Caution: The observations, conditions, and recommendations reported on this page are applicable only to the eastern counties of West Virginia. Use of the information reported here for making orchard management decisions outside of the immediate proximity of Kearneysville, West Virginia, is not our intent. Fruit producers outside the eastern West Virginia area are encouraged to consult their state extension specialists for information similar to that provided here.
- May 17, 2013
- The 10-day forecast shows that EIP will remain above threshold from 5/17 through the forecast period as daytime temperatures move into the upper 70's, 80's and perhaps low 90's. Any bloom remaining after 5/15 will be susceptible to fire blight infection (watch for wetting events) and you will need to make a decision about whether the amount of bloom is significant enough to require prophylactic measures. The period 5/22 and 5/23 shows especially high EIP and any wetting or trauma event will need to be dealt with immediately. Be aware that EIP and the threat of infection can build up rapidly if warmer weather than that forecasted occurs. The model graphic and interpretation are here.
- May 15, 2013
- Fire blight: every day for the next 10 days is a potential fire blight blossom infection day for any trees with bloom remaining (our Rome trees still have a lot of bloom); all that is needed to trigger infection is moisture in the form of heavy dew or rain (or an airblast application of a dilute spray mix). See below for blossom blight scouting instructions. Maryblyt predicts the first shoot blight symptoms to be visible on 5/23.
- May 13, 2013
- Begin scouting for first blossom blight symptoms on May 16 (infections from the April 19 infection period). Additional blossom blight infections occurred on May 10 and 11 - symptoms from these infections will develop rapidly and should be visible close to 5/20-5/21, according to the Maryblyt model.
- The 10-day forecast shows that EIP will decrease today and tomorrow and then increase again beginning on 5/15 as daytime temperatures move into the upper 70's and perhaps low 80's again. Any bloom remaining after 5/15 will be susceptible to fire blight infection (watch for wetting events) and you will need to make a decision about whether the amount of bloom is significant enough to require prophylactic measures. The model graphic and interpretation are here.
- Frost injury can cause trauma blight in situations where EIP is in the 200-250 range. We aren't there. If we were close to this level of EIP we would recommend that streptomycin be applied within 24 hours of any trauma event.
- Today, May 13, we are seeing the first apple scab lesions (likely from the April 28-29 infection period) on unprotected trees in our fungicide research plots. The lesions are just barely visible but large enough to conclude that they were likely sporulating during our most recent wet periods on May 10 and 11. This would indicate the possibility of secondary infections in any locations where fungicide coverage was not adequate during the 4/28-4/29 infection period. No cedar apple rust lesions are visible at this time.
- Apple scab and rust diseases: From 6 PM on 5/10 through 4 PM on 5/11, we had 0.79 inches of rain with a total of 21 hours of wetting at an average temperature of 64.5 F. These are optimum conditions for apple scab and the cedar rust diseases. (Scab infection #5).
- May 10, 2013
- In the graphic below from the
Maryblyt program we show a forecast beginning today, May 10, through Sunday, May 19. This forecast is for any apple varieties that are showing bloom, although as we approach petal fall on early and mid-season cultivars this will pertain mostly to later-blooming cultivars. Rain and moderate temperatures on Friday April 19 provided the conditions necessary for our first fire blight infection of the season with EIP at 102; however, symptom development is prolonged due to cooler temperatures. It looks like May 15-16 is the time to begin scouting for first blossom blight symptoms (see the BBS column, which shows 98% on May 15). In the graphic below, we can see that the recent rain caused Maryblyt to show "HIGH RISK" for a fire blight infection period on 5/9, although EIP was well below the threshold of 100. However, today, EIP is above the threshold for today and tomorrow and infection is likely. The 10-day forecast shows that EIP will decrease after tomorrow and then increase again beginning on 5/16 as daytime temperatures move into the upper 70's and perhaps low 80's again. Look at the period 5/9 - 5/10 as potentially needing prophylactic measures to prevent fire blight blossom infection for the May 10 -12 period. If there is any bloom remaining during the 5/16 - 5/19 period, then prophylactic measures will be required at that time. Remember the old saying, "90% of the fire blight gets established on the last 10% of the bloom." Be aware that EIP and the threat of infection can build up rapidly if warmer weather than that forecasted occurs. The model graphic and interpretation are here.
- Apple scab and rust diseases: From 6 PM on 5/9 through 8 AM on 5/10, we had 0.39 inches of rain with a total of 15 hours of wetting at an average temperature of 56.2 F. These are optimum conditions for apple scab and the cedar rust diseases. (Scab infection #4).
- May 8, 2013
- In the graphic below, we can see that the rain yesterday and today caused Maryblyt to show "HIGH RISK" for fire blight infection periods; however, EIP is well below the threshold on these days. The 10-day forecast shows that EIP will begin to increase rapidly on 5/10 as daytime temperatures move into the upper 70's and perhaps the low 80's. Look at the period 5/9 - 5/10 as potentially needing prophylactic measures to prevent fire blight blossom infection for the May 10 -12 period. Rain and moderate temperatures on Friday, April 19, provided the conditions necessary for our first fire blight infection of the season with EIP at 102; however, symptom development has been prolonged due to cooler temperatures. It looks like May 14 is the time to begin scouting for first blossom blight symtptoms (see the BBS column, which shows 99% on May 14). Be aware that EIP and the threat of infection can build up rapidly if warmer weather than that forecasted occurs. The model graphic and interpretation are here.
- Apple scab and rust diseases: From 11 AM on 5/7 through 8 AM on 5/8, we had 0.74 inches of rain with a total of 22 hours of wetting at an average temperature of 58.1 F. These are optimum conditions for apple scab and the cedar rust diseases. (Scab infection #3).
- May 6, 2013
- In the graphic below, we can see that the rain forecasted for tomorrow and Wednesday causes Maryblyt to show "HIGH RISK" for fire blight infection periods; however, EIP is well below the threshold on these days. The 10-day forecast shows that EIP will begin to increase rapidly on 5/10 as daytime temperatures move into the upper 70's. Look at the period 5/9 - 5/10 as potentially needing prophylactic measures to prevent fire blight blossom infection for the May 10 -12 period. Rain and moderate temperatures on Friday, April 19, provided the conditions necessary for our first fire blight infection of the season with EIP at 102; however, symptom development has been prolonged due to cooler temperatures. It looks like May 14 is the time to begin scouting for first blossom blight symtptoms (see the BBS column, which shows 105% on May 14). Be aware that EIP and the threat of infection can build up rapidly if warmer weather than that forecasted occurs. The model graphic and interpretation are here.
- May 3, 2013
- The 10-day forecast shows that EIP will begin to increase, albeit slowly, as daytime temperatures move into the low 70's. Look at the period from 5/5 to 5/10 as potentially needing prophylactic measures to prevent fire blight blossom infection. The model shows that 5/10 will be a potentially serious high risk day at 95% EIP and favorable temperatures for infection if moisture occurs. The model graphic and interpretation are here.
- May 1, 2013
- Happy first day of May! Adding up all the wet hours since 4/28 until our beautiful sunrise this morning gives us 44 hours of total wetting at an average temperature of 54.7 F with 0.39 inches of rain. These conditions were favorable for apple scab, cedar apple rust and quince rust infection. Remember to look for symptom development from this infection period in about 2 weeks. (Scab infection #2).
- Our recent rainfall on open blossoms on 4/28 through 5/1 are not fire blight infection periods according to the Maryblyt model. The 10-day forecast shows that EIP will begin to increase, albeit slowly, as daytime temperatures move into the low 70's. Look at the period from 5/5 to 5/10 as potentially needing prophylactic measures to prevent fire blight blossom infection. The model graphic and interpretation are here.
- April 29, 2013
- A significant apple scab infection period is occurring, beginning at about noon on 4/28 and continuing intermittently with leaf wetting for the past 16 hours (as of 8:00 AM on 4/29) with the average temperature at 53.3 F. This is very favorable weather for apple scab and is also favorable for cedar apple rust and quince rust, espcially with the long duration of the wetting period.
- Rainfall on open blossoms on 4/24, 4/28 and 4/29 are not fire blight infection periods according to the Maryblyt model. Rain on April 19 caused our first recorded fire blight infection period - cool temperatures will result in a prolonged symptom development period (well beyond the 10-day forecast period); the 10-day forecast shows that conditions continue to be too cool for fire blight infection over the forecast period, although there is a trend toward warming and increasing EIP (and infection risk) for the period May 6 - 8. We may be finished with bloom by then - stay tuned. The model graphic and interpretation are here.
- April 24, 2013
- Fire blight update: rain on April 19 caused our first recorded fire blight infection period - cool temperatures will result in a prolonged symptom development period; the 10-day forecast shows that conditions continue to be too cool for fire blight infection over the forecast period. The model graphic and interpretation are here.
- Powdery mildew is the most active disease in weather like this. Those who are tempted to extend intervals between fungicide applications will want to make sure that mildew is controlled on the susceptible cultivars.
- April 22, 2013
- 0.91 inches of rain on Friday April 19. Wet for 3 hours at 61 F. Enough wetting to stimulate the cedar rust galls, but not enough to cause infection for rust or scab infections. Powdery mildew continues to be the disease to be most concerned about, with favorable weather continuing this week. Fruit russetting from mildew infection can occur as early as the pink stage of bud development.
- Fire blight update: as predicted last week, rain on April 19 caused our first recorded fire blight infection period on susceptible cultivars with open blossoms; streptomycin applications during the period April 17 - 19 would have been sufficient to provide good protection; the 8-day forecast shows that conditions are too cool for fire blight infection over the forecast period. The model graphic and interpretation are here.
- April 19, 2013
- If the current 10-day weather forecast is accurate and temperatures stay in the high 50's and low 60's during the day (30's and 40's at night) then the risk for fire blight infection will remain very low during this period. Except for today, which is a very high risk day. We have 3 of the 4 risk factors satisfied today; the fourth, EIP, is 97% of the threshold, so that is close enough to be 4 out of 4.
- Here are the risk factors: 1) flowers must be open with stigmas and petals intact (stigmas exposed for colonization, flowers in petal fall are resistant); 2) accumulation of at least 198 degree hours (DH) > 65°F within the last 80 degree days (DD) >40°F for apples or within the last 120 DD > 40°F for pears (defines the epiphytic infection potential (EIP) for the oldest open (and, hence, most colonized) flower in the orchard); 3) a wetting event occurring as dew or >0.01 inch of rain, or >0.10 inch of rain the previous day (allows movement of bacteria from colonized stigmas to the nectarthodes); and, 4) an average daily temperature of > 60°F (this may influence the rate at which the bacteria migrate into the nectarthodes as well as the multiplication of bacteria needed to establish infections).
- April 17, 2013
- 0.17 inch of rain at KTFREC at around 1:00 AM. This is not an infection period in most orchards.
- Fire blight update: the 5-day forecast shows the potential for infection of any open blossoms on Friday, April 19; there is an 80% chance of rain on that day with a predicted EIP value of 121. The model graphic and interpretation are here.
- April 15, 2013
- Apple scab update: We received about 0.66 inches of rain on April 12, with temperatures in the 52 - 54 degrees F range, during the period from 4 AM to 10 AM. Later that afternoon, we had additional wetting in the 59 - 63 degrees F range around 5 to 6 PM and accompanied by some additional hours with relative humidity at or above 95%. If you count the dark hours (which are generally inhibitory to ascospore release) and tack on the high RH hours, then (the worst of all possible scenarios) we accumulated 98.2% of the temperature/wetting conditions for apple scab infection as described by Mills (and well over 100% of the conditions needed as described by Stensvand et al.). So, I think it is possible that high inoculum orchards could have experienced an apple scab infection on April 12. However, for the majority of eastern panhandle commercial orchards, infection conditions were most likely not met on April 12 because scab inoculum is generally low. For those of you keeping track, I'm going to describe these conditions for most commercial orchards as 7 hours of wetting at 56 F. These conditions are also not likely to lead to significant cedar apple or quince rust infection (we have some cultivars at the open cluster/(nearly) pink stage). Powdery mildew infection was possible during the day on April 11. (Scab infection #1).
- Fire blight update: Looking ahead to the possibility of first open apple blossoms on Wednesday, April 17, and the possibility of fire blight infection, the weather forecast shows generally favorable temperatures (average at 60 degrees F or higher) and the chance for precipitation in the form of thunderstorms (30%, 30%, 10%, and 60% chance on Tuesday, Wednesday, Thursday and Friday, respectively). Here is the potential scenario that could lead to infection: with first blossoms open on the 17th (Wednesday), and with 0.10 inches of rain or more on that day, Maryblyt shows that blossom infection will occur on the 18th (Thursday - remember, there is a 30% chance of rain). Rain on the 19th (Friday - 80% chance of that) also is likely to cause infection. After Friday, the temperatures look to be too cool for fire blight infection.
- January 29, 2013
- Average daily temperatures and records
- Average last freeze date map
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