May 8, 2026

First Fire blight Symptoms Visible on Flowers and Shoots in Madison County

As of 5 May 2026, first blossom blight and shoot blight symptoms were visible us in Madison County, Virginia (Figs 1 – 3). Most likely these infections of flowers have established either in the first week of April or mid April, with the latter being the more likely scenario (we reported these predicted infections in the previous blog posts on this website: (I) First Fire Blight Infections Predicted from 31 March – 3 April, Antibiotic Application Necessary on Open Flowers; (II) Add Fungicides as First Major Scab Infection is Predicted 31 March – 3 April and Fire Blight Infections 12-14 April in All Virginia as Announced Last Week. In cases where you now see blossom blight and shoot blight symptoms, you have active infections taking place and spreading to other actively growing shoots. If you do not act now to remove these symptoms by pruning, you need to assume that the fire blight bacterium will be probably be present for a long time in your orchard. If you see fire blight symptoms now, apply Kudos high rate and start pruning out the infected branches. Do not apply streptomycin as the bacterium is in the tissue, so it cannot be reached by the antibiotic, and there is a risk that if you do spray it you will promote streptomycin resistance in the fire blight bacterium Erwinia amylovora. This will reduce efficacy of this antibiotic, or even worse, lead to the loss of its efficacy through resistance.

At this moment, if symptoms are visible and you have 1-10% fire blight strikes, apply plant growth regulator (PGR) prohexadione-calcium (Apogee, Kudos) at 6 oz/100 gal to reduce susceptibility of not-yet-infected shoots and slow down the invasion shoots and wood by the fire blight bacterium. This PGR works by inhibiting hormones of growth in the green tissues and thus reduces the vegetative tree growth i.e. shortens the shoot length. More importantly, prohexadione-calcium shortens the period to reach terminal bud formation, reduces shoot growth, thickens the cell walls and thus reduces susceptibility of shoots to fire blight. Because the trees are no longer susceptible to fire blight infections when shoots stop its growth i.e. when terminal buds set on shoots, application of Apogee or Kudos will speed onset of terminal bud formation, thus reducing the period of shoot susceptibility to infection and reducing the chance for spread of fire blight on other shoots. If symptoms are more numerous, meaning you see 10 – 20% or more blighted flower clusters and shoot per tree, mature bearing orchards should be sprayed with 12 oz of Apogee per 100 gal, preferably in a dilute spray, to get a good coverage of all shoots. This will help reduce the number of fire blight cankers developing on wood by invasion from infected flowers and shoots. Management should also include spraying a copper material at 0.2 lb/A of metallic copper equivalent every 14-20 days. Keep in mind that if slow drying conditions occur after this application, even a low dose of copper could cause fruit russetting. So, apply copper during fast drying conditions to avoid this issue. After the copper spray, work on fire blight symptom removal by pruning. Copper will only kill fire blight bacteria present in bacterial white, yellow, or orange ooze droplets visible on the surface of both blighted and freshly infected flower cluster leaves, flowers, and shoots (Fig. 2).

Droplets of fresh bacterial ooze, which spread this bacterium to uninfected green tissues, emerge on infected green tissues much before the fire blight symptoms are visible (Fig. 2). This means that bacteria usually have ample time to extensively spread to the surrounding, uninfected flower clusters and shoots before the first shoot strikes are visible. Due to recommended low copper doses and the fact that copper does not kill bacteria inside the infected tissues, the effect of copper will be to slow down or prevent further spread of pathogen to new, uninfected shoots. More spray applications may be needed to achieve desired effect. High rates of copper and copper applied just before wet and slow-drying conditions could injure fruit skin up through at least mid-June. Cultivars differ in their susceptibility to copper related russetting. You will need to take into account how prone is each of your cultivars to russetting by copper, watch the weather forecast to avoid applying copper before wet and slow drying conditions, and apply low-doses of copper probably multiple times with lower water volume (to promote quick drying after spray). When considering use of copper, a tank mix of Cueva and Double Nickel might be the best choice since there are some indications that this mix may be less prone to cause fruit russetting.

If possible, remove fire blight symptoms as soon as they appear, after you applied Apogee or Kudos. Cutting out the infected strikes (Fig. 3) at 18 to 24 inches below the visible margin of infection on dead shoots or flowers aims to remove bacteria that might have penetrated into the symptomless wood far below the infection margin. If these length requirements below symptom edge could not be met, pruning should be done into the closest perennial wood (at least 2-yr-old, and 4-6 inches into this wood if possible). Prune on a cool dry day and never before, during or soon after rain of heavy dew. These conditions will risk spreading fire blight more. All pruned out brush should be left on the ground close to the tree to dry, and flail-mowed or removed from the orchard after the branches are completely dry (this means when cuts show no green cambium visible when bark is scraped with a knife). If there is enough space in the mid-rows to leave the brush on the ground, without preventing passage of air-blast sprays with a tractor, copper could also be applied after pruning. During symptom removal, pruning tools should be disinfected at least between each tree with 70% rubbing alcohol or 10% bleach solution. Even though the true benefit of using any specific disinfectant for tools is still debated or questioned, I would recommend using one of these disinfectant solutions. If pruning is done rapidly, as soon as first symptoms occur, continue daily scouting after the first pruning to remove any additional strikes that develop subsequently.