Tag Archives: Malusim

MaluSim models for 11 May 2015

For both Winchester and Central Virginia, the Malusim model is predicting a mild to no carbohydrate stress over the next week. Although temperatures at the time of application, are less important then the carbohydrate running average (2+4 Running Average), expect chemical thinners applied Sunday (10 May) or Monday (11 May) to cause more thinning than applications made late last week or for the rest of this week. Expect a “typical” response from chemical thinners applied Tuesday (12 May) through the rest of this coming week.

Peck Winchester MaluSim 5_11_15Peck Central VA MaluSim 5_11_15

The National Weather Service is predicting sunny weather later this week, as well as daytime temperatures in the 70s. This should result in ideal conditions for plant growth, and thus less carbohydrate stress in the apple trees.

One of the weaknesses of weather-based models, is the need to use forecast data to make decisions about future events. When I ran the MaluSim models for both Winchester and Central Virginia last Thursday, the forecast was for hot, cloudy weather. Although it was in the mid-80s in most of Virginia over the weekend, there was also a lot more sunlight than predicted. Temperatures are generally a lot more reliable than cloud cover predictions, but both seemed to be less severe than originally forecasted.

Cloudy weather predicted for later in the week is causing wild swings in the MaluSim model output. My expectation is that actual carbohydrate levels will be more moderate and that running average values will remain in the 20 to -20 g CHO/day range.

Full model output:

Peck Winchester MaluSim 5_11_15.pptx

Peck Central VA MaluSim 5_11_15.pptx

MaluSim Model Data for 7 May 2015

Due to warm days (>80F) and intermittent cloud cover, the MaluSim carbohydrate model is showing a strong carbohydrate deficit for both Winchester and Central Virginia over the next four to five days. Expect an aggressive to very aggressive response to chemical thinners applied today through early next week. Reduce rates, and/or do not include oil or other surfactants if overthinning is a concern.Peck Winchester MaluSim 5_7_15

Peck Central VA MaluSim 5_7_15

Pay close attention to the weather forecasts. If actual temperatures are closer to 90F and/or there are prolonged periods of cloud cover, then overthinning will likely occur.

The greatest amount of thinning occurs when fruitlets are on average between 8-12 mm in diameter. Thinning when fruitlets are slightly smaller or larger will result in less thinning, which may be desirable if there is a severe carbohydrate deficit.

Cooler temperatures forecasted for the middle to end of next week should result in less carbohydrate stress and reduced chances of overthinning. However, fruitlets that are greater than 15 mm in diameter are more difficult to thin with NAA or 6-BA.

During these warm days, expect the average fruitlet size to increase by at least 0.5 mm per day.

Full MaluSim model output:

Peck Winchester MaluSim 5_7_15.pptx

Peck Central VA MaluSim 5_7_15.pptx

Central Virginia MaluSim for 4 May 2015

Warmer temperatures and cloud cover from some rainstorms later in the week will cause a moderately stronger carbohydrate deficit for Central Virginia.

Peck Central VA MaluSim 5_4_15

Thinning applications made Tuesday through Thursday will result in the strongest response this week. Long term weather forecasts predict days in the 80’s and nights in the 60’s for the next 10 days. Carbohydrate levels will likely remain in the 0 to -40 range during that period.  To get the strongest response possible, make your applications when average fruit size is 8-12 mm in diameter.

Due to a technical glitch, I was unable to run the MaluSim model for Winchester. I hope to have the problem resolved Tuesday morning. I will post an update for Winchester as soon as possible.

Full MaluSim report:

Peck Central VA MaluSim 5_4_15.pptx

Central Virginia MaluSim for May 1

Moderate temperatures and adequate sunlight are resulting in slight carbohydrate deficits according to the MaluSim model.

Peck Central VA MaluSim 5_1_15

 

This means that chemical thinners applied today through the first part of next week should cause an “average” response. Warmer temperatures are forecast for the middle of next week, which should result in greater carbohydrate deficits. I will run another simulation for Central Virginia, as well as the first Winchester run on Monday.

Central Virginia MaluSim for 1 May 2015:

Peck Central VA MaluSim 5_1_15.pptx

MaluSim Model for Central Virginia, 27 April 2015

Today, I ran the first Central Virginia MaluSim model for 2015. I will start the Winchester models later this week.

For Central Virginia, I use data from a weather station set up at Silver Creek Orchards and managed by my colleague, Dr. Mizuho Nita. A big thank you to Dr. Nita for allowing me to install the necessary instrumentation and for maintaining the station and associated software.

This year, I will be using forecast data from the National Weather Service. In past years, I used Intellicast.com data because they provided 10-day forecasts with cloud cover predictions. Intellicast no longer provides the cloud cover data in an easy to use format, so I am switching to the National Weather Service’s forecasts. Note that these forecasts only project five days into the future.

We will discuss the details of the model at Tuesday’s meeting at Saunders Brother. Peck Central VA MaluSim 4_27_15

However, this first model run suggests that the relatively cool weather, and mostly sunny weather that has occurred since bud break has resulted in a moderate carbohydrate deficit in apple trees. Growers can expect average results from chemical thinners applied the last couple-few days through to the weekend. In blocks where significant thinning is needed, growers should apply carbaryl at petal fall and then look to the warmer weather that is predicted for the weekend and early next week for their 10 mm application.

Central Virginia weather data, MaluSim data, and an interpretation chart are in the pdf linked to below:

Peck Central VA MaluSim 4_27_15

MaluSim Carbohydrate Model for May 27, 2014

I ran a MaluSim model using data from the weather station located at the Alson H. Smith, Jr. AREC in Winchester. This will be the last model run for the year.

Slide3 No forecast data was used in this run. Based on the output, I would expect chemical thinners that were applied May 14-16 to have an average response, while thinners that were applied on and after May 17 to have minimal effect. The effectiveness of thinners is greatly influenced by fruit size, so if the model showed a carbohydrate status that was greater than 20 g per day, and fruitlets were greater than 15 mm at the time of application then chemical thinners may not have been particularly effective.

Growers should compare the results of their chemical thinning program with the modeled carbohydrate status to determine if the model accurately predicted the level of thinning you expected from your applications.

I would appreciate hearing from growers about how they used the model to make chemical thinning decisions. Both positive and negative feedback is appreciated.  You can use the comment feature in the blog site, or just send me an email.

Download the full report:

Winchester VA MaluSim 5_27_14

MaluSim Carbohydrate Model for May 22, 2014

On Thursday, I ran the MaluSim model for Winchester.

Slide3

As I suggested in my last post, the strongly negative carbohydrate balance forecasted for May 20 and 21 were a product of poor cloud cover forecasting. In fact, since May 16 the carbohydrate status has been in the positive range. Chemical thinning applications made from May 17 through the next several days will likely have an moderate to poor response. Now that fruitlets are 15 to 20 mm in diameter, NAA and 6-BA will have minimal thinning efficacy. Growers who need to thin additional fruit from their trees should consider ethephon applications.

Table 1. Fruitlet sizes at the Alson H. Smith, Jr. AREC in Winchester, VA.

Variety 12-May 15-May 20-May 22-May
Empire 10.4 12.2 15.1 17.9
Fuji 7.0 9.0 12.1 14.8
Gala 8.7 11.3 13.9
Goldens 8.0 9.5 12.7 14.9
Idared 8.1 9.5
Pink Lady 9.2 11.0 13.6 16.6
Red Delicious 8.0 10.1 11.4
York 7.9 10.7 13.8 16.1

As I did for the Central Virginia models, I will run one more season recap model early next week.

Download the full report:

Winchester VA MaluSim 5_22_14

MaluSim Carbohydrate Model for May 19, 2014

On Monday, I ran the MaluSim model for Winchester and a season recap for the Central Virginia region.

Slide3

For the Winchester area, the carbohydrate status has been in the -20 to 20 g CHO/day range since May 15. This means that thinning sprays made between last Thursday and today are predicted to have an average response. For the next couple of days, the model is showing a significant carbohydrate deficit. This is being caused by the cloudy weather that is predicted, as neither day nor night temperatures are forecast to be very high. Cloud cover remains the hardest variable to forecast. If the next two days are sunnier than forecast, or if the rain showers occur at night, then I would not expect the actual carbohydrate balance to go into such a low deficit. However, if the weather forecasts that I used in the model are accurate, then growers should avoid thinning on Wednesday. Either way, the best predictor of the potency of chemical thinners is the 2 days before, day of, and 3 days after (2+4-day) running average (the black line). As you can see, the running average remains between 0 and 20 g CHO/day, meaning that chemical thinners will have an average response.
Slide3

For the Central Virginia region, I’ve run a recap of the season using weather station data through Monday, May 19. Growers should compare their thinning results to the carbohydrate status at the time they made their application to see how well the model predicted the potency of thinners this year. From my experience, using the MaluSim model as a forensic tool can really help explain why chemical thinners work so differently from one year to the next. As I repeatedly have said, the most difficult part of using the MaluSim model to make real time decisions is having accurate weather data to use as inputs. As I mention above, cloud cover can really impact the carbohydrate status in the tree, and thus the responsiveness of thinners, but it is the hardest variable to forecast. Additionally, weather can be very local. We experienced this issue with the major differences between Tyro and Piney River weather forecasts. We also saw a lot of variable temperature data, with several days between May 8 and 14 being 5 or more degrees Fahrenheit warmer than forecast.

Even with these issues, I hope that the model is providing useful information that helps you make sound management decisions. If you have any feedback, please don’t hesitate to contact me.

I will continue to run the Winchester model until fruit size is too big to thin with NAA and 6-BA.

Download the full reports:

Central VA MaluSim 5_19_14

Winchester VA MaluSim 5_19_14

MaluSim Carbohydrate Model for May 15, 2014

Fruit in the Winchester area is at the ideal size for chemical thinning.

Slide3Thinning applications made on Monday through Wednesday of this week will likely see an excessive amount of thinning, especially if  fruit was 8-12 mm in diameter. Thinners that were applied on Thursday will likely have a moderate to strong response. Thinners applied Friday (if it stops raining!) through the weekend will have a normal to weak response. If the weather forecast holds, growers should consider slightly increasing rates and using a surfactant for thinning applications made over the weekend. I’ll run another MaluSim model on Monday.

Table 1. Fruitlet sizes (mm) at the Alson H. Smith, Jr. AREC in Winchester.

Variety  12-May 15-May
Empire 10.4 12.2
Fuji 7.0 9.0
Gala 8.7 11.3
Goldens 8.0 9.5
Idared 8.1 9.5
Pink Lady 9.2 11.0
Red Delicious 8.0 10.1
York 7.9 10.7

Download the full Winchester report:

Winchester VA MaluSim 5_15_14

Fruit in the Central Virginia region is now beyond the size where chemical thinning with 6-BA or NAA is effective. If additional thinning is needed, growers should use ethephon. While these late or “rescue” thinning applications are not very responsive to the carbohydrate status modeled with MaluSim, ethephon does tend to be more active when applications are made on hot days. I will run a season recap for the Central Virginia region in a few days (I was having technical issues accessing the weather station data).

MaluSim Carbohydrate Model for May 12, 2014

Fruitlets in the Central Virginia area are quickly sizing up (reports are in the 12-18 mm range), and growers have only a couple-few more days to use NAA and 6-BA products for thinning. In the Winchester area fruitlets are just entering the 10 mm thinning window, but with the hot weather over the past few days it is likely that fruit will be growing at a rapid pace (greater than 0.5 mm per day).

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Table 1. Fruitlet sizes at the Alson H. Smith, Jr.AREC in Winchester.

Fruit diameter (mm)
Cultivar 12-May
Empire 10.4
Fuji 7.0
Gala 8.7
Goldens 8.0
Idared 8.1
Pink Lady 9.2
Red Delicious 8.0
York 7.9

In Central Virginia, the MaluSim model is showing a moderate carbohydrate deficit for the next three days, and then the carbohydrates balance shows positive values through the weekend.  A large deficit that was predicted to occur over the past weekend never materialized, largely because there was more sunlight than forecasted. Additionally, as the expanding leaf surface transitions from being a carbohydrate sink to a carbohydrate source the model will continue to show a positive carbohydrate balance. Growers should target blocks that require more aggressive thinning on Tuesday and Wednesday at normal or slightly reduced rates (unless trying to thin larger fruit) and then target blocks with lighter starting crop loads towards the end of the week.

In Winchester, bud break was 6 days later than in Central Virginia, meaning that many leaves are still sinks for carbohydrates and more severe deficits occured over the past few days.  However, as the Winchester area enters into the thinning window, less severe carbohydrate deficits are predicted to occur. Growers should start thinning their earliest blooming cultivars on Tuesday evening or Wednesday and then move to more lightly cropped blocks towards the end of the week and over the weekend.

Click below to download the full pdf reports:

Central VA MaluSim 5_12_14

Winchester VA MaluSim 5_12_14