June 7, AppleTalk Conference Call

AppleTalk Conference Call Summary
Tuesday, June 7, 2016, 8:00 – 9:00 AM
Presenter: John Aue, Threshold IPM
Moderator: Peter Werts, IPM Institute of North America; questions or comments, pwerts@ipminstitute.org

June 7th Call download: Click Here

Monitoring trap updates

  • Refresh or hang lures for obliquebanded leafroller (OBLR), redbanded leafroller and dogwood borer (DWB). The first flight of OBLR occurs around 490 DD, base 50°F, from January 1st; DWB first flight occurs between 250-850 DD from January 1st.
  • If 1x or standard codling moth (CM) lures were hung May 1st, these need to be replaced. The field life for these lures is 4-6 weeks.
  • The field life for CM L2 “long-life” lures is 8-12 weeks. We typically hang these on May 1st and replace by July 1st.
  • Oriental fruit moth (OFM) and lesser appleworm (LAW): Long-life (L2) lures are available for OFM which also captures LAW, these will last 8-12 weeks.

Managing input costs for blocks with a light crop
Blocks with a reduced crop due to the May freeze need to consider that input costs could greatly exceed return on yield, e.g., mature semi-dwarfs with only one bushel of saleable fruit and located in the top 10% of the canopy.  If this applies to your blocks, apple scab, codling moth and apple maggot still need to be managed.  You have the option to opt out of managing plum curculio, leafrollers, mites, aphids, summer diseases and all the other secondary pests.

Codling moth could be managed using mating disruption where fruit load is light and codling moth pressure is low to moderate, e.g., less than 10 -15 moths/ trap/ week in most areas of the orchard.  This may be most suitable where a farm has only 10-20% of a full crop.  Using a half rate of a mating disruption product, e.g., 100 dispensers per acre with a base product cost $50/acre (plus labor), may effectively shut down 95% of the mating occurring in the orchard.  Mating disruption products include aerosol emitters, e.g., CheckMate Puffer CM-O, or individual dispensers, e.g., CheckMate CM-XL 100, IsoMate C TT.  Mating-disruption dispensers are generally the cheapest mating disruption product per acre, however have a higher labor cost to install.  Hand-applied dispensers may be more suitable for smaller blocks, but will require significantly more time to hang in the orchard than puffers.  The hang rate depends on the specific product, standard rates are 100-200 dispensers/acre; a higher rate is recommended for new mating disruption users and those with moderate to high pressure.  Aerosol emitters, “puffers”, offer growers a less labor intensive option since only 1-2 aerosol emitters per acre are needed, but may not be as suitable for blocks less than 20 acres.

Apple maggot will require monitoring at the usual densities, i.e., three traps per ten acres.  Blocks can easily be spot treated with several cheaper insecticides, e.g., Alias or Montana (imidacloprid).  Another option is to implement a trap-out program.  Matt Grieshopp, who runs the Organic Pest Management lab at Michigan State University will join us July 12 and may have some suggestions on how to best implement trap out or apply other low-input controls for apple maggot.

The light crop should not change how any non-bearing trees in the orchard are managed.  These trees still need to fill out their canopy and establish good vegetative growth.  Therefore, we are still concerned about aphids, leafrollers, powdery mildew and fire blight.

Apple scab and powdery mildew
Orchards without scab can continue to apply captan to protect against summer disease and black, white and bitter rot.  Maintaining a cover of captan will reduce incidence of rot infection which can occur if severe storms cause damage.  If scab is present continue using captan and avoid using systemic/single-site fungicides for secondary scab.

Where powdery mildew is a concern, foliar flagging should now be present.  Single-site fungicides provide protection against powdery mildew, whereas captan does not.  Where we don’t have scab, any of the single-site fungicides may be used without concern of losing efficacy for primary scab management.  If scab is a concern, and powdery mildew needs to be controlled it is recommended to use a powdery mildew fungicide that may no longer have activity on scab, these might include, Topsin (thiophanate-methyl), Rally (myclobutanil), possibly sulfur.  Do not use SDHIs or strobilurins, or the DMIs, e.g., Indar (fenbuconazole) or Inspire Super (difenoconazole, cyprodinil).  Note: Sulfur applications when made during hot weather, e.g., over 80°F, may cause russeting during application.  If applied under cooler conditions and warm weather follows several days later, the risk for russeting decreases.  Russeting potential decreases significantly when the sulfur, out of solution and dry on the plant surface.

Codling moth
Degree-day (base 50°F) updates from a May 23 biofix:

  • La Crescent: 256 DD
  • Lake City: 237 DD
  • Gays Mills: 258 DD
  • Woodstock: 276 DD

It is important to monitor LAW and OFM in blocks under mating disruption.  Injury from these pests looks nearly identical to CM injury and could help explain any injury that is found, where mating disruption is used.  For more information visit: http://www.fruit.cornell.edu/lof/ipm/pdfs/codling_moth.pdf.  This year we have had significant LAW flights in some orchards.  LAW and OFM are in the same genus which suggests that the pheromone lures for one species will catch both.  No thresholds are established for LAW, but higher numbers reflect a greater threat.  Three or four LAW per trap in a week may not be a concern, but more than 20 LAW/trap/ week could require treatment.  Oriental fruit moth are usually more of a concern in regions that grow a lot of stone fruit.

Plum curculio
Plum curculio (PC) migration from overwintering sites typically ceases at 308 DD, base 50°F, from petal fall.  Current degree-day accumulations from an approximate petal fall date of May 11 are:

  • La Crescent 342 DD
  • Lake City: 321 DD
  • Gays Mills: 332 DD
  • Woodstock: 359 DD

In areas with wild hosts who lost fruit due to frost, it is believed PC egg-laying activity may continue past the traditional 308 DD from petal fall, as females search for viable fruit to lay eggs on.  Therefore if fresh PC injury has been observed or if CM pressure is light it is suggested to treat the first CM spray with a material like Avaunt (indoxacarb), Assail (acetamiprid) or Belay (clothianidin) that have good activity on early CM and PC and to save the more expensive materials like Altacor (chlorantraniliprole) or Delegate (spinetoram) for peak-egg hatch (500 DD from biofix).  In uncontrolled orchards John has observed PC and apple curculio (AC) will continue to oviposit past July 4th.

If we find fresh PC injury, it is unclear how long they will keep moving and causing injury.  We have two really warm nights coming up (June 10-11) and female PC could be very active on these nights.  Organic orchards who expect they may have a population of females in the orchard could consider an application of PyGanic (pyrethrins), with the option of Surround (kaolin) added as a tank mix.  Applying this during the warmest night might help eliminate internal populations of PC.  To improve efficacy apply the higher rate of PyGanic.

Rosy apple aphid
Neonicotinoids applied for PC should have suppressed rosy apple aphid (RAA) populations.  Often begin to see signs of biological control from gall midge larva.  Rosy apple aphids eventually move to summer hosts which include broad-leaf weeds.  While unsightly, RAA are only an economic problem when a majority of the infestations are on fruit clusters.  Colonies on fruit clusters will result in deformed fruit.  If infestations are limited to water sprouts, RAA colonies are not likely as big of a problem.  Earlier blooming cultivars typically have more fruit injury.  Scout for RAA by checking rolled up or crinkled leaves.  Ants actively working through the canopy can also be a sign that aphid colonies are near.  John is seeing injury on Cortland.

Beneficials that can be found in the orchard at this time include: Gall midge larvae, coccinellids, e.g., ladybeetle larva and adults of spider mite destroyers, mullein plant bug nymphs, minute pirate bug adults, black hunter thrips and parasitic hymenoptera.

Woolly apple aphid
Woolly apple aphids (WAA) overwinter as nymphs on roots and migrate to shoots, tender bark areas and pruning cuts in the spring to create aerial colonies during the summer.  They have been a relatively minor pest the last several years, but in 2015 several growers had severe WAA explosions late in the season that resulted in fruit damage.  Traditionally we have waited to see if biological controls could manage WAA populations before targeting the colonies later in the season with a neonicotinoid.  If insecticides are required, the key to controlling WAA is understanding that small populations can grow rapidly in September.  Monitor and use historical pressure to determine if there is utility in treating population early.

Movento (spirotetramat) applied early, e.g. between 1st and 3rd, cover will offer the best control; apply with a penetrant, e.g., LI 700.  The product label recommends making a second application 14 days later where pressure is severe.  Unfortunately, the application window for Movento is before the impacts of biological controls can be assessed.  If Movento is applied for WAA this should be applied before the leaves harden off and no longer absorb a systemic insecticide.  Note: Do not apply with captan if a penetrant is used.

Many growers may be applying Delegate as their first or second codling moth insecticide.  Delegate has been found to be toxic to an important natural enemy of woolly apple aphid, Aphelinus mali.  You can learn more by visiting: https://www.nzpps.org/journal/68/nzpp_682990.pdf; http://www.northeastipm.org/neipm/assets/File/TFWG-Combs-WAA.pdf.

Green apple aphid/ spirea aphid/ apple grain aphids
Green apple aphid (GAA) alate (winged adults) are becoming visible.  Insecticides are rarely required to control this aphid, however, GAA do not move to alternate hosts and colonies will continue to spread and grow throughout the season.

San Jose scale
Scale has become a challenging and unpredictable pest in many orchards.  Light populations can leave unsightly blemishes on fruit, but severe infestations can lead to the decline and death of trees.  First generation crawlers are predicted to emerge approximately 500 DD after March 1st; current accumulation from March 1 are 580 – 620 DD.  Pre-bloom applications of oil and Esteem should have helped manage populations.

If you had scale last year, begin hanging black electrical tape with a layer of petroleum jelly on hot-spot locations.  Note: Traps need to be sampled weekly, since petroleum jelly turns scale dark.  We currently do not have economic thresholds, but have a low tolerance since there is also a high risk of false negatives, due to the limited ability to monitor scale.  Insecticides applied for WAA right now may help suppress 1st generation crawlers.  Movento may adequately control hatching eggs and scale crawlers but may not work on older nymphs that are in their last instar and molting into adults.

Leaf hoppers
White apple leafhopper (WALH) and potato leafhopper (PLH) may begin to show up in orchards.  Both species can reproduce within the orchard, however injury and species look different.  WALH are white and will move sideways across the leaf surface.  Injury to the plant appears as white speckling on the top.  These do overwinter in the upper Midwest and populations are often reoccurring in orchards.  PLH do not overwinter here and often are carried in on heat thermals and warm southern winds.  We have begun to see some adults in orchards and have not seen any nymphs.  PLH populations begin to increase after the 1st or 2nd cutting of hay/alfalfa each year.  Nymphs can cause economic injury to young orchards by stunting terminal growth and inducing some stress.  Generally large semi-dwarfs, e.g., M.7 and M.111 are not impacted by populations of PLH.

Between now and when terminal buds set is a critical time for weed control.  As forecasted temperatures begin to increase, so too will demands for water and nutrients of established and non-bearing trees.  Maintaining clean understory beneath the drip zone of the tree canopy with mechanical cultivation or herbicide applications are essential.  If you applied a residual herbicide last fall or early spring, you should have good control of weeds through the end of May and into early June.  Consider the following as you plan your next herbicide applications:

  1. Apply herbicides when weeds are actively growing and before they develop seed heads. Our goal is to suppress weeds with herbicides, cultivation or mowing before they go to seed.
  2. Know your target! Make 2016 the year we learn to identify some of these weeds, rather than just broadleaves or grass, determine if they are thistles, bindweed, nettles, shepherds purse, plantain, clover, sedges?
  3. Herbicide timing is often weed specific. Canada thistle is a good example of a weed that is often missed, you will have the best control if you can apply herbicides when it is less than 12” tall.  Morning glory, bindweed, and nettles are all weeds that growers have reported having a hard time managing.  If these weeds have been a problem, perhaps you should consider a different herbicide or see if your timing has been off.  Why keep doing the same thing if it has not been delivering results?
  4. Herbicide rotations and tank mixes need to be front and center in your weed management program. There are many herbicide choices for apples, but it takes some planning to be able to utilize the range of products we have available.
  5. Check the pre-harvest intervals (PHI) on your herbicides. Some products have 150 day PHIs.