Vol. 18, No. 8, June 3, 2003

In this Issue
Tree fruit news
2003 TNRC trapline data: Cherry fruitworm
Caution with Captan
Training peach trees - single and debud scaffold ends
Small fruit news
Blueberry sampling reveals fruitworm eggs and post-bloom management timing
A real opportunity for blueberry growers in 2003
Bloom: start of a critical period for black rot control in grapes
Other news
Preharvest Blueberry IPM Meeting
Regional reports
Weather news

Caution with Captan

Gary Thornton and Bob Tritten

Editor's note: The following article by Dave Rosenberger, Plant Pathology, Highland, has been taken from Cornell Scaffolds Newsletter (Volume 12, No. 11, May 27, 2003).

This spring has been cool as well as some cloudy periods. These climatic conditions can keep leaf cuticle development at a minimum. The following article from the Cornell University Scaffolds newsletter (Volume 12, No. 11, May 27, 2003) reminds us of the importance of treating each season as a unique in its own right and to spray accordingly.

Growers who wish to minimize any leaf injury from sprays applied should also try to keep the materials that they tank-mix together to a minimum. Our personal rule of thumb is to not tank mix more than four compounds at a time together, including surfactants.

Caution with Captan from Cornell Scaffolds

Fruit growers should be very cautious about using Captan during the next 7 to 10 days because weather conditions over much of the state have left apples, peaches, plums, and cherries unusually susceptible to Captan injury. Captan is an effective, broad-spectrum fungicide that is labeled for many fruit crops. However, when absorbed into plant tissue, Captan causes phytotoxicity that appears as leaf spotting, shot-holing, and leaf yellowing. When combined with other products that enhance uptake into leaves, Captan applied at this time of year can cause complete defoliation of peach and nectarine trees. To be safe, growers should avoid applying Captan until trees have had several days of sunny, dry weather.

The risk of Captan injury is greatest when the annual spring growth flush of fruit trees coincides with an extended period of cloudy, cool, damp weather. The growth flush on fruit trees begins when terminal shoots start growing during or shortly after bloom. The cuticle (the waxy layer on the leaf and fruit surfaces) develops in response to heat and water stress. During cloudy and damp weather, there is little danger from heat or water loss and trees therefore produce only a thin cuticle to protect the newly formed leaves and enlarging fruitlets.

The same waxy cuticle that serves to prevent water loss also prevents Captan from entering and injuring living cells beneath the plant cuticle. Some varieties of plums and cherries almost always develop a leaf spot or shot-hole after Captan is applied because, even under the best conditions, some Captan enters and kills leaf cells of these varieties. For most other fruit crops, Captan causes little or no injury except during unusual seasons when weather conditions inhibit cuticle development.

Even when plant tissue has only a thin cuticle, Captan by itself will rarely cause phytotoxicity (except to those plum and cherry varieties that are especially susceptible to Captan injury). Problems often arise, however, when Captan is mixed with other agrichemical products. Spray adjuvants that enhance the transport of Captan through the plant cuticle can greatly increase the phytotoxicity of Captan, especially when the plant cuticle is thin at the time spray is applied. Adjuvants that enhance uptake of Captan include spray oils, some spreader-stickers, and other petroleum-based carriers commonly found in products that are formulated as liquids or emulsifiable concentrates.

Where apple scab symptoms are appearing in orchards, the best option for stopping further spread of apple scab is to apply a combination of an SI fungicide along with the maximum label rate of Captan. To avoid phytotoxicity problems, however, growers may need to use an SI-plus-mancozeb combination for the next week to avoid the potential phytotoxicity that could result if Captan is applied at this time. This is especially true if Sevin XLR Plus will be applied for thinning or if spray oil will be applied with a miticide during the next week. Those who opt to apply Captan despite the risks are advised not to use spray adjuvants that might enhance trans-cuticular movement of Captan.

Training peach trees - single and debud scaffold ends

Bill Shane
SW Michigan Research and Extension Center

I would like to describe my experiences in peaches with a limb training technique called "single and debud." This technique, modified from the sweet cherry industry, appears to be useful to help avoid the need for large pruning cuts, and thereby reduce the potential for future Leucostoma (Cytospora) canker problems. Michigan State University District Agent Jim Nugent has posted a nice summary of the technique for sweet cherries on the Northwest Horticultural Research Station web site (http://www.maes.msu.edu/nwmihort/debudding.html).

Peaches are most commonly trained in the open center style with three to five permanent scaffold limbs developed over the first three to six years of growth. The end of a peach tree scaffold has many buds that develop into strong, closely clustered limbs (Figure 1). The traditional strategy for managing scaffold limbs is to make a heading cut to a side limb in a desirable position. The traditional heading cut is fast and simplifies the end of the scaffold, but the new side limbs sprouting from the vicinity of the cut.

The "single and debud" approach is to use your hand to remove all but the terminal bud from the top 3 to 4 inches of the branch end (Figures 2 and 3). The bud removal is done between bud swell and first bloom. With sweet cherries, the bud removal is done at bud swell to increase the tendency for normally latent lower buds to open. Delaying the debudding time closer to bloom in peaches makes it easier to thoroughly remove unwanted buds, especially on the branch end. Peaches are much more prone to develop lateral branches than cherries, so the delayed budding in peaches is not a problem.

In sweet cherries, it is then recommended to remove 50 to 67 percent of the remaining buds on last year's terminal growth to achieve a better distribution of new lateral branches. In my experience this additional bud removal does not appear to be needed in peach.

The advantage of the "single and debud" technique is a smooth juncture on the scaffold between last year and the current year's growth. A scaffold trained by this technique is relatively straight as opposed to the "dogleg" appearance of the traditional-headed scaffold. Side limbs arising on the scaffolds are relatively small diameter with relatively wide crotch angles, providing less opportunity for Leucostoma canker problems. Since there is no heading cut with this technique, tree size and limb calipers tend to be noticeably larger with the single and debudded tree compared to the traditional headed tree.

The disadvantages of the "single and debud" technique are that trees tend to be more upright. On occasion, it is necessary to use a heading cut to redirect scaffold limbs that are growing in the wrong direction. It is generally necessary to go back over the orchard two to three weeks after debudding to remove unwanted sprouts in the cleared zone and at the end of scaffold. Oriental fruit moth control is important to avoid damage by this insect to the terminal bud.

The single and debud technique appears to be most useful during the first three years of scaffold development to help to prevent canker problems on the most critical structural component of the mature tree. The single and debud technique is relatively easy to learn and quick to do. Try it for yourself.

Blueberry sampling reveals fruitworm eggs and post-bloom management timing

Rufus Isaacs
Entomology

As part of the Blueberry RAMP Project, ten commercial blueberry fields across Southwest Michigan are being scouted each week by MSU entomologists. Since petal fall started, we have been scouting for eggs of cranberry fruitworm and cherry fruitworm (see accompanying picture). At the furthest south farm in this project (Covert), eggs of cranberry fruitworm were found for the first time yesterday (June 2), and there are also reports of egg laying in Allegan County farms. Conditions are ideal now for this egg laying to continue and to spread north with the temperature accumulation. This is because fruitworm moths have been found in monitoring traps for a few weeks, the bushes have open calyx cups after petal-fall, and evening temperatures are increasing. Farms that are further south than Covert or in other warmer areas should consider either scouting for eggs or preparing for a post-bloom insecticide application in fields with histories of fruitworm infestation.

Scouting for eggs is not as difficult as it might seem at first. You'll need a 16 to 20 power hand lens and a site where fruitworm adults have been monitored in the past few weeks. Adult female moths must wait until petal-fall to lay their eggs in the calyx cup, so looking inside the open calyx cups in fields with a history of infestation near to wooded borders is the best site to find the eggs. In our experience, one egg is laid per berry, but an area of a bush may receive many eggs, while other areas receive none. Because of this clumped distribution, it is a good idea to spread your sampling along wooded borders to help improve the chance of finding eggs.

Finding eggs can provide more accurate information on the best time to apply an insecticide. Fresh eggs are light yellow, meaning that there are three to four days until the egg hatches and the tiny larva crawls to enter the berry. However, if the eggs are a dark orange color or if a head-capsule is visible inside the egg, then the larva is ready to hatch in the next day and fruit protection steps need to be taken. Another reason to better determine whether eggs are close to hatching relates to product selection. Insecticides that are safe for use during bloom, such as Dipel and Confirm, are most effective when targeted for the egghatch timing, to kill the youngest larvae before they enter the fruit.

The MSUE resources below can help with identification of fruitworms and making decisions on how to manage this blueberry pest:

Fruitworm fact sheet on the MSUE blueberry website: http://web1.msue.msu.edu/fruit/bluberry.htm

For fruitworm management options, see the recent CAT Alert article: http://www.ipm.msu.edu/CAT03_frt/F05-20-03.htm - 4

A real opportunity for blueberry growers in 2003

Mark Longstroth
District Horticultural Agent

This spring we are seeing a lot of winter injury in blueberries. We see cane dieback in Jersey, Rubel and some other varieties. I think that this dieback is a combination of winter injury from early cold in December and other stresses the plants suffered last year. I often see Phomopsis in affected fields and I think that last year's drought had a lot to do with the winter injury we see. The point is that many growers are pruning out lots of dead canes and some are even mowing off all the canes and hope to bring up new shoots from the crown. If you are going to be drastic enough to mow down the bush, you should seriously think about replacing them with a newer variety.

If you mow down a bush, you need to come back and thin out the canes that come up from the crown. If you want to get back in production quickly, you should do this in the growing season so that the plant puts its energy into the shoots you are going to keep instead of the shoots you are going to cut out. If you force that growth into fewer canes, you will get back into production sooner. And thinning out the canes makes disease control easier and more effective. In three years you should be back into production. In 5 or 8 years, you should be getting back into full production of 3,000-4,000 pounds of Jersey fruit a year.

If you plant with a new variety like Nelson, you will have the same yields in five years as you do with Jersey but yields will continue to increase. Most Michigan growers should be able to double their yields with newer, higher yielding varieties. The fruit from new varieties is larger and has higher quality that carries a premium in the fresh market. Ten years from now would you rather have a field of Jerseys averaging 3,000 pound/acre or Nelsons averaging 6 to 8,000 pound of high quality, fresh market fruit? How many years of higher production would you need to make up for the fact you could restore that old Jersey field in five years?

Most tree fruit growers need to replace their orchards with newer varieties as the trees age. Often the planting is replaced with new varieties or old varieties that have withstood the test of time and produce high volumes of quality fruit. We do not see this in blueberries because it takes so long for the fields to reach full production and our production does not fall off if we vigorously maintain the fields.

The loss of old, weak Jersey fields is a blessing in disguise. Examine the records of the fields that are most damaged and replace the poorer ones. Use 2003 to put everything you know about growing blueberries to good use and get the field ready for new plants and line the plants up to plant. How many years do you think you can make a profit on the best blueberry variety in 1960 when your competition is planting the best blueberry variety in 2003?

Bloom: start of a critical period for black rot control in grapes

Annemiek Schilder
Plant Pathology

Period of susceptibility

The period from bloom through early fruit development is crucial in protecting grapes from black rot infection. Grape berries are highly susceptible to black rot infection for the first two to three weeks after bloom. They become progressively less susceptible as they continue to develop after that, finally becoming highly resistant about four to eight weeks after bloom, depending on the variety and year. In general, 'Concord' berries become resistant to infection about four to five weeks after bloom, while some V. vinifera cultivars don't become fully resistant until 8 weeks after bloom. Thus, the key to control in juice grapes is preventing the establishment of early berry infections during the first few weeks after bloom. This means that most disease control is provided by the immediate pre-bloom and first post-bloom fungicide sprays.

Fungicide timing

In five years of trials in New York, good black rot control was achieved with one immediate pre-bloom and 1 to 2 post-bloom fungicide sprays. The second post-bloom application is strongly advised if black rot has been a problem in the vineyard the previous year and should be considered prudent if wet weather is anticipated. Only in one vineyard with a history of black rot problems did a spray two weeks before the immediate pre-bloom application improve disease control. Therefore, we do not advise sprays specifically for black rot during the early part of the season. Any EBDC applications made for Phomopsis will also control foliar black rot infections at that time. During three years of fungicide trials in a 'Concord' vineyard in Fennville, Michigan, just two post-bloom applications of SI fungicides have provided very good control under high black rot pressure. However, an immediate pre-bloom application is advised so as not to miss potential infection periods. Note that the immediate pre-bloom through early post-bloom period is also a critical time for control of powdery and downy mildews. Sprays for Phomopsis are also advised.

Effective fungicides

Sterol-inhibitor fungicides (e.g., Nova and Elite) provide outstanding control of black rot, and are labeled for up to 72 hours of post-infection activity. When using SI fungicides on a post-infection schedule, use the high label rates because post-infection activity is strongly rate-dependent, particularly when extended "kickback" activity is required. The strobilurin fungicides (Abound, Flint, Sovran) are excellent protectants but provide only limited post-infection activity (about 12 to 24 hours). Recent research suggests that their effective periods of post-infection activity might be one to several days longer than this, although extended post-infection applications should be made only under emergency situations. Flint should not be used on 'Concord' because of potential phytotoxicity. Strobilurins also are stronger against Phomopsis than the SI's. Mancozeb, ferbam, and ziram are good protectants but are more subject to wash-off than the strobilurins, so must be reapplied more frequently during high-pressure conditions. Some processors restrict the use of mancozeb after bloom has started. For those growers who are interested in "soft" materials, Armicarb (potassium bicarbonate salt) has provided good control (not quite as good as the SI's or strobilurins) of black rot when applied on a similar schedule.

Preharvest Blueberry IPM Meeting

Al Gaus
Berrien County

1 - Southwest

Mark Longstroth
Bill Shane
Al Gaus

Weather

Another week that was warmer at the beginning and then cooled down. About a third of an inch of rain fell on the morning of May 30. Scattered light frosts on May 31 and June 1 caused little damage. This week's forecast is for warmer weather and the chance of showers.

Insects

Insect activity has been low due to the cool weather. Old tarnished plant bug and plum curculio feeding scars were found in apples and cherries. Very few plum curculio egg-laying scars were found (apples, cherries, plums and nectarines). Warmer days and nights should bring plum curculio out. We are catching low numbers of Oriental fruit moth and codling moth. Potato leafhoppers were found in grapes and apples.

Tree fruit

Peach fruit are sorting out by size. The peach crop looks good. Tree color looks better but leaves are still pale. The trees should green up when the weather warms up later this week. We are now at 630 GDD45, 380 GDD since Biofix for Oriental fruit moth on April 24. We have not seen any shoot flagging from Oriental fruit moth in the shoot tips. Green peach aphids are out and forming colonies.

The tart cherry crop looks better and better. Plum curculio will be a problem later in the week. Growers need to protect against cherry leaf spot. Sweet cherries need to be protected from brown rot.

In plums, the June drop is ending the crop has thinned out well and the crop looks good. Growers need to protect against black knot (see accompanying photo) until shoot growth stops.

In apples, we have had poor thinning conditions. Quite a few growers have applied two thinning sprays and are wondering if they need to apply a third. In the last several days the size difference between the king fruit and side fruit has become more pronounced. It looks like most growers may not need to thin again. I am recommending that if growers have any doubts that they thin and knock off the small side fruit. Under these poor thinning conditions there is little chance that growers will take off too much fruit. One big worry is that all the thinners applied during these cool conditions will result in pygmy fruit.

No apple scab infections since May 19. Scab lesions from the May 19 infection should appear in the next few days. Lesions from the May 14 infection have already appeared. Primary infection period is ending. If growers have no scab lesion in their orchards they can relax their protection. If they have scab lesions they need to continue an active scab protection program.

Fire blight symptoms are appearing. Cool temperatures have kept fire blight symptom expression low. The most common symptom is spur or shoot wilting with a black line down the midvein of the leaves. There are oozing cankers in orchards with fire blight last year. Collapsing spurs and oozing shoots indicate that we are seeing blossom blight (see accompanying photo) May 11. Near the cankers there are more of symptoms, with few scattered spurs collapsing elsewhere in the orchard. This infection was preceded by strong, warm winds, and we are seeing what could be trauma blight on wind-damaged shoots.

We have accumulated 90 GDD, since we biofixed codling moth on May 18 at 300 GDD50. Controls are usually timed for 250 to 350 GDD after biofix. See the discussion on codling moth control in the 2003 Fruit Management Guide. European red mites are laying eggs. No spotted tentiform leafminer mines have been found yet. Leaf roller larvae can still be found in terminals. White apple leafhoppers are appearing.

In pears, there is a heavy drop but still lots of fruit. Pear psylla are easy to find.

Small fruit

Blueberry bloom is ending. Growers need to protect the fruit from anthracnose and alternaria. Mummy berry shoot strikes are becoming easier to find. Growers can use Confirm to control cranberry fruitworm and cherry fruitworm during bloom. Bts are best used under warm conditions so this week's cool weather is better for Confirm. After bloom when the bees have been removed from the orchard growers can use more conventional insecticides.

In grapes, the flower clusters are separating in the bunch. Wild grapes are close to blooming, and we expect bloom to begin next week. Phomopsis lesions are visible in some vineyards. Good fungicide coverage of the rachis in the flower cluster in necessary to prevent rachis infection. We are seeing poor growth in colder sites due to winter injury. We see short shoots (6 inches or less) with 2 to 3 clusters. Growers are reporting oozing trunks in low spots. I expect that we will see collapse of the canes and new shoots when we get hot, dry weather and put real stress on the vines. The yellow mottled appearance of the leaves is probably due to the cool weather. The vines will green up as the temperatures warm.

Grape berry moths are flying. Growers need to time their pesticide applications for egg hatch, near bloom time (a week away).

Strawberry bloom is ending. There are lots of small green fruit. The largest fruit are thimble sized. Berries from plasticulture plantings are being sold at the Benton Harbor Market. Harvest of Matted row berries should start late next week. Spittlebugs are out. Leaf rollers and leaf spots are problems we see in grower fields.

Raspberries are in full bloom.

Cranberries are at elongated bud. Fruit buds are appearing in the most advanced shoots. Now is the time for a fungicide application to control fruit rots.

Miscellaneous

The next Monday Fruit Management meeting will be at Bjorge's Fruit Acres Farm at the corner of Friday and Carmody roads, approximately 2 miles south of the Coloma exit I-94, on June 9 at 5:00 PM.

There will be a preharvest blueberry meeting June 19, 2003 at 6:30 PM. The focus of this meeting will be in blueberries. For more information check the Berrien County MSUE Fruit Hotlines (269) 944-4126 ext. 1.

2 - Southeast

Bob Tritten

Weather

Cool weather over the region continues to hold back development of insect activity and in some cases fruit growth. To say the least, this spring has been much different than most that we've experienced over the last 5 or 6 years. Scattered frost and freeze on the morning of June 1 was a problem across parts of Genesee, Lapeer, Macomb and St. Clair counties. While strawberry growers needed to protect from this freeze, it does not appear to have damaged any tree fruit crops. There was also an additional lighter frost event the next morning (June 2). Strawberry growers have frost protected about a half a dozen times this year, a few more than normal. However recall back to last strawberry season when many strawberry growers frost protected 12 to 15 times. Thinning is a major concern for apple growers at this time. Finding the proper thinning window for apples has not been easy thus far this season. Soil temperatures continue to remain on the cool side with most days being in the lower 60's at the 2-inch level.

Tree fruits

Apples (Red Delicious) are mostly at 12 mm to 15 mm in the south and 8 mm to 10 mm in the northern part of my region. Other varieties like Jonathon and Empire are mostly 2 mm to 4 mm larger in size. There are a few areas closer to Lake Huron that report that they are still in bloom at this time. There continues to be some lingering bloom in a few varieties in many apple blocks, so continue to watch these blocks for potential fire blight problems. Insect activity has been sporadic and on the light side this year, and many predators continue to work very effectively at controlling some of these insects. Plum curculio is typically a major pest at this time of the year. However, up until this point I only had one report of plum curculio stinging fruit. Typically by this time of year it is easy for me to find plum curculio stinging on a wide variety of fruit trees. It is thought that the cool nighttime temperatures have kept plum curculio activity at a much lower level. Codling moth trap catches have generally been up at many farms across the region. Those who are continuing to count degree days from biofix for codling moth note that degree days are accumulating slowly this year. Generally, there are very few larvae being seen in apples, but here is a list of ones that I've seen over the last week: fruit tree leafroller, redbanded leafroller, green fruitworm, obliquebanded leafroller, climbing cutworm and eastern tent caterpillar. Rosy apple aphid colonies are starting to form and a few curled leaves have been seen, however the level is fairly low at this time. White apple leafhopper adults are heavy at a few farms - at most farms they are under control. Potato leafhopper continues to be seen at very low levels. European red mites are present at low levels this year. I have seen little to no egg laying. We'll be keeping a close eye on mites over the next couple of weeks. Apple scab spore discharge continues with each rain event, and the numbers appear to be winding down. There was spore release from two rain events during the last week on May 29 and May 31. There are a couple of scattered reports of folks seeing fire blight in orchards. These have not been confirmed.

Pears are mostly at 14 mm to 16 mm in size. The only pest problem to report on pears thus far this year is pear psylla activity.

Sweet cherries are around 12 mm in size. I am continually surprised to see as many sweet cherries at many farms as I've seen over the last two weeks. It appeared at bloom time that there was going to be a disappointing crop of sweet cherries this year, however some how many of those bloom made it through the difficult pollination period and are now sizing quite nicely. Tart cherries are mostly at 12 mm in size.

Small fruits

Strawberries are at about 80 percent bloom to small size berries at many farms. Growers are not quite ready to predict an opening date for picking at most farms, however it will be later than last year.

Raspberries are now in bloom for summer berries, and fall red raspberry canes are at the height of 10 to 12 inches. Collapse and death of summer red raspberry cane continues to become more evident at many farms across the region. See a related article in the May 27, 2003 edition of CAT Alerts on winter damage to summer raspberries.

Blueberries are in full bloom. Blueberry growers continue to see the effects of winter injury on many varieties this year. While the list of effected varieties is not consistent from farm to farm, it seems that most farms have a significant amount dead twigs and canes this year.

3 - Grand Rapids Area

Phil Schwallier
Amy Irish Brown
Tom Kalchik
Carlos Garcia-Salazar

Tree fruit

Most apple varieties are in the post-petalfall stage right now with some lingering bloom still out there on one-year old wood and newly planted trees.

We were still catching spores with the rains over the past weekend, so primary scab is not over yet and you still need to keep orchards covered. Although spore numbers are really falling off, there are still lots of susceptible leaves and now fruits out there that could be infected by apple scab. Now is a very key time to scout your blocks very carefully to be sure you do not have any primary scab lesions.

The risk for blossom blight infection is very low because bloom is all but finished. Remember to cover newly planted trees that are just coming into bloom for conditions that are right for fire blight. There are some blight symptoms showing up in blocks that have had problems with fire blight in the past. This could be trauma blight from the Mother's Day high winds, but it really looks more like blossom blight. Strikes are not anything wide spread, but limited to hit spots in blocks. The first oozing cankers were found late last week and more should be seen with some warmer weather at any time.

Codling moth trap numbers are very high in some blocks even with the cooler than normal weather. Proper timing of cover sprays for codling moth will be very important this year, but we are probably at least ten days away from the 250 GDD50 threshold for early egg hatch spray timings. We have accumulated GDD50 since the regional May 19, 2003 biofix.

Obliquebanded leafroller are getting large and moving out of the window for good control at this time. White apple leafhopper continue to emerge and develop.

Spotted tentiform leafminer are mostly in the sap feeder stage.

Plum curculio egg-laying damage is just starting to be found in plums in light amounts. I would expect they will become active very soon in apple with some warmer weather.

Be sure to walk through your different varieties before thinning - some varieties are thinning down almost too well on their own. Try to hit a warming trend in the weather for thinner applications.

Small fruit

Blueberries in west central Michigan still are in bloom. However, Bluecrop and Blueray are in 50 to 75 percent petal fall while Jersey is in full bloom stage. In general, we are observing a small crop in the variety Jersey, but in some places Bluecrop shows similar conditions. This situation seems to be the result of the combined effects of last year's summer drought and winter damage. Jersey fields seriously affected by winter damage have been pruned heavily or mowed to the ground. Growers with fields affected by these conditions are reporting a decrease in the size of this year's crop amounting one third of the previous year.

Regarding insect pests, the redbanded leafroller (RBLR) moths still are flying but in low numbers. We have not had any captures of obliquebanded leafroller (OBLR) moths in pheromone traps, yet. However, leafroller feeding ranged from 2 to 4 percent. Larvae responsible for this feeding are a complex of leafrollers, OBLR, RBLR and Pandemis. In both Ottawa and Allegan Counties, one out of four larvae is a Pandemis larva while the rest are mainly OBLR, but in Ottawa County the complex includes RBLR larvae. There have been some insecticide sprays, mainly in Allegan County, against leafrollers and fruitworms. However, leafroller predation by birds and other predators ranged from 80 to 90 percent. Similar predation was observed the past year. Under these circumstances, it may be possible that in blueberry fields with high rate of predation, the use of insecticides against leafrollers could be delayed until the first fruitworm eggs are observed. This certainly will reduce the use of insecticides and may prevent the killing of honeybees and other pollinators still working in those fields or in adjacent fields planted with late season varieties.

Still we are observing emergence of adults of the cherry fruitworm (CFW) in both Allegan and Ottawa Counties with moth captures in the pheromone traps ranging from 2 to 10 moth per trap per week, and CFW eggs have been found in both counties. Regarding the cranberry fruitworm, adult moths continued emerging in south Allegan and some eggs have been found. However, no captures have been reported in Ottawa County.

Degree days accumulated

4 - West Central

Mira Danilovich

Weather

Weather continues to be cold and dry throughout the region. Sunday morning (June 1) we had some patchy frost that hit some previously missed spots. The weather station in Bear Lake was the "cold spot" registering only 28.5°F followed by Hart with 29.9° with the highest low temperature in Ludington where we had 30.9°F. The situation with the moisture is getting to be of concern. With the exception of Bear Lake, we have not received any significant precipitation in weeks. We are about an inch behind normal values since the beginning of the season.

Growing degree day totals as of Sunday, June 1

Tree fruit

Apples are looking good. Fruit set has been heavy in most varieties with the exception of Red delicious. Generally, the size is 5 to 7 mm and about 10 mm in Idareds and Honeycrisps. We are getting into the thinning window though the weather conditions are really not that great. On the other hand, this week might be the warmest we will have for a while. The long term forecast is calling for below normal temperatures with the highs only in high 60's.

A few sprinkles we had last week did produce scab spore discharge. Following the Mac Hardy model, we have reached 100 percent level in spore maturation. All we need is a good rain to flush them. Scouts are finding very few scab lesions resulting from the infections in early May. Cool weather has kept fire blight at bay. No symptoms of oozing canker margins as of yet.

In peaches (Red Havens), most of the fruit is 5 to 8 mm and is just about out of the shuck. Bacterial leaf spot is relatively common. Powdery mildew has been spotted and it might require more attention since the weather is favoring disease development. Oriental fruit moth applications for the first generation control have been applied in many blocks.

European plums are gaining in size. It appears that they have set a good crop. There is some bacterial leaf spot. No signs of plum curculio stings at this time.

The frost events we had, particularly the on May 22, have reduced the cherry crop potential. It is still difficult to accurately estimate what is there to stay since there is a great spread in fruit size, but it looks like we might have 50 to 60 percent of the potential. Sweet cherries, despite the problems with winter injury, are looking much better promising a fear crop load.

Last week we had a cherry leaf spot infection only in Manistee County. We are finding a very few lesions on the oldest leaves from the infections we might have not anticipated that early in a season. Powdery mildew is starting to show up. These weather conditions are favoring disease development. Complete and tight cover is needed. There have been no reports of plum curculio stings yet. Some mites, both European red mites and twospotted mites, are being found on occasion.

5 - Northwest

Gary Thornton
Jim Nugent
Jim Bardenhagen
Duke Elsner

Growing degree day accumulations

GDD42      604

GDD50            278

Weather

Scattered frost occurred on the morning of June 1. Small amounts of rain fell on May 30 and 31.

Tree fruit

Apple scab lesions can be found in many commercial blocks now, particularly on the older leaves. Late last week we had a moderate infection period in most areas of Northwest Michigan. Codling moth flight has been relatively high despite the cool temperatures. Trap catches for codling moth has averaged seven per trap in Leelanau County. Many blocks will be reaching biofix this week where monitoring is taking place. Actual spray timing for codling moth should take place 250 GDD50 after biofix. Spotted tentiform leaf miner trap catches are starting to decline now, with trap catches averaging 171 per trap. Sap feeding mines should be showing up shortly. Rosy apple aphids are curling the leaves of untreated apples, making control more difficult. European red mites are common in untreated blocks, though rarely above threshold. Keep in mind that the rapidly expanding leaf area will dilute the mite populations somewhat until the next generation starts to hatch out. Mite predators can be found both in the trees and in the ground cover.

With sweet and tart cherries out and/or coming out of the shuck now, plum curculio becomes a worry and is now beginning to lay eggs in cherries. Sweet cherry growers should be sure to have an appropriate insecticide on to prevent worms at harvest. Tart cherry growers who are monitoring can postpone their plum curculio sprays until 375 GDD50 after full bloom. Green fruit worm (GFW) are common in cherries this year; the largest are now about a half inch. Growers should monitor for this pest closely this year. The best options for controlling GFW in cherries are pyrethroids and or Lorsban (tarts only). Good results have also been achieved with tank mixes using a half rate of Guthion combined with a half rate of a pyrethroid or Lorsban. Avoiding the use of a pyrethroid in tarts reduces the risk of mite problems later in the season.

Gypsy moth has been found near the woods in both apple and cherry. American plum borer trap catches averaged nine moths per trap. Trunk sprays targeting this pest should start next week. If you are targeting lesser peach tree borer they should go on in about two weeks. If the current dry spell continues, early season weed control will be all the more important.

As peaches come out of the shuck they are very susceptible to tarnished plant bug injury. Tarnished plant bug nymphs can be easily found in untreated strawberry bloom.

Injury from road salt combined with cold weather has resulted in tree deaths in apple and reductions in bloom in stone fruits.

Weather news

Tracy Aichele
Agricultural Meteorology
Geography

The impact of the North Atlantic Oscillation (NAO) on Michigan weather is an active research topic in the department. Work done by the State Climatologist of Ohio, Jeff Rogers, suggests that the NAO affects Ohio weather and hydrology. This article, published in Newsday last week, presents a good introduction to the pattern and its impacts on the Northeast US.

http://www.newsday.com/news/health/ny-hsbrrr303307007may30,0,4352874.story?coll=ny-health-headlines

Why does it seem that the forecasts are so variable this year? We have been in a cool but stormy pattern, and predicting precipitation is always a challenge for meteorologists. Dr. Julie Winkler (MSU Geography) reminded me that there are different sets of models for the short-range (up to 48 hours) and the medium-range forecasts. When we give the weekend forecast on Tuesday, we are using the medium-range models, which tend to be more uncertain in the placement of the highs and lows. When we give the weekend forecast on Friday, we are using the short-range model results. Each National Weather Service (NWS) forecast is accompanied by a discussion of the models used and other factors affecting the forecasts. The MSU Agricultural Weather Office maintains a live feed from the NWS, and both the forecasts and the discussions are available at our website.
http://www.agweather.geo.msu.edu/agwx/forecasts/

For Tuesday night (June 3), low temperatures will be near 40 for most of the state. For the rest of the week, high temperatures should be near 70, and low temperatures should be near 50. Precipitation is in the forecast (as scattered showers and storms) for Friday, Saturday and Sunday. In the southern part of the state, rain and showers are likely Wednesday and Wednesday night.

In the 6-10 day forecast, normal precipitation is expected, while in the 8-14 day forecast, above-normal precipitation is expected. For both long-range time periods, below-normal temperatures are forecast. The 30-day forecast provides no guidance, with equal chances of above- or below-normal temperature and precipitation.