Identifying and Managing Fire Blight Apple Trees

Fire blight apple tree is a serious bacterial disease caused by Erwinia amylovora that affects apples, pears, and other members of the rose family. It earns its name from the scorched appearance of the infected leaves. 

What causes fire blight? The disease starts at the branch tips and moves downward, causing dieback. It primarily targets new growth, leading to noticeable wilting and browning or blackening of leaves, which often remain on the tree even after dying. 

Additionally, reddish water-soaked lesions may form on the bark, sometimes oozing orange-brown liquid on warm days. Fire blight can devastate blossoms, shoots, limbs, and in severe cases, entire trees.

This bacterium overwinters in infected bark and spreads through rain, dew, wind, and insects. It thrives in moist, warm conditions, particularly during blooming.

Symptoms of Fire Blight Apple Tree

What does fire blight look like? Fire blight apple trees show a range of symptoms that can affect various parts of the tree. Here’s what are the fire blight symptoms:

• Blighted Shoots and Branches: The disease starts at the tips of branches, causing new shoots to wilt and turn black or brown. These blighted shoots often curve downward, resembling a shepherd’s crook.
• Scorched Leaves: Leaves on infected shoots quickly turn brown or black but typically remain attached to the branch, giving the tree a scorched appearance.
• Blossom Death: Fire blight can kill blossoms, causing them to wilt, darken, and fall off.
• Bark Lesions: Infected branches and trunks can develop reddish or brown water-soaked lesions. These may exude a sticky, orange-brown bacterial ooze during warm, humid weather.
• Dieback: The disease spreads from branch tips downward, leading to dieback of entire branches or limbs.
• Infected Fruit: Fire blight can also affect the fruit, causing them to shrivel, turn brown or black, and eventually fall off the tree.

If you notice these symptoms on an apple tree, especially during warm, moist conditions, it’s likely a fire blight. Pruning and other fire blight treatments may be necessary to control the disease and prevent further spread.

How to Control Fire Blight Apple Tree?

There are various fire blight treatments. Here are some of the major ones:

• Plant resistant varieties when possible.
• Avoid heavy pruning or excessive nitrogen fertilizer, which promotes new growth susceptible to infection.
• Keep distance from wild hawthorn, apple, or pear plants.
• Prune and burn infected branches at least one foot below the diseased section, disinfecting pruning tools with a 10% alcohol or bleach solution between cuts to prevent spread.
• Early applications of liquid copper at the silver tip and bud break stages, repeating every 3 to 5 days up to petal fall, are effective. Use 0.5 to 2.0 oz per gallon of water, with a higher rate when disease pressure is high.
• Bacterial spread can be reduced with products containing BACILLUS VELEZENSIS. Start applications at bloom and continue every 5 to 7 days.
• Bactonus is an organic fire blight control by Novobac,which is an organic bactericide and fungicide designed to combat plant diseases like fire blight in apple trees. It contains beneficial bacteria like Bacillus safensis, Bacillus velezensis, and Pseudomonas chlororaphis, forming a protective biofilm around plant roots. This biofilm secretes substances that can control harmful bacteria and fungi​.

This organic fire blight control, specifically, produces antimicrobial compounds and induces systemic resistance in plants, helping manage fire blight. It promotes plant growth through growth-promoting substances and can be applied as a spray or via irrigation. You can also learn more about Novobac’s microbial solutions of other crops and plants disease and pest management here.

References:

1. Medhioub, Imen, et al. “Study of Bacillus velezensis OEE1 potentialities in the biocontrol against Erwinia amylovora, causal agent of fire blight disease of rosaceous plants.” Biological Control 167 (2022): 104842.
2. Singh, Daljeet, et al. “Selection of Bacillus spp. Isolates against Fire Blight of Apple on the Basis of Sequencing 16S rDNA.” Pesticide Research Journal 21.2 (2009): 195-201.