Vol. 20, No. 7, May 24, 2005

Tree fruit news
     2005 TNRC trapline data – Codling moth

     

     

Apogee on apples
      Certification of apples for shipping to Brazil or Arizona

     

     

     

     

David Epstein, MSU IPM Program
Larry Gut, Entomology
John Wise, Entomology

Another cool spring season following some early warm weather has many growers, once again, wondering how to approach first generation codling moth (CM) control. In the fruit growing regions furthest southwest in Michigan, CM biofix was recorded as May 8. Biofix, the first date at which moths are captured in traps, provided that moths are trapped on two successive trapping dates, is the point from which one begins accumulating degree days (GDD50) to predict CM biological development for targeting insecticide applications. The cool wet weather that followed the early May 8 flight of CM, though, was not very conducive to moth activity. Temperatures generally dropped below 60°F during evening twilight hours when adult moths are known to be most active and rain showers were common. These conditions severely limit CM flight, thus it is likely that little mating and egg laying occurred during this period. For most southwest orchards, flight activity was low enough leading up to the onset of cold weather, that biofix should be reset for when moths start being captured in traps again as evening temperatures rise, most likely sometime this past week. For those few farms where substantial catches (greater than six per trap) were recorded around the May 8 biofix, growers should track the degree day accumulations from May 8 and may choose to apply an insecticide. If a grower does opt to treat, a good approach would be to delay the timing by 25-50 degree days (GDD). For example, a material like Rimon that is recommended for application at an early timing of 100 GDD would instead be applied at 125-150 GDD.

In other apple production regions typically no moths or low numbers of moths (one to three per trap) were trapped during the early warm period before the colder temperatures set in. Under this scenario of minimal CM flight and lack of catching moths on successive trapping dates, a biofix should not have been established. Most areas of the state should have seen CM flight activity start up again this past week. Growers should use this renewed activity period to set biofix based on moth captures in traps on their farms.

Options for controlling CM once activity is underway include older insecticides like the organophosphate (OP) compounds Guthion and Imidan, and a number of pyrethroid insecticides. These materials are applied at a timing that primarily targets CM egg hatch, beginning at 250 GDD post biofix. Apple growers should be aware that resistance to the OP compounds has been detected in several Michigan orchards, most extensively in the Fruit Ridge and southwest production areas. The levels of resistance detected were high enough that heavy dependence on OP's for CM control would likely have failed to protect the crop from infestation.

Several new materials have become available for CM control and growers are encouraged to include these new products in their CM management programs. Their use will not only improve CM control in orchards experiencing problems, but also will help delay or avoid the development of CM resistance to OP’s in locations not yet experiencing control failures. One of the best CM resistance management strategies is to use pheromone-based mating disruption. Recognizing this, Michigan apple growers have treated approximately 4,000 acres with CM pheromone over the past few weeks.

Among the newer insecticides for CM control registered over the past few years are the insect growth regulators Esteem, Rimon (previously Diamond) and Intrepid. Esteem and Rimon act by suppressing development within the egg, as well as larvae that consume it. Hatching of eggs laid by treated adults will also be inhibited. Eggs are particularly susceptible to these products when laid on top of sprayed residue, thus sprays are timed earlier than most other CM control materials. Suggested timing for the first application is biofix plus 100 GDD – usually close to petal-fall. At this timing, Rimon will provide good to excellent control of Oriental fruit moth (OFM), obliquebanded leafroller (OBLR) and spotted tentiform leafminer (STLM), while Esteem will be highly active on rosy apple aphid (RAA) and San Jose scale (SJS). This is the first season that Rimon has been available for commercial use. However, in trials conducted at the MSU Trevor Nichols Research Complex and at other University experiment stations, Rimon has provided control at least equivalent to the best standard material used by growers.

Intrepid provides good control of CM with a residual action of about 10-14 days. This product is an insect growth regulator that primarily affects CM larvae, but also has some activity on eggs, and has sublethal effects on adults. The best results have been achieved by taking advantage of the sublethal affects and applying the first spray at biofix plus 150-200 GDD. At this timing, Intrepid will also control OBLR larvae that are still present in orchards harboring high numbers of this troublesome pest. The addition of an agricultural adjuvant is recommended to improve initial spray deposition.

The neonicotinoids, Assail, Calypso and Clutch are another group of compounds that have recently become available for CM control. Assail and Calypso will provide good control of CM with a residual action of 10-14 days. Proper timing and coverage is required to achieve control. The best results have generally been achieved when the first application is made prior to the start of egg hatch (ca. biofix plus 150-200 GDD). Assail is labeled for CM control at the rate of 2.5-3.4 ounces per acre, but the high rate has shown better performance, especially for second generation CM. Application rates near the high end of the label rate are also recommended for Calypso, especially where CM densities are high or for prolonged control. Field trials have indicated that use of Assail in combination with pyrethroids or carbaryl can result in outbreaks of phytophagous mites. Assail and Calypso are fairly broad-spectrum materials. In contrast to the insect growth regulators, the major secondary targets of these neonicotinoids are the sucking insects, specifically aphids and leafhoppers. The initial application of Assail or Calypso targeting first generation CM will also provide control of plum curculio (PC), OFM and STLM.

Clutch, a new neonicotinoid registered for use in pome fruits, is a broad-spectrum material targeting CM as well as aphids, leafhoppers, PC, STLM, OFM and pear psylla. Trials conducted at the TNRC in 2004 showed Clutch to be most effective against CM applied at the egg hatch timing of 250 GDD and at the high rate of 6-oz/ac rate. Significantly less control was achieved using a lower rate of 3 ounces per acre.

Avaunt, an oxidiazine insecticide registered in apples, is labeled for use on CM, leafhoppers, plum curculio, leafrollers and Oriental fruit moth. Because of its excellent activity on plum curculio, early season applications in non-OP resistance areas should also show activity on codling moth.

Warrior is a newly registered pyrethroid that can provide good control of CM. Like other pyrethroid insecticides, it appears to be more effective in the spring than summer and has a broad activity spectrum. Pyrethroids are highly toxic to mite predators and should be used carefully to avoid outbreaks of phytophagous mites.

Finally, growers should not overlook including granulosis virus in their CM management program. This is a naturally occurring virus that goes by the scientific name of Cydia pomonella granulovirus (CpGV). Two CpGv products were available for use last year, Cyd-X and Virosoft. Our MSU on-farm trials and grower feedback indicated both performed well. A third product, Carpovirusine, should be available for this year. There are many options for incorporating virus into your CM management program. Consult the June 1, 2004, article in the Fruit CAT Alert for a detailed discussion of CpGv and its use. Our overall experience is that frequent application of a low rate of product is the best approach for using this biopesticide.

Compound Trade Name

Chemical Class

Life-stage
Activity

Optimal Spray Timing for CM

Mite Flaring Potential

Guthion, Imidan

Organophosphates

Eggs, Larvae, Adults

Biofix + 250 DD

L - M

Asana, Warrior, Danitol, Decis

Pyrethroids

Eggs, Larvae, Adults

Biofix + 250 DD

H

Rimon

IGR
(chitin inhibitor)

Eggs, Larvae

Biofix + 100 DD
Residue under eggs

M*

Assail, Calypso, Clutch

Neonicotinods

Eggs, Larvae,

Adults (limited)

Biofix + 150-200 DD
Residue under eggs

M*

Intrepid

IGR (MAC)

Eggs, Larvae,
Adults(sublethal)

Biofix + 150-200 DD
Residue under eggs

L

Avaunt

Oxidiazine

Larvae

Biofix + 250 DD

L

Esteem

IGR (juvenoid)

Eggs, Larvae

Biofix + 100 DD
Residue under eggs

L

Phil Schwallier
District Horticulture Agent

Apogee was labeled in 2000 on apples and has since been used by growers to control vegetative growth on most varieties. Apogee also has a side benefit of suppressing fireblight infections and canker growth. Apogee will reduce vegetative growth of shoots, laterals and water sprouts when the correct rate per acre is applied. Apogee is only locally effective within the tree. Coverage is very important to achieve desired results. Apogee benefits include control of vegetative shoot growth, suppression of fireblight infections and reduce pruning time.

Table 1 lists suggested use rates and timing for different size trees. These rates are a guide for moderately vigorous trees and need to be adjusted up when used on highly vigorous trees. Table 2 lists factors to consider when selecting a rate to use. Apogee is compatible with all typical materials used during the time Apogee is applied except for calcium, boron and some thinners. Don’t mix Apogee with calcium and boron in the same tank. Table 3 lists suggested Apogee use on various varieties. Apogee will sometimes increase fruitset but it is not consistent. More aggressive thinning is suggested when using Apogee. Apply thinners separately from Apogee. Separate thinner treatments by two to three days before or after an Apogee treatment.

Apogee must be mixed with AMS or a substitute in equal amounts and with a surfactant. Empire and Winesap fruit can be checked by Apogee applications. The exact reason for the Empire checking and cracking is not known. Do not apply to Empire or Winesap.

Table 1. Apogee rates and timing oz/acre

*Empire cracking is a risk, Apogee is not recommended on Empire.

Rufus Isaacs
Entomology

In recent years, some vineyards across southwest Michigan have experienced significant pressure from grape berry moth (GBM), a pest with multiple generations through the season. This year as growers aim to trim costs, it will be important to focus insecticides where they are needed most. Pheromone monitoring traps have shown that the first generation of berry moths started flying in early May, but weekly scouting has detected no egglaying or larvae yet. Moths caught in the traps are males, but the female moths lay eggs and egglaying doesn’t start until around the time of bloom. This point is backed up by the research data presented below.

Over the past three years, our research has tracked the dates of important development stages in the first generation of GBM in a number of commercial vineyards. As shown in the accompanying figure, there is a long time between the first moth and the first eggs laid or the peak eggs laid. The graph also shows the average date of bloom in these vineyards. Looking across the graph, it is clear that egglaying in this pest typically coincides with bloom, and peak egglaying coincides with the 10-day post bloom timing of many pesticide applications.

Treatments applied earlier than the post-bloom timing can be washed off or degrade before most of the egglaying and are unlikely to protect the clusters from feeding by berry moth larvae. Because of this, insecticides to control the first generation of berry moth are typically timed for the 10-day post-bloom timing, and the accompanying figure shows why this timing is effective. If growers are aiming to reduce costs, scouting clusters just after bloom can be used to determine the level of infestation by this pest and whether an insecticide is warranted at the post-bloom timing (see photo). Although there is no formal threshold developed for first generation berry moth, if only a small proportion of clusters have larvae or if the level of feeding is low, there will be minimal effect on yield. Since clusters set only about a third of the potential berries produced, clusters can withstand some feeding and this is worth considering when weighing up the cost of a spray.

If a spray is required, an insecticide targeting the first generation can help reduce pest pressure later in the year. When selecting an insecticide, there are many options for control. Some of these are selective for this pest, while others will also provide control of leafhoppers, rose chafer and other insects that can occur at bloom. The organophosphate Imidan, carbamates Sevin and Lannate, and pyrethroids Danitol and Capture are all highly effective against GBM. Some regions of southwest Michigan have leafhopper populations with resistance to carbamates, so Sevin and Lannate should be avoided in those regions if leafhopper control is needed. Capture is a relatively new insecticide with an annual limit of 6.4 oz/acre. MSU research trials have found excellent activity of this product at 3.2 oz, leaving the option of a later-season use of this product if a 3.2 oz rate is used after bloom.

In the selective insecticide group, Intrepid 2F is an effective insecticide for control of GBM. This works on the molting system of the larvae, disrupting normal development, and trials at 8 and 12 oz/acre have provided control of first generation berry moth. Another selective insecticide to consider is B.t. (Dipel, Javelin, Deliver etc.), which only targets the larvae of berry moth. Both of these selective insecticides need to be eaten to be effective, so their activity is greatest when temperatures are above 70°F. Intrepid is highly water-resistant providing 10-14 days of activity, whereas B.t. formulations degrade under ultraviolet light, providing three to five days of activity. When applying any insecticides to control grape berry moth, target sprays at the clusters to maximum control.

The take-home message for berry moth management is to scout clusters regularly from just before bloom onwards to understand where the pest pressure is greatest. This will also provide information on when the pest is developing and will allow management costs to be focused at times when it makes economic sense.

Annemiek Schilder
Plant Pathology

In blueberries, mummy berry shoot strikes were reported from Allegan County early last week and in Ottawa County later in the week. The number of shoot strikes was not very high, up to about ten shoot strikes per bush, in plots not treated with fungicides. In fungicide-treated plots, the numbers were much lower. Some new shoot strikes may still develop, but we are nearing the end of the shoot susceptibility period. With a cool, extended flowering period and good pollinating conditions, however, we may get more fruit infection than would be expected based on the number of shoot strikes. Studies in Georgia have shown that while most shoot strikes occur downwind from a source of inoculum, most fruit infections tend to occur upwind from a source. This suggests that ascospores from the apothecia (the primary inoculum) are mostly wind-dispersed, while conidia from the infected shoots (the secondary inoculum) are mostly insect (bee) dispersed, since bees tend to forage upwind. Bees are attracted to the shoot strikes because of the resemblance of their UV patterns to flowers. They inadvertently pick up the spores from the infected shoots and carry them to the flowers, where they infect the stigma and ovaries.

Flowers are most susceptible right after they open and become progressively less susceptible over a period of three to four days. To prevent fruit infection, make sure fungicide coverage extends through petal fall until flowering is completed. Systemic fungicides are more effective in protecting the flowers than surface protectant fungicides. The most effective fungicide is Indar, but Topsin M+Captan may also be a good option. Both Indar and Topsin M also provide effective protection against Phomopsis twig blight and canker, which is important at this time. Captan also provides good protection against anthracnose. Indar can also be tank-mixed with Captan to increase the spectrum of control. With the recent precipitation events, the risk for both anthracnose and Phomopsis infections has increased. It is important to apply fungicides at this time for both of these diseases. Cabrio or Pristine are good options for simultaneous control of anthracnose and Phomopsis (but not mummy berry), while Abound is most useful for control of anthracnose but has less activity against Phomopsis and mummy berry.

In grapes, no disease symptoms have been reported yet. However, with the frequent rains and long wetting periods over the past couple of days, we expect the risk of Phomopsis to increase. The fungus typically needs a few closely spaced wetting events to fully gear up its spore production. Cool temperatures will slow down growth of the shoots, which allows more spores to land on the tissues close to the cordon. Each rain event is likely to result in dissemination of Phomopsis spores, particularly in the next few weeks. Sprays for Phomopsis are advised in grapes at this time. Dithane is advised for control of Phomopsis prior to bloom. After bloom, Abound, Pristine or Sovran would be better options. Remember that Dithane is strictly a protectant, so it will need to be applied more frequently and at higher rates during periods of heavy rainfall. Similarly, cool, wet weather will increase the risk of grape anthracnose infection. Grape anthracnose has primarily been a problem in table grape vineyards in Michigan. The disease is favored by cool, wet springs and early summers. Elite and Nova are good options for control of grape anthracnose at this time of the season. Dithane also works but is less effective and will need to be applied more frequently. Pristine and Endura are most effective, but since these are strobilurins (QoI inhibitors) and have restrictions on the number of applications per season, we prefer to recommend them during the bloom and post-bloom period for protection of the developing fruit. However, if disease pressure is very high (based on last year’s disease observations), Pristine or Endura could be applied at this time in the season as well.

Regional reports

1 – Southwest

Mark Longstroth
Bill Shane
Al Gaus

Tree fruit
Cool weather has kept insect activity low. Fresh plum curculio egg laying scars were found on Monday in plums. We expect to see more egg laying when we get warmer weather. See the notes on plum curculio monitoring in the May 3, 2005 Fruit CAT Alert.

In peaches, tarnished plant bug feeding scars have been found on young fruit. Plum curculio should be a pest later, as warm temperatures return. Oriental fruit moths in southern and central Berrien County are laying eggs. Biofix for the first flight was April 15 at 175 GDD45. We are now at 539 GDD, 354 GDD past biofix. Oriental fruit moth egg hatch has begun in Berrien County. For the rest of the region, Oriental fruit moth biofix was May 6 at 320 GDD45 and we are 220 GDD past biofix.

Fruit set in sweet cherries is very heavy and a significant June drop is underway.

Tart cherry fruit set looks better now that all the fruit is out of the shuck. It looks like most of the tart cherry fruit we see now will stay. Rain on May 19 was a cherry leaf spot infection. Growers should be monitoring for plum curculio when the weather warms into the 70s for several days. Now is a good time to apply Gibberellic acid (Pro-Gibb) to young cherry trees to suppress bloom and fruit next year.

In plums there are many smaller fruit that will fall off. Plum curculio feeding and egg laying scars were found in plums near Paw Paw.

Apple fruit are at a good size for thinning, generally 10 to 12 mm in diameter. Earlier varieties are about 15 mm in diameter. Fruit set is spotty and varies quite a bit from site-to-site and by variety. Many growers applied thinners late last week. Because of the cool temperatures predicted this week, thinning applications this week will probably be less effective. It would be better to wait until warm weather returns and then apply higher rates of thinning materials. There is still some rat-tail bloom, and a danger of fire blight is not past. Warm weather and rain resulted in blossom blight infection periods on May 20 and 22. Symptoms of systemic fire blight from overwintering canker are being found. Oozing cankers and collapsing shoots and spurs were found in several orchards. It is still too early for blossom blight infection symptoms to be visible. The May 19 rain was an apple scab infection period. No new apple leaf scab symptoms were found. We are at or near the end of primary scab. Growers should apply one last spray containing a protectant fungicide. If no new scab symptoms are found by the first week of June, then no more scab sprays should be needed. If scab lesions are found in the orchard, growers should continue to apply protectant materials to suppress fruit scab. European red mites are scarce. Redbanded leafroller trap catches are low. Spotted tentiform leafminer eggs should be hatching and growers should scout for sap feeders and mines. We have caught only a few codling moth adults to date. Cooler temperatures have shut down flight and many sites have not caught codling moth. We are initially biofixed for codling moth on May 20 at 334 GDD50. Traditional materials are applied at about 250 GDD after biofix, but some new materials need to be applied as early as 100 GDD past biofix. This means these early treatments should go on next week. Check the article on using new insecticide materials in the May 11, 2004, article in the Fruit CAT Alert, which includes information on timing.

Pear bloom is over. Fruit are 10 mm in diameter. Set is generally light or nonexistent.

Small fruit
Blueberry bloom is ending. Cherry fruitworm and cranberry fruitworm adults are being caught. Egg hatch has not begun so insecticide sprays can wait until after bloom. Mummy berry shoot strikes have been found. Fungicides should be focused on mummy berry and anthracnose control.

In grapes, Concord and Niagara flower clusters are elongated and beginning to separate. Grape berry moth adults are being trapped, but egg laying has not begun, so insecticide sprays are not needed now. Thursday’s rain was a black rot infection. Growers should be protecting the shoot and flower cluster from phomopsis and other diseases.

Strawberries are still blooming and early varieties have small green fruit. Growers should apply fungicides during bloom to control fruit rots.

Some summer raspberries are blooming (‘Prelude’). Fall raspberries primocanes emerged from the ground and have begun to elongate.

Cranberry buds are elongating. The most advanced buds show individual flowers. Cranberry beds have begun to green up.

Miscellaneous
There will be no Monday Update next Monday (Memorial Day). The next meeting will be Monday June 6, at the Fruit Acres Farm in Berrien County at 5:00 PM. There will be one MDA restricted use pesticide recertification credit available at this meeting.

Bob Tritten

Weather
With persistent cool temperatures over the last week, we have had little insect and disease activity. Even though we had a warm day or two, the cooler than normal nighttime temperatures have held things back. As I reported in last week’s report, it appears that this spring is still in an “on and off” pattern for growth and development of both fruit crops and insects. We’ve not had any frost or freeze events over the last week. It appears that we are in store for a few more mild days (note that I didn’t say warm) and then headed back toward lower than normal temperatures.

Our season is now running four to six days behind normal in terms of growth stages and even more behind normal in terms of degree days. Our degree day accumulations are much behind last year (which was an early year) at most reporting stations. The further north you go into the Flint and Romeo areas, the more dramatic the numbers are. For example, in the Flint area we are at 293 GDD42 behind last year and we are a bit over 100 GDD42 below the 30-year average. If you compare the 30-year averages for Detroit area and south, they appear to be more normal.

Most growers received between 0.4 and 0.8 inches of rain over the last week. Most growers have had one apple scab infection period over the last week from scattered rain events. However, there are still a few growers that have not had their first apple scab wetting event for the year. Fireblight does not seem to have been a problem due to cooler temperatures during the moisture events.

Soil moisture continues to be on the dry side in the southern tiers of counties. As you move further to the north, soil moisture increases and is more toward the adequate side. Soil temperatures are still on the cool side, ranging generally in the lower 60s and even the upper 50s at the four-inch depth.

Tree fruit
Apples are mostly at 8 mm to 10 mm with Red Delicious around 8 mm. There is still a fair amount of scattered late bloom in most of our apple varieties, which are still susceptible to fire blight infection. Most growers are now turning their attention to thinning applications. A few growers have applied one thinner when we had that brief warm spell late last week, however most are anticipating doing some major thinning activity in a few days as warmer temperatures are expected. We continue to have a nice crop of apples with the exception of some king bloom damaged from frost and freeze events of three weeks ago. Many growers have applied their first Apogee application to control growth. Leaves continue to look tattered from wind and cold, however new foliage is now emerging that looks more “normal.”

Insect activity was mostly slow again last week. The only two new pests to report include the first sighting of Campylomma and white apple leafhopper and a few growers who have biofixed for codling moth. Campylomma, or mullein bug, has been a sporadic pest at several orchards over the last 25 years. Damage from Campylomma, upraised bumps on the fruit surface, was seen last summer at 5 or 6 farms. Last week we caught the first Campylomma of the season in an apple blossom. Rosy apple aphid populations have risen dramatically at a few farms, and are now gathering in clusters. While rosy aphids are being found singularly, they have not congregated into masses or rolled leaves. Plum curculio activity has been rather slow to develop. We saw some activity during warmer temperatures the week before last, but since then very little to no plum curculio have been found. Last week we also saw the first activity from very light amounts of white apple leafhopper. This pest is currently very small and is not a threat. Apple grain aphids continue to be seen, however their numbers are fairly low. As mentioned earlier, codling moth trap catches rose, however the numbers have been very low at most farms thus far this season. Just a few growers biofixed with 5 moths per trap on May 15-18. Most codling moth trap catches remained at zero. Oriental fruit moth trap catches have been considerably lower last week with most being in the 4 to 6 adults per trap range. Redbanded leafroller and spotted tentiform leafminer trap catches have remained low for the second week as we are between generations. This morning we had the first repeat of spotted tentiform leafminer larvae being found in the leaf. Tarnished plant bug adults continue to be seen at low levels. European red mite eggs have been very slow to hatch this year with few adults being seen at this time and little to no egg laying. Larvae from several small fruitworms continue to be seen in very light numbers, these include obliquebanded leafroller, green fruitworm, redbanded leafroller, fruit tree leafroller, climbing cutworm, Eastern tent caterpillar and apple skeletonizer.

Predators continue to be seen in fairly good numbers this year, these include lady bird beetles, brown lacewing adults and eggs, minute pirate bugs, Amblyseius fallacies and Stethorus punctum. Velvet mites were seen for the first time last week.

Apple scab spore lesions are being seen in a few commercial apple blocks from an infection period on April 22, 23 and 24. The number of scab lesions are fairly low. Apple scab spore discharge continues with each rain event. We will continue to monitor spore release for the end of primary over the next couple of weeks. Most growers had another apple scab wetting infection last week, however it depended greatly on rain events in your area. A few lucky growers have not had any infection periods. I encourage growers to remain vigilant for apple scab development as well as powdery mildew development. While fire blight blossom strikes have not been seen yet, some continued scattered bloom in apples and warmer temperatures are expected later this week and there is still a possibility of fire blight infection during blossom stage. With cooler temperatures in the last couple of rain events, fire blight risk has not been a serious issue.

Pears are mostly at 8 mm to 9 mm in size. While there has been some drop in pears, it still appears that we have a good crop. All stages of pear psylla have been present for a few weeks now. The adults are getting more numerous and may need control.

Peaches are still mostly in the shuck, however a few varieties are now approaching early shuck split. There are some spots in peach leaves from bacterial spot. Most growers are anticipating an insecticide application on peaches fairly quickly as we are approaching shuck split.

Sweet cherries are mostly about 13 mm in size and are growing very quickly. However there is a wide range of sizes of sweet cherries. We are not yet at pit hardening. Sweet cherries have also thinned down a great deal over the last few weeks, mostly due to the frost and freeze events of this spring. It is odd to see such a spread of sizes of sweet cherries. Twospotted spider mites are being reported as of today (May 24).

Tart cherries are mostly at 8 mm to 10 mm in size. There continues to a fair amount of drop on tart cherries as well. There is also a fair amount of deadwood in many blocks.

Plums are 3 mm to 4 mm in size. Some varieties are heavy, however most varieties have a very light crop. It appears we’ll have a variable crop of plums. Bacterial spot symptoms also continue to be seen on plum varieties.

Small fruit
Strawberries are in full bloom for Earligrow, however some of the other later varieties are a few days away from full bloom. Very few small green fruit have been seen. We are expecting a very late harvest of strawberries. Most growers have not needed to frost protect over the last week. We have seen tarnished plant bug and strawberry clipper. For the most part, the levels are fairly low. I’m also seeing some continued high populations of slugs. I would encourage growers to begin to scout for slugs as we move through the next week or so.

Raspberries continue with flowering of summer red raspberries, and growth on fall red raspberries has now picked up to about 6 to 8 inches in length. I’ve not seen any bloom yet. Some varieties of summer red’s continue to look weak due to winter injury.

Blueberries are at full bloom, with an excellent crop of blueberries coming along.

Grapes are currently at 4 to 5 inches of new growth with young flowers present.

Phil Schwallier
Amy Irish Brown
Carlos Garcia-Salazar

Tree fruit
Most apple varieties are just past the petalfall stage, but there is quite a bit of secondary bloom still out there on many varieties – more than usual. Fruit set in apple appears to be heavy.

There is still time for Apogee applications to be made – be sure to leave a few days in between Apogee applications and thinning sprays. We are unsure if there would be any incompatibilities with these two applications yet.

Early thinning of apples is just beginning. Some early varieties are at the 10 to 12 mm size, and fruit set is heavy. Weather over the next several days will not be ideal for thinners to work well, so aggressive thinning is being recommended.

Risk for blossom blight infections has dropped to low because of the cool temperatures and the fact that many apple varieties have moved into the petalfall stage. Cankers are oozing. No blossom blight symptoms are visible yet, but they should start to show up soon – the cooler weather has probably delayed the development of blossom blight symptoms.

Apple scab has not been the big problem that it usually is due to the drier than normal weather. Most of the primary apple scab spores should be mature at this time, so a couple of good rain events and primary scab will probably be over for 2005. Spore numbers have been declining with the last rain events, but they are still present so growers need to continue to protect leaves and fruits for another week or so. This is a good time to do some very careful scouting for primary scab lesions to be sure that secondary scab won’t show up unexpectedly after fungicide rates are lowered.

Most trap numbers have been low or even at zero over the past two weeks, but there was a slight increase in codling moth and Oriental fruit moth in some blocks. Spotted tentiform leafminer adult flight is over for the first generation and sap feeders should start to be found at any time. Rosy apple aphids continue to be found with predators also being found in the colonies. Plum curculio damage has not been seen yet, but they should start being active at any time in early fruiting tree fruits such as plum and apricots as well in apples. There are small brown weevils being seen in apple terminals. They are notching the young leaves, but appear to be doing little other damage and shouldn’t be confused with plum curculio. Campylomma started to be found in apple 10 days ago and controls are recommended in blocks that had fruit damage from this insect last year.

Mira Danilovich

GDD totals Since March 1 as of Sunday, May 15

Tree fruit
Apples are in petal fall for most varieties. Some earlier varieties are expressing the fruit size differentiation. It looks like we will be getting into the optimum thinning window over the weekend or the first part of next week.

Pears have passed petal fall but the fruit is still too small to be measured. It looks like heavy fruit set. There has been one scab infection event since last week. The rain of May 18^th’-19 resulted in Hart and Ludington and May 19-20 in Manistee, resulted in infection periods throughout the area. Spore discharge, though still high, is on a way down. The rain event over the weekend did not result in infection but did trigger spore release. The spore count is declining. As of Sunday, May 22 there are 97 percent mature spores in Ludington, 99-100 percent in Hart and 99-100 percent in Manistee/Bear lake Area. Potential for fire blight infections has been downgraded to low. Powdery mildew is becoming more prevalent in many apple blocks. A few sunny days are responsible for more numerous sightings of codling moths. Biofix dates have been established for several blocks where there have been high and steady CM catches. Redbanded leafroller trap catches have dropped significantly. Throughout the area small tree fruit leafroller larvae and OBLR are present in terminals. STLM trap catch numbers are declining.

Sweet cherries are about 8mm in diameter. Given the unfavorable conditions during bloom, it is quite surprising to see any fruit on the trees. It looks like a low to moderate crop depending on the variety and location.

Tart cherries went from being in shuck to shuck split and out of shuck. Looks like quite a heavy set but indications are that many of the set fruit will end up dropping on the ground. Though it is very early to estimate the crop size, it looks very good for now.

European plums are in shuck. There is a heavy fruit set and the crop outlook is good.

Peaches are in shuck. Fruit set looks very good. Bacterial leaf spot has been found in many blocks throughout the area. Cherry leaf spot continues to be of concern with each wetting event. Conditions are favorable for powdery mildew development as well. Oriental fruit moth (OFM) trap catch numbers are going down. Biofix for the first OFM flight in Ludington was May 10 at 293 GDD45. According to the degree day model, 8-10 percent first generation egg hatch is expected 150-170 GDD45 post biofix or at 443-463 GDD45_. It is expected that the first egg hatch will start in about two to three days at present temperatures.

American plum borer trap catches are coming down. After the recent rains and a slight warm-up in temperatures scouts have noticed significantly higher activity of PC’s throughout the area. In many parts of the district, PC’s have been out for a while. Apricots, sweet cherries, tarts and other fruit need to be protected at this time since the gravid females will be looking for sites to deposit their eggs. Each one of them can lay more than 300 eggs resulting in significant fruit damage.

Petal fall spray is essential for their suppression. Control options besides the organophosphates (Guthion, Imidan) include pyrethroids (Asana, Warrior and Denital), neonicotinoids (Actara, Calypso and Assail) and oxidiazine (Avant).

Jim Nugent
Jim Bardenhagen
Duke Elsner
Nikki Rothwell

Weather
Warmer weather returned this past week at a critical time for pollination of apples in much of the region and tarts in the coolest blooming areas. Two rain events delivered some much-needed water. GDD42 accumulations are slightly ahead of the 15-year average at the NWMHRS, while GDD50 is at average.

In apples, a wetting event was reported for Friday, May 20 that resulted in a light to moderate scab infection throughout the northwest. Yesterday (May 24) we had another wetting event that lasted until this morning, and it resulted in some light apple scab infection in most areas in the northwest and some heavy pressure in Northport. There have been minimal changes in the pest insect status since last week, and overall numbers are still low despite warming temperatures. We captured our first codling moth here at the station, although three moths were caught in Benzie County on Friday and the Antrim County area has been catching moths for the past three days. Spotted tentiform leafminer catches have increased in the past week with an average of 665 insects per trap.

Overall, the wetting events of the past week did not result in much sweet cherry leaf spot (CLS) infection, but we did report a light infection period in the East Leland and Northwest Station areas. We have captured plum curculio in organic cherry blocks and areas where we are using the new, more effective lures. There has been no observed plum curculio egg-laying activity.

In tart cherry, there is no cherry leaf spot infection to report. American plum borer catches are on the rise in the past week.

Jeff Andresen
Agricultural Meteorology
Geography

A cool and unsettled weather pattern is setting up across Michigan for the next several days as an upper air low migrates slowly from northwest to southeast across the Great Lakes region. Cold air above the surface will result in a relatively unstable atmosphere and an almost daily chance for showers Thursday through Saturday (May 26-28).

In the short term, dry conditions are likely Tuesday and Wednesday, courtesy of an area of high pressure currently located across the eastern Great Lakes. That high pressure will slide eastward and be followed by an upper air low and a cool front, which will move across the state beginning late Wednesday and Thursday. Showers and thunderstorms will be a good bet beginning in northwestern sections of the state late Wednesday and statewide on Thursday. After the frontal passage, scattered showers will be a continuing possibility Friday and Saturday. Temperatures during the next several days will remain a few degrees below the climatological normals with highs in the 60s and lows in the 40s. Frost or freezing temperatures are not expected, but given cold air just above the surface, they remain a possibility late in the week should clear, calm conditions develop.

In the medium range time frame, latest forecast guidance calls for a continuation of upper air troughing across the eastern United States with a broad ridging pattern across the western United States. The NOAA Climate Prediction Center 6-10 day and 8-14 day outlooks (for May 28 through June 1 and May 30 through June 5) call for temperatures to fall back to below normal levels, with below near normal precipitation totals.