August 4th AppleTalk Conference Call

Posted on 04. Aug, 2020 by in Uncategorized

AppleTalk Conference Call Summary
Tuesday, August 4, 2020 8:00 – 9:00 AM
Presenter: John Aue, Threshold IPM, jgaue@mwt.net
Moderator: Peter Werts, IPM Institute of North America; questions or comments, pwerts@ipminstitute.org or send to Josie Dillon, jdillon@ipminstitute.org. 

August 4th Call Stream: CLICK HERE

Call Schedule

  • August 11th: No call this week.
  • August 18th: Final call of the season.

Regional update

Location Degree Days from January 1st

 (Base 50°F)

Petal fall Date Leaf Wetting Hours (LWH) from Petal Fall Codling Moth Biofix Date Degree Day Accumulation from Codling Moth Biofix (Base 50°F)
Eau Claire, WI 1605 May 28 228 June 1 1256
Gays Mills, WI 1717 May 27 134 May 24 1489
Hastings, MN 1777 May 27 150 June 1 1405
Rochester (Ela), WI 1617 May 31 164 May 24 1432
Trempealeau (Ecker’s), WI 1724 May 26 220 May 24 1472
Verona, WI 1706 May 29 171 May 24 1516

Table 1. Degree-day accumulations as of August 3, 2020 using data reported by Cornell NEWA Network.

John, Josie, and Peter have observed variation across the region in terms of overall pest pressure and second-generation codling moth. Some growers have high catches for second-generation codling moth, and have been managing high populations of mites, wooly apple aphids and leafhoppers, whereas some growers have had very little pressure.

This week, the weather will remain cool and evenings that drop below 62°F are too cold for codling moth flights and it will take longer to accumulate degree-days (DD) base 50°F. Some locations are only accumulating 10-15 DD base 50°F per day. Temperatures are to rebound into the mid-80s°F next week, but evening temperatures will still drop into the 60s. This will allow for a good amount of degree-day accumulations, even if it is too cool in the evenings for codling moths to fly. This suggests the next two weeks may have a spotty or inconsistent flight.

The best way to track second-generation CM biofix is to reset the degree day meter after the flight begins. Growers can restart at zero from second-generation biofix, rather than adding on degree days to the existing total, e.g., biofix at 1300 DD. Some growers have gone two weeks without an insecticide and are not catching any CM in traps or have not observed much in terms of insect activity. It is okay to wait until the 250 DD have accumulated in this case to target second-generation CM. It will take ~1000-degree days to complete the second-generation flight, which may go into the first week of September if the weather continues to remain cool.

Sooty blotch and flyspeck (SBFS) activity has been minimal and there are still several locations that have not hit 175 leaf wetting hours (LWH) from petal fall. Not all NEWA stations are recording relative humidity (RH) or precipitation correctly, which do add to the overall LWH count. Heavy dew can also add to LWH. Growers should test their weather station to see if LWH accumulate on mornings with heavy dew and precipitation. These locations that are reporting less than 175 LWH, probably have accumulated enough and would be ready for a treatment targeting SBFS. This does not mean that growers should not be applying a fungicide for bitter rot or black rot but is important to continue to monitor the growing LWH.

Foliar and soil sampling
Leaf and soil samples for nutrient analysis should be collected no later than the week of August 17th from this season’s growing shoots. The purpose of collecting the samples now is to inform nutrient management for next year. Samples may be sent to AgSource Laboratories (https://www.agsourcelaboratories.com/) or the UW Soil and Forage Lab in Marshfield Wisconsin (https://uwlab.soils.wisc.edu/). The UW lab includes soil and tissue samples for $25. Tissue sample pricing from AgSource Laboratories is dependent on your specific location. Contact your nearest lab for pricing options.

Soil analysis through AgSource includes the following soil-sampling packages:

  • Basic Package ($45) – includes: Soil Health Score, CO2Respiration, C:N Ratio.
  • Routine Package ($55) – includes: Soil Health Score, CO2Respiration, C:N Ratio.
  • Complete Package ($65) – includes: Soil Health Score, CO2Respiration, C:N Ratio

When collecting leaves, examine this year’s growing shoots and select several leaves from the middle of the shoot. Leaves should be collected from a representative sample of the block or variety. About 30 leaves are needed to have one cup of dry leaf material that will be ground up for the analysis. Samples should be separated by variety or by health of the tree. Analysis of unhealthy trees should be kept separate. We are unsure if the results in mixed-variety orchards would be skewed by collecting leaves from multiple cultivars and it is recommended to keep samples limited to specific varieties. Once we see nutrient deficiencies this time of year it may be too late to amend this year and results will be focused toward soil and tree health next year.

Insect management
Leafrollers
The first obliquebanded leafrollers (OBLR) of the second-generation flight were observed on the afternoon of August 4th in southern Wisconsin, however many locations are still likely waiting on the flight to begin. The second-generation of OBLR will hatch into late-August and can continue into September. This generation typically feeds on ripening fruit rather than on vegetative tissue. The OBLR larvae will only grow to a few millimeters in length before developing a pupa and going into diapause, where the OBLR’s growth and development is suspended until spring.

Redbanded leafrollers have a wider set of host species, fly further, and traps can capture a lot of males. We often times don’t see a lot of larvae hatching out in correlation with trap captures. This is not the case with OBLR, as female moths are more commonly captured.

The CM larvicides, e.g., Delegate (spinetoram), Altacor (chlorantraniliprole), will control these larvae, whereas the neonicotinoids, e.g., Assail, Admire Pro (imidacloprid), do not. The application rate for these insecticides is typically the same that is used for codling moth. Imidan (phosmet), had a real ability to become resistant to OBLR. We get little resistance with RBLR because of their wide-host range. Managing the second generation now, will reduce the overwintering population that may need to be controlled next spring. Three to five percent injury is possible at harvest and scouting needs to be used to determine if a treatment is warranted. A mistake with OBLR may discount an apple from US Fancy grade but is not usually a problem when selling pick-your own fruit since the injury is very small and there is no worm in the apple. Two traps per 20 acres is adequate to determine where treating is necessary.

The degree-day model for OBLR is based on a lower developmental threshold, 42-43°F. Using this lower-base threshold will allow degree days to accumulate faster. The important consideration is that no trap threshold exists to help time sprays. Typically sprays for OBLR are applied after large flights. Since OBLR have a narrower-host range and will not fly very far, trap captures are a good reflection of pressure within the orchard. Low captures of five or six OBLR, do not signify a problem. Captures of 15+ should be followed up with a typical spray we use for codling moth.

Michigan State and the Utah IPM program have similar degree-day models for OBLR. Utah suggests the first-generation flight occurs at 1025-1175 DD from January, 1 base 43°F. The flight for the second generation in Utah begins at 1100 and hatch begins at 1500. Michigan suggests that OBLR biofix occurs around 900 DD from January 1 base 43F. The peak moth flight for second generation OBLR will happen at 2300 from the biofix date and egg hatch will start at 2750 DD base 43°F.

The OBLR degree-day model is explained in the following two articles:

Apple maggot
Apple maggot (AM) pressure continues to vary from orchard to orchard. Early August tends to be the peak flight according to research and observations from Cornell University. In Minnesota and Wisconsin high apple maggot pressure has often been observed from early July through the end of August. It is important that late season control is maintained, and products like Assail (acetamiprid), Exirel (cyantraniliprole) and Imidan (phosmet) are used to kill the adult flies.

Blocks with attractive varieties that are almost ripe, e.g., Redfree, or with hand thinned or hail damaged fruit baiting a few red spheres or putting out additional traps may have utility to make sure trap are not showing false negatives. Baited traps do run the risk of drawing apple maggots in from outside the orchard. The Wisconsin Pest Survey Bulletin from DATCP mentions how many AM growers are catching throughout the state.

It is essential to continue monitoring for apple maggot through the end of August. At this juncture in the season we often ask, “How late do we need to monitor? If we catch AM on Labor Day weekend, do we need to spray?” Some literature suggests these late catches don’t need to be treated. An occasional catch is okay to ignore, but if you are getting multiple flies on multiple unbaited traps, you may need to apply an insecticide.

For growers using Imidan, there is no difference in the four-day restricted-entry interval (REI) for workers if applied at different rates, e.g., one lb./acre vs. four lb./acre. It is often recommended to use a low rate if just controlling apple maggot. More critically, when using Imidan, keep in mind the 14-day pre-harvest interval for apples and three-day pre-harvest interval for raspberries and blueberries. For growers who typically utilize Imidan to kill apple maggot flies later in the season, John has recommended a lower rate primarily to spare beneficial insects. John just recently had a grower increase the rate of Imidan from one lb./acre to two lb./acre for higher pressure of Japanese beetle along with apple maggot.

Assail is often a preferred insecticide for combined management of apple maggot and codling moth, especially late in the season. If a different insecticide is being used for second-generation codling moth, then products may be used for apple maggot management. The neonicotinoids have limited mortality on adult AM (two-to-three days) and increased mortality on eggs and their ability to hatch, plus repellency and avoidance of egg laying (up to 14 days). Rainfall following an application will impact efficacy. A final AM application of the season should be a material that has efficacy on the adult fly as well, like Assail (acetamiprid), Imidan (phosmet) or carbaryl. If a final product is applied that does not have efficacy on adults, this will result in maggots hatching out when residue efficacy is diminishing and may lead to metabolic resistance.

Note: Since neonicotinoids do not perform well against adult flies, trap captures will not be impacted by an application, whereas they would have been if a broad-spectrum material, e.g., Imidan (phosmet), were used. If pressure is localized spot spraying may offer adequate control.

Note: The fruit essence on baited traps is viable for one week and should be changed accordingly.

Second generation San Jose scale
John and Peter have observed San Jose scale (SJS) crawler evidence on fruit in the last three weeks. When SJS are killed, they will often fall off and leave a red “halo” on the fruit where the scale had bedded down. In an orchard where Beleaf 50 SG (flonicamid) had been applied for woolly apple aphid, extensive scale on a tree had been managed by two back to back applications of Beleaf applied in July. Beleaf has a supplemental label for SJS and codling moth in Wisconsin but is not labeled for SJS in Minnesota or Illinois. However, it is labeled for aphids including wooly apple aphid in all our midwestern states, and several states in the northeast including New York. Beleaf has a 21-day PHI.

The second generation of San Jose scale (SJS) crawler emergence is beginning. If you have found SJS on fruit or young shoots continue to monitor for this pest. As harvest begins, or while hand thinning, look for first generation adults (black cap stage) on fruit and continue to check scale tape on infested limbs for crawlers. Fruit injury should serve as the canary and John recommends continuing to maintain tapes on branches regardless of what you plan to do management wise. Second generation adults appear from late July through early September and the live young ‘crawlers’ from this generation can be found until a hard frost in the fall. When checking tapes, it is important to note that low trap captures do not reflect overall pressure, i.e., false negative, rather may indicate the beginning of the hatch. Catches of 10-15 crawlers in a couple of days or 10 crawlers on one tape with zero on all other tapes, may warrant an application. See the article below for more information managing summer generation and be aware of PHIs when selecting insecticides.

Second Generation San Jose Scale from The Jentsch Lab (Cornell): https://blogs.cornell.edu/jentsch/2018/08/06/san-jose-scale-2nd-gen-nymph-emergence-nearing-end-of-codling-moth-larval-emergence-6th-august-2018/

Woolly apple aphid
John has been finding several aphid mummies and is seeing some control via parasitic wasps. Though overall, beneficial insect activity has also been variable this year. Most orchards with woolly apple aphid (WAA) do not have any large colonies but rather sporadic smaller colonies. Some growers used a product at petal fall like Movento (spirotetramat) that has had longer term effects that may be reducing populations. John is seeing a few more WAA colonies than is comfortable seeing and doesn’t want them to be an issue going into September.

Growers need to keep in mind the pre-harvest interval (PHI) of products targeting WAA and mites. One product called Beleaf 50SG mainly targets aphids and some plant bugs but does have a 21 day pre-harvest interval. There is a supplementary label for Beleaf 50SG for CM and SJS, which would also have efficacy on aphids. This summer John worked with a grower that made two back-to-back applications for WAA. Another material is called Closer (sulfoxaflor) and is a translaminar, xylem mobile product. It goes through the leaf and moves within the tree via the evapotranspiration stream. It also has a narrow target pest list which includes aphids and SJS and has a seven day PHI.

Information on WAA from the Jentsch Lab (Cornell): https://blogs.cornell.edu/jentsch/2019/07/20/getting-wild-and-wooly-woolly-apple-aphid-management-july-20th-2019/

Dogwood borer trunk sprays post-harvest
Some locations across the region have had very high dogwood borer (DWB) trap captures, e.g., trap captures of 100 in a week. Orchards with low populations may only catch 10 moths in two weeks. Orchards with these high captures need to be inspected for frass at the graft union or even further up. If frass is found, it is recommended to treat these trunks. Fresh larvae are not likely to be found right now, but frass and pupa casing may be present at the graft union. Mating disruption will not cure an existing population in the orchard and would be used to prevent further infestations after an initial treatment is made.

Lorsban (chlorpyrifos) is the insecticide that has long been recommended to treat DWB. Lorsban is very toxic and very persistent. If applied with a lot of water, it soaks into the corky tissue beneath the bark, which is where DWB feeds. The label does not allow pre-bloom applications and is not allowed to come into contact with fruit or foliage. This must be applied with a hand wand and not with an herbicide sprayer. Lorsban should be applied with a minimum of 50 gallons per acre and should soak the tree. A study from Cornell in 2002 found that applications applied post-harvest provided season-long control of DWB the following year. This may also be beneficial because larvae will feed at temperatures of 40°F or above and if larvae are present, they will be working for several months on trees that may now look very healthy, before the trees go dormant. Therefore, a fall application may help manage larval populations that are active in late fall and early spring.

A grower commented that 50 gal./acre is approximately 10 fl. oz. per tree. Last year, the grower had one person on the sprayer while they walked behind with the hand wand and it does take a bit of effort. 50 gal./acre is the lowest recommended amount. It is important to really soak the trunk to allow the Lorsban to permeate the bark and enter the corky tissue.

John had one grower try a cultural control method called “trunk mounding”, where dirt is piled up around the graft union in an attempt to keep the DWB adults from laying any new eggs in the trunks. It will not kill the larvae already present. If the graft union is five inches or more above the ground, it may not be worth the effort to move so much soil.

Scaffolds (Cornell) article discussing Lorsban trunk sprays for DWB: http://www.scaffolds.entomology.cornell.edu/2015/SCAFFOLDS%204-20-15.pdf

Mites
European red mites (ERM) and to a lesser extent two-spotted spider mites (TSSM) have continued to be a problem in orchards where predators have not been successful at managing the populations. The threshold for August is 7.5 mites per leaf and while it is relatively easy to count ERM, populations of TSSM can be much more difficult to assess due to their webbing and size and do not have a specific threshold. The predator complex will be more effective with the cooler weather this week. The cooler weather will also allow for applications of oil.

Organic producers do not have many options for mite control, though many oils are OMRI approved. Oils should be applied in cooler temperatures, and most days in July were likely too warm for an application. Some larger growers have had problems with resistance developing to most of the miticides that are commercially available. As a result, one grower has experimented with summer oils this year and used a product called JMS Stylet oil, which is a paraffin based mineral oil. It is approved for organic use and has been in use since the 1960’s. Nutrien in Galesville, WI does have this product. Apply at a 1-2% rate per acre and John recommends using more water as it will increase the chance that the mite will suffocate. Keep in mind that when using oils, it will also kill predator mites.

If bronzing is still occurring while mite populations are below threshold, action is required to prevent further economic injury to the plant. This happens when a population of predators have remained active long enough to keep populations below threshold, yet enough mite feeding has occurred to cause leaf bronzing. Once leaf bronzing occurs, economic injury is happening to the tree and a miticide should be applied. This scenario is referring to what we call mite days, where the duration of mite activity is just as important as the actual population. If we reach threshold and still cannot see significant damage on any leaves, we may be questioning whether we need to make a miticide application.

Disease management
Bitter rot

In varieties like Honeycrisp, be on the lookout for red dots on fruit that are the early start of bitter rot lesions. John is just now beginning to see bitter rot growth expanding. If trees have a big canopy, make sure to look inside the canopy for lesions. The lesions that were observed a few weeks ago have now grown exponentially and a lot of smaller lesions are beginning to appear. Examine the orientation on the fruit because as branches bend from the cropload, the fruit orientation changes. Spores released from large lesions will affect where captan residue has washed away. If possible, remove fruit with large lesions and/or fruit that are oozing.

Pre-harvest interval reminder

Product Pre-harvest Interval
Actara (thiamethoxam) 0 – 2.75 oz./acre: 14 Days
2.75 – 5.5 oz./acre: 35 Days
Altacor (chlorantraniliprole) 5 Days
Assail (acetamiprid) 7 Days
Avaunt (indoxacarb) 14 Days
Captan 80WG (captan) 0 Days
Delegate (spinetoram) 7 Days
Esteem (pyriproxyfen) 45 Days
Exirel (cyantraniliprole) 3 Days
Flint (trifloxystrobin) 14 Days
Indar 2F (fenbuconazole) 14 Days
Luna Sensation (fluopyram, trifloxystrobin) 14 Days
Merivon (pyraclostrobin, fluxapyroxad 0 Days
Pristine (boscalid, pyraclostrobin) 0 Days
ReTain (-trans-2-Amino-4-(2-aminoethoxy)-3-butenoic acid hydrochloride 7 Days
Topsin (thiophanate-methyl) 1 Day

List of pesticides and pre-harvest intervals http://cpg.treefruit.wsu.edu/pesticide-intervals-impacts/preharvest-intervals/

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