Carbohydrate balances for the most part are positive across the state indicating the potential for trees to be less responsive to chemical thinner applications. (The exception is up along Lake Erie). IMPORTANT: Plant growth regulator label precautions supersede recommendations from thinning models when temperatures approach 90 degrees or higher.
The first treatment to control codling moth is needed early during the week of May 27th (around 250 DD50, 5 percent CM egg hatch on May 27th). If hand applied mating disruption materials (Isomate® or CheckMate® products) are planned for the control of CM, Oriental Fruit Moth (OFM), dogwood borer, peach tree borer and lesser peach tree borer, the dispensers should be already placed in the orchards. First generation Oriental fruit moth flight is winding down across the state. Plum curculio (PC) adults will need to be controlled for at least another week. Brown marmorated stink bug (BMSB) is continuing its movement away from overwintering shelters and feeding on multiple species of plants, most likely not inside orchards. All pheromone traps for monitoring fruit insect pests should already be placed in orchards.
Weather conditions are optimal for bacterial spot on stone fruit. Fire blight infection conditions forecasted through May 26. Bacterial spot and cherry leaf spot infection periods are also now posted.
Below are tables on four sites for the Cornell Carbohydrate model for apple thinning. Please note that values for May 21 and beyond are estimated forecasts.
Fire blight infection conditions forecasted for May 17 - 22 are high. Infection periods for apple scab, fire blight, cedar apple rust, and powdery mildew are being posted.
Below are the tables for the Cornell carbohydrate balance model from data derived from SkyBit and NEWA stations in Pennsylvania. The SkyBit stations are Wexford, Richfield and Morgantown. The NEWA stations are North East, Biglerville, Bendersville and York Springs. Remember that you should be looking at a multitude of factors when deciding on a thinning program. Following freezing temperatures at many locations on Tuesday morning, freeze damage assessment is an additional consideration. Be sure to keep good records as to when and what you apply as well as the results.
First generation Oriental fruit moth (OFM) flight is continuing across the state. Observations while in Erie County this week indicated that it is a good time to make an initial application to control hatching larvae. In southern counties, the second application of effective products should already be on. In Southern Pennsylvania, codling moth (CM) adults are active and, if needed, the first codling moth treatment should be planned sometime during the week of May 26th. In most orchards no special stink bug control activities are required at this time. Visual search for BMSB adults still remains the only reliable monitoring technique at this time of the season.
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.
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).
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).