May 13, 2003
In this issue
Tree fruit news
§ 2003 TNRC trapline data: Oriental fruitmoth
§ Plum curculio monitoring, identification and phenology models
§ Bacterial canker, ice nucleation, frost injury and infection
§ Tree fruit pollination
Small fruit news
§ Bloom-time management of tarnished plant bug and other pests of strawberry
§ Topsin M Section 18 granted for blueberries
Other news
§ Crop Disaster Assistance Program
§ Regional reports
§ Weather news
Plum curculio can be monitored by deploying pyramid traps next to orchard perimeter trees. As opposed to bulky, heavy wood pyramid traps of the past, pyramid traps are now made out of thin, lightweight corrugated plastic. Approximately 5 to 10 pyramid traps can be deployed in a five-acre block to effectively monitor for plum curculio populations. Traps should be concentrated in areas where plum curculio has caused large amounts of damage in the past. If this area is adjacent to a woodlot or habitat with alternative hosts (pin cherry, choke cherry, hawthorn, quince, wild plum, etc.), place a couple traps in this area early in the spring. You may be able to capture plum curculio here before capturing in the orchard. Traps should be deployed before buds begin to swell, baited with plum essence and monitored weekly to determine how large the plum curculio population is within the orchard.
Plum curculio is easily confused with other beetles that are captured in pyramid traps. To help you tell the difference between plum curculio and the plum curculio look-alikes here are three easy guidelines for properly identifying plum curculio.
1. General size. Although plum curculio range in size (with males smaller than females), a large plum curculio on the eraser of a standard pencil (1/4 inch circle) will fill up most of the area. Anything much larger or much smaller than this is probably not a plum curculio. Anything around this size or a bit smaller may be a plum curculio.
2. Shape of the back (side view). Looking at plum curculio from the side, plum curculio appears plump (not flat) and bumpy. Plum curculio look-alikes are either flat, smooth, or they have only one or two distinct bumps on their back.
3. Color pattern on back (top view). Plum curculio has black area in the center of its back, toward the back there is a brown/dark orange stripe which is interrupted by a white triangle. This coloration easily sets it apart from look-alikes, however it may take close inspection until you are familiar with these characteristics. It may be a good idea to carry around a hand lens or magnifying glass to take a closer look.
The critical timing period for plum curculio has historically been at fruit set just as the fruit begins to swell. However, recent research has shown that plum curculio females are reproductively mature well in advance of this stage. We estimate 95 percent of the females are mated after 290 GDD50, which is typically right at shuck split in stone fruits and fruit set in pome fruits. Females are ready to oviposit long before fruit are large enough to support the developing larvae.
Once eggs have been laid, plum curculio larvae need approximately 400 GDD50 to complete development. Because of the zero-tolerance standards for larvae in processed cherries, tart cherry orchards should have a comprehensive control strategy in place by 400 GDD50 before harvest to minimize the risk of larvae in harvested fruit.
Bacterial canker is a serious disease of sweet cherry in the Eastern United States caused by the bacteria Pseudomonas syringae pv. syringae (PSS) and Pseudomonas syringae pv. morsprunorum. Canker infections are initiated during bloom and are associated with frost injury or extended periods of cool, wet weather.
Ice nucleation is a trait whereby PSS cells can catalyze ice formation at temperatures only slightly below freezing. Pure water can supercool significantly below 32°F without freezing. However, the presence of ice-nucleation active PSS cells enables ice to form at temperatures of approximately 28°F or below. Once ice is formed, it rapidly propagates through sensitive tissue such as blossoms. The severity of frost damage plays a critical role in the occurrence of subsequent bacterial canker infection.
Ice formation initiated by PSS is dependent upon temperature and the number of cells present. At 28°F, one in one million PSS cells freeze. At 27°F, one in 10,000 cells freeze, and at 25°F and below, one in ten cells freeze. Sweet cherry blossoms in Michigan typically harbor relatively large PSS populations on the order of 50 to 50,000 cells per blossom. These populations tend to increase during the bloom period, and the bacteria can be spread by wind and rain.
Thus, successful management of PSS populations will
significantly lower the risk of a freeze event at temperatures above 27° to
28°F
and the possibilities of bacterial canker infection. Controlling populations
with copper fungicides will remain a challenge for many growers, as there is
evidence of resistance to copper by the PSS bacteria.
In 2002, a severe freeze event occurred late in the bloom period after PSS populations had an extended period to increase on blossoms. As evidenced by the occurrence of cankers on virtually every spur on many sweet cherry trees in Northwest Michigan, the PSS bacterium is widespread in this region and an excellent colonizer. PSS actually can grow as an epiphyte on blossoms and leaves even in the absence of infection. PSS is an opportunist meaning that for infection to occur it typically requires a predisposing condition such as a weather event. However, because of the severity of infection in 2002, PSS inoculum is expected to be significantly high this spring. Temperature management is another option in sweet cherry orchards if nighttime lows of less than 28°F are predicted.
Winter survival is lower this year compared to last. Many large operations lost about 80 to 90 percent of their colonies. The smaller beekeepers, on average, lost about 40 percent of their hives. We suspect the higher mortality is mainly due to a much colder winter and the change of temperature drastically around February and March did not help. Michigan has successfully obtained the emergency registration (Section 18) for Checkmite+ (containing coumaphos, an organophosphate miticide for controlling varroa) for the year 2003. However, more than 50 percent of states now have reported mites resistant to Apistan (a fluvalinate), and a few states (Florida and Texas) have seen mites resistant to Coumaphos.
The higher winter mortality has created a large demand for package bees from the south and people had to pay about $6 to $8 more for three-pound packages. For orchards who depend on small local beekeepers or who keep their own bees, they might be affected by the higher than average winter mortality. For larger growers, price for pollination might not be affected that much because about 80 percent of pollinating hives in Michigan actually are wintered in Florida, Georgia and other warmer states, which do not have the bee-killing winters we have. I met one person at a blueberry growers' meeting three weeks ago who provides pollination services with bees from Florida. They are charging $35 per hive, which I thought is pretty low a price to pay.
Right now, most cherry and apricot flowers are gone and already setting fruit if adequately pollinated. Apples are in full bloom right now for many varieties. Most likely the growers already have bees in their orchards.
What can you do to improve the pollination? Mowing the dandelion flowers off will help you greatly. This is because dandelion flowers, very common between the rows of apple trees, will attract up to 50 percent of your bee foraging population. Mowing them would not harm the bees, but would force the bees to forage on apple and get you better pollination results.
I have created a database for growers and beekeepers to find each other. The web address is at http://beebase.cyberbee.net/. The main page http://www.cyberbee.net/ has now been renamed to http://www.cyberbee.msu.edu/ and provides many useful links to bee research, bee biology and beekeeping.
The beebase in particular will be very useful for county
agents to know how many beekeepers are in your own county and where they are
located. Please email me at bees@msu.edu for a special password that
will allow you to list the beekeepers in the whole state or in your specific
county. Stay tuned for next week's newsletter for tips of how to rear your own
blue orchard bees for better cherry and apple pollination next year.
The period around bloom is a critical time for effective management of insects and mites in strawberry. In particular, the tarnished plant bug should be monitored and managed effectively to prevent catfacing damage. Strawberry clipper becomes active around bloom and early activity of spittlebugs and two-spotted spider mite can be detected during twice-weekly scouting.
The tarnished plant bug (TPB) Lygus lineolaris is a major pest of strawberries with two generations and a partial third per year in Michigan. This insect overwinters as an adult in protected areas including leaf litter and hedgerows. The adults are 1/4 inch long with greenish or brownish bodies and a yellow triangle marking on the wing. Egg laying occurs early in the year, and lasts for up to one month with females laying about five eggs per day. Adults become active and lay eggs in grasses, broadleaf weeds and in some crops including strawberry in early to mid-May once the 68°F temperature threshold is reached. Eggs hatch to nymphs in about a week depending on the temperature and nymphs may be present on the plants as early as the second week of May. First nymphs are often seen during full-bloom period of mid-season cultivars such as Kent. Using their needle-like mouthparts, the adults and nymphal stages can feed on berries and cause damage. Research in Ontario, Quebec and New York has found that nymphs of the first generation are the most important economically on June-bearing cultivars of strawberry. Feeding by TPB can cause death of flowers and depending on the degree of feeding, can make fruit unmarketable. Severe deformation is commonly referred to as "apical seediness," "button berries" or "catfacing." Generally the earlier TPB feeding occurs, the more severe the deformation/injury to the fruit is.
To determine whether TPB is active in strawberry fields, a monitoring program should be followed twice per week, starting at first bloom until first harvest. Monitoring should be done by cultivar or field depending on what is the smallest area of plants that the grower is willing to treat. Results from specific varieties should be kept separate, because later varieties usually have higher populations of TPB nymphs and potential injury. Monitoring is done by tapping of flower or fruit clusters into a shallow dish and the cluster scored as being infested or not. If a field is considered infested (see http://www.gov.on.ca/OMAFRA/english/crops/facts/92-108.htm for a sequential sampling plan), management action should be taken to reduce the level of berry damage.
An integrated program of different pest management strategies is essential for effective pest management in strawberry. Broadleaf weeds provide alternate hosts and encourage the build-up of resident TPB populations so good weed control throughout the season, in and around the strawberry field, can reduce overwintering TPB. Preferred weed hosts for TPB include dandelion, chickweed, wild mint and goldenrod. Monitoring dandelions growing close to a strawberry field is also effective in early detection of the presence of tarnished plant bug in the area. TPB will also migrate out of grassy areas after mowing, so mowing in nearby fields should be delayed during strawberry development.
For chemical control, the application of an insecticide should be considered when the threshold of 0.15 nymphs per flower cluster is reached (see sampling above). Our Michigan experiences with tarnished plant bug indicate that they are typically detected when about a quarter of the blossoms are open on an early season variety such as Early Grow. To control TPB, Brigade, Sevin, Thiodan and Danitol are registered for application in strawberry. Pyrethroids such as Brigade and Danitol are very toxic wide-spectrum products, which destroy beneficials and may induce two-spotted spider mite infestations. Repeated use of any of these insecticides should be avoided. Rotation of insecticides between pyrethroids and the other two available types, Sevin and Thiodan, should be practiced to avoid resistance by TPB and to lower the likelihood of mite problems from developing. Because of the potential for bee kills from use of insecticides during bloom, growers should use extreme caution when planning sprays for TPB. Consult the label carefully for how to avoid killing pollinators, and do not use wettable powder formulations.
If strawberry clipper weevil (SCW) is also observed at the time when TPB requires management, Brigade or Danitol should be used. Thiodan and Sevin are less effective on SCW. If meadow spittlebug is present in high numbers, than either Brigade, Danitol or Thiodan should be used to control both pests. Generally, these insecticides possess enough residual action to control nymphs for five to seven days under normal conditions. The interval should be shortened if TPB populations remain above threshold after application, or if a rain occurs within two days after an insecticide application.
The two-spotted
spider mite (TSSM) is a
widespread pest of strawberry, but it is often kept in check by natural
enemies. A good understanding of the role natural enemies play in the biology
of TSSM can enable mite management decisions that preserve natural enemy activity, while protecting strawberries from TSSM damage.
TSSM feed by rasping on the underside of leaf tissue, and their feeding causes
bronzing that becomes visible on upper surfaces if TSSM populations are very
high.
However, infestations rarely
become high enough to warrant the cost of an acaricide treatment, but regular
monitoring can help to determine whether populations get to this point. The
miticide market is one area where we are seeing rapid growth in the
availability of new products. For more details on mite management in
strawberry, see the article available in the May 14, 2002 issue of the Landscape
Alert online at:
http://www.ipm.msu.edu/CAT02_frt/F05-14-02.htm
- 4
A Section 18 emergency exemption has again been issued by the EPA for use of Topsin M WSB (thiophanate methyl) in blueberries in Michigan. The effective period runs from May 5 until September 30, 2003. This emergency exemption was requested to fill the void left by the withdrawal of Benlate. Many growers have used up their Benlate stocks and do not have access to additional product for the current season.
Topsin M is in the same chemical class (benzimidazoles) as Benlate and breaks down to the same active ingredient. Topsin M and Benlate are practically similar in their spectrum and efficacy of control. Topsin M has a full label for use in strawberries and grapes. Cerexagri, Inc. is currently working on obtaining a full registration for Topsin M use on blueberries. Growers who want to use this product should be in possession of a copy of the special label at the time of use.
Target diseases on the label are Phomopsis twig blight and canker, Fusicoccum canker, mummy berry, anthracnose fruit rot, and Botrytis blossom blight. The recommended application rate is 1 lb/acre, and a maximum of three sprays (3 lbs product) may be applied (this includes Benlate). Applications may be started at green tip and repeated at 7-10 day intervals. However, use of this fungicide will be most appropriate in the period from pink bud through early fruit development, as the Phomopsis, anthracnose and mummy berry pathogens are all active at that time.
Topsin M should be used in combination or rotation with non-benzimidazole fungicides, such as Ziram or Captan, to reduce the risk of resistance development. The pre-harvest interval is 7 days.
The sign-up for the Crop Disaster Assistance Program will begin on June 6, 2003. The program will provide payments for qualifying crop losses that occurred during either the 2001 or 2002 crop year.
Crop disaster payments will be calculated in a fashion similar to that employed for the 2000 disaster program. The crop value that will be used for payment calculations will be the larger of the Actual Production History (APH) price election of the national (NASS) season-average price.
The disaster payment may equal, but not exceed, 95 percent of what the crop’s value would have been under average conditions. Your local Farm Service Agency will handle the Crop Disaster Program enrollments. They would like to encourage growers and producers to contact them as soon as possible so you can start assembling the records necessary for participation.
A cool wet week. Rain fell for five of the last seven days. Total precipitation was from 2 to 4 inches and in some places more. Soils are wet with standing water in poorly drained fields. Generally lows in the 40's and highs in the 60's. Friday and Saturday (May 10-11) saw highs near 80. High winds and rain and some hail with cooler temperatures on Sunday. Leaves are tattered and old trees and limbs are down. Warm weather forecast for the end of the week promises a thinning window for apples and pears.
Growing degree day totals through May 11
|
|||
|
Location |
GDD 42 |
GDD 45 |
GDD 50 |
|
559 |
441 |
278 |
|
|
Lawton |
571 |
454 |
294 |
|
555 |
449 |
290 |
|
|
429 |
330 |
201 |
|
Apricots, peaches and sweet cherries should be protected from brown rot.
Apricots are growing rapidly. Smaller fruit are dropping. The crop is heavy and will require thinning. Wet windy conditions are perfect for bacterial spot and grower should apply materials to reduce losses.
The peach crop is heavy and will require thinning. Peach leaf curl symptoms are showing up. Oriental fruit moth trap catches are up again. We first caught Oriental fruit moth on April 15. Then cool weather shut down the flight until about April 19. Again cool weather shut down traps catch. Biofix is the sustained capture of moths in pheromone traps not the capture of a few adults on a warm night. We biofixed Oriental fruit moth on Thursday, April 24 at about 250 GDD45. In Southern Berrien County biofix was on about April 19 at 225 GDD base 45. We are now at 440 GDD45, 190 GDD since Biofix. Treatment for Oriental fruit moth is targeted for early egg hatch at 150 to 170 GDD45 after biofix. Treatment of peaches to prevent shoot strikes should be on now. To protect the fruit growers can wait until shuck split. Green peach aphids are out and forming colonies.
In cherries the crop is generally light. Growers need to maintain protection against cherry leaf spot. Plum curculio will be a problem later in the week. Sweet cherries have a light crop with fruit scattered and far between. Sweet cherries need to be protected from brown rot all season long.
European plums are in the shuck. Japanese plums are out of the shuck. Last week was favorable for black knot. Rain and temperatures above 55°F favor black knot infections. Growers need to protect against plum curculio.
Apple bloom is ending. Bloom was heavy for most varieties. Marginal scab infection periods occurred on May 4 and 7. We are finding young scab lesions now. Cool temperatures kept fire blight bacterial populations low or nonexistent through Thursday. Friday and Saturday were warm humid days with winds that preceded a cold front and rain on Sunday. Maryblyt predicted a blossom blight fireblight infection on Saturday. Conditions on Saturday and Sunday were also good for trauma blight. Bacteria populations were probably spotty; high is some orchards and low in others. Orchards that had fireblight last year have the greatest risk of sufficient population buildup in two days to cause infection on Saturday. There is still no ooze from over wintering fireblight cankers. Cool temperatures should keep bacterial populations low this week. A few codling moth adults were trapped Friday in Southern Berrien County. We expect sustained flight and biofix late this week when warm weather returns. European red mite egg laying has begun. Adult mites are scarce. No spotted tentiform leafminer mines have been found yet. Leafroller larvae are attacking fruit buds. Growers should plan on petal fall sprays after bloom to control insects including plum curculio and Oriental fruit moth.
Warm weather should return by late this week. This will be a good thinning window for apples with temperature rising from the mid 60s on Thursday into the 70s on Saturday and Sunday. This would be a good time to put on thinning sprays at the beginning of a warming trend with several days in the 70s. Keep track of the weather and read the apple thinning article by Phil Schwallier in the April 29 Fruit CAT Alert or the May Fruit Grower News. Here in the Southwest frost damaged leaves should make thinners more effective. Heavy set should also increase thinning. An early thinning application will allow time for a second thinning spray if needed.
Pears look good. There is still a little straggling bloom that can be infected by fireblight when warm weather returns. Now is the thinning window for pears. NAD is used after petal fall. Fruit drop has started in Southern Berrien County.
Blueberry bloom has begun. A few open flowers can be found in most fields. Growers need to continue to protect against mummy berry. Cherry fruitworm catch has begun but the cold weather as shut it down. Leaf roller larvae are attacking fruit buds. During bloom growers can use Bt formulations to control moth larvae as such as cranberry fruitworm and cherry fruitworm. Bts should only be used after egg hatch has begun because it breaks down rapidly and has a very short residual time. Also Bts are best used under warm conditions so this coming week's weather is poor for Bt use.
Grapes have two leaves out and both flower clusters exposed. Many grower applied protectant materials to reduce phomopsis. After the rain we had last week these sprays need to be reapplied. Cool wet conditions this weekend were a black rot infection period and probably were infection periods for phomopsis and powdery mildew as well. Rufus Isaacs reports that grape berry moth adults were trapped in Van Buren County. Growers need to time their pesticide applications for egg hatch, near bloom time and not the flight of adult males caught in traps. Early season trap catch is more an indication of population levels in a vineyard than the need to treat now.
Grape growing degree days totals from April 1 to May 11
|
|
|
Location |
GDD 50 |
|
SWMREC from April 1 |
217 |
|
Lawton From April 1 |
249 |
Strawberries are blooming. Spittlebugs are out. Growers need to apply fungicides during bloom to reduce fruit rots.
Raspberry buds are just visible in growing shoots. Fall Raspberry primocanes are 2 to 4 inches tall.
Cranberry beds are greening up and swollen buds are easy to find.
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 May 19 at 5:00 PM. For more information check the Fruit Hotlines at Van Buren (269) 657-6380 and Berrien (269) 944-4126 ext. 1 counties.
A cool wet week for
Southeast Michigan has brought between 2 and 3 inches of rainfall to most farms
across the region. Extreme wind over the weekend has made pollinating
conditions in apples very difficult, and some concern for trauma blight in
apples. Cool nighttime temperatures, with the exception of late last week, have
continued to hold back many insects. Soil temperatures remain cool for this
time of the year, mostly in the high 50’s to low 60’s. Soil moisture is now
adequate to above adequate. Many fruit growers are seeing farm ponds recharged
to a higher level than they have in the last four to five years. With all the
moisture a fair amount of spraying was done for disease prevention in tree
fruits.
Growing degree day totals for March 1 to May 13 |
|||
|
Location |
GDD42 |
GDD45 |
GDD50 |
|
Flint |
542 |
421 |
275 |
|
Romeo |
473 |
373 |
220 |
|
Petersburg |
531 |
415 |
269 |
Apples are at full bloom to early petal fall in the southern part of the
region, and king bloom on Red Delicious in the northern part of the district.
We did have some fairly good pollinating weather for several days last week at
which time bees were very active in apples.
For insect activity,
we have not seen codling moth larvae as of yet, however, they’re expected to
hatch later this week as temperatures begin to warm up. I’ve seen a low number
of larvae from the following apple insects; green fruitworm, fruit tree
leafroller, tufted apple bud moth, and redbanded leafroller. Oriental fruit
moth trap catches are generally low at most farms across the region, with 2 to
3 being caught per trap. However, I’ve heard of some reports with trap catches
as high as 35 to 40 and few even higher than that in special circumstances,
such as around bulk bin storage yards or previously heavily infested blocks.
Rosy apple aphid
stem mothers are starting to be seen, however very few colonies have been
detected as of yet. Spotted tentiform leafminer trap catches are down and
predators seem to be working fairly well. There are a good number of eggs in a
few apple blocks. European red mite egg hatch occurred late last week – the
populations are fairly low. There also continues to be reports of tarnished
plant bug adults. Apple scab lesions continue to be caught with each wetting
event. The numbers have dropped considerably from late April. I’m not quite
sure yet if these high spore rod trap catches in late April indicate that we
may be done with spore discharge early this year or not. Time will tell, so
stay tuned for details. I am catching spores in the range of 20 to 40 per rod.
No visible apple scab lesions have been seen.
Pears are at petal fall at many farms. Pear psylla egg hatch has occurred
with high numbers in a few blocks.
Peaches continue to grow well with a nice crop of young fruit developing.
Oriental fruit moth sprays will be going on in peaches over the weekend or
early next week. I have seen some early symptoms of peach leaf curl in a few
blocks. No green peach aphids have been detected.
Sweet cherries are currently at petal fall or in the shuck.
There is a tremendous amount of variability in our sweet cherry crop across the
region this year. Most blocks appear to have been hit hard with winter injury
from cold in early to mid December of last year. There are some blocks that
appear to have flowered normally and have a nice crop of sweet cherries coming
along. No major press problems to report in sweet or tart cherries at this
time.
Strawberry flowers continue to emerge from the crown at most farms. I expect to
see bloom in strawberries fairly quickly. Leaves from newly planted fields are
continuing to emerge quite well. Strawberry growth has improved a great deal
over the last week with adequate rainfall. Tarnished plant bugs have been seen
feeding on dandelion adjacent to several strawberry fields. Some spittlebug has
been seen at a few strawberry farms. No strawberry clipper has been seen in the
last week. However, it was detected at a few farms early the week before last.
A few two-spotted spider mites have also been seen in strawberries.
Raspberry canes from fall red raspberries continue to emerge from the soil, most are at a length of 3 to 4 inches. However there have been some farms where cane emergence seems to be delayed or is sparse at this time. Summer raspberries continue to see some cane tip collapse from cold weather last December. Flower buds are beginning to be visible on a few canes.
Blueberries are nearing blossom at a few farms. Mummy berry shoot strikes have also been seen at a few farms. Young twig death continues to be apparent in many blueberry plantings.
|
Weather Station |
GDD42 |
GDD50 |
|
West Olive |
468 |
228 |
|
Holland |
497 |
244 |
Most apple varieties are in the early bloom to full bloom stage right. The very first rosey apple aphids can be found in blocks that did not have pink sprays applied – mostly stem mothers present, but some colonies are just starting to form. Spotted tentiform leafminer continues to fly and eggs are being laid – expect the first tissue feeders to be found in the next week or so. Oriental fruit moth trap numbers have really increased in some areas with the warmer weather this past weekend – numbers will probably drop off a bit with cooler weather this week. Petalfall control timing for insects will be very important this year because of all the rain we’ve had since pink applications – it’s not too early to start planning your petalfall measures. Early varieties will show some petalfall most likely by the end of this week. Be sure bees are out of blocks – both in your blocks and your neighbors – before using any insecticides.
We’ve had five infection periods for apple scab this season and lesions from the first infection were just found late last week in unsprayed blocks. Lesions from the heavy infection on April 30 should be found soon.
Sweet cherries are in full bloom, and brown rot prevention should be considered. Buds appear to be healthy.
Because of the potentially large crop, apple growers are encouraged to consider petalfall thinning if the weather is favorable. There will be two thinning meetings in the Grand Rapids area – the final dates are a week later than reported in this article last week -- May 20 at Tom Rasch’s farm on 10 Mile in Belding and May 27 -- at Rasch Bros. Storage on Stage. Both meetings will start at 7:00 PM. Call the Clarksville Horticulture Experiment station (616-693-2193) for more information or check the Code-A-Phone at 616-451-8065.
Blueberries in west central Michigan are getting closer to bloom. Bluecrop and Blueray are in the late pink stage while Jersey is in early pink. Low temperatures that occurred in the region during the weekend brought rain to west central Michigan. Rain accumulation during the past 48 hours was in the range of 1 to 1.2 inches. Low temperatures have not been a problem since most of the early blueberry varieties are still in a growth stage where they can sustain up to 24°F without major problems.
However, there is an extensive damage to blueberry fields alongside the major highways around west central Michigan due to the combined effect of road salt and winter damage. In both, Ottawa and Allegan Counties, blueberry fields alongside US 31 and I-196 suffered up to 100 percent bud kill between the first 300 ft away from the road. Damage diminished at the back of the fields. However, this was higher than in fields located in secondary roads (see accompanying figure).
Growers have initiated application against the mummy berry and Phomopsis twig blight. The problem regarding the use of the fungicides Indar and Topsin M was solved since the EPA issued a Section 18 permit during the past week.
Regarding insect pests, redbanded leafroller (RBLR) adult moth catches in pheromone traps are in decline. But larvae and feeding damage can be found at low numbers in Ottawa and Allegan Counties (2 to 3 percent). No cranberry fruitworm (CBFW) or cherry fruitworm adult moths have been caught in pheromone traps, yet.
This past week was cooler than normal and quite wet. We have had about 2” of rainfall through out the area. In terms of total precipitation, we have already surpassed the normal values for the month of May. Some spotty hail was reported at the southern part of Oceana County.
|
Location |
GDD42 |
GDD45 |
GDD50 |
|
Hart |
322 |
270 |
155 |
|
Ludington |
344 |
256 |
135 |
|
Bear lake |
350 |
263 |
136 |
Most of the apple varieties are in pink to full pink. Idared has just started to open first king flowers. Pears are approaching full bloom.
Since last week, there have been two significant apple scab
infection periods. The good news about
all these rains is that they are flushing out the apple scab spores. Currently,
we have between 51 and 67 percent (depending on location) mature spores. The
highest spore discharge was at tight cluster. The rains of May 8-10
and 10-12 produced still high spore discharge, however, there is a
declining trend in the actual number of released spores. With the apples
entering the bloom period fireblight is getting more and more into the focus of
disease control. Normally, this would be the period of elevated concern,
however, with the temperatures that we have been having, fireblight is not
even a remote possibility at the moment. Maryblight is indicating "0"
for the EIP.
Scouts are reporting finding green fruitworms, rosy apple aphids, redbanded leafrollers, spotted tentiform leaf miners, first egg hatch of European red mites. In pears, pear psylla eggs could be found.
Peaches (Red Havens) are in full bloom. Canning varieties are showing 30 to 50 percent open blossoms. Brown rot and bacterial diseases are of concern. Complete coverage is necessary to insure good disease control under the weather conditions that favor disease development. Scouts are reporting finding Oriental fruit moth in traps. We are taking last Wednesday (May 7) as a biofix date -- at the time we had 222 GDD45 in Hart and 209 GDD45 in Ludington. No report of any catches in Manistee County yet.
European plums are approaching full bloom. Brown rot and black knot are of concern at this time.
Sweet cherries are in full bloom to first petal fall.
Tart cherries have 70 to 80 percent open flowers. With the exception of
Thursday and Saturday, last week’s weather was not very conducive to
pollination. The outlook for today and the next couple of days is much better,
which should result in very good pollination for the tart cherries. This is a
prime time for bacterial canker development. Brown rot (blossom blight) is
still of concern. There is an unusual flush of new leaves this early in a season.
This is due to the strong carbohydrate reserves in the trees from the lack of
crop last year. These young leaves are subject to cherry leaf spot infections.
Tight cover is recommended for best control.
GDD42 318
GDD50 133
Rainy, damp conditions have been common during the past week, with the exception of a warm, sunny day on Saturday, May 10. Degree day accumulation, base 42, is very close to a long term historical average, and hence the stage of tree development is "normal" at this time.
In sweet cherries, recent cool weather has been ideal for developing populations of the
bacterial canker pathogen, Pseudomonas syringae. Similar conditions in
2002 were followed by a hard frost on May 19, which led to the severe bacterial
canker infections. Let's hope this year we do not see any frost conditions in
the coming days. Bloom is generally very sparse due to the March 3 winter
freeze event. Winter injury in wood is becoming more evident as spring
progresses, particularly on young trees. Leaf tissue is exceptionally well
developed compared to the stage of flower development in trees with few
remaining flowers. Trees with few flowers have more resources than normal for
leaf development.
In tart cherries, spring frosts have damaged some buds, but at this point substantial bud
damage is generally present only in low areas of blocks. The crop potential in
NW Michigan appears to remain good. Balaton lost some flower buds to the March
3 winter freeze, and as in sweet cherry, we are seeing plenty of leaf tissue
that is susceptible to cherry leaf spot (CLS) infection before the tree reaches
bloom. Montmorency in some early sites also have fully expanded leaves, not
just bract leaves. These leaves are susceptible to CLS infection. Spore release
can occur during early bloom. Considering the early start that leaf spot had
last year, growers that have trees with fully expanded leaves should protect
for leaf spot from here forward. Brown rot pressure is light with the cool temperatures.
Apples experienced a moderate scab infection period
on Sunday and Monday, May 11 and 12. This occurred at a time when spore release
is typically high. With early varieties nearing pink, powdery mildew should be
controlled, particularly on susceptible varieties like Ida Red and Cortland.
Insect activity remains low. Rosy apple aphids are difficult to find. Spotted
tentiform leaf miner trap catches averaged 32 per trap. Populations of European
red mite eggs are light, with no hatch reported so far.
Pear psylla eggs are easy
to find on spurs and should be hatching out soon.
Climbing cutworms have not been very active with the cool temperatures, but as the nights warm, they will increase activity on newly planted tree fruit and grapes. Grapes that over wintered may have few live buds above the snow line, so in order to renew trunks, it may be critical to manage this pest this year.
Over the next week, high temperatures will be increasing to near 70°F. The 6-10 day and 8-14 day outlooks call for above normal temperatures.
The southern Lower Peninsula has a chance for rain Wednesday night (May 14) through Friday (May 16), while in the northern Lower Peninsula, no rain is forecast for the upcoming week. Since May 1, stations in the Lower Peninsula have had five to seven days with precipitation with significant amounts on May 1, May 5, and May 11. Daily rainfall totals were generally lower in the northern Lower Peninsula, but on May 11, Benzonia received 2.65 inches of rain. Flood warnings and watches are in effect in the Upper Peninsula. The storms on May 11 were accompanied by high winds. Soil moisture levels are now rated normal to above normal across the state.
