, often leads to visible symptoms of blossom blight​. Conversely, a cool, dry bloom period usually results in minimal blossom infection. After bloom, young shoots remain susceptible especially during periods of rapid growth or after events that cause injury (e.g., hailstorms or strong winds). Hail can create numerous entry wounds on fruit and shoots, and fire blight often flares up roughly 3–7 days after a hail event if weather is warm and humid​. Similarly, high winds can cause leaf rubbing injuries that serve as entry points. Bees and other pollinating insects actively spread the bacterium during bloom by visiting flowers (they pick up bacteria from ooze on infected blossoms and carry it to healthy blossoms)​. Once blossoms are no longer present, insects like flies, ants, and aphids may be attracted to the bacterial ooze on cankers or fruit and can inadvertently transport cells short distances. Long periods of rain or high humidity also allow cankers to produce more ooze, facilitating spread by rain splash and running water down branches. Optimal conditions for the bacterium’s spread and infection are often summarized by the “Maryblyt” or similar disease forecasting models: roughly, daily mean temps above 15.6 °C (60 °F) and at least 2.5 mm of rain during bloom constitute an infection event, and symptoms would appear about 5–30 days later depending on temperature​. In summary, warm, wet spring weather plus injury events (hail, wind) greatly favor fire blight, whereas cool or dry conditions keep it in check.

 

 

Transmission and Spread 🔄: Fire blight spreads locally via insects, rain, and contaminated tools, and over longer distances via infected plant material. During bloom, bees and other pollinators are the main agents moving E. amylovora from tree to tree​. Infected blossoms produce a sugary bacterial ooze that attracts bees; as bees forage, they get bacterial cells on their bodies and deposit them on other blossoms, causing new infections. Rain-splash is critical both in bloom and later. When it rains, bacterial ooze (which often appears as off-white, sticky droplets on blighted tissue or cankers) is washed off and splashed onto nearby susceptible tissue. Rain can carry bacteria into open blossoms, onto young leaves, or into natural openings like stomata and lenticels on shoots. Driving rain and wind can also force bacteria into the tree through stomata or small wounds. Insect pests (like plant bugs, aphids, or pear psylla) might also inadvertently spread the bacteria by carrying ooze on their legs or mouthparts as they move along shoots. Hail or storms that wound fruit and bark provide direct entry points for the pathogen; once inside, the bacteria can move through internal tissues. Human activities can significantly spread fire blight as well. Pruning tools that cut through a blighted branch can pick up millions of bacterial cells; if not disinfected, the next cut on a healthy tree can instantly introduce the pathogen deep into that tree’s tissue​. Similarly, workers’ hands or ladders can carry bacteria if they contact ooze. Orchard practices like summer pruning or pinching during an active outbreak can rapidly disseminate the disease – hence, such practices are discouraged when fire blight is present. The bacterium can travel via birds too (birds can get sticky ooze on their feet or beaks and carry it to another tree, though this is harder to quantify). At the colony level, bees have been shown to carry E. amylovora back to hives, but it doesn’t harm the bees; however, contaminated hives could theoretically introduce the bacterium to new areas when moved for pollination. Over longer distances, nursery stock, budwood, or rootstocks that harbor latent infections are the primary means. This is why many countries regulate the movement of host plants from regions where fire blight is present. There is evidence that asymptomatic but latently infected pear and apple buds can introduce the disease to new orchards. Once in a new orchard, the disease can escalate if conditions permit. In summary, fire blight has a multi-modal spread: insects (during bloom) and rain are key for natural spread, and human-mediated movement of infected plant material is key for long-range dissemination.

Pathogen Life Cycle ♻️: Erwinia amylovora survives the winter primarily in cankers on infected trees. As autumn arrives and temperatures drop, the bacteria retreat into the margins of expanding cankers on branches and trunks​. Within these cankers (in the living tissue at the edge), the bacteria overwinter in a dormant state – their population is low and metabolism slowed – essentially “hiding” within the tree. Unlike many fungi, they do not form specialized spores or fruiting bodies; they remain as bacterial cells embedded in the plant tissue. When spring temperatures rise (around mid to upper teens °C) and sap flow begins, the overwintering bacteria begin to multiply rapidly in the sap and parenchyma around the canker​. Moist weather in spring, especially around bud break and bloom, triggers the production of bacterial ooze on those canker sites​. The ooze is often observed as small droplets emerging through cracks or lenticels in the bark of the canker – it’s rich in bacterial cells (up to 10^9 cells per droplet). This primary inoculum is what initiates new infections: it attracts insects and gets splashed to open blossoms and young shoots​. During bloom, bacteria multiply epiphytically (on the surface) in the nectar and stigma of flowers, reaching enormous numbers. They then invade the flower through natural openings at the base of the ovary, causing blossom blight. From there, the bacteria travel through the plant – they can move intercellularly through the pedicel into the spur and twig. Fire blight bacteria are not strong vascular (xylem) invaders compared to some wilt pathogens, but once in the spur or shoot, they can move both in the xylem vessels and in parenchyma. This leads to systemic infection of shoots, turning them black and causing the characteristic shepherd’s crook. The infection can continue to progress into larger branches or even the trunk, especially if the pathogen reaches a rootstock or a highly susceptible area. At each new infection site (be it a blossom, shoot, or canker), the bacteria multiply and, when conditions are humid or wet, exude more ooze – thus setting up secondary infection cycles throughout the growing season​. For example, an initial blossom infection might lead to several blighted shoots; each of those can form cankers that produce ooze and infect more shoots after the next rain, including possibly on neighboring trees. As summer transitions to fall, bacterial activity slows; cankers form around the blighted areas. Many infected smaller branches die. The bacteria once again concentrate in the canker margins to overwinter, completing the cycle​. Notably, E. amylovora can survive in a wide range of host plants (over 130 species in 40 genera of Rosaceae)​, including ornamentals like firethorn (Pyracantha), hawthorn (Crataegus), mountain ash (Sorbus), and quince (Chaenomeles). These alternative hosts can harbor the bacterium and contribute to local overwintering and spread, often without immediate notice if they are in wild or unmanaged settings. Thus, the pathogen’s life cycle often involves these alternate hosts as reservoirs in addition to the main orchard hosts of apple and pear.

 

 

Control Methods 🛡️: Fire blight management relies on exclusion, careful monitoring, rapid removal of infections, and preventive treatments. Quarantine and exclusion: In regions where fire blight is not yet present, strict quarantine of imported plant material (buds, scions, trees) is essential. For known infested areas, avoid moving nursery stock or even beehives out of those areas during bloom. Monitoring: During bloom and early shoot growth, inspect orchards frequently (every few days in high-risk periods) for wilted blossoms or shoots. Blossom blight symptoms appear about 1-2 weeks after infection, so continued vigilance through and after bloom is needed. Many extension services provide fire blight forecast warnings using models (like Maryblyt or Cougar Blight); use these forecasts to know when conditions are high-risk​and be prepared to act. Pruning and rogueing: At the first sign of infection, promptly prune out or remove infected tissue. This is critical – each blighted spur or shoot can become a factory producing billions of bacteria that spread the disease. The recommended practice is to cut at least 20–30 cm (8–12 inches) below the visible margin of infection on twigs and at least 30–60 cm (1–2 feet) below in the case of larger limbs​, because bacteria can extend beyond the visible lesion. After each cut, disinfect pruning tools in 10% bleach or 70% alcohol (or a commercial disinfectant) to avoid carrying bacteria to the next cut​. Some protocols suggest carrying a separate set of tools in disinfectant so that one tool can be soaking while another is used. Do not just drop prunings on the ground – collect and burn or deeply bury them to destroy the bacteria​. If an entire tree is extensively blighted (for example, central leader infected), it may be best to remove and destroy the whole tree to protect neighboring trees. In the event of severe or orchard-wide outbreaks, some jurisdictions mandate tree removal and destruction (this is often the case in strict quarantine enforcement). Timing: Do any necessary pruning during dry weather if possible, and ideally when the tree is dormant or in early bloom; avoid summer pruning in an active outbreak, as cuts may invite further infection and spread. Chemical and biological control: Antibiotic sprays are the most effective chemical measure against fire blight during bloom. Streptomycin (an antibiotic) can reduce blossom infection by killing bacteria on the flower surface if applied just before infection events​. In areas like North America, streptomycin is widely used at 2-4 applications during bloom when conditions warrant, and it can provide 70-90% control of blossom blight. However, overuse led to streptomycin-resistant strains in some regions, requiring alternatives like oxytetracycline or new biologicals. Some countries (such as South Korea) do not allow antibiotics in orchards; instead, copper-based bactericides (e.g., copper oxychloride or copper hydroxide) may be applied during dormant or bloom stages​. Copper can help reduce surface bacteria but can also cause russeting on fruit or phytotoxicity if used after green tip stage – therefore, in-season use is limited (often just a delayed-dormant copper spray to knock back bacteria on cankers, and perhaps a light copper at bloom if absolutely needed). There are new biological controls like BlightBan (Pantoea agglomerans, a beneficial bacterium) and Bloomtime (Aureobasidium pullulans, a yeast) which can colonize flowers and outcompete E. amylovora; these can provide partial control and are often used in integrated programs, sometimes alongside lower rates of streptomycin to mitigate resistance. Pear-specific: Pears are extremely susceptible and often require additional focus – e.g., delaying thinning wounds until dry weather, etc. Hygiene: Disinfect tools and equipment that come into contact with trees. For example, tractor-mounted hedgers or pruners can spread bacteria unless cleaned. Workers should ideally dip their hands or gloves in sanitizer after handling infected material. Fertilization: Avoid excessive nitrogen fertilization in spring; overly vigorous shoots (with tender succulent growth) are more prone to infection and can make the outbreak worse​. Moderate nitrogen and balanced nutrients (especially adequate calcium) can reduce host susceptibility. Weed and alternate host management: Remove any wild Crataegus (hawthorn) or ornamental Pyracantha near the orchard if possible, as these can harbor the pathogen. If removal is not possible, at least monitor them for blight symptoms and remove infected parts. Mowing: If fruit mummies or blighted shoots fall to the ground, flail-mow them to speed decomposition (though this is secondary, since most inoculum comes from above-ground cankers in spring). Resistant varieties: Planting fire blight-resistant cultivars is a long-term strategy. Many apple varieties have some resistance (e.g., Enterprise, Liberty, Freedom, and certain crabapples are fairly resistant​, whereas popular ones like Gala and Fuji are susceptible). Most Asian pear varieties are extremely susceptible, but some European pears like Bosc are moderately susceptible whereas Kieffer pear is relatively resistant. Resistant rootstocks (like some OHxF series for pear, or certain Geneva series for apple) can also reduce losses (especially rootstock blight). However, even “resistant” varieties can get some fire blight under heavy pressure; they just tend to get fewer or less severe strikes. Regulatory: In many countries, fire blight is a regulated disease. For example, in South Korea, any detection requires immediate notification of authorities​, and control measures including orchard quarantine and destruction of infected trees under supervision. Compliance with such regulations is critical to prevent spread. In summary, a diligent integrated approach is needed: prevent introduction (clean nursery stock), monitor aggressively at bloom and after storms, promptly prune out infections under dry conditions, sanitize tools, apply antibiotics or appropriate bactericides during high-risk periods, and follow all regulatory guidelines. While fire blight cannot be completely eliminated once established, these practices can keep it at manageable levels and protect the orchard’s productivity for as long as possible.

 

 

 

References & Links 📖 :

- QIA Korea – Fire Blight pest data sheet​ :   https://www.qia.go.kr/plant/pest/plant_FireBlight.jsp#:~:text=Image%3A%20%EB%B3%91%EC%9B%90%EA%B7%A0%20%EC%82%AC%EC%A7%84%20%C2%A0%C2%A0%C2%A0%C2%A0%C2%A0%C2%A0,%EC%82%AC%EA%B3%BC%EB%82%98%EB%AC%B4%2C%20%EB%B0%B0%EB%82%98%EB%AC%B4%2C%20%EB%AA%A8%EA%B3%BC%EB%82%98%EB%AC%B4%2C%20%ED%94%BC%EB%9D%BC%EC%B9%B8%EB%8B%A4%20%EB%93%B1

- 농림축산검역본부 발표 (2022년 과수화상병 발생지 정보) : https://www.qia.go.kr/viewwebQiaCom.do?id=63277&type=3_80FBepid

2022년 과수화상병 신규발생지역 역학조사분석 보고서 - 과수화상병 역학분석 보고서 - 병해충

 

- University of Minnesota Extension – Fire Blight​ :? https://extension.umn.edu/plant-diseases/fire-blight#:~:text=Wilted%20shoot

Fire blight

 

- Morton Arboretum – Fire Blight (Plant Clinic)​ : https://mortonarb.org/plant-and-protect/tree-plant-care/plant-care-resources/fire-blight/#:~:text=Fire%20blight%20can%20affect%20several,Bark

 

 

- 국내 과수화상병 예측 시스템 안내 : https://www.fireblight.org/mobile/index/#:~:text=%EA%B3%BC%EC%88%98%ED%99%94%EC%83%81%EB%B3%91%EC%9D%B4%20%EB%B0%9C%EC%83%9D%EB%90%9C%20%EC%A7%80%EC%97%AD%EC%9D%98%20%EC%97%B0%EA%B5%AC%EC%9E%90%EC%99%80%20%EC%A7%80%EB%8F%84%EA%B8%B0%EA%B4%80%EC%9D%84,%EB%8C%80%EC%83%81%EC%9C%BC%EB%A1%9C%20%ED%99%94%EC%83%81%EB%B3%91%20%EC%98%88%EC%B8%A1%EC%A0%95%EB%B3%B4%EB%A5%BC%20%EC%A0%9C%EA%B3%B5%ED%95%98%EB%8A%94%20%EC%8B%9C%EC%8A%A4%ED%85%9C

 

 

Tags 🏷️: #Apple #Pear #FireBlight #Erwinia #BacterialDisease #FruitTrees