Healthy Fruit, Vol. 26, No. 7, May 15, 2018
Jon Clements, Author (unless otherwise noted) and Editor
Current degree day accumulations
UMass Cold Spring Orchard,
Base 43 BE (NEWA)
Base 50 BE (NEWA)
Current bud stages
Current bud stages. May 14, 2018, UMass Cold Spring Orchard, Belchertown, MA
Early petal fall
Rainier sweet Late petal fall - fruit set
Codling moth 1st catch
398 to 566
1st sustained trap catch = biofix set to start DD model for insecticide timing
Lesser appleworm 1st catch
276 to 564
Does anyone know if this pest is a problem in MA orchards, or is it taken care of with petal fall sprays?
Lesser peachtree borer 1st catch
480 to 671
Hang pheromone traps to monitor presence/absence?
Oriental fruit moth 1st flight peak
333 to 536
Pheromone traps should be hung to establish biofix; petal fall spray likely to resolve
Pear psylla hardshell nymphs present
493 to 643
Early season pear psylla management should have prevented these; if not, you are looking at season-long battle now with insecticide(s)
Plum curculio oviposition scars presents
485 to 589
Monitor for signs of activity during warm, muggy weather; fruit not particularly susceptible until it reaches 7 mm size; be proactive with petal fall insecticide
San Jose scale 1st catch
438 to 614
I have never been successful trapping these with pheromone traps; continue to monitor for sign of SJS infestation
Spotted tentiform leafminer leaf mines forming
367 to 641
If present, treatment may be warranted
McIntosh petal fall
439 to 523-415
From Heather Faubert @ URI:
Come join Sonia Schloemann (UMass) and me at Ward’s Berry Farm, 614 South Main St., Sharon, MA on Thursday May 24, 2018 at 5:30 PM. Guest speaker: Dale Ila Riggs, The Berry Patch in Stephentown, NY, will speak on exclusion netting to protect fruit against spotted wing drosophila and other pests. Sonia Schloemann, UMass Small Fruit Specialist and Heather Faubert, URI, will speak on current blueberry topics such as pruning, nutrition and insect management. Meeting is free with annual dues payment of $40, or $20 for non-RIFGA members. Light dinner will be served. Two hours of pesticide recertification credit available. Registration is not necessary.
Where do I start? Let me count the ways…
Effect of air temperature on plum curculio immigration:
It has been nearly two weeks since odor-baited traps captured the first PCs at the UMass Cold Spring Orchard (Belchertown, MA). The first PC was captured on May 2nd, 2018. Since then, and with the moderately warm (but not high) temperatures that have prevailed in the area, PCs have continued to colonize orchards on a gradual manner. This means that air temperature has not been conducive for a sizeable or 'large ' extent of PC immigration into orchards.
On this year, trap capture patterns indicate that PCs are approaching orchard trees more by means of crawling rather than by flight. With petal fall approaching soon, it is believed that PCs will continue to colonize orchards in a gradual manner. The graph below shows the mean number of PCs captured by black pyramid traps according to date. Mean air temperature for each period is presented in red font, in parentheses. Note that PC captures are not so related to air temperature. That is one benefit of using black pyramid traps: they are effective at monitoring for PC even during cool days.
Seasonal pattern of PC captures in black pyramid traps, May 2018
Below is a graph showing the effect of time of day and associated air temperatures using data collected at the peak of PC immigration in the year 2000. That spring was characterized by comparatively high temperatures for an extended period of time. Mean, maximum and minimum temperature values registered for each time period are depicted in the yellow boxes.
PC captures in traps according to time of day (year 2000)
As you can see, panel traps (blue bars) coated with Tangletrap (sticky material) captured nearly twice as many adults from 2:30 to 7:30 pm as from 7:30 pm to 7: 30 am, and nearly 4 times as many as from 7:30 am to 2:30 pm.
In contrast, pyramid traps (orange bars) captured fewer adults from 2:30 to 7:30 pm than from 7:30 pm to 7:30 am. Very few PCs were captured from 7:30 am to 2:30 pm.
Bottom line: PCs are much likely to fly during warm afternoons, and they are more likely to approach trees by crawling during cool days and also at night.
Do you have any suggestions for articles on arthropod IPM? Please let me know!
Contact info: email@example.com; (413) 545-1031 (campus office); (808) 756-2019 (cell).
Fire Blight Risk
Figuring out whether to treat for fire blight has been difficult this year. The risk factors vary quite a bit from orchard to orchard. It has been very warm, then cold, then humid and warm. This week, NEWA is showing High or Extreme Risk for Tuesday, Wednesday and Thursday in a number of places. Yet RIMpro is not showing risk in most areas. Which is correct?
To try to answer that, it’s probably worth listening to the guy who adapted Cougarblight and MaryBlyt to NEWA. Last week Kerik Cox wrote a piece on fire blight management in Scaffolds, and in it discussed NEWA, as follows.
As you consider model outputs from NEWA or other forecasting models, here are some things to consider before making applications of antibiotics or other costly materials for blossom blight:
1 - Predictions and forecasts are theoretical. The theoretical models predicting disease risk use the weather data collected (or forecasted) from the weather station location. These results should not be substituted for actual observations of plant growth stage and disease occurrence determined through scouting or monitoring.
2 - Consider the history of fire blight in the planting. If there was not fire blight the previous season or if you have never had fire blight, do not let excessive model predictions or extension alerts (including this article) "intimidate you" into applying unnecessary antibiotics each time an alert is released. Consider the timing of the last application and potential for material depletion as well.
3 - Consider the age of the planting and the susceptibility of variety and rootstock. These factors play a large role in the development of fire blight. None of the models consider these factors. If you have a young planting of a highly susceptible variety, it may be more important to protect these blocks based on model predictions than a 15-year-old 'McIntosh' planting on resistant rootstocks, which may not warrant the same level of protection during bloom. A listing of susceptible cultivars and rootstocks is linked from the NEWA model page for fire blight.
4 - The models only identify periods of weather that are favorable for infection. All wetting events are now color-coded light blue in NEWA to draw attention to the weather factors that promote bacterial ingress into the flowers. Despite words like "extreme" and "infection" colored in vibrant red, the models only predict favorable weather conditions. If favorable weather for infection is not predicted in the current forecast, if the apple variety is not highly susceptible, if there is no prior history of fire blight, and if the trees aren't being pushed into high vigor with nitrogen, the actual risk of fire blight infection may be low to non-existent.
5 - Weather forecasts can vary and change daily. When this happens, the model predictions will change drastically, and the risk will change as well. Bacteria double about once every 20 minutes under optimal conditions; for fire blight bacteria this is warm (>60°F) wet conditions. The models use degree hours, not degree days, to accommodate the rapid growth rate of these pathogens. Check the fire blight predictions, especially those in the forecasts, frequently. The 1- and 2-day forecasts are the most reliable; those at 3-, 4- and 5-days are less reliable as predictors. NEWA uses the National Weather Service forecasts. Compare these to your favorite local weather forecast provider.
Above, NEWA output for a site in Massachusetts generated on May 15
Basically, Dr. Cox is saying that NEWA tends to exaggerate fire blight risk, and that you should adjust its evaluations to fit your orchard, paying particular attention to variety, rootstock, history of fire blight and the accuracy of weather forecasts.
Weather forecasts in particular vary, depending on where they’re from. In Belchertown, we are looking at different sources of data, both virtual and from a weather station. Depending on which source is used, the same model suggests different risks.
If I were looking at the NEWA chart above, and had a block of Gala on M9 next to pears that had fire blight last year, I’d apply a strep treatment tomorrow, May 16, to that block and the pears. I’d wait until tomorrow because the weather forecast may change, which would change risk. In addition, a strep application tomorrow will cover the whole high risk period, May 15 to 17.
On the other hand, if I had a block of Macs on M7 and hadn’t had fire blight in the orchard, I wouldn’t spray, even though NEWA is trying hard to convince me to.
The bottom line is the bottom line: how much does a strep spray cost vs. what is the risk and the potential damage from fire blight? Generally, streptomycin is not that expensive compared to the damage that it can cause in some situations, like a high-density block of susceptible trees.
This little tidbit from Dan Donahue, Cornell’s Hudson Valley Horticulture team:
There has been a number of requests from growers about how to de-fruit newly planted and trees that should remain non-bearing for another year. Here is the recipe: Where you desire to totally eliminate the crop try a heavy rate of Maxcel (64 ounces) + carbaryl (2pts) + Oil (1pt) /100 gallon TRV dilute when fruit size is 8-10mm. I have received reports of trees being strongly shocked by this mixture, with growth set back slightly, but it does work.
Chemical thinning suggestions from Duane Greene
Apple phenological development is somewhere between bloom and petal fall in many areas in Massachusetts. As outlined last week this is an extremely important time to apply thinners in a chemical thinning strategy. This is also the safest time to apply a chemical thinner since excessive thinning is rarely experienced and erratic responses to erratic weather are much less likely to happen. If there is such a thing, thinning at bloom or petal fall should be much less stressful to orchardist stress than thinning later. If you have not applied a thinner at bloom or petal fall it is strongly recommend even given the changeable weather predicted for the next several days. At petal fall treatments that have worked well in the past are NAA at 10 ppm plus or minus carbaryl and Amid-Thin at 8 oz/100 gal plus a surfactant and carbaryl. A thinning spray containing only carbaryl is an extremely mild thinning treatment and you can expect only a modest thinning response. The important thing to do now is to get the spray on. There are several days where there is the possibility of rain. Last week I mentioned that as a general rule you will get at least 80% of the thinning activity of a thinning spray following rain if the spray has had an opportunity to completely dry.
Perhaps before you receive the next Healthy Fruit some orchards will be at the 6 mm fruit size stage. At that time you can assess initial set and make an initial assessment of how aggressive your thinning program should be during the 7 to 15 mm thinning period. Starting when fruit reach 6-7 mm fruit growth will be rapid and the energy required for fruit growth will be high. It is at this fruit size that guidance provided by the Carbohydrate Thinning model, located on NEWA can be very useful. The thinners most useful and effective at this growth stage are NAA, MaxCel, carbaryl and combinations of NAA or MaxCel with carbaryl. MaxCel is a relatively weak thinner when used by itself but when combined with carbaryl it is one of the most potent thinning combinations available. In order for MaxCel to be effective, warm temperatures will be required following application (70° F or higher). Guidance for use of these thinners will be provided next week when weather forecast will be known with greater clarity closer to the time of application.
Gypsy moth, yep, they’re still about and will continue move into the orchard. As you can see in the picture below, the caterpillars are sizing up as time passes, which means, they are moving inexorably towards being far harder to manage (fat and squishy gypsy moth larva are more resistant to pesticides). Good news! Dipel, or other B.t. is still effective at the current growth stage.
The good, the bad and the beautiful…
Assassin bug lays in wait to pounce on its next meal
Green pug moth attempts to make a meal of apple leaf
Gypsy moth caterpillar feasting on apple bloom
Native pollinator, doing her stuff
What else can I say? It’s a bit of a mixed bag this week. Apple scab and fire blight are still looming on the horizon. We are up to 80% chance of rain for Tuesday afternoon, according to NOAA, and with Monday’s gorgeous weather, ascospores have matured and are ready for release…
Plum curculio egg laying can already be seen in high pressure blocks…
Oh! One more thing. As Jon mentioned above, AgRadar is up and running for the season. One of the features provided is a honey bee activity/avoidance model. It provides handy guidance for when to make pesticide applications that reduce non-target insect exposure. Basically, the graph shows you when bees are active (orange), wind speed (purple dotted line), and when residues (blue) are still able to cause harm.
No Guest article this week...
Ed. note: we don’t have them here yet, or at least we don’t think we do?
UMass Fruit Advisor: http://umassfruit.com
Scaffolds Fruit Journal: http://www.nysaes.cornell.edu/ent/scafolds/
Network for Environment and Weather Applications (NEWA): http://newa.cornell.edu
The next Healthy Fruit will be published on or about May 22, 2018. In the meantime, feel free to contact any of the UMass Fruit Team if you have any fruit-related production questions.