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

(Click picture to enlarge)

FIRE BLIGHT: Above is a cropped graphic from the Maryblyt 7 program. Many cultivars still have some susceptible bloom. Here is a prediction for trees with first bloom open Monday, March 23, 2012. The temperature and wetting data are current through this morning, Apr 20. Predicted weather conditions are shown for Apr 20-29. 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). The risk column shows that fire blight infection could have occurred with any wetting from rain, a spray application, or heavy dew Apr 15-17. After a two-day decline, risk has again increased to an infective level today. After tomorrow, predicted cooler temperatures Apr 22-27 should suppress risk to low to moderate levels. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection and with any spray applications of other materials. Be aware that risks can abruptly increase with unpredicted warmer temperatures and wetting.  This graphic will be updated Apr 23. 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.

Scab infection period

An apple scab infection period occurred Apr 18-19 with 28-hr wetting at 47-50°F and 0.52 inches of rain. This length of wetting, coupled with the possibility of secondary infection from lesions that resulted from inadeqate protection Mar 24-25 could raise serious secondatry fruit infection issues in the coming month.

Temperatures are slightly lower than those presented in yesterday's Maryblyt graphic but still present a fire blight blossom infection threat for today.

Fire blight and apple scab forecast

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.

(Click picture to enlarge)


FIRE BLIGHT: Above is a cropped graphic from the Maryblyt 7 program. Many cultivars still have much susceptible bloom. Here is a prediction for trees with first bloom open Monday, March 23, 2012. The temperature and rainfall data are current through this morning, Apr 18. Predicted weather conditions are shown for Apr 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). The risk column shows that fire blight infection could have occurred with any wetting from rain, a spray application, or heavy dew Apr 15-17. After one-day breaks today and Apr 20, risk will again return to an infective level tomorrow, Apr 21-22. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection and with any spray applications of other materials. Be aware that risks can abruptly increase with unpredicted warmer temperatures and wetting. This graphic will be updated Apr 20. 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.

Also, today's wetting could result in a secondary apple scab infection period if it remains wet into tonight.

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

(Click to enlarge)

FIRE BLIGHT: Above is a cropped graphic from the Maryblyt 7 program. Many cultivars still have much susceptible bloom. Here is a prediction for trees with first bloom open Monday, March 23, 2012. The temperature and rainfall data are current through Apr 16. Predicted weather conditions are shown for Apr 17-21. 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). The risk column shows that fire blight infection could have occurred with brief showers Apr 14-15 and could again be triggered Apr 17 by wetting from rain, a spray application, or heavy dew. After cooler temperatures Apr 18, infection conditions could again exist Apr 19. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection and with any spray applications of other materials. Be aware that risks could increase with unpredicted warmer weather and wetting. This graphic will be updated 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.

Fire blight update for today and tomorrow

The Maryblyt graphic will be updated later today, but conditions remain essentially as predicted for today and tomorrow: blossom infection could result with wetting from rain, a spray application, or heavy dew, triggering infection Apr 15-17. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection and with any spray applications of other materials.

Scab and fire blight update

Scab lesions were observed today on unprotected trees at our AREC. This means there is a potential for secondary infection with the next significant wetting period.
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.




(Click to enlarge image)


FIRE BLIGHT: Above is a cropped graphic from the Maryblyt 7 program. Although some cultivars have reach petal fall of early bloom, many still have much susceptible bloom and a prolonged bloom period is expected. Here is a prediction for trees with first bloom open Monday, March 23, 2012. The temperature and rainfall data are current through this morning, Apr 13. Predicted weather conditions are shown for Apr 13-19. 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). After going through 11 days of light to moderate blossom blight risk, the risk column shows that risk of fire blight infection will increase with warmer temperatures through this weekend and into next week. For infection to be predicted, wetting must occur after the EIP (epiphytic infection potential) reaches 100 or higher and there must be wetting. Wetting from rain, a spray application, or heavy dew would trigger infection Apr 15-16, and infection conditions are predicted with wetting for Apr 17 and 19. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection and with any spray applications of other materials. This graphic will be updated Apr 16. 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.

Fire blight on the horizon

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.

(Click to enlarge image)

FIRE BLIGHT: Above is a cropped graphic from the Maryblyt 7 program. Although some cultivars have reach petal fall of early bloom, many still have much susceptible bloom and a prolonged bloom period is expected. Here is a prediction for trees with first bloom open Monday, March 23, 2012. The temperature and rainfall data are current through Apr 11. Predicted weather conditions are shown for Apr 12-19. 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). After going through 11 days of light to moderate blossom blight risk, the risk column shows that risk of fire blight infection will again increase with warmer temperatures through this weekend and into next week. For infection to be predicted, wetting must occur after the EIP (epiphytic infection potential) reaches 100 or higher and there must be wetting.Only wetting is lacking for Apr 15-16 and infection conditions are predicted for Apr 17. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection. This graphic will be updated Apr 13. 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.

Fire blight risk remains low-moderate

Fire blight risk has been low the past four days and should remain low to moderate with cool predicted temperatures through Friday. But risk should return to high with warmer weather predicted for this coming weekend. The fire blight outlook will be updated Apr 11. Expect a rather long bloom period this year, and later susceptibility.

Fire blight outlook for 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. With many cultivars with bloom open, and more bloom opening gradually over the next several days, here is a prediction for trees with first bloom open Monday, March 23, 2012. The temperature and rainfall data are current through Monday morning, Apr 2. Predicted weather conditions are shown for Apr 2-5. 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 risk of fire blight infection will be mostly low or moderate through Apr 5, and actually for several days beyond that. (It appears that we will be having a prolonged bloom period). For infection to be predicted, wetting must occur after the EIP (epiphytic infection potential) reaches 100 or higher. Note there had been an earlier threat of fire blight on apples at our AREC last weekend, but temperatures fell about 3 degrees cooler than would have been required, based on bloom first open Mar 23. For pears which had been in bloom earlier in the week, or apples in areas with bloom open Mar 22, infection would have been possible with wetting Mar 24. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection. This graphic will be updated 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.

Fire blight outlook

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 many cultivars with bloom open, others are at full pink, and more bloom opening gradually over the next several days, here is a prediction for trees with first bloom open Friday, March 23, 2012. The temperature and rainfall data are current through Friday morning, March 30. Predicted weather conditions are shown for March 31-April 3. 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 risk of fire blight infection will be mostly low or moderate through Apr 3, but higher if wetting occurs with showers Apr 1. For infection to be predicted, wetting must occur after the EIP (epiphytic infection potential) reaches 100 or higher. Note there had been an earlier threat of fire blight on apples at our AREC last weekend, but temperatures fell about 3 degrees cooler than would have been required, based on bloom first open Friday, March 23. For pears which had been in bloom earlier in the week, or apples in areas with bloom open Mar 22, infection would have been possible with wetting Saturday, Mar 24. In high-risk situations, a protective streptomycin application is recommended ahead of predicted infection.

This graphic will be updated April 2, or sooner if significant change warrants it. 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.

Scab and rust infection period

As predicted Saturday, extended wetting from March 24-26 resulted in scab, quince rust and cedar-apple rust infection periods at our AREC. A split wetting period was recorded with 8 hours of wetting at 61 degrees, followed by four hours of marginal wetting/drying, then 13 more hours of wetting from 55 to 48 degrees and 3 hours of intermittent wetting. An inch of rainfall, early in the wetting period, likely depleted the residual effects of any protective fungicide residues applied before these events. Cedar-apple and quince rust spores were released within four hours of the start of the wetting period Saturday. For the record, wind direction from potential cedar tree rust spore inoculum sources during the spore discharge period, was mostly from the east or northeast.

In areas where rusts are a common problem, it is advised that an SI fungicide be included in the mix to be applied this week for after-infection control of rusts; in areas where scab is resistant to the SIs, other fungicides are advised to be included for after-infection and protective control of scab and suppressive effects on powdery mildew which infected last week and will continue this week.

The threat of fire blight on apples did not materialize at our AREC, with temperatures about 3 degrees cooler than would have been required, based on bloom first open Friday, March 23. For pears which were in bloom earlier in the week, or apples in areas with bloom open Thursday, infection was possible with wetting Saturday. Cool forecasted temperatures should minimize any threat of fire blight for the rest of this week.

Threats of fire blight, rusts and scab.

Scab ascospores and rust spores are mature, and there are threats of cedar-apple and quince rusts and scab infection with the forecast of relatively warm, intermittent showers through tomorrow. Where bloom was open yesterday and there was wetting last night, there is also a threat of fire blight infection. Mildew infection occurred with moderate temperatures throughout this past week.

Scab infection period

Wetting last night at our AREC gave us less than 0.01 inch of rainfall, but it stayed wet 14 hr at 57-67 degrees, and resulted in our first apple scab infection period of 2012. As noted in yesterday's post below, the spore target was big for many varieties. Other areas of Frederick County had more rainfall. With the relatively warm temperatures, cedar-apple rust and quince rust spores matured quickly, but probably did not infect last night, at least in our situation. Blossoms beyond tight cluster with their bases exposed would be susceptible to quince rust. Also as noted yesterday, mildew spores were available and infection has already occurred. So these constitute the present apple disease control spectrum concerns. But with the way it's going this year, we may be concerned about fire blight on early bloom before we know it.

It's a new season!!

Bud development of apple trees is mostly at tight cluster stage and peaches are near full bloom.

Apple scab ascospores were first trapped last Friday, March 16, but it was not wet long enough for infection to occur. Today abundant powdery mildew spores are present on emerging infected tissue, as shown below, and conditions are favorable for mildew infection.

Here is a healthy Idared terminal bud on the left; and a mildew-infected terminal bud on right. Mildew spores on emerging leaf tissue (below) are being dispersed for infection today.

Extended wetting September 12 to 19

This past week we had wetting periods of 12 hr Sept 12-13, 18 hr Sept 14-15, 13 hr Sept 16-17 and 11 hr Sept 17-18; total rainfall for the week was 0.74 in. Total wetting hours last week was 58 which brought us to 768 total accumulated wetting hours, more than 200 hr ahead of last year.

Lee's left-overs

Tropical storm Lee brought us rainfall that totaled 2.72 inches over several days, Sept. 4-7. The ground seemed to soak up this volume of rain surprisingly well, and it will be beneficial for sizing the apple crop. Of course this amount of rain and the extended wetting should be expected to have some consequences for disease development, particularly if fungicide residues were low. Keep watching for sooty blotch and flyspeck, as well for as fruit rots such as bitter rot.

For the record, we had extended wetting periods of 16 hr Sept 4-5 at 69º F, 47 hr Sept 5-7 at 69º F, 12 hr at 64º F Sept 7-8 with Lee, and a more recent one of 22 hr at 68º degrees. Generally, wetting in the higher temperature ranges favor more rapid rot infection and development, and ripening fruit are more susceptible to infection. Typically, residues of a protectant fungicide such as captan do not weather through more than two inches of rainfall in a one week period.

Effects of Hurricane Irene

Considering the lack of rainfall the past three months, Irene's effects in the vicinity of our AREC were mostly beneficial; we received 1.2 inches of rain. The longest continuous wetting period during the weekend was 12 hr, but there were numerous showers earlier, all with temperatures in the 70s, and favorable for rot development. In spite of earlier drought, we have been seeing a lot of bitter rot in our fungicide test plots, a caution to commercial processing orchards with light fungicide programs.

Last week's total for wetting hours was 34, giving us 542 accumulated wetting hours for the season.

Strong winds resulted in some fruit drop of cultivars that won't be ripe for a month, but it was interesting to note that ripening Gala apples, treated with Fruitone (NAA "stop-drop") on Aug 15, held on nicely.

Extended wetting periods and accumulated wetting hours

We have had the following additional extended wetting periods in August:
Aug 6-7; 15 hours at 74º  with 0.85" rainfall.
Aug 13-14; 12 hours at 69º with 0.01" of rain.
Aug 14-15; 14 hours at 67º with 0.18" rainfall.
 
As of today we have reached 491 accumulated wetting hours- almost twice the threshold for development of sooty blotch and flyspeck. This is running about 70 hours ahead of this time last year.
 
We are observing sooty blotch and flyspeck and bitter rot on poorly protected apple trees.

Last week we accumulated an additional 16 wetting hours which brings us to a total of 360 hours, 110 hr past the 250-hour action threshold for development of sooty blotch and flyspeck on unprotected fruit. Total rainfall for the week was 0.22 inches.

Below is a picture of brown rot on Klondike White peach, taken last week. The dieback of shoots indicates high susceptibility of this cultivar, similar to what we have occasionally seen on Redgold nectarine. Klondike White is also very susceptible to bacterial spot. In this case the brown rot infection was probably initiated by hail injury followed by cracking of the fruit with increased growth. At our AREC, brown rot pressure has not been unusually high yet this year but this does not bode well for this local situation, and removal of early infected fruit might be beneficial to prevent spread to later ripening cultivars.

Summer disease pressures

Last week we accumulated an additional 58 wetting hours to brinus to a total of 344 hours, 94 hr past the 250-hour action threshold for development of sooty blotch and flyspeck on unprotected fruit. There was an extended wetting periods with rain July 8-9 (8 hr at 69º). Total rainfall for the week at our AREC was 0.42 inches.

Summer diseases

Extended wetting last night, July 7-8:  8 hr at 70º with 0.15 in. rain. Consider wetting periods 70º and above to be more favorable for rot diseases, especially bitter rot.

Sooty blotch and flyspeck

Sooty blotch symptoms were observed on unprotected fruit at our AREC July 5, with symptoms probably appearing in lower areas of the farm late last week.

Last week we accumulated 26 hours of wetting from rain and dew, bringing us to a total of 288 hours, 38 hr past the 250-hour action threshold for development of sooty blotch and flyspeck on unprotected fruit. There were two extended wetting periods from rain in the last week: June 27 (11 hr at 67º with 0.05 in. rain) and July 4-5 (14 hr at 84-66º with only 0.01 in. rain at our AREC, but with lightning to the north of Winchester as a backdrop for the fireworks display).  The last two nights brought an additional accumulation of 16 wetting hours from dew.

Wetting hour accumulation from dew may be more likely in lower areas, while wetting from rain will probably affect higher and lower elevations in an orchard more uniformly. Typically, symptoms appear earlier in lower areas but it is prudent to begin scouting for symptoms in those areas most likely to show symptoms, whether because of low elevation or lack of recent fungicide protection.

Appearance of sooty blotch/flyspeck symptoms probably also indicate a lack of fungicide residue to effectively control rot development. Where present, fire blight-killed shoots should be viewed as a potential fruit rot inoculum source.