SW Michigan Fruit Update

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Southwest Michigan, May 26, 2008

Mark Longstroth, Bill Shane

Weather

Last week’s temperatures were cool with highs in the 60s and lows near 40.  Warmer temperatures finally arrived Sunday with highs near 80 Sunday and Monday.  Monday morning lows were about 60.  This was our first warm night of the season.  Rain showers fell Monday morning.  Rainfall totals were a tenth to a third of an inch with a wetting period of about 6 hours with temperatures around 60F.  Soils are beginning to dry out.  We expect cool temperatures for the next couple of days and then back into the mid 70’s by the weekend.  There is a chance of frost Wednesday morning.  There is a chance of rain this weekend.  Our GDD totals are about ten days behind normal. 

Southwest Michigan Growing Degree Day Totals March 1 through May 25, 2008				Grapes, from April 1
Location	GDD 42	GDD 45	GDD 50	GDD 50
Berrien Springs:	692	532	344	334
Scottdale:	662	522	335	327
SWMREC:	605	475	302	296
Bainbridge:	628	498	323	316
Hartford:	592	467	300	296
Lawton:	673	536	348	343
Grand Junction:	686	549	366	360
South Haven:	569	448	287	280
Fennville:	559	435	274	270

Tree fruit

Insect activity remained generally low last week.  We are now in the treatment window for Oriental fruit moth.  Codling Moth Biofix was set as May 26 for the stations that did not biofix before Monday.  We expect codling moth egg hatch to occur at 250 GDD past biofix.  Fresh plum curculio egg laying scars have been found.  Leaf roller larvae are getting bigger.

Apricots fruits are about an inch in diameter.

Peach fruit are about 10 mm in diameter.  Peach crop varies by variety, and generally looks lighter than last year.  Now is the time to apply Oriental Fruit Moth controls.  Oriental Fruit Moth was biofixed on May 4 at SWMREC.  Treatment is timed for 200 GDD45 after biofix and with the warm temperature Sunday and Monday we reached that mark Monday.  Green peach aphids are curling peach leaves.

Sweet Cherry fruit are about 14 to 16 mm in diameter and the pits are hard.  Fresh plum curculio egg laying scars have been found.  The rain event Monday was too short and cool for brown rot.  But some areas were wet longer enough for cherry leaf spot.  

Tart Cherry fruit are 10 to 12 mm in diameter.  The tart cherry crop looks pretty good.  The crop is throughout the tree, not just on the outer shell.  Fresh plum curculio egg laying scars were found in tart cherries also.  Monday’s rain was a light cherry leaf spot infection period in some areas.  Many growers applied protectant materials before the rain. 

Plums: Japanese plums are about 12 to 14 mm.  European plums are about 8 to 10 mm.  Plum curculio egg laying scars were found in Japanese plums.  Growers still need to protect against black knot before rains. 

Apples still have scattered bloom.  Fruit size is generally in the 8 to 12 mm range.  Apple scab symptoms have been found in sprayed orchards.  These are probably from the May 4 infection period.  Monday’s rain was not an apple scab infection period, and it occurred at night so there was little spore discharge.  We are nearing the end of primary scab season.  Almost all the scab spores are mature and about 80% of the spores have been released.  Scab protection will be necessary at least through the next rain event.  Last week’s cool weather kept bacterial populations low until Monday when warm temperatures and rain precipitated a fire blight infection.  Some growers with open bloom have applied controls Monday.  No symptoms of systemic fireblight were visible in apples Monday.  We do not expect to see blossom blight symptoms for at least a week with the cool temperatures forecast.

Southern Berrien County biofixed for Codling moth on May 14 at 278 GDD50, some other orchards in the region Biofixed May 23 at 284.  With the cool week and warm weekend we are at about 70 and 40 GDD50 Tuesday May 26.  We expect most of the region to biofix Monday May 26, during the warm evening.  The application timing of control materials varies greatly (see the article on codling moth in this week’s Fruit CAT Alert.  Spotted tentiform leafminer sap feeders should be out and will leaf mines soon.  European red mites are moving about.  Expect to see San Jose scale crawlers at 500 GDD50 soon.

Apple fruitlets are 8 to 12 mm in diameter, and we can now see initial fruit set.  Some growers applied thinning spray during the weekend.  The cool weather forecast means that we will not have another good apple thinning windows until Thursday or Friday when the temperature will again be in the 70s.  A warming trend when temperatures climbing above 70 for several days will offers the best thinning windows.  I am recommending a moderate thinning strategy if set looks light or there are good size differences between fruits in the cluster.  There are wide differences in fruit set between varieties and sites.  Some blocks have a heavy set and I recommend aggressive use of combination sprays of Sevin and either NAA (Naphthalenacetic acid) or BA (Benzladenine)

Pears fruit are 10 to 12 mm in diameter.  The crop is variable.  Pear psylla adults and nymphs can be found in unsprayed trees.  Growers should continue to protect against pear scab.

Small fruit

Blueberry bloom continues.  Bluecrop is past full bloom; Jersey and Elliot are at full bloom.  Leaves are greening up with the warm weather.  Cranberry fruitworm biofix was expected Sunday or Monday.  Growers should scout for eggs in the calyx cup of fruit.  Sprays of bee safe materials are planned when the weather warms up.  .

Grapes growth varies widely.  Many vineyards look pretty raged.  Concord and Niagara shoots fall into 3 distinct groups; 9-11 inches, 6-8 and secondary shoots of 4 inches from the base of primaries.  There are also new shoots tertiary shoots and bud burst about an inch long.  Most primary shoots have 3 clusters.  Shoots in mechanically pruned vineyards with many shoots are shorter and generally only have 2 clusters.  Secondary and tertiary shoots have four-inch long shoots, with one or two flower clusters.  Flower clusters on primary shoots are beginning to elongate.  The conditions generally have been too cool for powdery mildew and, downy mildew.  Monday’s rain was marginal for black rot but was probably a good phomopsis infection.  Phomopsis lesions have been reported at the base of this year’s shoots.

Strawberries are at past full bloom.  Most of the primaries have thimble-sized fruit.  Avoid using insecticides during bloom.  Spittlebug is easy to find.  Fungicides are applied at bloom to reduce gray mold, anthracnose, leaf spot diseases and leather rot. 

Raspberry and Blackberry flower bud clusters have emerged. 

Cranberry buds are elongating.  Growers may need to frost protect Wednesday morning. When the shoots begin active growth before bloom is time for a protectant fungicide spray to protect new foliar and reduce fruit rots.

Miscellaneous

The next Monday Fruit Update meeting will be, Monday June 2, at the Fruit Acres Farm in Berrien County.