AppleTalk Conference Call Summary
Tuesday, May 24, 2016, 8:00 – 9:00 AM
Presenter: John Aue, Threshold IPM
Moderator: Peter Werts, IPM Institute of North America; questions or comments,
May 24th Call download: Click Here
Precipitation deficits and long-range forecast
There is significant regional variability in total rain fall and most locations are short on rainfall by four to five inches for the months of April and May. Some locations are down nine inches of rain from November 2015 to May 2016.  The weather patterns are predicted to be extended, where high and low pressure systems will have longer duration than normal, e.g., extended wetting or extended dry periods. Storms are predicted all week, but may not result in significant precipitation.
Growers are advised to monitor soil moisture on small-root stock trees.  Historically, a fully mature M7 with a crop would require a minimum of four to five gallons of water every four or five days, under predicted temperatures we will experience. Evapotranspiration data and soil-moisture sensors can aid in these irrigation decisions.
May 15 Freeze
Many growers are still assessing crop injury from the May 15, 2016 freeze event. At this point, fruit that has set, either king fruit or side bloom are beginning to show more significant signs of frost injury. If you have experienced a significant loss, please report it to your local Farm Service Agency office!  The more offices that heart the message, the greater likelihood of receiving disaster assistance.
Orchards with a minimal crop still need to manage codling moth, plum curculio and apple maggots. These insects, if ignored can cause significant problems in 2017. Fire blight, scab and powdery mildew are diseases which require continued monitoring and management. Pesticide applications may be reduced by utilizing spot treatments and applying mating disruption for codling moth. In bearing orchards with no fruit, we are less concerned about the potential impacts from mites, aphids and leaf hoppers. Injury from these pests may be unsightly, but can be easily managed during the next season.
Non-bearing orchards still need to be managed for vegetative growth and long-term health. This will require management of aphids and lepidopteran which feed on terminals, borers, scale, powdery mildew and fire blight. Direct-fruit pests are less of a concern on non-bearing trees.
Thinning
Please review Dr. Schwallier’s thinning recommendations from last week for a more in-depth discussion. Phil is suggesting growers avoid nibble thinning and wait until king fruit are beyond 10 mm before applying a thinner. Last week many growers applied Promalin within the 96-hour window in hopes of saving fruit injured by the freeze. John Aue has observed orchards where Promalin was applied and notes an obvious distinction between fruit that appear to no longer be growing versus those which are starting to swell. Fruit that are growing are now between 5mm and 10mm.
If chemical thinning is planned this week it is important they are allowed adequate time to dry and be absorbed into the leaf and fruit before a rain event. If we do have a light rain, trees are more likely to absorb additional thinner, than wash off. If trees dry before the rain we are less concerned about wash off. Waiting for an extended dry period may not have any utility, if the fruit grow significantly during the waiting period.
- Applications of NAA or MaxCel may be applied at lower rates, considering the unknowns about fruit set and how damaged fruits are influencing tree stress.
- Carbaryl is a more mild thinner and tends to reduce set to one fruit. If there is a dominate fruit, e.g., king fruit or a side bloom that has shown more growth than the rest, this will set while the rest will drop.
- 18 mm is the last size at which we can thin, which is close to the June-drop size.
Disease updates
Non-bearing trees: We are under an extreme warning for fire blight on first-year trees with open blossoms. Orchards with cankers have been developing a lot of fire blight bacteria and there is much more bacteria now than when we were in bloom. Fire-blight risk can be mitigated by removing blossoms, applying strep or copper to newly planted or non-bearing trees. Low rates of copper can be applied when open blossoms are open or about to open.  Another option is to apply a high rate of NAA and knock off all the blossoms.
Apple scab: We are beginning to find leaf scab showing up. Scab lesions may be found on the undersides of leaves.  If you are starting to find scab lesions, count leaves up from this year’s growth and identify which number leaf you are finding the scab lesion on. This can help determine which wetting event caused the infection. John is finding many scab lesions on leaf 3 and 4, vs. 1 and 2. By locating these lesions, we are narrowing the window of possible infections and can identify which infection may have caused the infestation.
Cedar apple rust (CAR): The risk of rust infections has largely subsided, though some rain events in Iowa are forecasted to have long wetting events and may still be at risk.  In southwestern Wisconsin, John Aue could not get galls harvested from red cedar to swell and inflame with spores when soaked in water. If we are concerned about CAR, remember that pressure from the pathogen increases during long and cool-wetting periods, which are not forecasted across Illinois, Minnesota and Wisconsin.
Powdery mildew (PM): We are now expecting more PM pressure from the higher temperatures and dryer weather that is forecasted. These conditions are excellent for powdery mildew and applying sulfur or a single-site fungicide will help manage PM.
Insect updates
Codling moth: Most growers should have experienced a flight over the weekend and need to determine if they had a biofix. Biofix is the first sustained flight of codling moth where at least one moth is captured in each or all traps for several nights in a row. Three moths in one trap but none in the other, does not necessarily indicate biofix, rather it is important we catch moths in more than one traps on consecutive nights!  Below is an example of flight captures from one orchard located in southern Wisconsin and would set 5/23/2016 as the biofix date:
|
Date |
Trap 1 | Trap 2 | Trap 3 | Trap 4 | Trap 5 | Trap 6 | Trap 7 | Trap 8 |
| 5/20 |
1 |
1 | 0 | 0 | 0 | 0 | 0 |
0 |
| 5/21 |
0 |
0 | 0 | 0 | 0 | 0 | 0 |
0 |
| 5/22 |
2 |
0 | 0 | 0 | 0 | 0 | 0 |
0 |
| 5/23 | 2 | 3 | 0 | 1 | 0 | 1 | 1 | 0 |
| 5/24 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
0 |
The total population for each generation emerges in the shape of a bell curve over a 600 to 900 degree-day period, where we typically have 1000 degree days between each generation of a biofix. This suggests that after 250 DD from biofix, only a small portion of the total population has emerged, i.e., 3%. Orchards with high pressure often apply the first larvacide at this time. When there is a period of time with an inconsistent flight, e.g., due to cool down or rain and this results in a new and stronger flight two weeks after the first biofix, we can delay the first spray to 350 DD. When this happens, more eggs are being laid with this second biofix in the first generation and we can maximize our sprays by delaying the first spray.
Note: It is not too late to apply mating disruption, or increase MD density and organic growers are highly recommended to use mating disruption. As discussed earlier, if we are in a wet period once we reach 250 – 350 DD base 50, it may be hard to apply conventional or organic larvacides.
Note: Remember these parameters for a flight. Â Codling moth fly between 6-11 pm and there is no flight when wind is in excess of 3 mph, temperatures are below 62 F or if it is raining.
Plum Curculio: We are expecting increased activity with the warm-evening temperatures, i.e., above 55-60 F and loss of fruit on wild hosts. Scouting is the primary tool for monitoring and determining a management threshold for PC.  Scout for crescent-shaped oviposition scars and adult weevils.  Beating trays can aide in scouting.  Effective monitoring requires we scout hot spots several times per week.  If damage is noticed on the perimeter of a block scout interior rows to determine how far PC has traveled into the orchard.  If a petal fall insecticide has already been applied continued to scout for activity.  In blocks with high pressure a perimeter and spot spray for PC may prove beneficial.  Our recent scouting across the region is showing plum curculio are now active. Additionally many of the wild hosts have been de-fruited by the freeze and PC will look for viable fruit to lay eggs on! Most injury over the weekend John observed was small-round feeding holes and not much oviposition injury. If organic growers are using pyganic, it should be applied at night since it lacks the piperonyl butoxide that is added to pyrethroids as a UV stabilizer.
The threshold for PC is one oviposition scar or one adult weevil. Once this threshold is reached an insecticide can be applied.  Note: Insecticides targeting PC should be applied on a warm night, when PC is most active.  Insecticides targeting PC can cease at 308 DD (base 50°F) from 95% McIntosh petal fall. It is expected that after 308 degree days, base 50°F, PC will no longer be moving into orchards from overwintering sites.  If no additional injury is found at this time, insecticide applications should be ceased. Heavy applications of surround may also help as a repellent. Options for perimeter and cover sprays for conventional growers include Imidan (phosmet), Avaunt (indoxacarb), Actara (thiamethoxam), and Belay (clothianidin).
Secondary-pest roundup
The importance or need to manage secondary pests will vary greatly. Growers with a limited crop may be less concerned about these pests, while growers with a full crop this year will want to keep these on their radar. There are many secondary pests and we will begin to discuss these as they become important. Below are some of the more notable secondary pests we have been observing.
- Spring lepidopteran: We are seeing a wide range of larval stages of green fruitworm and obliquebanded leafroller. Now is about the time when many growers see the terminal injury and large larva. Generally by the time these larva are over an inch long, they are nearly done feeding and may not ingest enough insecticide to be managed effectively.
- Aphids: We are beginning to see symptoms and populations of both rosy apple aphids (RAA) and wooly apple aphids (WAA). RAA first appear during pink in low populations and right now will have the appearance of causing leaf curling with the colonies on the insides of curled leaves. RAA will eventually move on to summer hosts and are only a problem in the spring. They can cause fruit deformations, which can be significant if populations become too large. WAA are just beginning to appear as little-white colonies the size of a pea in small cracks in the tree bark. If growers had severe populations last fall, treatments with Movento may be warranted, however, syrphid fly maggots and predatory wasps are an excellent biological controls of WAA and often provide excellent control of smaller populations. We typically see these predators in July.
- Scale: San Jose scale are reaching the adult stage. The best time to manage this pests is with our dormant oil and early applications of Esteem. There are some insecticides which still may be applied to target late nymphs but would prefer to manage the next generation of crawlers.
Resources
Cornell Scaffolds, May 23: http://www.scaffolds.entomology.cornell.edu/2016/SCAFFOLDS-5-23-16.pdf
Michigan State University, Apogee Application Timing for Apples: http://msue.anr.msu.edu/news/apogee_application_time_in_apples?utm_source=Fruit+Production+-+MSU+Extension+News+-+05-24-16&utm_campaign=Fruit+05-24-16&utm_medium=email
