West central Michigan small fruit update – June 27, 2017

Blueberry harvest started in Allegan, Van Buren and other southern counties. Fruit quality is excellent but for some early varieties, fruit size could be an issue due to the loss of king blooms to late spring frosts.

Weather conditions in west central Michigan continue with daily temperatures in the low 70s with a few rain showers. For the past seven days, the daily minimum temperatures averaged 57 degrees Fahrenheit and the daily maximum 73 F. Also, a few rain showers over the same period left approximately 0.5 inch of rain in the area. Depending on the location, total precipitation accumulation in west central Michigan ranges from 15.5 to 17.5 inches since Jan. 1.

Regarding the conditions of small fruit crops, strawberry harvest is over for the most part, but a few fields still are open taking advantage of the prevailing dry and cool weather. Fruit has been of excellent quality and with a few fruit root problems.

One concern for strawberry growers should be the presence of the spotted wing Drosophila fly in strawberry fields. This season, the fly has shown up very early in strawberries. In the past, we found the pest only on day-neutral strawberries in late July. Michigan State University Extension recommends agricultural practices like renovation or elimination of unproductive fields to prevent the buildup of large spotted wing Drosophila population on unattended fields.

The removal of alternate host for the reproduction of the spotted wing Drosophila is very important for those growers that, in addition to strawberries, also produce raspberries and blackberries. Elimination of alternate host species prevents a large buildup of spotted wing Drosophila at the time of ripening of these other berries.

Blueberries, on the other hand, are in harvest in Allegan, Van Buren and other southern counties. Although fruit quality is excellent, for some early varieties fruit size could be an issue due to the loss of king blooms to late spring frosts.

For early varieties like Bluetta, Duke and others, the early harvest could be complicated by the presence of the spotted wing Drosophila. As of June 27, spotted wing Drosophila is already present in blueberry fields being hand-harvested. Our last inspection of spotted wing Drosophila traps deployed last week yielded an average of 9 spotted wing Drosophila flies per trap and 95 percent of those were overwintering females.

Blueberry fields need to be sprayed as soon as the flies are detected. There is not waiting time between the arrival of the flies and the infestation of the fruit. That has been reported by MSU Entomology professor Rufus Isaacs through research he has conducted in west Michigan since 2015.

Also, there is not an economic threshold for spotted wing Drosophila control. The economic threshold is the insect’s population level or extent of crop damage at which the value of the crop destroyed exceeds the cost of controlling the pest. In the case of spotted wing Drosophila, its reproductive potential and the short time between generations make it almost impossible to establish a number of flies that need to be caught on traps before you start spraying.

Based on that, if you are harvesting and you are finding spotted wing Drosophila in your traps, spray immediately after removing the fruit. On the other hand, if you are going to start harvesting in a few days and the flies are already present in your field, do not hesitate to spray before harvesting. That will prevent headaches when you deliver the fruit at the packing facilities. 

Before spraying, check the weather conditions for the next 24-72 hours to determine what class of insecticide you need to use in your field. Remember pyrethroid insecticides are affected by high temperatures but are excellent tools at low temperatures and not affected by rain. Lannate and Brigade, and to a lesser degree Imidan, are not affected by high temperatures and remain in the fruit if rains occur after the application. Other alternatives can be found at the MSU Extension bulletin E0154 “Michigan Fruit Management Guide”. If you need assistance with your spray program call your local MSU Extension office. There you will be directed to the right person that will be able to assist you with your questions.

2017 Blueberry Pre-Harvest Meeting

Blueberry harvest is already underway and Growers need to review their controls for spotted wing Drosophila and fruit diseases management at harvest time. This season we will host only one pre-harvest meeting. Our blueberry pre-harvest meeting will take place Thursday, June 29, 2017, from 5 to 8 p.m. at the MSU Trevor Nichols Research Center , 6237 124th Ave., Fennville, MI, 49408.

Growers attending this meeting will receive two Restricted Use Pesticide credits. This meeting is free but we ask you to pre-register so we will be able to estimate the number of handouts and refreshments. Those with special needs may request assistance by calling the meeting hosts.

For Van Buren County, call Mark Longstroth at 269-873-8983 or email .(JavaScript must be enabled to view this email address).

For Ottawa County, call the Ottawa County MSU Extension office at 616-994-4540 or email .(JavaScript must be enabled to view this email address).

For registration and the meeting’s agenda please visit 2017 Blueberry Pre-Harvest Meeting.

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