June 10, 2003
In this issue
Tree fruit news
§ Impact of cool weather on codling moth monitoring and management
§ Apple scouting through the summer months
§ TNRC trapline data: Oriental fruit moth
Small fruit news
§ Section 18 labels approved for Admire and Provado in Michigan blueberry
§ Japanese beetle survey: Help us help you
§ Rainy weather conducive to phomopsis development in grapes
§ Pre-harvest Blueberry IPM Meeting
Other news
§ Field Day at Trevor Nichols Research Complex
§ Regional reports
§ Weather news
The cool temperatures over the last three weeks have prolonged the calendar time normally necessary for codling moth to go from first sustained flight (biofix) to egg hatch. Most counties in the central and southern regions of the state biofixed for codling moth on the May 17-18 weekend, but have only accumulated 150 GDD base 50 since that time. The research that the codling moth degree-day model is built on shows early egg hatch to be at 250 GDD after biofix. Therefore the eggs that were laid by those initial codling moth adults three weeks ago still require an additional 100 GDD base 50 to hatch. This illustrates the benefits of monitoring GDDs, which correlate to insect development, instead of making management decisions solely on a calendar date basis.
It should be noted that not all insecticides should be timed for the 250 GDD egg hatch timing. For example, if you plan to use the insect growth regulator, Intrepid, then biofix + 150 GDD spray timing is optimal. The following chart, modified from the Michigan Fruit Management Guide (E-154) should help distinguish optimal timing and use of some insecticide options.
|
Common name (Trade name) |
GDD timing post-biofix |
Rate/acre |
PHI |
REI |
|
Azinphosmethyl (Guthion
50WP) * 14 day REI for activities like hand thinning (see label) |
250 |
2 lb |
14 d |
48 hr* |
|
Phosmet (Imidan 50WP) |
250 |
2.25-3.0 lb |
7 d |
24 hr |
|
Esfenvalerate (Asana XL 0.66EC) |
250 |
9.6-14.5 oz |
21-28 d |
12 hr |
|
Fenpropathrin (Danitol 2.4EC) |
250 |
10.6-21.3 oz |
14 d |
24 hr |
|
Spinosad (SpinTor 2SC) |
250 |
7.5-10.0 oz |
7 d |
4 hr |
|
Acetamiprid (Assail 70WP) |
200-250 |
3.4 oz |
7 d |
12 hr |
|
Methoxyfenozide (Intrepid 2F) |
150 |
16 oz |
14 d |
4 hr |
|
Pyriproxyfen (Esteem 35WP) |
100 |
5 oz |
45 d |
12 hr |
The summer period covers over three months of the growing season and in some cases several generations of a single pest. In this article, we will introduce pests and the appropriate scouting techniques in the chronological order that they will most likely appear in the orchard. The pests are: European and twospotted spider mites, green apple aphids, spotted tentiform leafminer, tarnished plant bug, apple scab, plum curculio, and white apple and potato leafhoppers.
European red mite and twospotted spider mite scouting continues through the season, although thresholds may change. We monitor mites using a 100-leaf sample, 50% spur leaves and 50% shoot leaves, throughout the summer period. Control measures may be warranted for mature, healthy trees based on the following thresholds:
§ 2-3 mites per leaf from petal fall to mid-June
§ 5-7 mites per leaf from mid-June through July
§ 10-15 mites per leaf in August
The presence of predaceous mites (more than 1 per leaf) may justify delaying a treatment and repeating the cycle the following week.
Monitoring for green apple aphids (GAA) will continue as long as new terminal growth is present. GAA prefer to feed on the underside of leaves on growing shoot tips and stems. Estimate the average number of aphid infested leaves on terminals. Generally, an average of three to four infested leaves is needed before fruit damage from honeydew occurs. In young orchards, lower levels of aphid infestation (1 to 2 leaf colonies) will inhibit growth of trees.
Continue to monitor egg and larval stages of spotted tentiform leafminer, but now include the tissue-feeding stage. Use the accompanying table for monitoring and treatment decisions.
|
STLM |
End
of 1st generation |
Early
2nd generation |
Late
2nd generation |
Early
3rd generation |
|
Monitoring |
Check
50 tented mines from 25 trees to determine % parasitism. |
Sample
50 or 100 leaves per block, count # mines per leaf. |
Sample
50 or 100 mines and determine % parasitism. |
Sample
50 or 100 leaves per block, count # mines per leaf |
|
Threshold
(vary based on tree structure and variety) |
|
2-3
per leaf, higher if 30-35% parasitism was found in first sample. |
|
5-8
mines per leaf, higher if 35% parasitism |
Continue to monitor for tarnished plant bug, mindful that orchard mowing or drought conditions may drive adults from the ground cover into the trees. Also continue to monitor for new apple scab lesions on fruit and leaves, new symptoms of powdery mildew, and fire blight infections.
Monitoring for plum curculio adults and egg-laying should continue for at least 6 weeks after petal fall. Any new fruit damage should be noted as to location and severity. Oriental fruit moth monitoring will continue with traps, but the focus for damage assessments should now be on fruit. Fruit injury from Oriental fruit moth is often indistinguishable from codling moth injury. Control treatments for first generation Oriental fruit moth egg hatch occurs at 150-170 degree days post biofix base 45ºF, second generation egg hatch at 1125-1150 degree days base 45ºF, and third generation at 2250-2280 degree days base 45ºF.
Within two weeks of petal fall, you may begin to see white apple leafhopper nymphs and potato leafhoppers. White apple leafhoppers are the most significant of the two and will appear as pale white nymphs on the lower surfaces of older leaves. These nymphs will develop into adults over a 30-day period, the second generation emerging 30 days later. Note the difference between the white apple leafhopper and the potato leafhopper, which is green and stays mostly near the actively growing terminal leaves. We will monitor for first generation white apple leafhopper by counting the number of nymphs found on 100 leaves selected from leaf clusters and reporting this as the average number of nymphs per leaf. For the second generation we will select our 100 leaves from the mid-shoot area. Thresholds for trees with sparse canopy and a heavy crop load is less than for trees with luxurious canopies. Generally, 1 to 3 leafhoppers per leaf will bleach around the midrib only, 8 per leaf will stipple the entire leaf and create problems for workers at harvest.
Obliquebanded leafroller pheromone-baited traps should be placed in the orchard three weeks after petal fall, and monitored for the first sustained catch for biofix purposes. The obliquebanded leafroller model will predict egg hatch and help determine when to start monitoring for larvae. Larvea from the first, or summer generation, may be found in a couple of different locations in the tree. Newly hatched larvae frequently head for the tip of the new terminal growth where they will feed on unfolding leaves. Larvae may also feed on fruit, especially where it is clustered, by attaching a leaf to the fruit and feeding underneath it. These larvae are more difficult to detect but are important due to their potential of causing significant economic loss. Monitor by counting the number of larvae found on100 terminals and fruit clusters.
|
DD° Base
42 (Post Biofix) |
Event |
Action |
|
Tight
cluster |
Majority
of larvae have emerged from shelters |
Examine
fruit buds for larval activity |
|
0 DD°
=biofix (~900 DD° after Jan 1) |
1st
sustained moth captures |
Set
DD° = 0 |
|
220-250
DD° |
Peak
moth flight - overwintering generation |
|
|
400-450
DD° |
Start
of egg hatch |
Timing
for treatment |
|
1000
DD° |
End
of egg hatch |
|
|
2300
DD° |
Peak
moth flight - 2nd generation |
|
|
2750
DD° |
Start
of 2nd generation egg hatch |
Timing
for treatment |
San Jose scale should be monitored with pheromone-baited traps if there is a history of pest problems. Yellowish crawlers generally are present 300-350 degree days base 50ºF after the first catch of either generation. Note the presence or absence of crawlers and their subsequent damage to fruit.
Dogwood borer overwinters as larvae in the burr knots or trunk of the tree. You should be scouting for reddish-brown frass and pupal skins in and around burr knots as an indication of an infestation. Codling moth monitoring will continue with traps, but with the addition of damage assessments on fruit. Note the location and severity of any fruit injury.
|
DD° Base
50 (Post Biofix) |
Event |
Action |
|
Pink
bud |
Development
of overwintering larvae |
Set
traps |
|
0
DD° =Biofix (~200 DD° after Jan 1) |
1st
sustained moth captures |
Set
DD° = 0 |
|
250
DD° |
Start
of 1st generation egg hatch |
Timing
for 1st treatment if over threshold |
|
1000
DD° |
Expected
end of 1st generation activity |
|
|
1200-1250
DD° |
Start
of 2nd generation egg hatch |
Timing
for 1st treatment if over threshold |
|
2100
DD° |
Expected
end of 2nd generation activity |
|
Approximately 6 weeks after petal fall or before 900 days base 50 (late June in southern Michigan to second week of July in northwest Michigan), apple maggot sticky traps should be placed in the orchard. Adult fly emergence often follows rainfall events, with emergence typically delayed if the soils remain dry. Peak emergence generally occurs between 1400 and 1700 growing degree days base 50, but is highly dependent on site specific weather conditions.
Emergency Section 18 labels have been granted by the Environmental Protection Agency for use of two formulations of imidacloprid against Japanese beetle in Michigan blueberries. The labels for Provado 1.6F and Admire 2F cover all Michigan counties, and allow application of these two products until September 30, 2003. This article provides some recommendations for blueberry growers to achieve maximum effect from applications of these products.
Admire is the soil-applied formulation of imidacloprid,
which targets the young larvae hatching from eggs that will be laid in the soil
this summer. Application of Admire is therefore a preventative treatment to
reduce beetle infestation in 2003. It is important to realize that this
treatment will have minimal effect on beetle emergence this year because most
grubs are fully grown by late June and are not at a susceptible stage.
Admire should be applied to grassy regions of blueberry fields where egg laying is expected to be highest (this is likely to be grassy row middles, drive lanes, and headlands). Application must be made by the start of Japanese beetle egg laying (typically by July 4) for it to be present in the soil when larvae hatch. Applications must be watered in with 0.5 to 1 inch of applied water or rain for it to move through the thatch layer and be present in the root zone where larvae start feeding. There is a seven-day pre-harvest interval (PHI) with this product.
Our research trials on Japanese beetle grubs in Michigan blueberry soils conducted in 2002 showed similar activity of the 16 oz and the 25 oz rates when applied in mid-July, providing over 85 percent reduced grub density in the fall compared to untreated areas. Even greater control is expected from an application timed before egg laying begins. Imidacloprid is quite stable in the soil, and so only one application is required per year, providing control of larvae throughout the two to three month egg-hatching period. This longevity makes this insecticide one of the few where effectiveness is not greatly affected by application a week before egg laying begins.
The greatest densities of Japanese beetle grubs have generally been found in permanent sod around blueberry fields. An economical use of Admire might be to apply it only to headlands and drive lanes where beetle egg laying and grub densities are highest. Using this approach on a 20-acre field this year would be expected to significantly reduce the amount of beetle immigration in 2004, spraying to less than one acre of total land (the headlands and drive lanes).
The foliar formulation of imidacloprid, called Provado, can be used to help protect foliage and fruit from feeding by Japanese beetle. Application of this product at 8 oz per acre provides initial lethal activity against adult Japanese beetle. As the compound is absorbed into the leaves, lethal activity declines and sub-lethal effects, such as reduced feeding and paralysis continue for seven to ten days. This product has a three-day pre-harvest interval. This product requires thorough coverage for optimal control, because beetles can move to untreated regions of bushes if residues are not throughout the bush.
Regardless of the formulation used, a maximum of 0.5 lb active ingredient is allowed. This means that if Admire was applied to a field at the 16 oz rate (0.25 lb active ingredient), then two applications of Provado at 8 oz could still be made. However, if the 25 oz rate of Admire was used, then only one Provado application could be made.
Environmental safety considerations outlined on the labels should be closely followed, particularly near bodies of water. As always, label directions should be carefully followed when using these products, and the label must be in the possession of growers applying these products. Copies can be acquired from suppliers, or the Emergency labels can be downloaded by visiting these links. Admire in blueberries:
http://www.ipm.msu.edu/CAT03_frt/pdf/6-10-03Admire.pdf
Provado in blueberries:
http://www.ipm.msu.edu/CAT03_frt/pdf/6-10-03Provado.pdf
Editor’s note: Another resource for labels is the MSU Fruit Area of Expertise Team web site. The team posts all pesticide Section 18 and 24c labels throughout the season at: http://web1.msue.msu.edu/fruit/MIfrt_s18.htm
As many growers, gardeners and homeowners in the Lower Peninsula know, Michigan faces a prolific pest in the Japanese beetle. This iridescent beetle has moved from the eastern coast of the United States, where it was introduced, and is now a significant pest of turfgrass, small fruit and some field crops. In 2002, the National Agricultural Pest Information System (NAPIS) reported Japanese beetles within the southern most counties of the Lower Peninsula (Figure 1). However, we anticipate its spread to continue to the north and west across Michigan.
Effective management of this pest requires a proactive approach. To better inform the public and assist researchers and state extension agents, our colleagues at the University of Illinois have designed a website to help us track this pests’ spread across Michigan: http://www.pmcenters.org/northcentral/jbeetle/
At this website, you can click on the reporting beetles link, and follow the subsequent instructions to report the location and level of Japanese beetle infestation. We invite all who have encountered this beetle in their home or commercial fields to report them to this website. This information will be reported back on the website as regional maps, illustrating the current range of Japanese beetle.
Reporting Japanese beetle infestations will help us better understand the landscape and climate factors that may impact this invasive species’ ability to spread across the US. In return, there are several pages describing the biology of the beetle and management options for the adults and grubs. By helping us to identify the current range and population level, we can better help you to manage this destructive pest.
Figure 1. 2002 reported range of Japanese Beetle (JB) in US. Data from National Agricultural Pest Information System. Figure from National Agricultural Pest Information System web site:
http://www.ceris.purdue.edu/napis/pests/jb/imap/jb2002.html
The rainy, cool spring so far has been conducive to spore release and infection by Phomopsis viticola, the fungus that causes Phomopsis cane and leaf spot in grapes. Early in the season, spore release tends to be patchy in vineyards, but later on, spores are detectable at most sites. Rainwater caught in traps (5-inch-diameter funnels attached to 2-liter soda bottles) that were placed in vines in a Niagara vineyard in Van Buren County has contained infectious spores every week since mid-April of this year. Over a million spores per trap have been collected on occasion. Phomopsis spores are rain-splash dispersed and their dispersal range is generally limited to the distance that rain drops splash. However, rain accompanied by high winds can lead to dispersal over longer distances. More typically, Phomopsis spreads within vines and between neighboring vines. Spread across rows is less common.
Conditions also have been good for infection. The optimum temperature for infection of shoots is 60ºF, and of leaves is 60-68ºF. However, infection of both tissues is possible between 50º and 86ºF. At least 6 hours of leaf wetness is required at the optimum temperature and up to 20 hours of wetness are needed at the extremes. Evidence of Phomopsis infection, such as numerous small yellow spots with dark brown specks in the center, can now be seen on leaves in unsprayed or lesser sprayed areas in vinyards. Large numbers of lesions can lead to puckering of the leaves. Some shoots are also starting to show small brown to black scabby areas. If you are seeing a lot of leaf lesions, this indicates a high risk of rachis infections. While some rachis infections on flower clusters may have occurred already, the probability of spores hitting the rachis may be greater now that flower clusters have expanded. All indications are that spore release will continue through bloom and early fruit development, so be sure to protect the clusters during this period.
Control of Phomopsis is recommended at least through berry touch. In areas where bloom has not yet occurred, EBDC sprays are the most economical option for disease control. Where bloom has started, strobilurins (e.g., Sovran or Abound) or Ziram are good options. After bloom, strobilurins have consistently provided better control of Phomopsis than strictly protectant fungicides in small plot trials in Michigan. However, this could be related to canopy density and coverage. Since rachis infections are mostly to blame for yield losses, thorough coverage of clusters is crucial in protecting the rachis and berries from infection. Increased spray volume, spraying every other row or even every row, and reduced speed can help achieve this.
Berrien County MSU Extension will host a twilight pre-harvest blueberry IPM meeting on Thursday, June 19. It will start at 6:30 PM and end at 8:00 PM. It will be held at Klug’s Blueberry Farm, Edward Klug, owner, 11984 Landon Rd, Baroda, Michigan. The farm is located just north of Browntown between Cleveland and Holden Roads (southwest of Baroda, southeast of Bridgman). It will include updates on disease, insect and weed management by Drs. Annemiek Schilder, Eric Hanson, and Rufus Isaacs, as well as other helpful information for the pre-harvest time frame.
This meeting has been approved for be one RUP recertification credit. There is no cost to attend the meeting.
We will be having a research field day at the Trevor Nichols Research Complex (TNRC) on Thursday, September 25 from 1:00 PM to 5:00 PM. The field day will focus on insect and disease research and efficacy trials that were carried out this season at the TNRC by Larry Gut, Rufus Isaacs, Mark Whalon, Annemiek Schilder and John Wise. A social time will precede the tour with food and refreshments starting at noon in the new “Angus J. Howitt IPM Training Room.” The TNRC is located at 6237 124th Ave. in Fennville, MI.
See the TNRC web page for directions: http://www.maes.msu.edu/tnrc/
Warmer more normal weather returned after a cold and cloudy beginning of the week. A cold front with high winds and thunderstorms passed through on Sunday (June 8). Hail was reported in some areas. This storm did not affect Lake Shore area growers but the storm gathered strength as it moved inland. A third of an inch of rain or more fell from scattered thunderstorms. This week's forecast is for warmer weather and the chance of showers. Highs by the weekend are predicted to be in the 80s.
Southwest Michigan Growing Degree Day Totals through June 8
|
|||
|
Location |
GDD 42 |
GDD 45 |
GDD 50 |
|
923 |
730 |
454 |
|
|
Lawton: |
981 |
786 |
508 |
|
952 |
767 |
502 |
|
|
763 |
591 |
358 |
|
Insect activity remained low. Rose chafers are emerging. Tarnished plant bug feeding scars were found in apples and peaches. Some plum curculio egg-laying scars were found (apples, cherries, plums and nectarines). Warmer days and nights should bring plum curculio out. We are still catching good numbers of Oriental fruit moth and codling moth. Potato leafhoppers were found in grapes and apples.
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 730 GDD base 45, 480 GDD since Biofix for Oriental fruit moth on April 24. One grower reported shoot strikes but we have not seen any shoot flagging from Oriental fruit moth in the shoot tips. The first rose chafer were found in peaches in northern Berrien County. Tarnished plant bug feeding injury can be found on peach fruit. This is especially a problem after cover crops are mowed and the adults move into the trees and attack the young fruit. Bacterial spot symptoms can be found in some peaches.
In tart cherries, Sunday's high winds caused trees to blow down and blew fruit out of the trees. In some orchards the fruit is marked by frost and wind whip. Bacterial canker leaf and fruit symptoms can be found in tart cherries and are easy to find in sweet cherries. Cherry leaf spot symptoms are beginning to appear. Some plum curculio egg laying scars were found, but so far pressure has been light. We expect that there will be more egg laying later this week with warm humid conditions. Growers need to protect against cherry leaf spot. In sweet cherries early varieties are starting to yellow to straw color. Ripening cherries need to be protected from brown rot.
In plums, the June drop is ending. The European plum crop has thinned out well and looks good. Bacterial spot symptoms can be found on plum leaves. Pits are hardening in Japanese plums. The Japanese plum crop is very spotty.
Apple king fruit are an inch in diameter. We seen very little drop even though the size difference between the king fruit and side fruit is pronounced. I hope that most of the small side fruit will drop. Some growers are considering thinning with Ethephon. I recommend that they wait for warmer weather later this week.
No new apple scab infections. Scab lesions are easy to find in some orchards on the fruit and leaves. 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 increasing. Cankers and collapsing shoots are oozing and we are seeing secondary spread to other shoots. Strong winds, rain and hail Sunday will cause trauma blight in infected orchards.
We have accumulated 150 GDD, since we biofixed codling moth on May 18 at 300 GDD base 50. Controls are usually timed for 250 to 350 GDD after biofix, in about a week. New materials such as Intrepid are timed earlier. See the article on codling moth control in this issue of the Fruit CAT Alert . European red mites are scarce and are laying eggs. No spotted tentiform leafminer mines have been found yet. Leafroller larvae can still be found in terminals. White apple leafhopper nymphs and potato leafhopper adults are increasing.
Blueberry fruit are pea-sized. The fields still seem yellow and pale. The cool weather has made virus symptoms apparent in many older fields. Growers need to protect the fruit from anthracnose and alternaria. Mummy berry shoot strikes are dry and easy to find. The normal shoestring virus symptoms are small strap-like leaves and reddish streaks on young shoots. However, this year we are seeing a red stain, associated with the leaf veins in the center of the leaves, that resembles a red oak leaf. Cherry fruitworm and cranberry fruitworm trap catch numbers are up and egg hatch has begun. Leafroller larvae are feeding in the shoot tips.
Concord and Niagara flower buds are separating in the cluster. Wild grapes are blooming and we expect bloom later this week. Both phomopsis and black rot leaf lesions are visible in unsprayed vineyards. Grape berry moths are flying. They will probably start to lay eggs during bloom. Growers need to time their pesticide applications for egg hatch, a week away.
Southwest Michigan Grape Growing Degree Days Totals from April 1 to June
8
|
|
|
Location |
GDDbase 50 |
|
SWMREC from April 1: |
405 |
|
Lawton From April 1: |
465 |
Strawberry fruit are coloring and harvest has begun.
Raspberries are still blooming.
Cranberries are
at the jewel stage. Bloom has started on the most advanced shoots.
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 16 at 5:00 PM.
There will be a pre-harvest blueberry meeting June 19 at 6:30 PM. The focus of this meeting will be in blueberries. For more information check the Fruit Hotlines at Van Buren (269) 657-6380 and Berrien (269) 944-4126 ext. 1.
Rain and cold temperatures were the main story of last week. Damp weather mid- to late in the week brought more disease control pressure in tree fruits. More heavy rainfall and severe weather swept across Southeast Michigan on Sunday evening (June 8). Many people reported hail and a few tornados (one at the Tritten home). Warmer weather does not seem to have advanced many of the insects as quickly as what I had expected. Most farms are reporting adequate amounts of soil moisture. Strawberry harvest is expected to begin very late this year.
|
Southeast
Michigan growing degree day totals for March 1 to June 10, |
|||
|
Location |
GDD42 |
GDD45 |
GDD50 |
|
Flint |
992 |
767 |
525 |
|
Romeo |
878 |
679 |
435 |
|
Petersburg |
958 |
739 |
503 |
Apples are mostly in the 14 mm to 16 mm range. Apples are finally at petal fall to 6 mm for fruit growers close to Lake Huron. Codling moth flight has been heavy at many farms this year. Even pheromone disruption blocks seem to have heavy codling moth numbers. Plum curculio has been notably absent in most apple blocks this year. I have seen a few stings on fruit, but very few. Rosy apple aphid colonies are more frequent on the insides of trees. Some leaf curling is beginning to develop from rosies. White apple leafhopper populations are still present, however adult numbers are fairly low. Spotted tentiform leafminer adults are still flying, however at fairly low levels. We are seeing nymphs at a few farms and sap feeders at others. Overall leafminer populations seem to be low this year. Oriental fruit moth trap catches have dropped considerably in the last week. I am seeing a few shoot strikes from Oriental fruit moth. A few obliquebanded leafroller and redbanded leafroller larvae are still present, however numbers are very low. These larvae are now fairly large in size. European red mite eggs are now present and numbers are fairly high on a few trees, however most surrounding trees have low levels of mites. At this time very few blocks have reached a point where miticides need to be applied. There is a distinct lack of predators in most tree fruits this year. Apple scab spore discharge is still taking place in the Romeo area (equipment in the Flint area was damaged from tornados and will not be available for the rest of the season). So, I am not calling an end to primary apple scab season as of yet. No confirmed fire blight strikes have been seen yet.
Peach fruits are growing well, however many blocks of peaches have poor color this season. A few Oriental fruit moth shoot strikes have been seen.
Strawberries are at thimble size to early pink at a few farms. Most farms are considering beginning harvest around June 18 to 22. However, first harvest is a bit hard to predict at this time. This will be one of the latest strawberry harvest seasons that we have. I am continuing to see a low level of strawberry clipper at several farms. Some leaf spot diseases have been reported at a few farms.
Raspberry growth on fall red raspberries is continuing quite well with most being about 12” to 15” tall. Summer red raspberries are now in bloom.
|
Weather Station |
Base 42 ºF |
Base 50 ºF |
|
West Olive |
892 |
459 |
|
Holland |
906 |
458 |
Most apple varieties are in the 10 to 18 mm stage now. Growers have been applying thinners where needed, but some varieties are thinning down on their own. Apple leaves still look pale from the cold weather. We are also seeing tree decline – possibly due to winter injury – in both apple and sweet cherry.
We did not catch any apple scab spores with the last rain and have called an end to primary apple scab for the 2003 season. Scab is showing up in some blocks. Some fire blight is showing up in commercial apple blocks in light amounts. This is most likely from the Mother’s Day (May 11) weekend and appears to be blossom blight, but we had high winds that weekend and some of the symptoms could be from that trauma event. Symptoms seem to be isolated to hot spots in orchards where blight has been found before.
Codling moth trap numbers are still 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 still 7 days away from the 250 GDD50 threshold for early egg hatch spray timings. We have only accumulated 155 GDD50 since the regional May 19 biofix. Degree day accumulations are normally about 15 per day for base 50, but the cooler than normal temperatures have been giving us daily accumulations of less than 10 per day, therefore slowing the development of this model.
Obliquebanded leafroller are getting large and moving out of
the window for good control at this time – most are pupating. White apple
leafhopper continue to emerge and develop. Spotted tentiform leafminer are
mostly in the sap feeder stage and mines should be seen at any time. Plum
curculio egg-laying damage continues in apples in normal amounts. Cover sprays
for plum curculio should be maintained for another 10 days.
Blueberries in west central Michigan are still in bloom. The varieties Bluecrop and Blueray are in early green fruit while Jersey is in petal fall stage. In general, the bloom period has been delayed for most of the varieties. In some instances, the difference between bloom stages among varieties is at least one week apart. For instance, in some fields the variety Bluecrop is in green fruit stage but in the same sites Jersey just started the petal fall stage. Since most growers have a mix of early and late season varieties, this long bloom period is causing logistic problems for pest and disease control. In early season varieties that are in green fruit stage sprays against fruit worms and early season blueberry diseases have been delayed because pollinator insects are still working in late season varieties adjacent to them.
Regarding
insect pests, the emergence of the redbanded leafroller has concluded and the
obliquebanded leafroller has not emerged, yet. Still we are seeing leafroller
feeding ranging from 1.5 to 4 percent but leafroller predation by birds and
other predators ranged from 80 to 90 percent. Larvae responsible for this
feeding are a complex of leafrollers: OBLR, RBLR and Pandemis.
The flight
of cherry fruitworm moths has continued in both Allegan and Ottawa counties
with moth captures in the pheromone traps ranging from 2 to 10 moth per trap
per week. Cherry fruitworm eggs and fruit damage by the larvae have been found
in both counties. Regarding the Cranberry fruitworm, adult moths continued
emerging in both Ottawa and Allegan counties. We observed a large emergence of
cranberry fruitworm adult moths over the weekend and we expect a large
oviposition in the next three to five days. So at this time scouting for eggs
is recommended to time pest control actions against this pest.
There will be a blueberry growers meeting on July 8, from 1:00 – 5:00 PM at the Trevor Nichols Research Station in Fennville.
With the high temperatures only in the 60’s the weather is
still rather cool. We are more than 100 GDD50 behind normal. We did get some
much-needed rain over the weekend. All three automated stations in the district
registered comparable amounts of only about 0.3-inch. This is not nearly enough
to erase nearly 1.5 inches of deficit that we have incur since the beginning of
April.
|
West Central
Michigan growing degree day totals As of Sunday, June 8. |
|||
Location |
GDD42 |
GDD45 |
GDD50 |
|
Hart |
698 |
579 |
355 |
|
Ludington |
687 |
524 |
307 |
|
Bear Lake |
704 |
553 |
334 |
Apples are sizing well. In the southern and eastern parts of the district we are in the optimum window for thinning. Ludington and Manistee areas are just getting into it. The weather has not been the best for thinning so far. Hopefully the next week’s forecast will materialize and push those temperatures into the 70’s so we can have more efficient and successful thinning. Red Delicious continues to self-thin. In some blocks Golden Delicious appears to be thin, while others will require multiple thinning applications.
Wetting events of June 7 and 8 did not produce any spore discharge. We might assume that we are officially out of the primary scab infections. Scouts are finding a few lesions in a very few blocks. Some of the fire blight symptoms are evident although we did not have the weather conditions to favor disease development. Earlier today we had first reports of the bacterial ooze in a few blocks that had a bad case of fire blight last year. Powdery mildew and nectria blight have been spotted in a few blocks scattered throughout the area.
Insect activity has been relatively low. Codling moth numbers in traps have dropped since last week. There is great variation in the average trap catches among the blocks. The numbers are between 1 and 26 moths per trap. The average biofix date is May 20 (212 GDD50). We’ve found a small number of white apple leafhopper nymphs throughout the district. We are still finding leafrollers in terminals. Most of them are obliquebanded leafrollers though there is fair number of redbanded and other species of leafroller present.
Red Havens peaches fruit is sizing well. The fruit is out of the shuck and exceeding 10 mm in diameter. It looks like there is a good crop load. Bacterial leaf spot and powdery mildew are becoming more of the problem in many blocks. The emergence of lesser peach tree borer has been reported. Scouts are finding green fruitworms.
There is a good crop of European plums. Fruit is sizing well. There is some bacterial leaf spot. No signs of plum curculio stings at this time. Scouts are finding green fruitworms feeding on a fruit.
The cherry crop is quite elusive. Some of the cherries that many growers were quite sure would “stick since they had long stems” have started to drop. We have blocks from 20 to more than 60 percent of the crop potential. Cherry leaf spot and powdery mildew have been reported. In sweet cherries, scouts are finding various degrees of bacterial spot. Plum curculio feeding scars have been found but not the egg-laying stings. Mites are found in relatively low numbers. Green fruitworms are still present in many scouted blocks.
GDD42 729
GDD50 347
Recent rains this past weekend (June 7-8) delivered 0.25" to 0.72" of rain.
In apples, the rains that started on Sunday resulted in a heavy infection
period for apple scab in all areas except the Benzie County weather station.
Spores are still being caught in some areas in southern Michigan, so primary
has not ended yet for scab. Fire blight was not a threat during recent rains,
however, the warmer temperatures forecast for later this week indicate that
growers with open bloom in their orchards will need to spray if a rain is
imminent. Codling moth trap catches have been higher than usual this year. Trap
catches averaged 7.3 moths per trap this past week in Leelanau County. Most
growers have biofixed by this time. Rosy apple aphids are curled up tightly now
and are difficult to control. Obliquebanded leaf rollers remain active in some
orchards; control is difficult when they are rolled up in leaves. Spotted
tentiform leaf miner trap catches were down to 88 per trap in Leelanau County.
Cherry growers experienced a heavy infection period for cherry leaf spot. European brown rot was found in one tart cherry block in Northport. Indar and Benlate/Captan are the two main control options. Green fruitworms are up to ¾-inch long. Plum curculio stings have been found in tart and sweet cherry. Sweet cherries need to be protected from now until harvest. In tart cherries with low populations of plum curculio, treatments will not be needed until 375 GDD50 after full bloom. Currently the NWMHRS is 208 GDD50 past its full bloom date of May 17.
Salt injury to trees along the highways desiccated the buds and fine wood, but did not kill the structural wood. Adventitious buds are breaking or will break, even on tart cherry. Most of these trees will recover.
Rose chafer was found in Southwest Michigan, so be on the watch for it in Northwest Michigan. This is the week it typically shows up here.
Peaches are just coming out of the shuck. This is a critical time for tarnished plant bug injury. Growers should be sure to have an insecticide on, particularly prior to mowing.
Strawberries have shown some crown injury where there was no snow and straw covering. This injury doesn't appear to be severe and should heal.
A change in the weather is predicted for this week, as temperatures climb toward and into the 80s. Low temperatures will be in the mid-50s to low-60s. Because of the probability of an upper-level ridge in the Great Lakes, above-normal temperatures are forecast for the 6-10 and 8-14 day periods. In the 6-10 day range, below normal precipitation is expected, while in the 8-14 day range, normal precipitation is anticipated.
Storms move through the state this afternoon and tonight with potential for strong winds. Rainfall accumulation may total up to a half inch. In today’s model runs, rain is not in the forecast for most of the state for the weekend as forecasters think high pressure will keep the fronts to the south for the weekend. For those in the south, the Michiana zone forecasts do call for storms Friday and Saturday (June 13-14).