Monday, May 2, 2016

Recent scab and rust infection periods and fire blight outlook, May 2, 2016

At our AREC in Winchester, we have had four scab or rust infection periods within the past four days. April 28-29: a heavy apple scab and rust infection period: 31 hours at 53-46° with 0.67 in. of rain; Apr 30: 10 hours at 51° with 0.01 in. of rain; Apr 30-May 1: 18 hours at 53° with 0.53 in. of rain; May 1-2: 12 hours at 59° with 0.16 in. of rain. Locally, some of these wetting periods may have been extended by showers or foggy conditions. Apple blossoms and small fruit are still very susceptible to quince rust so it would be prudent to include a sterol-inhibiting fungicide for after-infection rust control in the next fungicide application.

FIRE BLIGHT: Below is a cropped graphic from the Maryblyt 7 program. Susceptible blossoms are still present on some cultivars. The temperature and rainfall data are current through Monday morning, May 2. Predicted weather conditions are shown for May 2-7. 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. The fire blight risk remains high for May 2-4, and slightly warmer temperatures with wetting could result in infection. For optimum control, a protective streptomycin application is recommended ahead of predicted infection, but it can also provide about one day after infection suppression.


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 risks on late bloom can change quickly with unpredicted warmer temperatures and wetting. 

Friday, April 29, 2016

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.

Wednesday, April 27, 2016

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.

Monday, April 25, 2016

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, 

Friday, 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.

Wednesday, April 20, 2016

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.

Monday, April 18, 2016

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.

Friday, April 15, 2016

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.

Wednesday, April 13, 2016

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.

Wednesday, March 30, 2016

Gradual bud movement to pre-pink



We have seen gradual bud movement at Winchester since the previous post on March 18. Above are the same Red Delicious buds that were pictured previously at green-tip stage. They now are showing some color in the pre-pink stage. Most cultivars at our AREC were at tight cluster stage, but will advance more rapidly in the next couple days.

It looks like we are headed for the first 2016 apple scab and cedar-apple and possibly quince rust infection period at our AREC Thursday night and Friday morning Mar 31-Apr 1. Hopefully there has been ample opportunity to protect the developing buds as they moved through the tight cluster stage. Cedar-apple rust galls are plentiful in some areas, even to the point of causing browning of the foliage as shown below.


Cedar-apple rust galls on eastern red cedar near Winchester, VA

I noted that we had seen apple powdery mildew conidiospores by March 17, and in the interim we have already recorded 8 mildew infection days. So you might say that, in this Spring Training exercise, the mildew has outscored scab 8-0!


Redhaven peach trees (shown below) are now approaching full bloom.




In-depth meeting March 31:
Finally, this is a reminder that our first In-Depth Meeting of the new season will be held at Alson H. Smith Jr. AREC, 595 Laurel Grove Road, Winchester, VA, starting at 7 PM Thursday, March 31. Following an entomology update by Dr. Chris Bergh, we will address early season disease management issues and end with some recent pathology questions and answers.

Friday, March 18, 2016

It's a new season!




At our AREC we had green tip on Red Delicious (shown above) and other apples March 16 and about 1/4-inch green by March 17. 55 hours of wetting, with discharge of apple scab ascospores, had occurred from March 13-15. This was more than three times the length of wetting required for scab infection where green tissue was exposed, but our buds had not advanced to that stage by that time. 

Scab infection was likely in areas where buds were more advanced to the green-tip stage. In Tyro, Virginia, 51 hours of wetting was recorded at temperatures that were about 5 degrees warmer than at Winchester, resulting in more than four times the length of wetting required for scab infection. Apple scab ascospore maturity at green-tip stage is normal and should be expected except in years when buds advance rapidly without any moisture to mature the spores. 

Powdery mildew spore production is advanced compared to most years. Typically, buds infected with overwintering mildew are somewhat delayed compared to their healthy counterparts. However, I was surprised to see mildew-infected buds as advanced as healthy ones (upper right, below), and they had an abundance of conidia (below). In contrast to wetting conditions needed for scab infection, powdery mildew is able to infect on dry days with temperatures above 53 degrees F.

Mildew infected Idared bud, upper right.

Mildew conidia on Idared. Winchester, March 17, 2016
Cedar-apple rust galls are also ready to produce infective basidiospores with the next warm wetting period, so protective apple fungicides should now be included for mildew and rusts as well as for scab. 
Cedar-apple rust gall ready to produce spores March 16. Virginia Tech AREC, Winchester.
Redhaven peach bud development at Virginia Tech AREC, Winchester, March 17, 2016.
Peach buds (above) were more advanced than apples, and unprotected buds would have been readily susceptible to leaf curl infection with wetting March 13-15. Because spores of the leaf curl fungus are carried on the surface of the tree from the fall to spring, fungicides applied in the fall or during the winter give good protection from leaf curl. Fall applications help to avoid the spring rush to spray before pruning brush is removed from the orchard.

Friday, September 4, 2015

Bitter rot and summer disease pressures

This week we have had several reports of bitter rot showing up in Frederick County. For several weeks we have also seen it in our research plots at the AREC. Some may be associated with fire blight strikes, but more frequently they seem to be related to the presence of small fruit or flower mummies that served as the likely inoculum source.
Bitter rot on an Idared fruit with a small mummy, a probable inoculum source
Although it was quite dry throughout most of August, the bitter rot infection relates to warm wetting conditions as early as mid-May. From May 16 to Aug 11 we had 21 extended wetting periods at temperatures in the 70s and higher 60s, favorable to bitter rot activity. At our AREC we had only 0.14 in.of rain from Aug 11 to Sept 2, but some county locations have recorded considerably more rainfall than we have had at the AREC in the past month, so that adds to the potential problems. Although these conditions could also favor Glomerella leaf spot development, so far we have not had reports of this from Frederick County.

While we lacked wetting from rainfall, we continue to add accumulated wetting hours from dew. As of the Monday morning, Aug 31, total accumulated wetting hours (ACW) at the AREC were: at 909 ft elevation, 975 hr; at 952 ft elevation, 673 hr; and at the 983 ft elevation, 576 hr ACW. Since accumulation of wetting hours began May 14, this represents an increase of 5.5 wetting hours per foot of elevation drop from 983 to 909 ft. Continue to scout for sooty blotch, flyspeck, and fruit rots, especially at lower elevations in an orchard.

At Tyro, in Nelson County, total ACW as of Monday morning, Aug 31, were: at 941 ft elevation, 792 ACW; at 1165 ft, 415 ACW; and at 1465 ft, 473 ACW. An extended wetting event with substantial rainfall was recorded at Tyro Aug 18-19, 25 hr wet at 74-69° at the highest elevation.

Thursday, August 20, 2015

Summer disease update

Summer disease pressures remained steady last week.  The extended wetting event Aug 10-11, in progress at the time of the last post, amounted to 12 hr wet at 71° with 0.31 in. of rain.

As of the Monday morning, Aug 17, total accumulated wetting hours (ACW) at the AREC were: at 909 ft elevation, 864 hr; at 952 ft elevation, 611 hr; and at the 983 ft elevation, 539 hr ACW. Since accumulation of wetting hours began May 14, this represents an increase of 4.4 wetting hours per foot of elevation drop from 983 to 909 ft. The wetting hour accumulation differential is greater during times when wetting is from dew rather than during wetting from rain, because rain tends to wet both locations similarly. In the past 10 days we have recorded only 0.17 inch of rainfall, but recorded 87 hours of wetting from dew at the 909 ft elevation.  This is why we say to scout for sooty blotch, flyspeck, and fruit rots at lower elevations in an orchard.

At Tyro, in Nelson County, total ACW as of Monday morning, Aug 17, were: at 941 ft elevation, 718 ACW; at 1165 ft, 385 ACW; and at 1465 ft, 433 ACW. An extended wetting event with substantial rainfall was recorded at Tyro Aug 18-19, 16 hr wet and 1.2 in. of rain at 74-69°.

Tuesday, August 11, 2015

Increasing summer disease and brown rot pressures

Summer disease pressure increased in the past week, with two extended wetting events at our ARECAug 6-7, 16 hr wet at 68-65° with 0.11 in. of rain and Aug 9-10, 16 hr wet at 74-72° with 0.52 in. of rain. (Another extended wetting event is in progress at the time of this post).

As of the Monday morning, Aug 10, total accumulated wetting hours (ACW) at the AREC were: at 909 ft elevation, 796 hr; at 952 ft elevation, 567 hr; and at the 983 ft elevation, 518 hr ACW. Since accumulation of wetting hours began May 14, this represents an increase of 3.8 wetting hours per foot of elevation drop from 983 to 909 ft.

At Tyro, in Nelson County, total ACW as of Monday morning, Aug 10, were: at 941 ft elevation, 670 ACW; at 1165 ft, 368 ACW; and at 1465 ft, 409 ACW. 

The recent wetting events will again increase brown rot pressure on ripening peaches, as well as sooty blotch, flyspeck and rots on early ripening apples.

Wednesday, August 5, 2015

Summer disease update

Summer disease pressure was moderate in the past week, with one extended wetting event at our ARECJuly 28-29, 13 hr wet at 72-66° with 0.59 in. of rain. A thunderstorm during the early morning hours Aug 4 resulted in only 0.15 inch of rainfall and 4 hr wetting at our AREC, but the rainfall was likely much heavier in some Frederick County orchards.

As of the Monday morning, Aug 3, total accumulated wetting hours (ACW) at the AREC were: at 909 ft elevation, 739 hr; at 952 ft elevation, 522 hr; and at the 983 ft elevation, 476 hr ACW. Since accumulation of wetting hours began May 14, this represents an increase of 3.6 wetting hours per foot of elevation drop from 983 to 909 ft.

At Tyro, in Nelson County, total ACW as of Monday morning, Aug 3, were: at 941 ft elevation, 643 ACW; at 1165 ft, 352 ACW; and at 1465 ft, 393 ACW. 

Wednesday, July 29, 2015

Dry weather great for sweet ripening peaches

At our AREC we have recorded only 0.2 inch of rain and no extended wetting periods with rain in the past two weeks. Although it is starting to get pretty dry, this has been a welcome break for ripening peaches, producing sweeter fruit with less brown rot pressure.


Ripening Redhaven peach: Dry and bright sunny weather reduces brown rot pressure in the pre-harvest period
But the blemishes from scab lesions are an indicator of earlier season disease pressures. The incubation period for scab infection to appear can be as long as 6-7 weeks, sometimes leading to the question "Where did this come from?"

Earlier rot activity is showing up as bitter rot and other rots on Honeycrisp apples, and this brings reminders that anything that causes injury such as Japanese beetle, will increase the possibility of rot activity, especially as sugar levels increase.

As of the Monday morning, July 27, accumulated wetting hours (ACW) at the AREC are related to elevation: at 909 ft elevation, 687 hr; at 952 ft elevation, 486  hr; and at the 983 ft elevation 444 hr ACW. 

At Tyro, in Nelson County, total ACW as of Monday morning, July 27, were: at 941 ft elevation, 595 ACW; at 1165 ft, 311 ACW; and at 1465 ft, 354 (with the 250-hr threshold reached July 5). 

Thursday, July 16, 2015

Summer disease update

Summer disease pressure continued this past week with several extended wetting events at relatively warm temperatures and some locally heavy rainfall.

At our AREC we recorded three such extended wetting periods with rainfall: July 11, 9 hr wet at 71-66° with 0.28 in. of rain; July 13, 9 hr wet at 70° with 0.13 in. of rain (but as much as 4 inches with flooding locally in the Woodstock area of Shenandoah County)July 14, 11 hr wet at 70° with 0.34 in. of rain; . These frequent infection periods with rain deplete fungicide residue and continue to favor development of rots such bitter rot and white rot, as well as Alternaria and Glomerella leaf spots.

As of the Thursday morning, July 15, accumulated wetting hours (ACW) at the AREC are related to elevation: at 909 ft elevation, 588 hr; at 952 ft elevation, 467 hr; and at the 983 ft elevation 423 hr ACW. Since accumulation of wetting hours began May 14, this represents an increase of 2.2 wetting hours per foot of elevation drop from 983 to 909 ft!

At Tyro, in Nelson County, total ACW as of Thursday morning, July 15, were: at 941 ft elevation, 531 ACW; at 1165 ft, 299 ACW; and at 1465 ft, 345 (with the 250-hr threshold reached July 5). The 250-hr ACW threshold reached at all sensor elevations at Tyro early last week, and this probably true for all orchards in the central Virginia region.

The recent frequent wetting periods also favor development of brown rot on ripening peaches and other stone fruits.

Thursday, July 9, 2015

Continued summer disease pressure

Summer disease pressure continued this past week with a pattern of afternoon or evening showers followed by wetting through the night, all at relatively warm temperatures.

At our AREC we recorded five such extended wetting periods with rainfall: July 2, 10 hr wet at 64-73° with 0.16 in. of rain; July 3-4, 15 hr wet at 72-65° with 0.01 in. of rain; July 6, 9 hr wet at 70° with 0.14 in. of rain; July 6-7, 15 hr wet at 68° with 0.04 in. of rain; July 8-9, 15 hr wet at 68° with 0.05 in. of rain (but more than 1 inch in some local areas). These frequent infection periods all favored bitter rot and Glomerella leaf spot development, as well as other rots, and depleted much fungicide residue for sooty blotch and flyspeck control.

Accumulated wetting hours (ACW) at the AREC are related to elevation: at 909 ft elevation, 497 hr; at 952 ft elevation, 390 hr; and at the 983 ft elevation 347 hr ACW. 

At Tyro, in Nelson County, total ACW as of Monday, July 6 were: at 941 ft elevation, 449 ACW; at 1165 ft, 250 ACW; and at 1465 ft, 264 (with the 250-hr threshold reached July 5). Note that the threshold has now been reached at all sensor elevations at Tyro.

The recent frequent wetting periods also favor development of brown rot on ripening peaches.

Wednesday, July 1, 2015

Sooty blotch and flyspeck and other summer diseases

Early signs of sooty blotch and flyspeck were observed in lower elevation areas at our AREC Monday, June 29. At this elevation (909 ft) we had reached the 250-hour total accumulated wetting hour (ACW) action threshold June 10. At higher elevations, the dates that the 250-hr threshold was reached and ACW totals June 29 were: 952 ft elevation- June 13, 332 hr ACW; 983 ft elevation- June 21, 297 ACW. Note that the threshold had been reached by June 21 at all AREC locations ranging from 909 to 983 ft elevations.

At our AREC we had two more extended wetting periods that favored summer disease development: June 25-26, 14 hr wetting at 72-64° with 0.02 in. of rain; June 26-28, 32 hr wetting at 72-59° with 1.62 in. of rain. This latter volume of rainfall would have depleted most fungicide residue available for sooty blotch, flyspeck and rot control.

At Tyro in Nelson County, a sensor placed at at 941 ft elevation had already recorded the 250-hr ACW threshold by June 3 for a total of 384 hr by June 29. By June 29, the ones at higher elevations, 1465 ft and 1165 ft, had not yet reached the 250-hr threshold with only 216 and 212 wetting hours, respectively.

Thursday, June 25, 2015

Summer disease update

Several extended wetting periods at warm temperatures in the past 10 days strongly favored summer disease development: June 14-15, 22 hr wetting at 80-70° with 0.50 in. of rain; June 17-18, 19 hr wetting at 71° with 0.32 in. of rain; June 19-20, 15 hr wetting at 72°with 0.06 in. of rain; June 20-21, 12 hr wetting at 75° with 0.73 in. of rain. Note that all of these were above 70°, indicative of bitter rot and Glomerella leaf spot activity.

For the purpose of predicting the development of the sooty blotch and flyspeck (SBFS) fungal complex, we record accumulated wetting hours from rainfall or dew, starting 10 days after petal fall. We are tracking this as we have for the past 21 years using a hygrothermograph located at 952 ft. elevation. The start of wetting hour accumulation was from May 14. At this elevation we reached the 250 total accumulated wetting hour (ACW) action threshold June 13. As of the morning of June 24, ACW at the 952 elevation was 288. We also have electronic recorders at 909 ft and 983 ft elevations. At 909 ft ACW was more rapid with the 250-hr threshold reached June 10 and total ACW at 368 hr.  At 983 ft ACW was slower with the 250-hr threshold not reached until June 21; total ACW at 983 ft was 256 as of June 24 hr. 

For the central Virginia areas, represented by three weather stations at different elevations at Tyro in Nelson County, we started accumulation May 13.  A sensor placed at at 941 ft elevation had already greatly passed the 250-hr ACW threshold June 3 for a total of 335 hr by June 24. By June 24, the ones at higher elevations, 1465 ft and 1165 ft, had not yet reached the 250-hr threshold with only 175 and 183 wetting hours, respectively.

Tuesday, June 9, 2015

Extended wetting for scab and summer diseases

An extended wetting period last week, still in progress at the time of the last post June 5, ended at 14 hr wetting at 60°with 0.04 in. of rain

For purposes of predicting the development of the sooty blotch and flyspeck (SBFS) fungal complex, we record accumulated wetting hours from rainfall or dew, starting 10 days after petal fall. This year we have chosen May 4 as our petal fall start date for Winchester, and the start of wetting hour accumulation is from May 14. Last week we also had two nights with wetting from dew, totaling 18 hr. With a total of 96 wetting hours last week, our total accumulated wetting hours (ACW) came to 195 hours as of Monday, June 8. The threshold for specific treatment against the SBFS fungal complex is 250 wetting hours. 

A note to those farther south and east of the Blue Ridge: Your petal fall date may have been a week or more ahead of ours and I have updated the start date for accumulation of wetting hours by weather stations at Tyro, VA to May 3. One of the purposes of having three weather stations at this location is to compare wetting hour accumulation at different elevations. As of June 8, a sensor placed at at 941 ft elevation had already greatly passed the 250-hr ACW threshold for a total of 315 hr while the ones at higher elevations, 1465 ft and 1165 ft, had nearly identical ACW of 144 and 140 wetting hours, respectively. 

Alternaria leaf blotch, confirmed on Red Delicious leaves from Rockingham County May 21, continued to advance, as expected, with the extended wetting last week.

Friday, June 5, 2015

Fruit scab still a serious concern with extended wetting this week

After wetting periods of 16 hr May 30-31(0.13 in. rain) and 20 hr June 1-2 (1.2 in. rain), we have recorded almost continuous wetting 47 of 56 hours since 10 PM June 2. (It is still wet at the time of this post).

As fruits enlarge, they become more resistant to scab than the youngest leaves, so that at five weeks after petal fall, they require about double the length of wetting period at a given temperature than growing shoot tip leaves. But the several extended wetting periods the past week have easily surpassed the requirement for fruit infection. It is important to maintain protective residue now, to prevent fruit scab infection as well as early sooty blotch/flyspeck SBFS development.

Lower elevation orchards in central Virginia have passed the 250-hr accumulated wetting for SBFS. Also, we have confirmed Alternaria leaf blotch symptoms on Red Delicious leaves in Rockingham County.