If you still have a window for thinning apples, the majority of sites in Pennsylvania show a normal carbohydrate deficit, indicating that standard chemical thinner rates can be used.
The primary infection period for apple scab continues, although available spore numbers are decreasing. Growers should be scouting for fire blight infection thanks to the ideal conditions we have been experiencing throughout the month. In light of the hail some growers experienced this week, a reminder that diseases still need to be managed despite a damaged or minimal crop during the season. Going into June, growers need to be mindful about controlling for sooty blotch and flyspeck soon.
In the Biglerville area the 2015 biofix for Oriental fruit moth (OFM) was established on April 26; spotted tentiform leafminer on April 12, codling moth on May 07, tufted apple bud moth on May 10 and obliquebanded leafroller on May 21st (Penn State Fruit Research and Extension Center [FREC] orchards). According to the insect developmental model provided by SkyBit Inc. as of May 29th the egg hatch of the first OFM generation is already completed while the first generation egg hatch periods for codling moth (CM) and tufted apple budmoth (TABM) are underway and will continue for the next few weeks.
Based on weather station data, we had only low risk fruit rot events in both Pennsylvania and Maryland up until mid-May, when several warm rains soaked the region, leading to two to three dispersal events. There are likely more to come, which means that throughout the region, there is an increased risk leading up to harvest of strawberries, and bloom time for many fruit crops. Protection of these highly susceptible flowers and fruits is critical.
Whether you are in matted-row or plasticulture production, please be sure to remove the petioles from strawberry leaf samples that you send in to labs.
The bi-annual Penn State Fruit Research and Extension Center (FREC) Grower Field Day will be held Thursday, July 9, 2015. The Field Day program begins at 1:00 p.m. and concludes at 5:30 p.m. with dinner to follow. Arrive 12:15-1:00 p.m. to check in and view educational displays. To see pre-field day equipment demonstrations, arrive at 9:30 a.m. (Please Note: NEW start time). Concurrent research and educational sessions will be held throughout the afternoon. This event will occur rain or shine.
A band of strong storms blew through Pennsylvania and Maryland this afternoon. If you experienced hail, apply streptomycin to apple and pear trees within 24 hrs of the hail event to prevent trauma blight. More heavy thunderstorms are in the forecast until early Thursday. Please be on alert.
This is the time of the season when next year’s flower buds are initiating and beginning to form. Your return bloom program should begin after this year’s crop becomes unresponsive to chemical thinning but before the crop becomes sensitive to the ripening effects of NAA or ethephon.
Erin Dugan recently joined Penn State Extension as Specialty Crop Innovations Program Manager and Young Grower Alliance Coordinator.
Today's carbohydrate model indicates that most sites have a low deficit and that the standard thinner rates can be reduced by 15%. The one exception is the northeastern part of the state where a high deficit is predicted for today.
Carbohydrate model recommendations from today’s run call for increasing rates for all sites except for the northeastern part of the state. Fruit size in some locations is in the 15 to 17 mm stage, and the window for a thinning response to either NAA or 6-BA is rapidly closing. Saturday may be the best option for obtaining additional thinning in these sites. Where there is a potential for frost, avoid the addition of oil to the tank because oil can increase frost susceptibility.
To provide Asian pear growers with more sustainable, cost-effective thinning strategies, a SARE-funded team of researchers and farmers studied how effectively Asian pears were thinned by benzyladenine. They found that MaxCel, one of several chemical thinners that contain benzyladenine, can reduce the cost of hand-thinning by up to 50 percent while delivering fruit yields and sizes comparable to those of untreated, hand-thinned control trees. Rutgers University has produced a fact sheet that provides a brief introduction to plant growth regulators and directions on how to use MaxCel as a crop thinner for Asian pears.
Codling moth egg hatch is at about 10 percent and Oriental fruit moth egg hatch is at almost 100 percent. The flights of obliquebanded leafroller (OBLR) and peach tree borer (PTB) are expected to start within the next few days. Green peach aphid (GPA) (on stone fruit) and spirea aphid (SA) (on stone and pome fruit) colonies are being observed in some orchards. Watch for predator populations such as ladybird beetles or syrphid fly larvae.
The rain occurring today could have the potential to produce an apple scab infection event if adequate leaf wetness hours are achieved. Growers are encouraged to monitor conditions in their orchards and spray accordingly to protect for apple scab. In addition, be mindful of rust: the cedar galls have made their appearance, making spores available to cause infection in apple trees.
Temperatures will gradually increase to more seasonable weather beginning Monday. Bright sunny days with seasonable temperatures will mean it will be harder to remove fruits.
If the rain in the forecast comes to fruition this weekend, be prepared for a major apple scab infection period for the region. Growers in northern PA still in bloom need to be vigilant for fire blight conditions this weekend and next week. Although many are past bloom in the region, we experienced fire blight conditions from May 5 – May 12 and growers should begin to scout for infections during the coming week. Be on alert for powdery mildew infections, thanks to the dry weather lately. Control measures are needed to manage bacterial spot on stone fruit.
As the first insecticide application after petal fall should already be completed in most orchards, it is time to plan for the early summer control of other insect pests.
The MaluSim Carbohydrate model was run the morning of May 15 for 11 sites across the state. Results for May 15 through May 18 are predicted data based on weather forecasts.
Generally only a sporadic minor pest, green fruitworm is showing up in orchards across the state in much higher numbers than ever seen before.
All except the two farthest north stations have reported full bloom. This past weekend temperatures shortened bloom as most sites are either past petal fall or into petal fall.