In this issue
Tree fruit news
§
Post harvest pruning in cherries
§ Post-harvest control of two-spotted spider mites in cherry
§
Will we have a third partial codling moth
generation in west
Small fruit news
§ 2005 TNRC trapline data – blueberry maggot
§ Controlling Japanese beetles
§ Controlling mid-season grape berry moth
§ Grape disease update
Other news
§ NWMHRS Open House and Equipment Show
§ Regional reports
For over a decade the cherry industry has been doing more and more pruning of bearing trees between cherry and apple harvest. This is a time of year when we have labor available and don't have to fight the inefficiencies inherent with dormant pruning in the snow and cold.
To date we have observed no negative impact on winter hardiness of trees, nor any effect on spring flower bud hardiness. However, because of the concern for potential increased susceptibility to winter injury, and possible influence on next season's growth, we suggest the following precautions:
1) Do not prune after mid September.
2) Avoid exceptionally heavy pruning, particularly of sweet cherries, at this time.
3) Do not prune young tart or sweet cherries that have not filled their space in late summer.
Having said that extra heavy pruning should be avoided in late summer, we want to comment that many sweet and tart orchards need exactly that! Too many orchards are getting too tall for the spacings at which they are planted. The result is excessive shading in the lower canopy which results in loss of lower fruiting wood, trees too tall to get adequate spray coverage for controlling cherry leaf spot and brown rot, and a large drop for cherries onto the harvester, which will increase fruit bruising and softening.
In 2004, we conducted a preliminary study to evaluate the effect of drop height on soft fruit problems in tarts. While this preliminary study was very limited in scope, the data show a strong trend towards increased damage as the drop height increases. For all of these reasons, it is very important that tree height be limited!
1) For triangular shaped trees, the height of the bearing area of the tree should be no more than three times the clear alleyway width. The clear alleyway is the distance between the branches of the trees from row to row, not the plant distances between rows. For example, a six-foot clear alleyway would imply the tree height could be up to 3 X 6 ft., or 18 feet plus about four feet from the ground to the base of the desired fruiting area, for a total height of about 22 feet.
2) For a
rectangular shaped tree, the height of the bearing surface should be twice the
drive alleyway distance. For example,
again assuming a six foot clear alley- way implies a height of 2 X 6 ft., or 12
feet plus four feet from the ground to the desired base of the fruiting area,
for a total height of 16 ft.
These formulas address light only. You need also to consider the capability of your sprayer to adequately cover tops of trees and possibly the propensity of the block to have soft fruit problems.
Twospotted spider mites (TSSM) can be a complex problem on cherry in hot, dry years. Cherry growers are often faced with the crucial decision of applying a miticide before or after harvest. If growers intend to spray for mites before cherry harvest, the pre-harvest intervals (PHI’s) of most miticides are 14 days or longer, which is an important factor in the decision-making process. Another confounding factor of pre-harvest mite control is that often the mite count is low early in the season, and the numbers may not warrant a miticide at that time. Because of these issues, many cherry growers apply a miticide after harvest when the mite numbers are higher and when PHI’s are no longer a concern.
Twospotted spider mites are pests
of many plants, but in
Under typical droughty summer conditions, the groundcover vegetation becomes a poor food source for the mites, and they move up into the cherry trees in mid- to late summer. In a hot, dry year such as this one, the mites move up into the tree sooner than in a year under normal moisture conditions. Older, inner spur leaves are often first infested as the females move to those locations first. However, with warm, dry weather, mite populations can increase dramatically in a short time, and the mites will move off these older leaves to all parts of the tree canopy.
Although TSSM are very small, they can be seen with a 10X hand lens. Females are larger than males, and they reach 0.42 mm in length when they are full grown. Adult female TSSM range in color from light yellow to brown to green with two distinct black spots; irregular dark splotches may appear after feeding. Male TSSM are more variable in color than females, and they have a distinctly pointed abdomen. When comparing TSSM to European red mite (ERM), ERM tends to be rounded and not quite as long as TSSM. TSSM also have fewer “bristles” than ERM and obvious black spots. ERM are often red, but color differences are not always as dramatic as both species can have greenish colored stages. TSSM infestations are often accompanied by silk webbing on the leaf surface.
Bronzing of leaves is a visual sign of damage caused by high populations of TSSM; this phenomenon can cause a reduction in photosynthesis and fruit bud initiation. Leaf bronzing caused by TSSM is often more gray in color than bronzing by ERM. Although bronzing presents an obvious challenge, one of the biggest threats of mites in cherry in a hot, dry year is “firing.” Firing is an immediate result of increased temperatures and droughty conditions, most often in combination with high mite populations. Firing results in a collapse of a portion of the tree; this malformed segment can be a branch, a terminal or a whole section of the tree. The leaves of a fired part of a tree turn brown very quickly, with no prior wilting, and the overall effect is similar to fire blight in apple. Although firing may occur with low mite populations, it is found most commonly where mite numbers are high. At one time, firing was reported only to occur with plum nursery mite infestations, but more recent observations suggest TSSM plays the major role in firing.
Scouting for mites can begin as early as mid-May and continue through August. In orchards with high mite populations the previous summer, an early start to mite monitoring can alert growers to population increases requiring pre-harvest treatment with enough time to avoid conflicts with a miticide’s PHI. In a droughty year, a good practice is to begin monitoring earlier than usual. One method of monitoring TSSM motile populations consists of sampling 25 leaves at each of three to five sites within a block, using 50 percent spur leaves and 50 percent shoot leaves.
Treatment for TSSM should be based on the following thresholds (double the treatment thresholds for TSSM in tart cherry):
1) Two to three mites per leaf from mid-May to mid-June.
2) Five to seven mites per leaf from mid-June through July.
3) Ten to 15 mites per leaf in August.
Presence of predaceous mites (greater than one per leaf) may justify delaying a treatment and repeating the cycle the following week.
Conservation of predator mites in a cherry system is critical to
control plant parasitic TSSM. The three predaceous mites commonly found
in
Twospotted spider mite infestations may be controlled with a post-harvest miticide. When using chemical control, good coverage of all tree surfaces is critical. Some miticides are active on eggs (ovicides) and should be applied before egg-hatch; Apollo and Savey are miticides with ovicidal properties. Savey also works on mite larvae. An early application of superior oil does not work well for TSSM as it does with ERM populations because first generation TSSM eggs are laid in the ground vegetation rather than in the tree. Other miticides are only active on motiles (adulticides) and should be applied after populations start to build: Nexter, Omite-CR (post-harvest only) and Vendex. Field evidence suggests Nexter is not as effective on TSSM as it is on ERM. Envidor is newly registered for mite control in cherries and is active by contact to all life stages. The active ingredient, spirodiclofen, controls mites by inhibiting lipid synthesis and is active by contact to all life stages. Envidor has a novel mode of action and is not known to have risk of cross-resistance with other currently registered miticides. Envidor 2SC has a rate range of 16 to 18 fluid oz per acre, seven day pre-harvest interval for pome and stone fruits (14 days in grapes) and is restricted to one application per acre per season for all labeled fruit crops.
With so many control materials from which to choose and because
of concerns with the development of mite resistance to miticides,
no miticide should be applied more than once per year
(The one exception is superior oil.). We are currently testing the effectiveness
of a summer oil for control of TSSM in tart cherries;
however, at this time, the repercussions of oil use are not yet known. Please
see the accompanying table for more information on miticides.
|
Compound trade name |
Life-stage activity |
Mite species controlled** |
Residual activity |
|
Savey |
egg/larvae |
TSSM, ERM |
8-12 weeks |
|
Apollo |
egg |
TSSM, ERM |
8-12 weeks |
|
Nexter |
motiles* |
TSSM, ERM, PNM |
6-8 weeks |
|
Omite-CR |
motiles* |
TSSM, ERM |
6-8 weeks |
|
Vendex |
motiles* |
TSSM, ERM |
6-8 weeks |
|
Envidor |
eggs, larvae, adults |
TSSM, ERM, PNM |
8-12 weeks |
* Motile forms include mite larvae, nymph and adult stages.
** TSSM - two spotted spider mite, ERM – European red mite,
PNM – plum nursery mite.
Successful control of codling moth is heavily dependent on precise timing of pesticide applications coincident with exposed eggs, first instar larvae or adults. Timing is achieved through the use of phenology models simulating the codling moth’s development through the apple growing season. These models provide growers with information on the best timing for pest control. The number of generations predicted by phenology models is degree day dependent. But they do not account for the photoperiod-temperature interaction that controls diapause induction or aversion. Diapause regulates the number of generations in a given geographic location by removing or adding individuals to the seasonal population. Thus, the codling moth pressure that we might expect in an orchard during the season depends on: 1) the size of the population entering diapause during the previous year, and 2) the GDD accumulation during the present season before the onset of diapause conditions.
In
There is a way to estimate the likelihood of having a third
partial codling moth generation if we understand how the codling moth population
dynamics are regulated by the induction and termination of diapause.
The two major environmental factors controlling diapause
in codling moth are daily temperature and prevailing photoperiod in which the
larval population develops. From research conducted at MSU and elsewhere, we
know that the critical photoperiod for diapause
induction (the photoperiod at which 50 percent of a larval population is
induced into diapause) is
Our estimates for the 2005 fruit season (if weather conditions remain as in the last 10 days of July) are that the critical photoperiod could be shifted toward the long days portion of the summer; 14:33 (L:D). This shift will result in only approximately 37 percent of the larval population going into diapause; the remaining 63 percent could continue development yielding a third partial adult codling moth generation. This situation is very similar to that observed in 1983 (see Table 1).
This prediction is not final because the prevailing daily temperatures reaching 90°F may change in the next 15 days rendering useless the average temperature used to produce this forecast. However, considering that the daily average GDD accumulation during the past 30 days is 23.6 GDD50, by the time we reach August 4 it is very likely that the accumulation will be above 1,750 GDD. This accumulation allows for the development of two complete codling moth generations by the first week of August. As we can see, these conditions may provide the codling moth with enough time for further development of a third partial generation
|
Year |
GDD50 April 1 to August 4 |
Average temp. ºC July 27 to August 12 |
Modified CPhP 50 (August 4, |
Equivalent date |
Percent diapause induction |
|
1983 |
1,798 |
24.7 |
|
Jul 29 |
37.0 |
|
1984 |
1,738 |
23.9 |
|
Aug 1 |
40.0 |
|
1985 |
1,652 |
19.8 |
|
Aug 16 |
55.0 |
|
1997 |
1,439 |
19.12 |
|
Aug 18 |
62.0 |
|
1999 |
1,811 |
21.80 |
|
Aug 10 |
40.0 |
|
2002 |
1,674 |
22.54 |
|
Aug 6 |
44.0 |
|
2003 |
1,334 |
20.68 |
|
Aug 23 |
55.0 |
|
2004 |
1,440 |
18.57 |
|
Aug 27 |
58.0 |
Japanese beetles have been causing headaches for many fruit growers over the past month since their early July emergence. Although this species has only one generation per year, the beetles emerge over a long period, and they live for over 30 days. This article provides information on insecticide options, based on tests over the past few years conducted at the Trevor Nichols Research Complex and at growers’ farms.
The organophosphates Guthion and Imidan (buffer to pH 6.0) provide excellent lethal activity on adult beetles, although it can take a few days for their effects on Japanese beetles to be seen as the beetles take up the insecticide. They provide 10 to 14 days of activity with five- to 21-day PHI depending on the crop. The carbamates Sevin and Lannate provide some immediate kill of beetles, and they are also stomach poisons, so if beetles eat treated foliage they will also receive a higher dose. This can be a good property for Japanese beetles since they eat so much that a strong dose of insecticide is taken up. Lannate has a short residual activity of a few days, whereas Sevin provides a week or more of protection. Sevin has a three- or seven-day PHI depending on the crop and Lannate ranges from three to 14 days. The pyrethroids Danitol, Asana and Capture give instant knockdown and mortality of adult beetles with seven to 10 days of activity. It is important to remember that pyrethroids break down faster under hot, sunny conditions, so performance in midsummer will be less than that expected in the spring. Toward the end of the residual activity of pyrethroid applications, beetles may also be repelled from treated bushes. PHI’s for this class vary widely, so check the label before use.
The labeling of Provado for some fruit crops provides a selective option for Japanese beetle management. Provado provides two to three days of lethal activity from the surface residues before it is absorbed into the foliage. Thereafter, beetles must eat treated foliage to get a dose of the insecticide. During this period, however, Provado is rainfast and provides significant sub-lethal effects of repellency and knockdown activity, but with much less direct mortality from the residues. This neonicotinoid will also control aphids and leafhoppers. It has a zero- to seven-day PHI depending on the fruit crop. Another member of this chemical class, Assail, can provide some protection of foliage from feeding by Japanese beetles, though the level of beetle mortality may be lower than expected from the broad-spectrum options. The rate allowed in different crops will have a big impact on how effectiveness of Assail.
For growers looking for beetle control immediately before
harvest, some selective insecticides with zero-day PHI’s
can provide a tool to repel beetles and help achieve beetle-free fruit during
harvest. Compounds containing neem (Azadirect, Ecozin, Neemix etc.) have a zero-day PHI and pyrethrum (Pyganic) has a 12 hour PHI. These compounds are labeled for
organic use and have a short but effective impact on adult Japanese beetles
with some mortality, some knockdown off the crop and some repellent activity.
Typically there is only one to two days of activity against beetles because the
residues do not remain active for long. The non-organic form of Pyganic, called Evergreen, also has a 12 hour PHI, but is much
more effective against Japanese beetle than Pyganic
due to the addition of a chemical that inhibits the beetle’s ability to break
down the insecticide.
The third week of July is a good time to scout vineyards for the effectiveness of post-bloom insecticides and to decide whether another insecticide application in early August is needed. For many vineyards, the post-bloom spray will have been sufficient to control this pest. For other vineyards where grape berry moth (GBM) is usually a problem late in the season, and particularly where the crop was heavily infested with berry moth last year, this generation will require active management to keep the population under control.
In our research vineyards in southwest
By scouting now, an informed decision can be made as to
whether to spend time and money on berry moth control at this time or wait
until later in the year. At the same time, looking closely at the vines can
detect the level of leafhopper and beetle infestation. If GBM infestation is
detected near harvest, it is often too late to get it under control because of
pre-harvest interval restrictions. Because of this, proactive scouting and management
now are key to protecting the fruit.
If damage is above the threshold of 6 percent infested
clusters (one to two clusters in each 25 cluster sample), the decision to treat
with an effective insecticide should be made. About one week of activity can be
provided by broad-spectrum insecticides Imidan (use
pH 6.0 spray water) and Sevin.
A little longer activity can be provided by the pyrethroids
Danitol and Capture, but at the current high
temperatures and UV conditions, pyrethroids are
likely to break down more quickly. SpinTor is a new
class of insecticide that has some contact activity and works best when eaten
by the insect. It has about a week of activity but is susceptible to wash-off.
The previously-listed chemicals may be active on other co-occurring insects and
can provide varying levels of control of leafhoppers and Japanese beetles. One
highly selective insecticide that has shown good performance against grape
berry moth is Intrepid. This acts by disrupting molting of the larvae, and so
it has to be applied in enough water to get excellent coverage of the grape
clusters. Once on the clusters, it has 14 days of activity and is highly
resistant to being washed off. A spreader-sticker can help get cluster coverage
with this product. Check on the pre-harvest interval if you choose an
insecticide, as some of these products have a 30 day PHI.
Achieving control of grape berry moth with any product requires good cluster coverage, so it's a good idea to focus sprays on the fruiting zone if targeting cluster pests only. The insecticide must get past the leaves to the clusters, and cover them, to be effective. Use of more water (50 gallons per acre is recommended for a full canopy), driving more slowly, and spraying every row will all help improve efficacy. Pesticide longevity is also very important because recent research has shown that egglaying by second generation GBM is very spread out. Choose an effective insecticide with enough residual activity that eggs and young larvae are controlled as they develop on the cluster. Short-acting products will be immediately effective but will leave the fruit at risk during the long period of egglaying if they are not reapplied. Finally, remember resistance management: Change the class of insecticide from whichever was used earlier in the season. This will help prevent grape berry moth becoming insensitive to the currently effective tools that are available.
Taking the time to scout vineyards during the next month to determine infestation and see how well the spray program is working will reduce the chance of “late season-surprises.” Because vineyards can vary greatly in their level of infestation, this scouting should be done in as many different vineyards as possible. Most growers know the hot-spots in their farm, and can focus this sampling there to determine the need for sprays against second generation grape berry moth.
The dry weather has generally delayed the onset of a number
of diseases, but eventually some symptoms have started to appear. Downy mildew
was noted in a table grape vineyard in Onondaga,
Black rot symptoms are coming on strong now in unsprayed vineyards and plots. Symptoms on berries are brown areas, some of which have cream-colored spots in the center; the lesions are quickly advancing, resulting in clear delineations and “growth rings” on the berries. Fungicides should have been sprayed between bloom and about five to six weeks after bloom. At this point, it is mostly too late to do anything about the disease. Some wine grape berries may still be susceptible (up to about eight weeks after bloom) and may need protection. Sterol inhibitors (Elite, Nova, etc.) or strobilurins (Sovran, Abound) are good options.
Powdery mildew has been seen on
Phomopsis lesions are mostly visible on leaves and canes at this point, although a few infected berries have been found. Mostly, berry rot occurring right now is related to grape berry moth infestation. Full disease symptoms are not expected until several weeks before harvest. In most years, spore release peters out after bunch closure, so disease risk should be limited at this time and sprays no more needed. If you still wish to maintain some fruit protection, the best fungicide options are ProPhyt, Phostrol, Abound, Pristine, or Ziram, all of which also provide downy mildew control.
Botrytis bunch rot has not reared its ugly head yet because basically it is too early in the season. However, the fungus was isolated from the small dead tips of grape clusters and from a rotten berry found in a grape cluster, so the potential for disease development is there. Sprays are advised at veraison and about two weeks before harvest, especially in tight-clustered varieties like the Pinots. Good fungicide options are Vangard, Elevate and Scala. Please note the pre-harvest intervals (zero days for Elevate and seven days for Vangard and Scala). Leaf removal is another method for reducing humidity around the clusters and consequently disease development. Be careful not to remove too many leaves, since hot weather with lots of sunshine can scald the berries. Sun-scalding has been observed in some wine grapes already.
The Northwest Michigan Horticultural Research Station Open
House and Equipment Show will take place on Thursday, August 25. This year’s
open house will feature a vendor showcase, an educational session, an equipment
demonstration and a dinner. The vendor display area will open at 1:00 PM. MSU
researchers will be on-hand to present their latest findings and future plans
for orchard management from
A social time with local wine and cherry juice tasting will
begin at 5:15 PM. Dinner at
The cost for the dinner is $10. Tickets can be purchased in advance by calling the Leelanau County MSU Extension office or purchased at the door.
Sponsors for the event include the Michigan Agricultural Experiment Station, MSU Extension, Northwest Michigan Horticultural Research Foundation, the Leelanau County Horticultural Society and local vintner associations. For more information, contact the NW Michigan Horticultural Research Station at (231) 946-1510 or Leelanau County MSU Extension at (231) 256-9888.
Last week was hot and humid with highs in the 80s and 90s and lows in the 70s. Numerous thunderstorms have moved across the area in the last two weeks. This general rain has relieved drought stress except close to the lake. Precipitation totals range widely from less than an inch to three and more inches. Drought stress symptoms are still common close to the lake. Soil temperatures are in the 80s. This week’s forecast is for cooler weather.
GDD totals: March 1 through July 24
|
Grapes
|
|||
|
Location |
GDD 42 |
GDD 45 |
GDD 50 |
GDD 50 |
|
2489 |
2171 |
1685 |
1663 |
|
|
2542 |
2220 |
1725 |
1702 |
|
|
2337 |
2025 |
1547 |
1527 |
|
|
2566 |
2246 |
1752 |
1727 |
|
|
2334 |
2027 |
1554 |
1534 |
|
We are catching a few picture wing fruit flies such as apple maggot, blueberry maggot and cherry fruit flies. Japanese beetles numbers are high in some areas. The second generation of codling moth is flying. Aphid and mite numbers are building in many crops. The flight of second generation of Oriental fruit moth continues. The summer flight of obliquebanded leafroller is over. Redbanded leafroller trap catches are down.
Apricot harvest is ending.
Peach harvest
continues. Garnet Beauty and Early Red Haven are being harvested in
Cherry harvest is over and cherry growers
should protect against cherry leaf spot. European red mite
numbers are high in some orchards. Japanese beetles are
common in cherries and causing damage in young plantings. There are still a lot
of yellow leaves. There is little sign of cherry leaf spot. So the yellow
leaves are from pre-harvest Ethrel sprays. Post harvest to early September is generally a
good time to prune mature tart and sweet cherry trees.
In apples, we are catching a few more apple maggots after
the rain. See the article on apple maggot monitoring and control in the June 28 Fruit CAT Alert. The second generation
of codling moth
began to emerge last week. We biofixed
codling moth on
July 20 at 1581 GDD50. We are now at 1717 GDDs,
135 GDD after biofix. Treatment is timed for 250 GDD
after biofix, and with cooler weather this week,
sprays should be timed for this weekend or early next week. In southern
Sooty blotch and fly speck leaf wetness sensors in for the MAWN network indicate that we are reaching the 200 to 250 hours of leaf wetness since petal fall. Now is the time to resume fungicide sprays in cover sprays to control sooty blotch and fly speck.
|
Location |
Hours of leaf wetness |
|
170 |
|
|
230 |
|
|
290 |
|
|
285 |
|
|
240 |
|
|
|
305 |
In pears, European red mites are turning pear leaves black. Pear psylla numbers are building even though growers have recently treated for this pest.
In blueberries, growers
are harvesting Bluecrop and
Grape berries are
pale and veraison will start soon. Early color has
been seen in early varieties. Grape
berry moth feeding continues. Growers should be protecting the fruit and leaves from
downy and powdery mildew. Rain and heavy dews this last week have been good
conditions for downy mildew
infection. These hot humid conditions are also perfect for powdery mildew, and we have found
powdery mildew symptoms on
Strawberry growers should protect against leaf diseases and potato leafhopper.
Summer raspberry harvest is underway. Fruit size is small and crumbly berries are common due to drought.
Much-needed moisture
has finally arrived over the entire southeast corner of
Continued hot
weather persisted over the last two weeks with many days having high
temperatures in the 90s and nighttime low temperatures in the low 70s. Degree
day totals have continued rolling along rapidly. Our season is now ahead of
normal in terms of degree days and growth stages.
Sweet and tart
cherry and summer raspberry harvest seasons have wrapped up with blueberry and
early peach variety harvest now underway.
|
Location |
GDD42 |
GDD45 |
GDD50 |
|
|
2353 |
2049 |
1584 |
|
Romeo |
2343 |
2040 |
1574 |
|
|
2429 |
2115 |
1648 |
Apples continue to size very well with most being around 2 to 2.5 inches. Apple
maggot catch on yellow sticky boards and on red balls continues, although not
at the very high level that I reported two weeks ago. The first apple maggot
catch in commercial orchards was on July 7 or 8. These unusually high and early
trap catches are still a bit puzzling. I continue to encourage growers to do
frequent scouting for apple maggots to determine levels. Codling moth trap
catches are generally steady in the two to four range
in most conventional blocks and near zero in mating disruption blocks. The
second generation flight has not started, but I expect to see it begin any day
now. We are now beyond the 1250 degree day biofix
mark from the first generation. Growers will need to monitor their trap catches
closely over the next week or so to determine their own second generation biofix date. Green apple aphid populations have generally
been declining over the last two weeks with predators continuing doing a good
job controlling them. Wooly apple aphids are being seen in increasing levels on
new growth of primarily young trees and on the inside middles of older trees. Obliquebanded leafroller trap
catches have dropped off with an average number of two to three per trap. Oriental
fruit moth trap catches are generally low, but I have seen high trap catches. Potato
leafhopper burn is just starting to be seen in a few scattered apple blocks. I
continue to see higher numbers of potato leafhoppers. Japanese beetle
populations seem to be high on apples and other tree fruits. Dogwood borer
adults continue to fly. Fall webworm larvae continue to be seen. European red
mite numbers have exploded. There appears to be a fair amount of adults at this
point in time with good numbers of mite eggs. Many apple growers have applied a
miticide to control them in hot spots. Apple rust
mite numbers are also very high. Twospotted spider
mite populations continue to build. San Jose scale is now being seen on fruit. We
continue to see a good number of predators, although their numbers are staring
to drop off as aphid populations are declining. I continue to see good numbers
of ladybird beetles in all stages, Stethorus punctum, minute pirate bugs, big eyed bug, syrphid fly, assassin bugs, solider bug, six spotted thrips, velvet mites and Amblyseius fallacies.
I have not seen
signs of sooty blotch or fly speck. Fungicide applications are needed now to
control it as we have now reached the required number of wetting hours for it be active. Cedar apple rust is starting to show. Apple scab
appears to be under control in most blocks. It is generally possible to find
scab in almost every block of apples. Fire blight shoot strikes continue to be
seen more prominently, however I have found very few new strikes in the last
four weeks. Necrotic leaf blotch leaf yellowing and drop is starting to be seen
in Golden Delicious.
The typical leaf
modeling or blotching on Honeycrisp is much more
pronounced this season then most years.
Pears continue to size with most being around 1.75 inches in diameter. Pear psylla and aphid populations seem to be under control in
most blocks. European red mite levels are well above threshold levels in many
blocks of pears, causing severe leaf burning in several blocks.
Peach harvest for Red Haven variety on early sites is about a week away. Early
peach variety harvest began late last week. Size has been a problem on these
early varieties. I hope Red Haven take on a big late swell over the next week.
Sweet cherry harvest has wrapped up. Most folks had a
light to moderate crop of sweet cherries with the exception of Romeo which has
a good crop. Many growers had high populations of cherry fruit fly this season
with some reports of cherry fruit fly larvae being found in fruit. Last season
there was an increase in trap catch and infected fruit, and this year that
trend continued. Next year, earlier scouting and monitoring of cherry fruit fly
needs to take place to determine population levels. I encourage growers to
consider making a post harvest fungicide application to control cherry leaf
spot.
Tart cherry has also wrapped up. Tart cherries have also suffered from leaf spot
infected foliage drop over the last couple years. I encourage growers to make a
post harvest fungicide application here as well.
Plums have not sized much over the last two weeks with most being around 1
to 1.25 inches in diameter.
Strawberries have rebounded well from renovation. In new
plantings, I encourage growers to continue to scout for twospotted
spider mites and potato leafhopper. I’ve seen numerous farms with potato
leafhopper damage on new plantings.
Raspberry season for summer red raspberries was very quick this year. The heat
of the last two weeks was very hard on summer raspberries, causing canes to
collapse. Fall red raspberry harvest has just begun for some of the early
varieties. Growth continues with most being around 2.5 feet in height. I am
continuing to see some potato leafhopper burn in fall red raspberries.
Blueberry harvest is now under way. While picking is light and berries have been
slow to ripen, it appears that we have an excellent crop of blueberries coming
along. Blueberry maggot adults have been caught on traps over the last few
weeks. I have also seen one farm that had a low population of larva infected
fruit. I encourage growers to continue to monitor populations very closely. Remember
that blueberry maggot is a close relative of apple maggot, if not the same
pest, and we are seeing very high populations of apple maggot this year. Birds
continue heavy feeding on blueberries.
Grapes are sizing quite nicely with
According to 30-year averages from the
Terminal buds are setting in many apple varieties. Apples are sizing nicely.
We continue to see powdery mildew in apple and other fruit crops because of all the hot, dry weather. Fungicides for summer diseases in apple should be added in over the next month.
Codling moth trap numbers have started to increase again,
indicating that second generation flight has started. A second regional biofix was set on July 18 for this next generation. We have
accumulated 173 GDD50 since this biofix, so cover
sprays will again become important by the end of this week or the weekend when
we should reach the 250 degree day post biofix, which
indicates early egg hatch will be starting. If growers have blocks that have
been trapping steady numbers of codling moth that have never dropped below five
moths per week per trap, these blocks should have cover sprays on earlier to
prevent stings. Many blocks have seen codling moth trap numbers go to zero
between generations this year – something we haven’t experienced for several
years in the
Obliquebanded leafroller flight larvae can still be found and are mostly in the later instar larval stages, getting fairly large and more difficult to control.
In the last few weeks, there are many European red mite eggs present in some blocks. Now these blocks have seen an explosion in the numbers of nymphs and adult red mites from the hot and dry weather we’ve had over the last several weeks. Continue to scout mites closely. Bronzing should start to be easy to see very soon in blocks with no controls applied.
A few more apple maggot were caught last week. With the rain that occurred early the morning of July 26, growers and scouts should expect to find more apple maggot on sticky traps this week.
The same story continues
– hot and humid. However, there has been one significant change. We did get
some much-needed rain a couple of times over the course of the week, with the
most intense precipitation occurring over the weekend. Radar images for
Saturday and Sunday (July 23-24) indicated that the rain was scattered with
wide range of intensity and amounts. For the past week, our automated weather
stations registered 0.54 inches for
|
Location |
GDD42 |
GDD45 |
GDD50 |
|
Hart |
2215 |
1947 |
1486 |
|
Ludington |
2103 |
1806 |
1359 |
|
Manistee |
2264 |
1966 |
1512 |
Cherry harvest is in its third week. As of July 16 we have harvested about 30 million pounds or just about 50 percent of the estimated crop of 62 million pounds. CIAB report can be viewed at: http://www.cherryboard.org/ . Quality is excellent, and size is very good. Blocks not yet harvested need to be protected from cherry fruit flies. In the last two weeks we have averaged more than three cherry fruit flies per trap. American plum borer numbers are still high, though they have dropped to an average of 13 moths per trap from 25 per trap the previous week. Rain events resulted in cherry leaf spot infections. Lesions from previous infections are present but not to the extent to present a serious problem this year. Still, post-harvest spray is highly recommended.
Apples are sizing
well. Here too, the rain events resulted in scab infections. We are finding
some scab lesions on the fruit, but it is not in alarmingly high numbers. Most
of the blocks have had very good primary scab control. Powdery mildew has been
more common throughout the area as a result of increased humidity. We are
finding symptoms of fire blight scattered in parts of the district. As already
mentioned, the weather in
Codling moth numbers have dropped, though we had a second “spike” towards the tail end of the first generation. We are starting to find small larvae in the fruit. Blocks need to be covered. Scouts are reporting finding potato leafhoppers. Obliquebanded leafroller egg hatch appears to have started. We are finding some very small larvae scattered throughout the area. Second generation spotted tentiform leafminers are out and getting stronger. European red mites and some twospotted mites have been reported in large numbers in a few blocks. Green apple aphids are being found in low numbers throughout the district. There are increased numbers of various stages of ladybugs, lacewings, syrphid flies and various predatory mites.
Peaches are looking good. We are finding a touch of powdery mildew in some blocks, but nothing major. Green peach aphids are present in relatively high numbers. Greater peachtree borer numbers continue to decline. Numbers have gone down to one per trap from three the week before. Lesser peachtree borer numbers have significantly gone down since last week and are averaging seven per trap compared to 21 per trap a week before.
GDD 42 2308
GDD 50 1532
Some welcome relief arrived in the past few days from the severe
drought that has gripped northwest
We finally received
rain. The apple scab model predicts secondary infection in leaves and
some minor incidence in fruit. Codling moth trap catches increased to 10.6
moths per trap. In areas where trap catches have not fallen to zero, we
recommend growers use the 1,250 GDD days for second generation egg hatch rather
than setting a second biofix for this upcoming
generation. We captured 12 Oriental fruit moths per trap this past week. Spotted
tentiform leafminer catches
have declined to 171 moths per trap. Obliquebanded leafroller moth catches are at 6.3 per trap, and dogwood
borer catches are up to 14.3 per trap. Here at the NWMHRS, we have not captured
apple maggot yet, but there are reports of isolated captures in the area. We
expect this rain to enhance emergence this week.
Light sweet cherry harvest is complete and dark sweets are nearing completion. With no rain, size was an issue while cracking was not. Size was particularly problematic because the crop load was extremely heavy. The heavy crop also accentuated the drought stress on trees. This stress combined with excessive heat resulted in many problems with ethephon injury. Ethephon injury was first expressed as yellowing leaves and is now exhibiting clear gummosis from limbs.
Tart cherry harvest is currently at its peak. Fruit size is generally small (particularly where crops are heavy), but overall quality is excellent. Fruit firmness has been excellent. Brix levels have been high, color good, and below normal wind damage. As with sweets, ethephon induced leaf yellowing and gummosis is common.
The much-needed rain in the past few days resulted in light
to moderate cherry leaf spot infection. American brown rot may also be on the
rise with the increased moisture in the orchard, especially in dark sweets that
have yet to be harvested. American plum
borers are at 11 moths per trap. No lesser peachtree
borer numbers were captured this week, and greater peach tree borers are still
at 17.6 moths per trap. Twospotted spider mites are
still high and increasing in many cherry blocks, but these rains may wash off a
percentage of them. The rain, if we receive enough to reduce drought-like
conditions, will increase mite thresholds with greater moisture in the orchard.
Firing has been reported in all areas of the northwest; this symptom is an
immediate result of increased temperatures and droughty conditions, most often
in combination with high mite populations. Cherry fruit fly catches are decreasing in the entomology block, but we
have captured an average of 9 flies/sticky board in three conventionally
sprayed blocks.
Grape berries are
enlarging rapidly with some varieties near berry-touch. Clusters will soon
"close up" and greatly reduce pesticide penetration to the inner area
of the berries. Sphinx moth larvae are now getting very large but few in
numbers at most sites. Watch closely for these caterpillars in young vineyards
where they can completely defoliate small vines. Powdery mildew remains the
main disease threat at this time, but very little of it has been reported thus
far.