Farm Data Tools
PomeBlight

Pomeblight

Fire blight is a bacterial disease of apple and pear trees that can devastate whole orchard blocks during severe infections. The most critical time of the disease cycle is the blossom blight phase. Flowers have open nectar pores where the disease-causing bacterium Erwinia amylovora gains entry during favourable weather. Properly timed management with antibiotics at bloom can prevent infection to protect the health of your trees.

The user interface included in your subscription has been designed and tested by with biological input and review by Perennia’s Tree Fruit Specialist Michelle Cortens, MSc. P.Ag. It has also been beta-tested by real tree fruit farmers in Nova Scotia, to ensure ease of use and usefulness.

PomeBlight is a responsive web-based tool for tree fruit growers to help monitor for fire blight infection risk. This decision-support tool is intended to save you money and time by helping you identify optimum management opportunities. Good management decisions can reduce the risk of costly response measures to disease outbreaks.

Supporting Documents

Changing the working year

Choose the date under ‘Growing Year’. The current year offers current conditions and a summary of the forecast. Historic years offer the data from what happened previously. Data is available for only years in which a subscription was held.

Can I export the data?

Yes, in the heading next to the forecast and historical records there is the option to download the CSV file.

How often is the model re-calculated?

Every time you make a change or every time the weather station sends new information. This means that an infection prediction could change based on your changes or observed or forecast conditions. The last time that a weather station reported is stated within current conditions if you hover over the ‘i’ icon.

If the forecast for today is +15C but then the actual temperature is +16C, will the observed temperature overwrite the forecast temperature?

Yes. Actual conditions that exceed the expected conditions will overwrite the forecast values.

Why doesn’t the forecast line up exactly with the Environment Canada daily predictions?

Environment Canada does not report the daily maximum and minimum temperatures that are required by the PomeBlight model. Environment Canada reports the low nighttime temperature from 5 PM to 5 AM and the high daytime temperature from 5 AM to 5 PM. We know that the morning temperatures are most likely the coldest in a day. Therefore, we have shifted the forecast to use the previous day’s nighttime low temperature with the current day’s daytime high temperature.

If another user in my business updates the temperature, spray, or other parameter in the model, does it update my model as well?

No, you have separate user accounts on the same subscription that share the farm and field structure but everything else is independent. It was designed this way to prevent unwanted changes between users that could cause unintended consequences. Account users are in charge of their own changes.

Why is the wetness requirement sometimes satisfied when it has not rained today?

More than 2.5 mm of rain one day will satisfy the requirement for wetting on the following day because water stays in the base of the flower. In this case, the model has an asterisk next to 0 mm of rainfall on the current date.

Why are some data values red?

The blossom blight infection risk level depends on four factors: 1) bud stage, 2) EIP, 3) wetting and 4) average temperature. When a data value associated with any of the four factors exceeds its threshold limit, it will turn red to indicate that the risk factor has been met. Pay attention to the missing factors because they help to determine your risk if you can estimate their likelihood of happening.

Why are the infection risks coloured?

The infection risk levels of low, moderate, high and infection are coloured for emphasis. Low is green, moderate is yellow, high is orange and infection is red.

An INFECTION was predicted by the model but I input an antibiotic spray, so why is the infection risk still HIGH?

Remember, the blossom blight infection risk level depends on four factors: 1) blossom, 2) EIP greater than 100, 3) wetting and 4) warm average temperature. The risk level depends on how many of the four factors have been met. One factor = low, two factors = moderate, three factors = high, and four factors = infection. The EIP is an important factor to pay attention to because it represents the bacterial population. If EIP is at or near 100 then bacterial levels are expected to cause epidemic levels of infection. An antibiotic spray kills the bacteria, so antibiotics set the EIP to zero and the infection risk is averted, even though three other factors are still present.

Can we micromanage fire blight?

No. The model is a daily model, not an hourly model. A prediction of the bacterial population (EIP) is therefore made for the entire day, taking into account the forecast maximum and minimum temperatures. When it takes 12 hours or more to spray an entire orchard, hourly predictions are not often helpful anyway. Also keep in mind that the model is a daily snapshot whereas bacterial growth is a continuum. With such risk and uncertainty, protection is the best option when called for.

How do I choose the first blossom date and does it matter?

The first blossom date is the day that the first blossom opens in your orchard. The date will matter for about the first four days until the model assumes that the early flowers are old and no longer hospitable to bacterial growth. The model continues to predict for all subsequent flowers that develop and it becomes synchronized with equal EIP risk.

If I make edits to the forecast, do they overwrite the predicted forecast?

YES. To return to the current forecast, select undo on the changes that you made.

What if I observed a very light rain that was not recorded by the weather station?

You cannot edit precipitation in the historical records. However, you can satisfy the wetting requirement by inputting a dew instead.

How important is a dew for the infection risk?

Heavy dew creates a channel of water on a high proportion of flowers, more so than even a light rain. Bacteria require a channel of water to move down the flower, so the risk from a dew is significant. Watch for low areas of the orchard where heavy dew is most common.

How do you input a spray into the daily model if it’s applied from 11 PM to 2 AM?

The model is not sensitive enough to allow us to enter the time when an antibiotic was sprayed, only the day. For night-time sprays, choose the earlier day for a conservative approach. By spraying at night, you are protecting the flowers that opened earlier that day and not the flowers that have yet to open when the new day begins. On any newly opened flowers, the internal flower parts will not have been sprayed directly to protect against bacterial growth.

Is the EIP value relevant during trauma events?

No. After ooze becomes active, trauma events are always cause for concern because bacteria are transported from active infections to open wounds. EIP is the epiphytic infection potential of Erwinia amylovora. Epiphytic growth happens during the floral phase of fire blight, so the EIP is modeling only the epiphytic growth phase on blossoms.

Is the temperature relevant during trauma events?

No. Bacterial populations contained in rehydrated ooze can be delivered to open wounds regardless of the temperature. Temperature matters for blossom blight risk because bacteria rely on heat to grow on the floral stigma. Whereas for trauma blight, the source of the bacteria is active infections that already have excessive bacterial populations contained in ooze.

Does water wash away bacteria?

No. Bacteria use water to disperse and colonize new flowers. The model does not reset after a rain because there is still a lot of bacteria present. Rain also helps to maintain bacterial survival. Sometimes a rain will correspond with cooler temperatures, in which case it is actually the cooler temperatures that are responsible for less bacterial growth.

When are flowers no longer at risk of a blossom blight infection?

As flowers age, the stigmas become less susceptible hosts for the bacteria Erwinia amylovora. Yet, late blooms are especially important because bacterial populations have had time to build throughout bloom, and bees have broadly dispersed the bacteria in the landscape. Petal fall on the entire tree is the only time we can be sure that the bacteria cannot grow on stigmas to be washed into the flowers. Therefore, flower protection until petal fall is recommended.