Tuesday, May 19, 2015

Recent scab and rust infection periods; rust galls still active

We have seen two recent significant scab and rust infection periods: May 16-17 (22 hr wet at 74-71° with 0.77 in. rain) and May 18-19 more than 13 hr at 72-64° with 0.88 in. of rain.These are important for secondary scab infection where primary infection was not well-controlled earlier and, at temperatures in the 70s and higher 60s, also could signal some early Glomerella leaf spot and bitter rot activity. Cedar-apple rust galls are still actively producing spores.

We have had 22 dry weather powdery mildew infection days since mildew spores were first available Apr 6.

Yesterday we had reports of fire blight symptoms in the region, probably from infection that occurred May 5-7, which Maryblyt predicted to appear May 11-14.

Thursday, May 7, 2015

Continued fire blight risk; scab and rust infection May 5-7

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. Many trees still have susceptible bloom. Here is the prediction for trees with first bloom open Apr 17-18, 2015. The temperature and rainfall data are current through Wednesday night, May 6. Predicted weather conditions are shown for May 7-11. 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, EIP will remain at an infective level through this  weekend, requiring only wetting to trigger infection conditions wherever susceptible bloom is present. Wetting from rain occurred at the AREC May 5 and 6. Other forms of wetting capable of triggering infection conditions include heavy dew, fog or routine spray applications-- anything that can splash the fire blight bacteria from the flower stigma into the nectaries in the base of the flower. Infection conditions remain possible with wetting wherever bloom is present May 7-11. This situation generally applies to other areas in the mid-Atlantic region well beyond Winchester. It is recommended that streptomycin be included with routine spray applications in high risk situations this week. Under the temperature conditions shown for this week, expect streptomycin to 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. (Actually on May 4 we saw early symptoms from test inoculations Apr 20). Yesterday, May 6, blossom blight symptoms were observed in a Rappahannock County orchard, also likely from Apr 20 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, with 100% of the degree-hour requirement May 1. Canker blight symptoms on new growth, due to extension of overwintering cankers are predicted for May 8. Canker advancement cannot be prevented by treatment 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.

Fungal diseases: Apple scab, quince rust, and cedar-apple rust infection periods occurred, with temperatures in the 60s, the nights of May 5 and 6. Blossoms are still susceptible to quince rust infection at petal fall.

Monday, May 4, 2015

Fire blight and fungal disease update

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 my intent. Fruit producers outside of that area are encouraged to consult their state extension specialists for information similar to that provided here.

(Click image for larger view)
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 Monday morning, May 4. Predicted weather conditions are shown for May 4-9. 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, EIP will remain at an infective level through this entire week, requiring only wetting to trigger infection conditions wherever susceptible bloom is present. Wetting from rain is shown as being predicted for May 5 and 6; other forms of wetting capable of triggering infection conditions include heavy dew, fog or routine spray applications-- any wetting event that will move the fire blight bacteria from the flower stigma into the nectaries in the base of the flower. It is recommended that streptomycin be included with any routine spray applications in high risk situations this week. Under the temperature conditions shown for this week, expect streptomycin to 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. (Actually we are already seeing early symptoms from test inoculations Apr 20). The CBS column at the right in the graphic predicts the appearance of canker margin symptoms due to extension of overwintering cankers by Apr 30. Canker advancement cannot be prevented by 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.

FUNGAL DISEASES
We recorded our 7th apple scab infection period of the year May 1-2 (15 hr at 58-53° with 0.21 in. of rain). This also favored quince rust fruit infection and cedar-apple rust on foliage and flowers. Apple scab lesions were first observed at our AREC last week; now some leaves on unprotected trees have as many as six lesions per leaf. Also present are cedar-apple rust lesions, probably from infection that occurred April 14. 

Powdery mildew is our only "dry weather" fungal disease on apples. So far, we have had 13 “mildew infection days” since spores first became available Apr 6.

Friday, May 1, 2015

Scab and rust infection Apr 30-May 1

Last night's wetting (14 hr at 63-54° with 0.21 in. of rain) was favorable for scab, quince rust, and cedar-apple rust. The blossoms are now very susceptible to quince rust and, if protection was questionable, a follow-up including an SI fungicide for after-infection is advised.

This was our 6th apple scab infection period this year. Apple scab lesions were observed on unprotected trees at our AREC this week. Where protection was inadequate during early primary infection periods Apr 7-10, consider this and any additional infection periods in the Winchester area to be secondary ones, with high inoculum potential on very susceptible blossoms and leaves. 

Outlook for fire blight in the Winchester area remains similar to what was posted yesterday: with warming through the weekend and warmer temperatures predicted all of next week, essentially all of the components will be such that any wetting of susceptible, unprotected blossoms could trigger infection any day next week.

Thursday, April 30, 2015

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.

Monday, April 27, 2015

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.

Thursday, April 23, 2015

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.

Monday, April 20, 2015

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.


Friday, April 17, 2015

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.

Wednesday, April 15, 2015

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.

Friday, April 10, 2015

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.

Wednesday, April 8, 2015

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.

Tuesday, April 7, 2015

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.

Saturday, October 18, 2014

Some late season disease pressures


After enjoying some good harvest weather in September, with only 0.4 inches of rain in the Winchester area, the past two weeks have brought some significant late season disease pressures, but also with much needed rainfall. Extended wetting events occurred last week October 10-11 (27 hours at 55° with 0.4 inches of rain).  This week we had an extended wetting period of more than 60 hours with only intermittent drying Oct 14-17. Much of this was at relatively warm temperatures favorable for rots, including 9 hours at 71°. 

The most recent extended wetting, our longest since late April, also favored fruit scab infection wherever active scab was present in the orchard as a result of poor coverage or missed applications or fungicide resistance early in the season. Rainfall Oct 14-17 totaled more than 2.3 inches and likely depleted fungicide residue, even from applications in the past two weeks. This extended wetting at favorable temperatures was enough to cause "pin-point scab" (storage scab) of late cultivars, and early marketing (rather than long-term storage) is suggested for fruit from fresh-market orchards lacking recent fungicide protection where there was earlier evidence of active scab. 
  

Tuesday, July 29, 2014

Summer disease pressures: extended wetting and accumulated wetting hours

In the past two weeks we have had several extended wetting periods with rainfall, and more than 150 hours of wetting from rainfall or dew. Although the rainfall was not excessive, this amount of wetting at relatively warm temperatures does increase summer disease pressure considerably.

These were the extended wetting periods from rain at our AREC:
July 14-15, 19 hr with just 0.01 in. of rain at 73° (very favorable for rots).
July 18-19, 10 hr with 0.09 in. of rain at 68°.
July 19-20, 16 hr with just 0.04 in. of rain at 69°.
July 27, 11 hr with 0.39 in. of rain at 70° (also favorable for rots).
July 27-28, 12 hr with just 0.17 in. of rain at 69°.

We track the number of extending wetting periods above 70° as an indication of potential bitter rot weather. This is not an absolute cut-off temperature but gives a basis for year-to-year comparison of relative bitter rot pressure. Since June 1 this year we have had 13 such wetting periods while last year by this time we had only five.

 As of Monday morning, July 28at our usual AREC monitoring site at elevation 950 ft, we had accumulated 440 wetting hours since May 18, well beyond the 250-hour threshold for specific treatment against the sooty blotch/flyspeck (SBFS) fungal complex But at the 910 ft. elevation cumulative wetting hour (CWH) total continues to run about 100 ahead, now standing at 557 CWH. Sooty blotch/flyspeck symptoms (signs of the fungi) are now readily visible. Unprotected fruit that we collected about four week ago have now developed bitter rot as well as SBFS. 

Orchards at lower elevations in Nelson County (Tyro area) have greatly exceeded the 250-wetting hour threshold for presence of the SBFS organisms on unprotected fruit (total 475 CWH at 941 ft elevation). The CWH total at our highest monitoring location (elev. 1465 ft) stood at 272 CWH as of Monday morning, July 28; CWH accumulation at a middle elevation (1165 ft) has consistently lagged behind the other two and is now at 190 CWH. Scout lower areas of your orchards regularly for onset of SBFS appearance and adjust your fungicide program accordingly. 

Below is a picture of bitter rot on a Honeycrisp apple as seen in a commercial orchard in Nelson County June 26. Fruit mummy inoculum, such as that shown with this fruit, and inadequate spray coverage were likely factors that contributed to this problem, but it shows the importance of being vigilant to any and all possible developing problems.


Bitter rot on Honeycrisp apple fruit. Note the presence of small fruit mummies associated with the bitter rot problem.

Friday, July 11, 2014

Extended wetting for fruit rots July 8-9; accumulated wetting hours.

July 8-9 we had another extended wetting period: 15 hr with 0.24 in. of rain at 72°. This wetting period was favorable for rots.

As of Thursday morning, July 10, we had accumulated 293 wetting hours since May 18, well beyond the 250-hour threshold for specific treatment against the sooty blotch/flyspeck (SBFS) fungal complex at our usual AREC monitoring site at elevation 950 ftBut at the 910 ft. elevation cumulative wetting hour (CWH) total continues to run about 100 ahead, now standing at 391 CWH. Early sooty blotch symptoms (signs of the fungi) are now visible.  

Orchards at lower elevations in Nelson County (Tyro area) have also exceeded the 250-wetting hour threshold for presence of the SBFS organisms on unprotected fruit (total 345 CWH at 941 ft elevation). CWH total at the higher elevation stood at 200 CWH as of Thursday morning, July 10. Scout lower areas of your orchards regularly for onset of SBFS appearance and adjust your fungicide program accordingly.

Tuesday, July 8, 2014

Sooty blotch symptoms; extended wetting for fruit rots July 3-4.

Last week July 3-4 we had another extended wetting period: 9 hr with 0.6 in. of rain with a mean 71°. This wetting period was favorable for rots.

As of Monday morning, July 7, we had accumulated 270 wetting hours since May 18, well beyond the 250-hour threshold for specific treatment against the sooty blotch/flyspeck (SBFS) fungal complex at our usual AREC monitoring site at elevation 950 ft. But at the 910 ft. elevation we have recorded 372 CWH and early sooty blotch symptoms (signs of the fungi) are now visible.  

Orchards at lower elevations in Nelson County (Tyro area) have also exceeded the 250-wetting hour threshold for presence of the SBFS organisms on unprotected fruit.
 Scout your lower orchard areas regularly for onset of SBFS appearance and adjust your fungicide program accordingly.

Thursday, July 3, 2014

Sooty blotch and flyspeck on unprotected fruit; rot infection period

Last night we had an extended wetting period following afternoon rains: 16 hr with 0.22 in. of rain at 75°. This wetting period was favorable for rots.

As of this morning, July 3, we had accumulated 258 wetting hours since May 18, surpassing the 250-hour threshold for specific treatment against the sooty blotch/flyspeck (SBFS) fungal complex at our usual AREC monitoring site at elevation 950 ft. This is the elevation from which we have reported cumulative wetting hours since 1994, and this is the latest we have reached that threshold since 1999. But we have recorded 352 CWH at a lower AREC site (elevation 910 ft).  

The wetting hour threshold indicates the time at which we would expect the SBFS organisms to be present, but not yet visible on unprotected fruit but we expect symptoms in the more advanced area shortly. Remember to scout your lower orchard areas regularly for onset of SBFS appearance and adjust your fungicide program accordingly.

Tuesday, July 1, 2014

Accumulated wetting hours for sooty blotch and flyspeck; mildew remains active; fire blight and rot inoculum levels.

 Each year we record accumulated wetting hours (CWH) from rainfall or dew, starting ten days after petal fall for purposes of predicting development of the sooty blotch and flyspeck (SBFS) fungal complex,. This past week wetting at our AREC occurred almost entirely as dew, with only traces of precipitation which dried quickly. 

As of yesterday morning, June 30, we had accumulated 228 wetting hours since May 18, approaching the 250-hour threshold for specific treatment against the SBFS fungal complex at our usual AREC monitoring site at elevation 950 ft. But at a lower AREC elevation (910 ft), we have greatly surpassed this threshold with 334 CWH.  Again this illustrates the importance of elevation for wetting hour accumulation. Remember to scout your lower orchard areas regularly for onset of SBFS appearance and adjust your fungicide program accordingly.

With the continued dry weather this past week, powdery mildew remains active where shoots are continuing to grow. Since mildew spores were first observed Apr 9, we have had 49 dry weather “mildew infection days”.

This past week in visits to Frederick County and central Virginia orchards, we saw more fire blight than we would like to see. This seemed to occur as a result of marginal protection at late bloom. For the most part, it does not appear to be spreading actively any more, but the presence of dead wood in the trees raises the concern of increased inoculum levels for the rot fungi, especially bitter rot, as we approach harvest. Bitter rot was already evident in one Nelson county orchard and small, over wintering fruit mummies seemed to the likely inoculum source in that situation.

Friday, June 20, 2014

Extended wetting events, mildew still active; wetting hour accumulation related to elevation

We had two more extended wetting events at our AREC this past week: June 16-17 (12 hr, mean 71° with 0.6 in. rain) and June 19-20 (14 hr, mean 71°, with 0.4 in. rain).

The temperatures and length of wetting during these events favored secondary apple scab and early summer disease developmentSecondary spread of fire blight was possible where growing shoot tips are still susceptible. Cedar rust galls are mostly depleted now. 

Powdery mildew remains active with continued shoot growth. Since mildew spores were first observed Apr 9, we have had 42 dry weather “mildew infection days”: 15 in April, 20 in May and 7 in June. So it is not hard to find secondary infection in susceptible unprotected orchards.

For purposes of predicting development of the sooty blotch and flyspeck (SBFS) fungal complex, we record accumulated wetting hours (CWH) from rainfall or dew, starting May 18, ten days after petal fall. This week there was about twice as much wetting hour accumulation at Winchester than at the central Virginia location. 

By Friday morning, June 20, at our usual AREC monitoring site at elevation 950 ft, we had accumulated 176 wetting hours toward the 250-hour threshold for specific treatment against the SBFS fungal complex. But at a lower AREC elevation (910 ft) we have already surpassed this threshold with 289 CWH.  At Tyro, VA as of June 20, the sensor at 1165 ft. elevation had accumulated 99 wetting hours from May 11, while one placed at 941 ft had accumulated 193 hr. Both of these locations illustrate the importance of elevation for wetting hour accumulation. Scout your lower orchard areas for early onset of SBFS appearance and adjust you fungicide program accordingly.

Saturday, June 14, 2014

Extended wetting events this week

It has been a wet week at our AREC this past week, with significant infection events five consecutive days, including the one noted in the previous post for June 8-9. These were as follows: June 9-10 (8 hr, mean 70° with 0.02 in. rain); June 10-11 (16 hr, mean 76°, with 0.19 in. rain); June 11-12 (14 hr, mean 70° with 0.11 in. rain); June 12-13 (16 hr, mean 70° with 0.44 in rain). Total rainfall for June 9-13 at our AREC was 1.36 inches but volumes with the several storms varied widely throughout the local area and there was also scattered hail in some locations.

Temperatures and length of wetting during these events favored secondary apple scab and early summer disease development. Cedar rust galls were producing spores through all of these events, but are nearly depleted now. Secondary spread of fire blight was possible where growing shoot tips are still susceptible.

In addition to developing activity by the usual summer diseases, with these recent warmer wetting periods, be alert for possible early indications of Alternaria leaf blotch on Red Delicious and Glomerella leaf spot on Gala, Golden Delicious and Cripps Pink (Pink Lady) apples. This is also a critical time for protection against Brooks fruit spot.

For purposes of predicting development of the sooty blotch and flyspeck (SBFS) fungal complex, we record accumulated wetting hours (CWH) from rainfall or dew, starting 10 days after petal fall. As of Friday afternoon, June 13, we had accumulated 136 wetting hours toward the 250-hour threshold for specific treatment against the SBFS fungal complex. 

Infection conditions for June 9-13 were similar at Tyro, VA. As of June 12, a sensor placed in an apple tree at 1165 ft. elevation had accumulated 90 wetting hours from May 11, while one placed at 941 ft elevation had accumulated 172 hr. The station at the highest elevation (1465 ft) apparently spent some time in the clouds this week and continues to register more wetting hours than the intermediate one, 125 CWH.

Monday, June 9, 2014

Spring and summer disease update

In the past five days we have had two more apple scab and cedar-apple rust infection periods at our AREC June 4-5: 23 hours wetting at 73-60°, and June 8-9 at 74-66°. Note that cedar rust galls are still actively producing spores.

In addition to developing activity by the usual summer diseases, with the recent warmer wetting periods, be alert for possible early indications of Alternaria leaf blotch on Red Delicious and Glomerella leaf spot on Gala, Golden Delicious and Cripps Pink (Pink Lady) apples. This is also a critical time for protection against Brooks fruit spot.

For purposes of predicting development of the sooty blotch and flyspeck (SBFS) fungal complex, we record accumulated wetting hours (CWH) from rainfall or dew, starting 10 days after petal fall. As of this morning, June 8, we had accumulated 80 wetting hours toward the 250-hour threshold for specific treatment against the SBFS fungal complex. 

At Tyro, VA we selected May 11 as the start date for accumulation of wetting hours by weather stations at Tyro, VA. As of June 5, a sensor placed in an apple tree at 1165 ft. elevation had accumulated 62 wetting hours from May 11, while one placed at 941 ft elevation had accumulated 128 hr. It is interesting that the station at the highest elevation (1465 ft) registered more wetting hours than the intermediate one, 81 CWH.