The following general observations are offered to help you assess your apple crop load potential in 2013, and help you determine the appropriate action plan for chemical thinning. Close observation of your blocks may show bloom or fruit set that differs from our observations, in which case you should adjust your decision-making accordingly. Monitor your orchards for damage from this morning's freezing temperatures before making thinning decisions.
Below are the latest runs of the Cornell carbohydrate model. For most regions this past weekend showed carbon deficits but not very strong. The cool weather this week predicts a carbon surplus, meaning trees will be less responsive to thinners.
The 2013 season biofix for Oriental fruit moth was established on April 17, spotted tentiform leafminer on April 09, codling moth on May 06, and tufted apple bud moth on May 09. Obliquebanded leafroller adults are still not active (as of May 10).
The Cornell apple carbohydrate thinning model calculates a balance of apple tree supply to demand using the data entered from a chosen weather station. The general carbohydrate balance calculated has been found to correlate well with tree sensitivity to natural drop and with sensitivity to chemical thinners. Cool sunny periods of good carbohydrate supply lead to reduced natural drop and less response to thinners. Cloudy hot periods result in carbohydrate deficits and lead to stronger natural drop and stronger response to thinners. Beginning with this report, we will provide regular carbon balance updates for four regions of the state. These reports are part of a project being funded by a Penn State Cooperative Extension grant and the State Horticultural Association of Pennsylvania Extension Committee.
Fire blight infection conditions forecasted for May 10 to 12 are to be moderate to high. Possible apple scab infection conditions continue through the weekend.
Apple bloom stage across the state ranges from early pink in Bradford County to petal fall in Bucks County. Carbon balance models for various regions will be posted in the near future.
We evaluated the use of the Equilifruit disc, developed in France, as a hand-thinning gauge on three cultivars trained to tall spindle. While the disc was developed for trees that have been trained to the centrifugal system, our results suggest that the Equilifruit has potential as a hand-thinning gauge in tall spindle apple (Kon et al., 2012).
Retail Farm Market Schools will be held in Gettysburg on May 21 and in Stroudsburg on May 23.
The 2013 season biofix for the Oriental fruit moth was established on April 17 and for the spotted tentiform leafminer on April 09. Codling moth, tufted apple bud moth and obliquebanded leafroller adults are still not active (as of April 30).
Rain and winds moved through Pennsylvania from west to east on Sunday. Monday and Tuesday were cloudy and cool across much of the state. For those wanting to apply thinners weather conditions for thinning based upon SkyBit do not look promising for the remainder of the week.
Bloom is well underway for apples and pears. Be alert since this is a susceptible time for fire blight when conditions are favorable. Primary scab infection is still an issue. Dry weather diseases can still be problematic.
Dinotefuran received a time limited supplemental label for use on peach and nectarine trees, valid until Aug 31, 2015. Calypso 4F received an additional registration for use on stone fruit. The label for all products containing chlorpyrifos allows for only a single application of this ingredient-containing products per season, either as a dormant application or as a trunk application. Endosulfan remains registered for use on pears only until July 31, 2013 and on apples until July 2015.
Although the April weather continued the mix of cold and very warm days, insect development seems to be following a much more normal pattern than during the previous few years. While the biofix dates (first sustained moth flight detected by pheromone traps) for redbanded leafroller and spotted tentiform leafminer were a few days later than usual, April 6 and April 9 respectively, the biofix for Oriental fruit moth was established on the same day as during three other years in the last ten (April 17). As of April 26, we still have not yet established the biofixes for codling moth or tufted apple bud moth.
While the monitoring practices for our common pest species are relatively well defined, monitoring for the newly introduced pest species can be more challenging. A good example of such a challenge is exemplified by our effort to develop an effective monitoring system for brown marmorated stink bug (BMSB).
Monitoring insect pests continues to be one of the pillars of integrated pest management in Pennsylvania orchards. During the last fifteen years, the use of insect sex pheromone traps transformed from an intriguing tool used by researchers into a common pest management practice utilized by many growers.
While fruit bud development is later than last year, there is still the potential for freeze injury to flowers. There were some clear, cold nights this past weekend.
Two strawberry viruses, in combination, are causing problems for Eastern strawberry growers. The viruses (strawberry mottle virus, abbreviated SMoV; and strawberry mild yellow edge virus, abbreviated SMYEV) have now been discovered in Pennsylvania, and growers are advised to check plants propagated from runner tips obtained from Nova Scotia.
Penn State Fruit Research and Extension Center (FREC) faculty are planning a grower field day to be held Wednesday, July 17th, 2013, 1:00 to 5:30 pm. Participants will learn about the latest research on effects of invasive insect pests in fruit IPM programs, managing pesticide resistance for tree fruit diseases and the science of dormant pruning.
Apple bud stages range from green tip in the Lake Erie region of Pennsylvania to a few blossoms opening in Lancaster County. Peach bloom stages range from pink bud in State College to petal fall in Lancaster County.
Be on alert for early season disease development: We have optimal conditions for brown rot (blossom blight) on stone fruit and growers are encouraged to apply fungicides during this critical period. This also continues to be a critical period for controlling primary apple scab infection.