Heavy scab and possible rust infection period; fire blight outlook

As of 8 AM April 29 we had recorded a heavy apple scab and possible rust infection period: 30 hours at 53-46° with 0.44 in. of rain. The cedar galls and quince rust cankers are now in "full bloom", producing basidiospore inoculum, and the apple blossoms and small fruit are very susceptible to quince rust. The first 12 hours of wetting at 53° would have have been more favorable for infection by the rusts than the later 18 hours with temperatures down to 46°. With continued sporadic wetting in the 50s likely, it would be prudent to include a sterol-inhibiting fungicide for after-infection rust control in the next fungicide application.

Maryblyt outlook for Winchester, VA, April 29.

FIRE BLIGHT: Above is a cropped graphic from the Maryblyt 7 program. Susceptible flowers are still open on many cultivars. The temperature and rainfall data are current through Friday morning, April 29. Predicted weather conditions are shown for April 29-May 2. 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, the risk column shows infection conditions for Apr 21, 22 and 24-26.

 Cooler temperatures Apr 29-30 should reduce risks through Apr 30, but predicted warmer temperatures Sunday, May 1 will again increase the risk going into next week. For optimum control, a protective streptomycin application is recommended ahead of predicted infection, but it can also provide about one day after infection suppression. Risk can change quickly with unpredicted warmer temperatures and wetting.

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. The fire blight outlook will be updated Monday, May 2.

Fire blight infection conditions today

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. Susceptible flowers are still open on most cultivars. Here is the prediction for trees with first bloom open Monday, April 11, 2016. The temperature and rainfall data are current through Wednesday morning, April 27. Predicted weather conditions are shown for April 27-May 1. 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). For infection to be predicted, wetting must occur after the EIP (epiphytic infection potential) reaches 100 or higher, which has been true since Apr 18. Based on predicted temperatures, the risk column shows infection conditions for Apr 21-22 and 24-27. (Note that the outlook for Apr 25-26 changed from the previous post due to unpredicted showers both days). For optimum control, a protective streptomycin application is recommended ahead of predicted infection, but it can also provide about one day after-infection suppression. Predicted cooler conditions after today and through APPLE BLOSSOM FESTIVAL weekend should reduce risks during this time. (The cooler temperatures will probably also ensure that a few apple blossoms will be present through the weekend for those who come to the area looking for them).

The BBS column is tracking predicted symptom development for the first infection Apr 21. Yesterday we could already see symptoms from experimental inoculations Apr 18. The CBS column predicted for the appearance of canker margin symptoms Apr 26, due to extension of overwintering cankers from last year, and it is now tracking the predicted appearance of canker blight symptoms when that value reaches 100. Canker blight cannot be prevented by chemical treatment and the presence of symptoms would 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 WeatherChannel for Winchester, supplemented by site-specific data from SkyBit Inc. Be aware that risk can change quickly with unpredicted warmer temperatures and wetting. Unless the outlook changes appreciably form currently predicted conditions, the fire blight outlook will not be updated until Monday, May 2.

Fire blight and other disease threats this week

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.

  

Maryblyt outlook April 25, 2016

FIRE BLIGHT:  Above is a cropped graphic from the Maryblyt 7 program. Susceptible flowers are still open on most cultivars. Here is the prediction for trees with first bloom open Monday, April 11, 2016. The temperature and rainfall data are current through Monday morning, April 25. Predicted weather conditions are shown for April 25-29. 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). For infection to be predicted, wetting must occur after the EIP (epiphytic infection potential) reaches 100 or higher, which has been true since Apr 18. Based on predicted temperatures, the risk column shows infection conditions for Apr 21, 22 and 23 and only wetting is lacking for Apr 25-27. In situations where all other requirements for infection have been met except wetting, wetting from a maintenance spray application can provide the wetting trigger for infection to occur. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection. A streptomycin spray remains effective about 3 days in warmer conditions when it is needed most and can provide about one day after-infection suppression.

The BBS column is tracking predicted symptom development for the first infection Apr 21. The CBS column indicates progression toward the appearance of canker margin symptoms due to extension of overwintering cankers from last year, which are predicted to occur when that value reaches 100 Apr 27. 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. The fire blight outlook will be updated Wednesday, Apr 27.

OTHER DISEASES:  We recorded a 15-hr scab, cedar-apple rust and quince rust infection period Apr 22-23. The infection period was as long as 23 hr in Tyro, VA. Where fungicides were not applied recently enough to cover through this infection event, we suggest ones with after-infection activity for scab and rusts, applied as soon as possible. 

Cedar-apple rust galls with expanded spore horns April 22, 2016.

Meanwhile, powdery mildew has been by far our most active apple disease so far this year. Mildew is our only "dry weather" disease and we have had 24 infection days since spores were first available March 16. Secondary infection, shown below, has been evident for at least two weeks. 

Secondary powdery mildew infection, Ginger Gold apple.

Peach leaf curl infection occurred at our AREC as early as March 13. Complete control can be achieved with a single application of an effective fungicide in the dormant season any time from leaf drop in the fall until just before infection occurs with wetting after first bud swell in the spring.

Peach leaf curl, Turk Mt. Overlook, Skyline Drive, Virginia

Finally, after the early season we have had this year, we are happy to see peach and apple trees making little fruits at our AREC!

Shuck-split stage on Redhaven peach, April 22, 2016, 

Current fire blight conditions

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. Susceptible bloom is open on all cultivars. Here is the prediction for trees where first bloom was open Monday, April 11, 2016. The temperature and rainfall data are current through Friday morning, April 22. Predicted weather conditions are shown for April 22-26. 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). For infection to be predicted, wetting must occur after the EIP (epiphytic infection potential) reaches 100 or higher, which has been true since Apr 18.

Based on predicted temperatures, the risk column shows infection conditions for Apr 21-24 and Apr 26 and only wetting is lacking for Apr 25. In situations where all other requirements for infection have been met except wetting, wetting from a maintenance spray application can provide the wetting trigger for infection to occur. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection. A streptomycin spray remains effective about 3 days in warmer conditions when it is needed most and can provide about one day after-infection suppression.

The BBS column is tracking predicted symptom development for the first infection Apr 21. The CBS column indicates progression toward the appearance of canker margin symptoms due to extension of overwintering cankers from last year, which are predicted to occur when that value reaches 100 Apr 26. 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. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection. The fire blight outlook will be updated Monday, Apr 25.

Continued fire blight risk into next week

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. Susceptible bloom is open on all cultivars. Here is the prediction for trees with first bloom open Monday, April 11, 2016. The temperature and rainfall data are current through Wednesday afternoon, April 20. Predicted weather conditions are shown for April 21-25. 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). For infection to be predicted, wetting must occur after the EIP (epiphytic infection potential) reaches 100 or higher, which is occurring today, Apr 18. Based on predicted temperatures, the risk column shows high risk for Apr 18-23 and Apr 25. Infection is indicated with predicted thunderstorms Apr 23. Be aware that in situations where all other requirements for infection have been met except wetting (Apr 18-22 and 25), wetting from a maintenance spray application can provide the wetting trigger for infection to occur. 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, which would be predicted to occur when that value reaches 100. 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 WeatherChannel for Winchester, supplemented by site-specific data from SkyBit Inc. Be aware that risk can change quickly with unpredicted warmer temperatures and wetting. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection. The fire blight outlook will be updated Friday, Apr 24.

Fire blight active this week!

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. Susceptible bloom is open on all but late cultivars (Even Rome Beauty clusters are waking up!), and earlier cultivars are approaching full bloom. Here is the prediction for trees with first bloom open Monday, April 11, 2016. The temperature and rainfall data are current through Monday morning, April 18. Predicted weather conditions are shown for April 18-23. 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). For infection to be predicted, wetting must occur after the EIP (epiphytic infection potential) reaches 100 or higher, which is occurring today, Apr 18. Based on predicted temperatures, the risk column shows high risk for Apr 18-22, with only wetting lacking as the trigger for fire blight infection these days. Infection is indicated with predicted showers for Apr 22. Be aware that in situations where all other requirements for infection have been met except wetting (Apr 18-22), wetting from a maintenance spray application can provide the wetting trigger for infection to occur. 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, which would be predicted to occur when that value reaches 100. 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 WeatherChannel for Winchester, supplemented by site-specific data from SkyBit Inc. Be aware that risk can change quickly with unpredicted warmer temperatures and wetting. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection. The fire blight outlook will be updated Wednesday, Apr 20.

Fire blight outlook for the Winchester area, April 16-22

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. Susceptible bloom is open on most cultivars. Here is the prediction for trees with first bloom open Monday, April 11, 2016. The temperature and rainfall data are current through Friday afternoon, April 15. Predicted weather conditions are shown for April 16-22. 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). For infection to be predicted, wetting must occur after the EIP (epiphytic infection potential) reaches 100 or higher, which is predicted to occur Apr 18. Based on predicted temperatures, the risk column shows high risk for Apr 18 and Apr 20-22, and only wetting is lacking as a trigger for fire blight infection those days. Be aware that in such situations, the wetting by a maintenance spray application can meet the wetting requirement for infection to occur when the EIP is above 100 and all other requirements for infection have been met. 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, which would be predicted to occur when that value reaches 100. 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 WeatherChannel for Winchester, supplemented by site-specific data from SkyBit Inc. Be aware that risk can change quickly with unpredicted warmer temperatures and wetting. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection. The fire blight outlook will be updated Monday, Apr 18.

Fire blight outlook for the Winchester area, April 13-18

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. Early bloom is now open on many apple cultivars. Here is the prediction for trees with first bloom open Monday, April 11, 2016. The temperature and rainfall data are current through Wednesday morning, April 13. Predicted weather conditions are shown for April 13-20. 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). For infection to be predicted, wetting must occur after the EIP (epiphytic infection potential) reaches 100 or higher.  

Based on record temperatures and wetting, the risk column shows high risk for Apr 11, but the EIP had not yet reached 100 and would have required max/min temperatures 9 degrees warmer to reach the infective level. There were occasional blossoms open at our AREC as early as Apr 8, but with the indicated temperatures, that would have made little difference in the risk interpretation for Apr 11. With cooler predicted temperatures through the rest of this week, fire blight risk should remain low to moderate. However, with warmer predicted temperatures Apr 17-18, the EIP would again approach the infective level by Apr 18.

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. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection. This fire blight outlook will be updated Friday, April 15.

FUNGAL DISEASES: Powdery mildew remains our most active early season apple disease, with 13 dry weather mildew infection days recorded since March 16. Primary and secondary mildew infection will likely become more evident after we get some consistently warmer growth conditions.