Northwest Michigan fruit update - July 17, 2018

Sweet and tart cherry harvests are well underway; we will harvest tart cherries at the research station this week.

Weather and crop report

The trend of warm and dry conditions was temporarily interrupted by rainfall that totaled 0.29” at the research station on July 12-14. Temperatures have continued to be warm, in the 80s over the last week. Although the early part of this week has been cooler, temperatures are predicted to bounce back up into the 80s mid-week and drop down again by the end of the week. Wet weather is also in the forecast for the weekend with the greatest chance for rain on Friday, July 20 and Saturday, July 21; there is also a possibility of rain predicted for Sunday and Monday, July 22-23. According to MSU Enviroweather totals, we have accumulated 1965 GDD base 42 degrees F and 1322 GDD base 50 degrees F since January 1.

Sweet and tart cherry harvest is underway in the region, and we will begin harvesting tart cherries at the station this week. Small size of cherries has been a concern this season, and rain late last week helped to size some varieties. We hypothesize that hot and dry weather played a significant role in these smaller cherries, particularly sweet cherries, and we are currently collecting data to establish how much of a role weather played in fruit size. Apples quality is looking good thus far, and our high-density apples under irrigation at the station have been steadily sizing despite the lack of rainfall.

Pest report

Cherry harvest is underway, and most orchards have very little disease incidence as a result of a drier season. Cherry leaf spot infections were possible during variable wet weather late last week  July 13-14, but there is very little leaf spot in orchards at this time. American brown rot incidence also remains low, but we have received reports of isolated orchards with American brown rot infections. The current forecast is calling for a rainy weekend; multiple days of wet weather and high humidity will be conducive for diseases, and if cherries crack, the potential for brown rot will be concerning. Powdery mildew has also continued to spread at the research station as well as in commercial blocks.

Spotted wing Drosophila (SWD) trap numbers decreased last week, and we hypothesize that recent wet weather will stimulate SWD activity; traps will be checked and data will be reported later this week. Previous research has shown that hot and dry conditions like those we experienced in early July are related to decreased SWD activity. Despite lower trap catches last week, the total numbers of flies in traps this season suggest that SWD populations are higher this season than previous seasons. Fortunately, the weather has been conducive for good coverage and growers have been extra cautious with management programs to ensure clean fruit at harvest. Please refer to SWD Update for Cherry Growers – July 13, 2018, for additional information.

Most San Jose scale crawlers are settling down and developing protective waxy coatings that will cover the scales as they mature into adults. Most sprays will not be effective against crawlers that have developed this waxy coating. As mentioned in last week’s report, we will monitor for the late summer male flight and crawler emergence to assist growers’ with timing post-harvest management tactics.

Two spotted spider mite numbers have continued to build in tart cherry blocks at the station, and numbers are also building in commercial blocks. Mite management may be needed to prevent premature leaf loss.

Obliquebanded leafroller (OBLR) flight is ongoing and trap numbers have continued to decline this week. We continue to receive reports of larvae in commercial blocks. 

We have not detected cherry fruit fly at the station this season, but this pest has been detected in our region.

In apples, codling moth numbers were down to zero this week. Based on our biofix May 28, we have reached 966 GDD base 50 degrees F. Degree day predictions suggest that we will reach 1060 GDD base 50 by the end of this week. Although evening temperatures are predicted to be a little cooler for the next few days, we could see second generation flight by the end of the week or early next week as temperatures are predicted to warm again into the 60s in the evenings.

We have not detected apple maggot at the station at this time.

Table 1. Avg. number of cherry and apple pests in the NWMHRC trap line by date.

Cherry - NWMRHC

7-May

14-May

21-May

28-May

4-June

11-June

18-June

25-June

2-July

9-July

16-July

APB

0

0

5

6

7

7

6

0

1

7

22

LPTB

   

Set

4

11

11

3

1

12

4

4

GPTB

     

Set

1

0

1

0

0

1

5

OBLR

       

Set

0

8

19

10

1

2

CFF

       

Set

0

0

0

0

0

0

                       

Apple - NWMHRC

7-May

14-May

21-May

28-May

4-June

11-June

18-June

25-June

2-July

9-July

16-July

OFM

Set

0

0

0

0

0

0

0

0

0

0

STLM

Set

13

18

32

25

1

1

4

5

10

24

CM

 

Set

0

1

8

1

3

0

1

3

0

OBLR

       

Set

0

2

3

1

1

0

AM

               

Set

0

0

 

APB = American Plum Borer

LPTB = Lesser Peachtree Borer

GPTB = Greater Peachtree Borer

CFF = Cherry Fruit Fly

OFM = Oriental Fruit Moth

STLM = Spotted Tentiform Leafminer

CM = Codling Moth

AM = Apple Maggot

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