The weather during May 2014 has provided excellent conditions favorable for disease. Disease control recommendations are covered for fire blight, apple scab, powdery mildew, rust, and bacterial spot on stone fruit. This is an updated version of the Disease Update posted on May 14, 2014.
2014 season weekly average captures of adult moths in pheromone traps and accumulated degree-days base 43°F.
The after petal fall treatment on apples is the best time to control plum curculio and European apple sawfly. During the 2014 season, the after petal fall insecticide treatment on apples (and shuck split on peaches) should also be effective in controlling Oriental fruit moth.
Weather conditions affect an apple tree’s response to chemical thinners. The Cornell Carbohydrate model is an attempt to factor in the interaction of environmental conditions and a tree’s physiological status. The model utilizes temperature, solar radiation and day length based upon site-specific ground based measurements from a weather station in a grower's orchard.
Fire blight risk remains high through the week. When applying streptomycin, it is effective for 24 hrs before and 24 hrs after a rain event. Apple scab spore dispersal is peaking, and with the predicted rain events this week, we are in for a very rough, serious infection period. There is potential for secondary spread if fungicide protection earlier this year was less than adequate. The humid conditions are also optimal for mildew and rust infections.
Clopyralid is a selective, post-emergence herbicide that has been labeled in stone fruits for many years. The addition of a supplemental labeling for apples (Stinger https://tinyurl.com/k7me49m ) will allow growers to control several important problem weeds. Right now, prior to bud stage, in mid-May, is especially good timing for Canada thistle control with clopyralid.
In the majority of orchards no stink bug control activities are required at this time. It is time to start more intensive insect pest management activities in peach orchards. The petal fall treatment on peaches should focus on controlling Oriental fruit moth and plum curculio. Pheromone traps for monitoring spotted tentiform leaf miner, Oriental fruit moth, redbanded leafroller, European apple sawfly, codling moth, tufted apple budmoth and lesser peach tree borer should already be placed in orchards.
The apple blossoms are open and conditions are soon to be optimal for fire blight infection. Keep an eye on the weather for favorable temperatures and moisture since forecasts indicate May 9th to 12th (and possibly beyond) to be an infection period. Blossoms need to be protected.
Brown marmorated stink bug (BMSB) started emerging from overwintering shelters. In the majority of orchards no stink bug control activities are required at this time. If hand applied mating disruption materials are planned for the control of codling moth, Oriental fruit moth, dogwood borer, peach tree borer or lesser peach tree borer, now is a time to place dispensers in orchards.
Recently, there has been a lot of press related to pollinator health, and some troubling information indicates that certain fungicides, when used during bloom, can negatively affect the health of honey bees. This is a complicated problem with the solutions relying on understanding the detailed relationships among chemicals, pollinators and pest management needs. It is not prudent to treat this topic with a broad brush with statements such as "All neonicotinoid insecticides are bad for all pollinator species," or "No fungicides should be sprayed during bloom." Research is on-going, and we do not know all of the details yet.
Apple scab spores continue to rapidly mature and be released. With the expected rainfall accumulations predicted for tonight to Wednesday night to be at least three inches, the stage could be set for a severe apple scab infection period. Growers are encouraged to apply a spray prior to rainfall, particularly to susceptible cultivars and areas known for high scab inoculum.
Early season apple disease management is primarily directed at controlling scab. At 39°F, 28 hours of continuous wetting are required for infection, while at 61 to 75°F, only 6 hours are required. The Revised Mills Table in this article will help you calculate apple scab infection periods.
The 2014 spring temperatures—the lowest Degree Day accumulations in the last 10+ years—are keeping development of most insects at a slower pace than experienced during previous seasons. So far, all insect biofixes are later than in the past. It appears the lower temperatures, which are slowing the growth of plants, are also helpful in lowering the initial spring pressure from brown marmorated stink bugs.
The importance of knowing the weed species present and the extent of the spread can provide you with valuable insight on possible control strategies. The Penn State Center for Turfgrass Science developed this interactive site to help growers identify weed species. The chemical recommendations are not for tree fruit, and you will need to refer to Penn State fruit production guides for control options.
Weeds can surprise you with the amount of competition they create in the springtime, especially when they've been protected under snow or plastic and row covers. Here we'll discuss control of some of our common winter annual weed problems, and also two perennials.
Due to low winter temperatures and spring frosts, some peach varieties may have no crop this year. Below are some considerations for managing trees with no crop.
Significant damage to cherry flower buds was observed following the freezing temperatures last week. While some of this damage may have occurred during the winter, most appears to be recent.
I received a phone call from Dr. Greg Peck at Virginia Tech’s lab in Winchester, VA following last week’s freezing temperatures. Greg said that he was seeing a surprising amount of freeze injury to apple flower pistils. I mentioned that our minimum temperatures hadn’t dropped below the critical values for apple buds between half inch green and tight cluster, (23° F and 27°F, respectively).
Apple scab spores continue to rapidly mature and discharge. Rain and thunderstorms are forecasted for Tuesday, April 22, 2014, and combined with temperatures in the upper 60s to low 70s, these are once again great conditions for scab infection. Apple cultivars with green tissue need to be protected.
Apple scab spores are rapidly maturing and beginning to discharge. Combined with the rain and temperatures in the 60s, these are great conditions for scab infection. Early season apple cultivars with green tissue need to be protected.