Weekly Fruit Update - June 29, 2022

Photo: The fruit & vegetable Extension team toured farms along the north shore last week, including a community orchard in Grand Marais.

 

Author: Annie Klodd, Extension Educator - Fruit Production, kloddann@umn.edu

It's strawberry season! Insects and diseases to watch for this week are fairly similar to last week, but spotted wing drosophila, apple maggot and Japanese beetles are starting to appear in traps in very small numbers. We continue to experience dry, hot weather that reduces disease pressure.

Note about mentions of weather events: It's a big state, and we don't always know about the weather events in each region. Always check the NEWA model using a weather station in your area before deciding whether or not to spray fungicides.

Apples

Fruitlets are over 30 mm diameter near the Twin Cities, and were about 10 mm in Grand Marais when we visited last week. We observed that pollination was low along the north shore, probably due to cool temperatures during bloom.

Insects: Codling moth traps in White Bear Lake contained between 0-9 moths per trap. One apple maggot was caught in one trap, while all other traps contained zero apple maggots. This indicates that they are beginning to emerge in that area but do not need to be sprayed yet. Growers should watch for apple maggot using red sphere sticky traps, and use that to decide when to spray.

Diseases: Growers are unlikely to need to spray fungicide this week if the general weather forecast holds true. Weather conditions have been dry, which discourages pathogen infection, and we are also past the point of primary apple scab ascospore release. However, always check the NEWA model using a weather station in your area before deciding whether or not to spray. It's a big state, and we don't always know about the weather events in each region.

Grapes

Grapevine canes and clusters are both growing vigorously at this time. Grape berries are at about pea-sized. Complete fruit zone leaf removal at this time - this practice has several well-documented benefits. Research in the US has shown that pea-sized berry stage is a good time to do leaf removal around the clusters. It is early enough that the berries can acclimate to the sunlight without much risk of sunburn. Watch a video about leaf removal, from our friends at Penn State Extension, here: https://extension.psu.edu/grapevine-fruit-zone-leaf-removal

Diseases: Weather conditions have been dry, which discourages pathogen infection. Spots and lesions from phomopsis infection during pre-bloom may now be visible to the naked eye. However, the visibility of past infection does not necessarily mean that spraying now will be useful. Target sprays around rainfall events, which is when pathogens of most diseases spread. Growers are unlikely to need to spray fungicide this week if the general weather forecast holds true.

Strawberries

Demand for strawberry picking is high, and so are the temperatures! Strawberry harvest season is in full swing. A general feeling among growers seems to be that this season will be fast and furious.  

Once strawberry season wraps up, it will be time to think about renovation. Stay tuned for that in the next couple of weekly updates.

Raspberries

In the metro, floricane raspberries have set fruit. Berries are growing but are not ripe yet (except, perhaps, for some high tunnel berries). 

High tunnel raspberries are growing quickly. You may need to thin out the canes, in addition to cutting off canes that are growing into the rows. There is no strongly established rule for how many canes to thin to, but you may try thinning to one cane every 4-6 inches. Another way to maintain some semblance of order would be to tie the canes to the trellis, so half of the canes are going left and half are going to the right. The point of thinning is to make it easier to find fruit during harvest and to allow better airflow for disease prevention. Thinned patches will still produce plenty of fruit, especially in a high tunnel.

Other

Please contact Annie Klodd at kloddann@umn.edu with questions, or for information on other crops not discussed here.