Horticulture Update

We received much needed rain in most corners of the state; however, growers may still want to monitor for irrigation, as the rain received was helpful, but may not have saturated the soil. Slow-release fertilizer and many herbicides require rain to be effective. So, growers should monitor fields to see if an effect is observed before reapplying, particularly where herbicide was applied over the past weeks.

We are approaching the first pick harvest for early season cultivars like ‘Patriot,’ the “blues” (‘Bluetta,’ ‘EarliBlue,’ and ‘Blueray’), and ‘Duke’. The recent bouts of rain make fruit rots like Colletotrichum spp. more prominent (see Time Miles’ note below). With the exception of ‘Duke,’ most of these early-season cultivars are susceptible to this disease. Overhead irrigation should be minimized to manage Colletotrichum. 

Pest Update: Insects

Blueberry maggot flies have been trapped in the past week in SW Michigan. This includes in Berrien County and in Ottawa County. Catches are very low in commercial farms, but this still indicates that their emergence was triggered by the recent rains. This is in line with ripening of the earliest varieties and highlights the need for growers to be monitoring for this pest and managing it. The dry weather has delayed SWD emergence and population growth this season, so be sure to monitor BBM this season to know if you need to start fruit protection against this pest.

Disease Update

We have received rain throughout much of the state and there have been several infection events for Colletotrichum spp. (causal agent of anthracnose fruit rot). This fungus is splash dispersed from old stems and buds and infects fruit with as little as 6 hours of leaf wetness. The most effective fungicides belong to FRAC codes 3, 7, 9, 11, 12 and 29 to control this disease. Since we are approaching harvest, it might make sense to utilize a product that contains FRAC 12 because it will provide additional control for Alternaria fruit rot and Botrytis fruit rot.  

Don't Guess, Test!

Growers have been submitting samples to the diagnostic clinic that range from stem blights to viral symptoms. Remember the Michigan Blueberry Commission has a program to subsidize any testing through MSU Plant & Pest Diagnostics. Click below to get more information about how to submit a sample.