West central Michigan tree fruit update – July 21, 2022
Tart cherry harvest is continuing across the region. Warm weather this week is advancing fruit growth in apple, pear and peach.
The temperature has been warmer over the past few days with high temperatures in the 80s and lows in the 50s and 60s across the region. The rest of the week will cool slightly with highs in the mid to upper 70s. Fruitlets of apple, peach, and pear continue to grow steadily while cherries are mature and are being harvested (Figure 1).
Based on the Hart weather station for July 21, current degree-day (DD) accumulation is 1933 DD42 and 1224 DD50 (Figure 2). Accumulation of DD has increased by about 179 DD42 and about 132 DD50 over the past week. Degree day accumulation is similar to the 5-yr average according to Enviroweather.
On July 12, heavy rains provided much needed water to increase soil moisture available to trees. Weather stations across the region reported 1-2 inches of rainfall. Scattered thunderstorms may develop later today on Thursday, July 21, and Saturday, July 23.
Watch the current and longer-term weather report presented by Jeff Andresen, MSU Department of Geography, Environment, and Spatial Sciences.
Weather data was gathered from MSU Enviroweather.
More information and reports on normal weather conditions and departures from normal can be found on the NOAA Climate Prediction Center website, NOAA U.S. Climate Normals website, NOAA Climate Normals Quick Access Page (which may be searched by region) and Midwest Regional Climate Center website.
For many growers, sweet cherry harvest has finished, and tart cherries continue to be harvested. Some growers will be finishing harvest this week while others will continue harvest through next week. Apples, pears, and peaches continue to grow and size well.
Apple varieties in Oceana County have average fruit diameters ranging from 50 - 65 mm. Early varieties, such as Zestar, have diameters ranging from 60 - 65 mm. Average fruit diameter for Honeycrisp was 56 mm, and for empire, average fruit diameter was 46 mm. Predicted harvest dates are now available from MSU Extension.
Peaches have been thinned throughout the region, and average Venture peach diameter was measured at 44 mm in Oceana County.
Pear fruit diameter was measured at an average of 45 mm for Bartlett in Oceana County.
Pest and disease update
In the west central region, growers should continue scouting blocks to target hot spots for active pests in the orchard according to growth stage. Woolly apple aphids have been reported across the region. Japanese beetle adults are now present as well. Oriental fruit moth was trapped in Oceana County with an average of 9.5 moths per trap. Codling moth was also trapped this week with an average of only one moth per trap.
Dogwood borer numbers decreased this week (average of 29 per trap). Lesser peach tree borer, American plum borer and peach tree borer were trapped in a tart cherry block in Oceana County, and numbers of adults have been declining. Adult obliquebanded leafrollers were also trapped this week with an average of three adults per trap. Spotted wing drosophila (SWD) were found in traps this week in Oceana County but trap numbers remain low. Apple maggot was trapped this week with an average of one apple maggot adult per trap.
Low numbers of aphids were observed on peach and apple leaves this week. Woolly apple aphids have been reported in many orchards throughout the region.
The moderate dry weather has helped keep some diseases at bay this season. American brown rot has been found in some tart cherry blocks this week. Growers should consider protecting trees against cherry leaf spot after harvest to keep trees healthy. Powdery mildew has also been reported in cherry and apple and growers should monitor blocks where disease pressure has been high in the past. Scab lesions were observed in apple and pear in the region, and some observations of cherry leaf spot were reported. In addition, fire blight strikes in apple and pear orchards continue to be reported. Growers should scout orchards to monitor for fire blight symptoms and remove disease branches as soon as possible.
American plum borer was trapped this week with an average of 15 adults per trap. Our tools to manage American plum borer are limited with the loss of Lorsban (chlorpyrifos). Growers should continue to monitor borer populations. American plum borers are attracted to wounded trees, and wounds allow easy entry for borers into the tree cambium tissue. Growers are encouraged to minimize tree stress and wounding when possible. For more information about the borer pest complex and control alternatives, read “Control alternatives for borer pests of tree fruits” by John Wise and Julianna Wilson, MSU Entomology.
Codling moth biofix is predicted to be in the second generation according to Enviroweather for Hart. Adults have been caught in two locations in Oceana County the past 2 weeks. Only one moth per trap was caught on July 18. Egg lay was predicted to occur on July 18, and first egg hatch is predicted for July 22.
Dogwood borer was observed this week in Oceana County with an average of 29 borer adults per trap. Adult emergence is typically in mid-June, and egg laying occurs over a four-six-week period. Trees with burr knots (adventitious roots) are highly susceptible to dogwood borer infestation. Burr knots typically develop on the above ground portion of the of clonal rootstocks. Dogwood borer larvae feed inside the burr knots, and if larvae continue to feed below the bark, damage can eventually girdle the tree. If trees are infested with borers, growers should consider treating with Assail. For more information about the borer pest complex and control alternatives, read “Control alternatives for borer pests of tree fruits.”
Peach tree borer was observed in traps this week with an average of 4 borers/trap. Management for borers is limited this year with the loss of Lorsban (chlorpyrifos). For more information about the borer pest complex and control alternatives, read “Control alternatives for borer pests of tree fruits.”
Lesser peach tree borer has been observed in the region this week with an average of 15 borers/trap in Oceana County. Management is similar to greater peach tree borer, and more information about the borer pest complex and control alternatives, read “Control alternatives for borer pests of tree fruits.”
Obliquebanded leafroller adults were found in traps this week with an average of three adults per trap. Larvae were also observed on leaves of apple and tart cherry trees in Oceana County this week.
Oriental fruit moth biofix 2 was predicted to have occurred on June 22 for the Hart weather station. On July 18, an average of 9.5 moths/trap were reported in Oceana County. Adult flight has increased from last week. Early egg hatch should be also underway, and cover sprays in stone fruits are critical to prevent shoot and fruit infestation. Monitor for shoot flagging – particularly non-bearing and nursery trees where oriental fruit moth can do a lot of damage.
San Jose scale is present in some orchards in the region. First generation crawlers were observed on June 14. Targeting the first-generation crawlers will prevent mating and reproduction and will minimize the population of second-generation crawlers which typically emerge in mid-August. For infested trees, targeted sprays or oils can be used to manage scale until crawlers develop a waxing coating. Growers should monitor in blocks where scale was present on fruit in 2021. San Jose scale may feed on apple, pear, plum, apricot, and sweet cherry. See “Summer options for controlling San Jose scale in Michigan tree fruit crops” to review summer options for controlling San Jose scale.
Spotted wing drosophila (SWD) were observed in low numbers this week with zero to four SWD per trap. Hot and dry weather will keep SWD activity low during the day, but they will be more active during cooler times of the day in the morning and evening. The Enviroweather model for Hart is predicting high risk for SWD since fruit is ripe which will continue through harvest. Pest pressure appears to be lower this year than in some years.
Woolly apple aphid has been found throughout the region over the past few weeks. When scouting for woolly apple aphid, feel in the white fuzz to make sure aphids are still alive. The fuzz will remain even if the aphids are dead. There can be several individuals in that white fuzz. It will be important to manage woolly apple aphid so they do not because a nuisance in the canopy at harvest. Check out this video of woolly apple aphid in action.
For woolly apple aphid management recommendations, see “Managing woolly apple aphid.” Julianna Wilson is looking for woolly apple aphid populations to sample from across our region. Please contact Emily Lavely at email@example.com if you have woolly apple aphid that could be sampled from your blocks.
Apple scab: Primary scab is officially over. After the last rain, no more spores were observed on spore rods at an orchard in Oceana County. While highly unusual, primary scab spores were released later this season compared to normal years. This may be due to 1) low number of rain events that occurred this spring and 2) some rain events occurred at night when spores are not likely to be released.
Cherry leaf spot: Risk of infection by the cherry leaf spot fungus, Blumeriella jaapii, continues to be low; however, recent rain events may lead to some cherry leaf spot development. Cherry leaf spot should be managed in both bearing and non-bearing orchards. Some cherry leaf spot infections have been reported in the region, but cherry leaf spot incidence is low so far this season.
Fire blight: Growers are encouraged to scout for symptoms of shoot blight and continue management with an Apogee and Actigard program if needed. If growers suspect the presence of streptomycin resistance in their orchard and would like infected tissue to be tested for resistance, please contact Emily Lavely at firstname.lastname@example.org or George Sundin at email@example.com. For some orchards in the region, shoots with blight were tested for streptomycin resistance. Presence of the fire blight pathogen, Erwinia amylovora, was confirmed, and streptomycin resistance were confirmed.
Powdery mildew: Warm temperatures this week may result in powdery mildew infection, but infections should lessen now. Powdery mildew causes infections on the underside of the leaf that leads to chlorotic patches or spots on the upper side of the leaf. Growers should continue to spray for powdery mildew through midsummer.
For pest and disease management recommendations, please refer to the E-154 for product guidelines.
For more information about regional reports, please visit the Michigan State University Extension webpage.