Fruit Update - SW Michigan

Mark Longstroth
Bill Shane
Al Gaus

Last week brought warm weather. Average temperatures were in the 70s. Plant growth and insect activity increased with the temperature. Rain on June 12, 15 and 18 caused some infections for diseases. Precipitation totals ranged from 1 to 2 inches. Soils are still wet, with water standing in some fields. Soil temperatures are near 70.

Rose chafers appeared in large numbers. No plum curculio activity was noticed. Potato leafhoppers are becoming more common. Growers with young trees will want to scout and treat if they find this pest.

Apricot fruits are 1.5 inches in diameter.

Peach fruits are 1.25 inches in diameter. Growers are thinning. Few shoot strikes and flagging from oriental fruit moth have been reported. Tarnished plant bugs are scarce.

In cherries, yellowing leaves are common. Cherry leaf spot and bacterial canker are often the culprit but some symptoms due to copper toxicity were noticed as the high temperatures climbed over 90. Sweet cherries are ripening. There is a good crop in most orchards. Fruit cracking is a problem. Growers need to maintain protection against brown rot. Tart cherries are red. Cherry leaf spot symptoms appeared with the warm weather. Cherry fruit fly traps should be out.

European plums are 22 mm in diameter. Japanese plums are 1 inch in diameter. Sprays to control black knot are still needed.

In Apple, the fruits are 1.25 inches in diameter. June drop is ending. Fruit set varies widely. We did see some more June drop with the hot weather last week, and growers report success using NAA and carbaryl to thin. Fireblight symptoms have increased with warming weather. Shoot blight symptoms are appearing in orchards with blossom blight symptoms. Where shoot blight is light, cutting out shoot blight as soon as it is visible, reduces the summer spread of the disease. Growers with scab in their orchards should continue fungicide applications.

Insect trap catches are up. Oriental fruit moth trap catches increased. This is the flight of the second generation of adults. The second generation begins to emerge at 950 GDD45. We are at 1072 GDD45, 870 GDD45 since BIOFIX (203). Codling moth trap catches also increased. We are at 752 GDD50, 502 GDD50 since codling moth BIOFIX (250). The second peak in the first generation flight (after a 2-week lull due to cold weather) was at 592 GDD50. BIOFIX for obliquebanded leafrollers was at 1050 GGD42. We are at 1292 GDD42, 240 GDD42 since BIOFIX. Timing varies for sprays to control obliquebanded leafroller, depending on the material used. Dogwood borer traps should be out in orchards to determine if this pest is present. Trunk sprays to control egg hatch and larval entry into the trunk should be applied after the adults begin flight. Spotted tentiform leafminer mines, larvae and pupa can be found. Traps for the second generation should be out. European red mite numbers are building.

Bartlett Pears fruits are 1 inch in diameter.

In Blueberries, cranberry fruit worm adults are flying and larvae can be found in the fruit. Traps for blueberry maggot traps should be out. Fungicides to protect against fruit rots are needed because of the wet humid conditions.

Grapes are at cluster shatter. Fruit drop is heavy in some vineyard over 50% of the berries have fallen leaving ragged clusters with poor fruit set (10-20 fruit cluster). Grape berry moths trap catches are up. Berry moth feeding is easy to find in some vineyards. Rose chafer has arrived in force. Grape growing degree-day totals from April 1 to June 10, 2001 are 747 GDD50. There are few disease symptoms visible but another fungicide application is due to protect the young fruit that remain.

Strawberries harvest is in full swing. Fruit ripened and softened rapidly with last week's hot weather.

Raspberry fruit set is light in some varieties. Prelude and Reveille, two early Raspberry varieties are being harvested.

Cranberries are still blooming. Most of the flowers have not yet opened. Those blooms that have been open may not have been pollinated. Fungicides should be applied when bloom is half completed.

The weekly Monday Fruit IPM meetings cover all fruits and are held in Allegan and Berrien counties this year. The next weekly Monday Fruit IPM meetings are on June 25 at the Alan Overhiser Farm north of South Haven in Allegan County then in Berrien County on June 18 at the Fruit Acres Farm south of Coloma,

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Posted: June 19, 2001