July 25, AppleTalk Conference Call

AppleTalk Conference Call Summary
Tuesday, July 25 2017, 8:00 – 9:00 AM
Presenter: John Aue, Threshold IPM
Moderator: Peter Werts, IPM Institute of North America; questions or comments, pwerts@ipminstitute.org

July 25th Call Stream: CLICK HERE

Grower  question: Japanese beetle
Japanese beetles (JPB) have one generation per year and emerge over a long period, beginning in late June through August and live for over 30 days.  It often seems like there is one large brood in July and then sometimes they don’t come back for the rest of the season.  John has observed a phenomenon with the JPB, where a growing population finds a desirable host, e.g., apples, raspberries or grapes, and then they only infest one variety, e.g., Honeycrisp.  However, this year JPB has been widely observed across varieties, with lower population concentrations.  John’s theory is they need a critical mass with the aggregation pheromone that pulls them all into one location.  Comparatively, where it is a light year in the population they seem to have a more dispersed population.

Insecticide options for this pest are rather limited.  Neonicotinoids, e.g., Assail (acetamiprid), Actara (thiamethoxam), will offer good repellency if applied before large aggregations of JPB begin to appear.  If populations are large, applying a “knock-down” or contact insecticide, e.g., organophosphate or PyGanic (pyrethrins), may offer good control.  This year John has found a combination of 1 – 2 lb. of Imidan (phosmet) tank mixed with a neonicotinoid may give better management of this pest.  Carbamates, e.g., carbaryl, also work, but are much more disruptive to biological controls and other natural enemies that may be active in the orchard.  If you are avoiding organophosphates, carbamates or pyrethroids, then it is very critical to make an application of a neonicotinoid at the first sign of their feeding injury and before the aggregations appear.  If imidacloprid products are applied for AM, e.g., Wrangler, Alias, Montana, these should also offer some repellency and anti-feeding properties for Japanese beetle.

Organic producers have the option of applying neem (azadirachtin) oil products, e.g., Azadirect, Trilogy, or PyGanic.  It is important to be aware that a botanical insecticide such as neem may be phytotoxic if tank mixed with other pesticides.  The new product called beetleGONE! (Bacillus thuringiensis galleriae) is out of production for 2017.  Last season an IPM grower used it on raspberries, for the short pre-harvest interval, and definitely found that it performed well.

Cautionary note on vinyl-spiral-tree guards
Be aware that certain vinyl-spiral-tree guards do not expand as the tree grows and can constrict and girdle the trees if they are not adjusted seasonally.  Trees with severe constriction are often found with dead vascular tissue in the trunk, which can lead to infection by a whole host of diseases that may cause the tree to slowly collapse.  This year, phomopsis and cytospora cankers have been isolated from trunks where tree guards were used and these infections are not the typical black or white rot cankers that are normally seen.  These diseases cannot be eradicated from the tree.  If you have spiral guards now is the time to inspect the trunks and determine if they need to be loosened as the trunks will continue to grow and expand until early fall.  Not all spirals are created equally and none of them should be depended on to expand.

One of the primary functions of the spiral tree guards is to protect against rodent injury and if they are forgone other practices need to be implemented to avoid injury.  Good weed management and maintaining a weed-free area around the trunk, e.g., herbicide/cultivation strip, will help reduce the attractiveness of the trees as a food source.  Additionally, close mowing and cleaning up dropped fruit in the fall will also help reduce desirable habitat and food sources.  If rodenticides are used, apply the product directly to the tree rows or use bait station; avoid broadcasting grain-based rodenticides to reduce the risk of non-target birds and mammals consuming the poison.  In new blocks close to hedgerows or woods mouse guards may be the best option to protect against injury, just be aware of the maintenance requirements when installed.

Wet soils
Flooded orchards and soils saturated for more than a week create a severe risk of tree stress and conducive conditions for root injury from soil pathogens, e.g., Phytophthora, and roots drowning from lack of oxygen, as the soil biota becomes anaerobic.  Significant death of tree roots can occur after three weeks of over saturation in an anaerobic environment.  We don’t need water on the surface for this type of injury to occur.  John recommends that if your trees have been sitting in saturated soils (if you take soil and squeeze in your fist and it stays in a clump) to apply a phosphorous acid fungicide, e.g., Aliette, Fosetyl-Al, Phostrol, Rampart, after the soil has dried out a little bit.  If you have wet soils apply to everything one year old and everything else.  The phosphorous acid fungicides are highly systemic and short acting and all function the same way.  They are applied as a foliar spray – absorbed through leaves and are translocated into roots where the fungicide change the environment around the root hairs that kills back Phytophthora and soil-based pathogens.  We can get resistance to these fungicides when over used.  Additionally, make sure to look at the pre-harvest intervals on these fungicides.

Pesticide wash-off
Diseases are not as forgiving as our insect thresholds and with the rain we are experiencing, we may need to be reapplying fungicides more often than desired, whereas we might have a bit of wiggle room with reapplying an insecticide for pest like apple maggot.  When we are getting a lot of rain events and wash-off and have high humidity, diseases that have not been an issue can begin to show up.  John has observed pin scab on the inside of the tree canopy in an orchard that has otherwise been scab free for many years; pin scab is small and when scouting needs to viewed under magnification.

Rainfast characteristics of insecticides on fruit, John Wise, Michigan State University Extension, http://msue.anr.msu.edu/news/rainfast_characteristics_of_insecticides_on_fruit

Bitter rot
Characteristics of bitter rot, fruit: (Adapted from June 28 2015, AppleTalk Conference Call with guest speaker Patti McManus, University of Wisconsin- Madison)

  • Generally takes several weeks following infection before symptoms develop, may become visible before other rots.
  • Symptoms first appear as small, light-brown, circular spots. Many spots per fruit may be found.
  • Under high temperatures initial lesions may rapidly enlarge and change to dark brown in color.
  • 1/8 to 1/4 inch in diameter lesions are distinctly sunken or saucer shaped.
  • When lesions reach 1/2 inch in diameter, small, black fruiting bodies appear in the sunken lesion. Fruit bodies may be arranged in concentric rings.
  • Fruiting bodies will begin to ooze a gelatinous, salmon-pink mass of spores, which is washed by rains onto other fruit.
  • Beneath the surface of the spot, the flesh is light brown and watery in a cone or V-shaped area, with the small end of the cone toward the fruit center.
  • Cankers can form on vegetative tissue, but are rare.

Orchards that have received hail need to be scouted for bitter rot lesions around the cracked skin or bruises.  Lesions will be irregular shaped rather circular, if rot is found use magnification to look for black fruiting bodies and/or ooze a gelatinous, salmon-pink mass of spores.  Hand thinning is also a good opportunity to scout for bitter rot lesions.

If control is needed based on scouting or block history apply a strobilurin, e.g., Flint (trifloxystrobin), Pristine (boscalid, pyraclostrobin) or SDHI, e.g., Merivon (fluxapyroxad, pyraclostrobin), PLUS captan (4-5 lb./A).  If scab is present in target blocks apply a high rate of captan, alone.  Heat injury may be a predisposing factor to infection and fungicide can be applied before or shortly after a predicted heat-wave (= 90°F).  Applications need to be made on a 14-day interval when bitter pit inoculum is present and weather is favorable for infection.

In blocks where bitter rot is an annual problem, fallen fruit can be removed from beneath trees post-harvest.  Fire blight, black rot cankers and dead wood should be removed from trees during winter pruning and destroyed to reduce sources of overwintering inoculum.  Additional information on bitter rot can be found at the links below: