As during previous years, the Penn State Fruit Research and Extension website located at: http://agsci.psu.edu/frec is again providing the information related to seasonal observations on insects and diseases (http://agsci.psu.edu/frec/growing-season-information).
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.
A critical time to control the second generation of pear psylla is during the first week of hatch of the young nymphs and then a repeat application should be made 12 to 14 days later.
The 2013 spring weather conditions created a fortunate pattern for combining effective management options for some of our most important fruit pests—codling moth (CM), tufted apple bud moth (TABM) and obliquebanded leafroller (OBLR).
Many growers applied chemical thinners during the week of 5/13 to 5/18, and the effects of these applications are just becoming apparent. The forecast for our region calls for temperatures in the high 80s to low 90s for Wednesday through Sunday, with lows in the mid-60s throughout that time. Under high temperatures, all thinning chemistries are more effective than when temperatures are more moderate.
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. 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.