West Michigan tree fruit update – April 24, 2018
First signs of spring are here, for a few days anyway.
Weather, degree days and crop stages
Cold weather continued to stay in place much of last week, but the weekend brought some temperatures that started to push fruit tree growth ever slightly forward. Cooler weather will move back in for the next several days and most likely keep everything at a standstill. The forecasts for next week are calling for a noticeable weather change with much warmer weather settling in – this will get things moving for sure.
Degree day totals for the general West Michigan area are very much behind normal average with many days seeing very few additions to the totals due to cold temperatures. The MSU EnviroWeather station at Sparta has accumulated 114 degree days base 42 which is 14 days behind the average for January 1 through April 24. Degree days base 50 at Sparta are 35 which is 20 days behind normal from January 1.
Tree planting continues as soil conditions are just about perfect right now to get this task done. Remember to keep the graft union at least 4 inches above the soil line if not higher to account for settling and therefore avoid the potential for future scion rooting.
Tree fruit diseases
There is some small amount of green tissue in apples in the earliest known sites and varieties. Most trees are stuck at silver tip. A few growers have started their copper sprays and I suspect many more will get that started in the near future. Copper sprays are best placed as close to green tip or even at ¼-inch green in apple to get the most longevity from this early apple scab and fire blight management tool. Copper applications in sweet cherry should be considered at this time as well to help with bacterial canker. Peach leaf curl sprays could be key this season if we continue to get a slow, cool weather pattern during bud swell, so best not to miss fungicides for this sporadic disease.
As for apple scab, I caught one lonely apple scab spore with the rain on April 12, 2018, and no more since then. We have had wetting events (snow, mostly) since April 12, but no infections due to the very cold temperatures and no green tissue to infect. With a delay to spring, spore numbers could be higher with the early season infections compared to a more typical year.
Tree fruit insects
We’ve got very little insect activity with such cool weather. There were probably a few green fruit worm and redbanded leaf roller adults flying about Sunday and Monday evenings with warmer temperatures. Black stem borer could become active at any time with warmer temperatures, probably next week. Start planning now for placement of oriental fruit moth traps in apples and stone fruits. Lures should be in place prior to flight, which could begin later next week. Dormant or delayed dormant oil sprays for San Jose scale, European red mite and aphid management could be applied at any time, but be mindful of freezing temperatures with oil and green tissue for a few days before and after oil applications. As green tissue expresses, oil rates should be reduced.