Fire blight update April 30-May 6

CAUTION: The observations, conditions, and recommendations reported for Winchester, VA are provided as a guide to fire blight risk assessment only for the immediate area of the Virginia Tech AREC located six miles southwest of Winchester. Use of the information reported here for making orchard management decisions outside of that area is not our intent. Fruit producers outside of that area are encouraged to consult their state extension specialists for information similar to that provided here.

FIRE BLIGHT: Above is a cropped graphic from the Maryblyt 7 program. Most cultivars still have much susceptible bloom. Here is the prediction for trees with first bloom open Apr 17-18, 2015. The temperature and rainfall data are current through Thursday morning, Apr 30. Predicted weather conditions are shown for Apr 30-May 6. The components of fire blight risk are indicated in the columns labeled B (blossoms open), H (degree hours for epiphytic bacterial populations), W (wetting by rain or dew), and T (average daily temperature 60 F or above). Based on recorded temperatures and wetting, the risk column shows that fire blight infection was possible Apr 20 and would have been possible with slightly warmer average temperatures for Apr 19 and 21. For infection to be predicted, wetting must occur after the EIP (epiphytic infection potential) reaches 100 or higher.  Based on predicted temperatures, risk will remain moderate through May 1, but warmer weather this weekend and into next week will increase risk to where only wetting is lacking for infection to be predicted for May 4-5, and with wetting, infection is predicted for May 6. (Be aware that routine spray applications can provide enough wetting to meet the wetting requirement for infection if all other infection conditions have been met). In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection. Under the warmer temperature conditions shown for next week, streptomycin will remain residually effective for only about 3 days.

The BBS column is tracking predicted appearance of blossom blight symptoms from infection that occurred Apr 20, and this is predicted for May 6. The CBS column at the right in the graphic indicates progression toward the appearance of canker margin symptoms due to extension of overwintering cankers from last year, with 100% of the degree hour requirement by May 1. Canker advancement cannot be prevented by chemical treatment at this time and the presence of symptoms will signal build-up of inoculum which could become a factor in the event of a trauma blight situation due to hail injury, etc.

The weather conditions used in the predictive part of this graphic come from the Weather Channel for Winchester, supplemented by site-specific data from SkyBit Inc. Be aware that risk can change quickly with unpredicted warmer temperatures and wetting.

Fire blight update for Apr 27-May 4.

CAUTION: The observations, conditions, and recommendations reported for Winchester, VA are provided as a guide to fire blight risk assessment only for the immediate area of the Virginia Tech AREC located six miles southwest of Winchester. Use of the information reported here for making orchard management decisions outside of that area is not our intent. Fruit producers outside of that area are encouraged to consult their state extension specialists for information similar to that provided here.

 FIRE BLIGHT: Above is a cropped graphic from the Maryblyt 7 program. Most cultivars are now near full bloom. Here is the prediction for trees with first bloom open Apr 17-18, 2015. The temperature and rainfall data are current through Monday morning, Apr 27. Predicted weather conditions are shown for Apr 27-May 4. The components of fire blight risk are indicated in the columns labeled B (blossoms open), H (degree hours for epiphytic bacterial populations), W (wetting by rain or dew), and T (average daily temperature 60 F or above). Based on recorded temperatures and wetting, the risk column shows that fire blight infection was possible Apr 20 and would have been possible with slightly warmer average temperatures for Apr 19 and 21. For infection to be predicted, wetting must occur after the EIP (epiphytic infection potential) reaches 100 or higher.  Based on predicted temperatures, risk will remain low-moderate through May 1, but warmer weather for the coming weekend will increase risk to where only wetting is lacking for infection to be predicted for May 3-4. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection.

The CBS column at the right in the graphic indicates progression toward the appearance of canker margin symptoms due to extension of overwintering cankers from last year, with 100% of the degree hour requirement by May 2. Canker advancement cannot be prevented by chemical treatment at this time and the presence of symptoms will signal build-up of inoculum which could become a factor in the event of a trauma blight situation due to hail injury, etc. The BBS column is tracking predicted appearance of blossom blight symptoms from the predicted infection Apr 20, with 64% of the degree hour requirement for predicted symptom appearance by May 4.

The weather conditions used in the predictive part of this graphic come from the WeatherChannel for Winchester, supplemented by site-specific data from SkyBit Inc. Be aware that risk can change quickly with unpredicted warmer temperatures and wetting.

Fire blight update April 23

CAUTION: The observations, conditions, and recommendations reported for Winchester, VA are provided as a guide to fire blight risk assessment only for the immediate area of the Virginia Tech AREC located six miles southwest of Winchester. Use of the information reported here for making orchard management decisions outside of that area is not our intent. Fruit producers outside of that area are encouraged to consult their state extension specialists for information similar to that provided here.

 FIRE BLIGHT: Above is a cropped graphic from the Maryblyt 7 program. All cultivars are now in bloom and most of them are near full bloom. Here is the prediction for trees with first bloom open last Friday or Saturday, April 17-18, 2015. The temperature and rainfall data are current through Thursday morning, April 23. Predicted weather conditions are shown for April 23-27. The components of fire blight risk are indicated in the columns labeled B (blossoms open), H (degree hours for epiphytic bacterial populations), W (wetting by rain or dew), and T (average daily temperature 60 F or above). Based on recorded temperatures and wetting, the risk column shows that fire blight infection was possible Apr 20 and would have been possible with slightly warmer average temperatures for Apr 19 and 21. For infection to be predicted, wetting must occur after the EIP (epiphytic infection potential) reaches 100 or higher.  Infection for Apr 19-21 would have been more likely in areas where bloom is more advanced, and temperatures warmer than those shown, and if wetting also occurred Apr 19 and 21. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection. Based on predicted temperatures, risk should now remain low to moderate through Apr 27 (and well into next week).

The CBS column at the right in the graphic indicates progression toward the appearance of canker margin symptoms on new growth, due to extension of overwintering cankers from last year, 89% of the degree hour requirement by Apr 27. Canker advancement cannot be prevented by chemical treatment at this time and the presence of symptoms will indicate a build-up of inoculum which could become a factor in the event of a trauma blight situation due to hail injury, etc. The BBS column is tracking predicted appearance of blossom blight symptoms from infection Apr 20, now with only 12% of the degree hour requirement for predicted symptom appearance, which will be much delayed with cooler weather into next week. 

The weather conditions used in the predictive part of this graphic come from the Weather Channel for Winchester, supplemented by site-specific data from SkyBit Inc. Be aware that risk can change quickly with unpredicted warmer temperatures and wetting.

Fire blight update; scab and rust infection Apr 19-20

CAUTION: The observations, conditions, and recommendations reported for Winchester, VA are provided as a guide to fire blight risk assessment only for the immediate area of the Virginia Tech AREC located six miles southwest of Winchester. Use of the information reported here for making orchard management decisions outside of that area is not our intent. Fruit producers outside of that area are encouraged to consult their state extension specialists for information similar to that provided here.

  

FIRE BLIGHT: Above is a cropped graphic from the Maryblyt 7 program. With all but the latest cultivars in bloom, and many approaching full bloom, here is a prediction for trees with first bloom open last Friday, April 17, 2015. The temperature and rainfall data are current through Monday evening, April 20. Predicted weather conditions are shown for April 21-24. The components of fire blight risk are indicated in the columns labeled B (blossoms open), H (degree hours for epiphytic bacterial populations), W (wetting by rain or dew), and T (average daily temperature 60 F or above). Based on predicted temperatures and wetting, the risk column shows that fire blight infection was possible for Apr 20 and would also be possible with slightly higher than predicted temperatures Apr 21. For infection to be predicted, wetting must occur after the EIP (epiphytic infection potential) reaches 100 or higher.  Infection is more likely in areas where bloom is more advanced, and temperatures warmer than those shown for Apr 19-21, and if wetting occurs. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection.

The weather conditions used in the predictive part of this graphic come from the Weather Channel for Winchester, supplemented by site-specific data from SkyBit Inc. Be aware that risk can change quickly with unpredicted warmer temperatures and wetting.

Wetting last night Apr 19-20 was enough for  scab and rust infection: 15 hr wetting at 67-50 F with 1.12 in. of rain.

Fire blight infection predicted for April 20 or sooner

CAUTION: The observations, conditions, and recommendations reported for Winchester, VA are provided as a guide to fire blight risk assessment only for the immediate area of the Virginia Tech AREC located six miles southwest of Winchester. Use of the information reported here for making orchard management decisions outside of that area is not our intent. Fruit producers outside of that area are encouraged to consult their state extension specialists for information similar to that provided here.

  

FIRE BLIGHT: Above is a cropped graphic from the Maryblyt 7 program. With early cultivars with bloom open, and more bloom opening over the next several days, here is a prediction for apple orchards with first bloom open Friday, April 17, 2015. The temperature and rainfall data are current through Friday afternoon, April 17. Predicted weather conditions are shown for April 18-22. The components of fire blight risk are indicated in the columns labeled B (blossoms open), H (degree hours for epiphytic bacterial populations), W (wetting by rain or dew), and T (average daily temperature 60 F or above). Based on predicted temperatures and wetting, the risk column shows that fire blight infection is possible if wetting occurs Monday, Apr 20. For infection to be predicted, wetting must occur after the EIP (epiphytic infection potential) reaches 100 or higher. Infection is more likely in areas where bloom is more advanced, and temperatures warmer than those shown for Apr 17-21. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection. Following this high risk period, predicted cooler temperatures should reduce risk Apr 22 and later in the week.

The weather conditions used in the predictive part of this graphic come from the Weather Channel for Winchester, supplemented by site-specific data from SkyBit Inc. Be aware that risk can change quickly with unpredicted warmer temperatures and wetting.

Heavy apple scab, cedar-apple rust and quince rust infection period Apr 14-15

We recorded a heavy apple scab, cedar-apple rust and quince rust infection period with wetting starting at 2 AM Apr 14 and still not quite dry at 9 AM Apr 15. Temperatures ranged from 70 F to 45 F with 18 hours above 55 F. Total rainfall was 0.62 inches. Apples in the Winchester area are mostly at open cluster stage with Yorks at tight cluster this morning. Rust galls and cankers actively discharged spores and blossoms are susceptible to quince rust by the tight cluster stage; leaves and blossoms are susceptible to cedar-apple rust. This time similar wetting conditions, but with variable amounts of rainfall, occurred over most Virginia fruit areas.

Some central Virginia apples came into bloom by Apr 11 showed Maryblyt infection conditions for the night of Apr 13. This would generally be true for any areas that came into bloom by Apr 11 and had rain the night of Apr 13.

More early season scab pressure

We have had three scab infection periods the past three days, with one of them still in progress with split wetting today. With these three wetting periods, rainfall at our AREC had totaled one inch and any earlier fungicide protection is probably depleted.

Some rust spores had been discharged with the warmer wetting period Apr 7, and others are fully mature. In areas where rusts are a common problem, it would be prudent to follow-up with a fungicide application that includes, as part of the fungicide mix, an SI for after-infection cedar-apple and quince rust control as well as for scab suppression.

Scab and possible rust infection period

We recorded a definite apple scab infection period at our AREC last night, with wetting from 4 PM Apr 7 until at least 9 AM this morning Apr 8, and temperatures ranging from 67 to 46 F with 0.4 inch of rain. Some cedar-apple rust and quince rust spores were also released, and where trees were not well protected, a follow-up spray including an SI fungicide is suggested for after-infection rust control.

Most apple tree cultivars are at tight cluster stage, a pretty large target, as shown on Golden Delicious below:

Drying is not very good today so these conditions may continue on into tonight.

Early season disease update

Yesterday Idared, Gala and Red Delicious apples at our AREC were at half-inch green-tip to tight cluster stage as shown below. 

Idared apple fruit buds, Apr. 6, 2015. The bud on the left is typical of one infected with overwintered powdery mildew, compared to a healthy one on the right.

Heavy production of condiospores on emerging Idared flower cluster leaves at tight cluster stage, Apr. 6, 2015

Heavy production of conidia was observed on emerging Idared flower cluster leaves and the temperatures was favorable for infection. (Powdery mildew infects susceptible leaves and flowers in dry weather when the temperature is above 53 degrees F).

Apple scab ascospores were first trapped at our AREC March 25 when Cripps Pink (Pink Lady) and Gala apples were just at the earliest green-tip stage. Wetting recorded at our AREC March 26-27 was not quite long enough for scab infection. Scattered shower activity, but with longer drying periods, occurred Apr. 2-3 and probably did not result in scab infection; however, some local areas may have had longer wetting and less drying between showers, and at relatively warm temperatures this could have quickly resulted in infection. With light rainfall risks of scab infection from these wetting events could have been averted with a protectant fungicide such as copper applied March 26. Expect more ascospore discharge and extended wetting at moderate temperatures several days this week.

In central Virginia, weather instruments at Silver Creek Orchards, Tyro, VA, indicated that wetting was more than adequate for early scab infection March 26-27. Uncontrolled scab lesions from infection at that time would be expected to emerge later this week and early next week.