May 1, 2007
In this issue
Tree fruit news
§ Fire blight, blossom blight
§
Fire blight and streptomycin resistance in
§ TNRC trapline catch: Spotted tentiform leafminer
§ Applying Apogee
Small fruit news
§ Gibberellin to enhance blueberry fruitset
§ Strawberries may need extra nutrition this season
Other news
§ Honey bee CCD update
§ Locating a local beekeeper for fruit
pollination
§
Application technology for small acreage
producers
§ Regional reports
§ Weather news
Fire blight is caused by the bacterium Erwinia amylovora, an organism that is capable of infecting blossoms, fruits, vegetative shoots, woody tissues and rootstock crowns. There are several distinct phases of the disease including blossom blight, shoot blight and rootstock blight. The diversity of host tissues, combined with the limited number of management tools available to control the disease, has made it difficult to stop or slow the progress of fire blight epidemics. Fire blight is particularly difficult to manage, and the situation is exacerbated by three major problems: (1) most of the popular apple cultivars selected by growers are either rated as susceptible or highly susceptible to fire blight; (2) many of the popular dwarfing rootstocks utilized in Michigan are also highly susceptible to fire blight; and (3) the few chemical control options available are further limited by the development of streptomycin resistance in some areas of Michigan.
The development of fire blight is heavily tied to weather conditions. For example, pathogen cells grow well at temperatures above 70ºF and do not grow well when temperatures are below 60ºF. The availability of moisture is important for growth -- this moisture can come from rain or heavy dew. Rain also disseminates pathogen cells among blossoms. Initial fire blight inoculum comes from cankers on trees in the form of bacterial ooze; this usually orange- or amber-colored goo contains pathogen cells in a sugar matrix. It is important to note that viable bacteria can also be present in cankers that are not oozing. The pathogen is disseminated by wind, rain and insects such as ants and flies, to blossoms where growth occurs on stigmas. Honeybees do not visit the ooze and are not responsible for the primary dispersal of the pathogen. Rain is particularly important in spread, for example, in the downward spread of inoculum in trees with cankers in the upper branches.
The fire blight pathogen is exceptionally adapted to growing on the stigmatic surface of blossom pistils. Populations can readily reach 1 million to 10 million cells per blossom. Each open blossom is only susceptible to infection for a few days; however, the pathogen is adapted to successfully infect blossoms during this window of time. After explosive growth on stigmas, rain or dew facilitates the movement of pathogen cells to the hypanthium (floral cup) where infection occurs through nectarthodes.
The blossom phase of fire blight is the only phase where the
pathogen is located on the surface of trees and can be targeted by chemical
sprays. Blossom blight can be controlled by killing pathogen cells on blossoms
or by limiting pathogen growth on blossoms. The antibiotic streptomycin is the most effective control compound available for
blossom blight. Reducing blossom populations and thereby reducing fire blight
inoculum is critical to the control of the blossom blight phase of the disease
and also in reducing disease pressure for the shoot blight phase of the
disease. Streptomycin is so effective because this antibiotic kills pathogen
cells on blossoms. The antibiotic oxytetracycline
(Mycoshield) is also effective for blossom blight control. A Section 18
specific exemptions for the use of Mycoshield was granted by the EPA for the
2007 season. Mycoshield is bacteriostatic and does not kill pathogen cells but
does inhibit cell growth. This growth inhibition is sufficient to keep pathogen
populations low providing blossom blight control. However, inoculum remaining
in trees can cause shoot blight later in the season. The biological control
material Serenade Max provides some
blossom blight control under low to moderate pressure conditions. This material
can be used as a resistance management tool, but will be less efficacious under
high pressure conditions. Finally, a Section 18 specific exemption for the use
of Agry-Gent was granted by the EPA for Berrien,
The MARYBLYT model developed by Dr. Paul Steiner is an important tool for growers to assess the potential for fire blight infection. This model, used in conjunction with accurate weather information (available at the Enviroweather site) continually assesses the upcoming risk of infection. The MARYBLYT model sets a requirement of four factors that must be reached for a fire blight infection:
1) Blossoms open with stigmas and petals intact.
2) Current average daily temperature above 60ºF.
3) Accumulation of at least 110 cumulative degree-hours above 65ºF from the first open bloom.
4) Wetting event of > 0.01" or heavy dew or fog sufficient to wet foliage or rain of ≥ 0.1" the previous day.
In addition, other major factors important for the occurrence of blossom blight include:
§ Previous history of fire blight (active cankers in orchard).
§ Varietal susceptibility.
§ Trauma event, including hail, sustained winds, or heavy rain.
With bloom upon us in many areas of the state and relatively high temperatures (conducive for fire blight pathogen growth) forecast for later this week and next week, it will be critical for apple blossoms to be protected in advance of these potential infections.
In 2006, we detected streptomycin-resistant Erwinia amylovora, the fire blight
pathogen, for the first time in orchards in
There are four points that I would like to make about applying Apogee in apples. First is timing, second is rate per acre, third is thinning relationships and fourth compatibility.
Timing. Apply Apogee when vegetative shoot growth is less than 3 inches. This is about a 7 to 10 day window commencing at the king bloom petal fall stage. Most years all varieties can be treated at this time. The second application should be applied two weeks later and the third application two weeks after the second. Sometimes a fourth application is needed, but that is optional based on crop load and tree vigor. Excessive rainfall and light crops will promote vegetative growth; therefore an additional fourth application may be needed.
Rate. Rate per acre is usually calculated on a tree row volume basis and adjusted to 2/3 of the label full rate. This 2/3 rate/acre is a season long rate per acre. For example, if your trees are 75% tree row volume then 24 ounces per acre is the seasonal rate (48 * .75 * 2/3). Best results occur when seasonal rate is split into three or four sprays. For example, 8 + 8 + 8. When fire blight is a severe risk, the first application at king bloom petal fall timing should be increased, perhaps as much as 150% of a split rate. For example, increased from 8 ounces per acre to 12 ounces per acre. Subsequent sprays, the second and third sprays could be reduced, so the seasonal application would be 12 + 6 + 6 = 24 ounces per season.
Thinning. Apogee tends to increase fruit set, therefore more aggressive thinning is needed. Increase your thinning by 10 or 15%.
Compatibility. Apogee is not compatible with calcium or boron in the tank. Also, we suggest that Apogee be applied after a thinner. If the two-week timing interval is also the ideal time to thin, make your thinning application first and then a couple days later follow with Apogee. Remember to include the label recommendations for AMS and surfactants.
In a summary; Apogee is an excellent tool to help control vegetative growth and especially suppress fire blight spread among shoots and within shoots. Follow these tips to get the most out of Apogee.
Compared to most fruit crops, a high percentage of blueberry flowers normally produce fruit. When bees are numerous and weather is warm and calm, 80-95 % of flowers may set fruit. However, cold, rainy weather during bloom restricts honey bee activity and pollination, resulting in lower fruit set and often reduced berry size. Flowers that are not pollinated within 3-5 days after opening are unlikely to set fruit. After normal pollination, berry growth is dependent on the production of gibberellin and perhaps other growth promoters in the ovary tissues and viable seeds. If flowers are not pollinated, they abort. If only a few ovules are fertilized, the fruit may set, but not contain enough seeds to grow to full size.
When pollination is limited by poor weather, gibberellin (GA) sometimes improves % set and berry size. Several GA products (ProGibb, GibGro) are labeled for highbush blueberries. GA may result in retention of some seedless (parthenocarpic) fruit that normally drop, and increases the size of berries with low seed numbers. GA can be applied in a single spray during bloom (80 gram active ingredient per acre) or two 40 g sprays, one during bloom and the second 10-14 days later. Higher spray volumes (40 to 100 gallons per acre) may improve coverage and effects. Slow-drying conditions also increase absorption. Also make sure your spray water pH is not above 7.5.
Since the cost of 80 g of GA is over $100, it is important to know when to use GA. If weather has been reasonable good for bee activity and the white corollas fall easily from the bushes, pollination is probably adequate. Keep in mind that blueberries can bloom over a long time, and often only a few days on good conditions is enough to provide adequate pollination. Consistently cold, rainy and/or windy weather through bloom causes pollination problems. If the corollas stay on the bushes longer than usual and turn red/purple before eventually dropping, pollination may have been inadequate. The corollas of pollinated flowers drop readily while still white. Varieties with fruit set problems (Jersey, Coville, Earliblue, Berkeley, Blueray) are most likely to benefit from GA. Jersey, for example, is relatively unattractive to honeybees, and berry numbers and size are often limited by inadequate pollination. GA does not always provide a benefit, and effects can be subtle. A key to learning about GA benefits is to leave non-treated check rows. This is the only way to tell if your money was well spent.
2006 Trial. Because weather during bloom was poor, we
treated Jersey bushes at the Southwest Michigan Research and Extension Center
with ProGibb applied twice at 40 g a.i./acre (17, 27 May) or applied once (17
May) to a single application of 80 g/acre on. On 17 May, 30% of
Results were fairly
typical for years when there is a response to ProGibb. The 80 g rate applied
once increased yield by about 30% over control plots, and there was a trend
towards a response from the 40 g treatment as well (Table 1). The higher yield
appeared to result from more berries rather than an increase in average berry
weight. During the week prior to the first ProGibb spray, measurable rain
occurred every day, and maximum daily temperature exceeded 60oF only
on one day. These are the type of conditions when growers are likely to see
benefits from ProGibb.
|
Table 3. Effect of ProGibb applications
of average berry weight and yield of ‘ |
|||||
|
Treatment |
Average berry weight (g) |
Yield (lb/bush) |
|||
|
1st pick |
2nd pick |
1st pick |
2nd pick |
Total |
|
|
Control |
1.22 a |
0.78 a |
4.1 a |
0.9 a |
5.0 a |
|
ProGibb 40 g twice |
1.18 a |
0.82 a |
5.0 a |
1.1 a |
6.1 ab |
|
ProGibb 80 g once |
1.27 a |
0.85 a |
5.0 a |
1.5 b |
6.5 b |
Many strawberry fields that I have observed over the last
two weeks across east
While it is typical for me to recommend to strawberry
growers that they apply light rates of nitrogen in springtime, this year I am
suggesting extra nitrogen be applied immediately to strawberry fields to help
improve their vigor and to be prepared for our fruiting season. The typical
rate of fertilizer that I would suggest on strawberries growing on our heavier
soils of east
If you have been listening to radio or reading papers the last few weeks, chances are that you have already heard about the alarming honey bee die-offs around the country. The phenomenon is officially named Colony Collapse Disorder (CCD). This disorder has the media all excited because it is large in scale (27 states are affected), came in quick (Colonies that were fine in August or September became collapsed around October and November.), and hit people hard (Many beekeepers with hundreds to thousands of colonies are losing 50 to 90 percent of their colonies.). Nationally, it is estimated that we have lost about 600,000 colonies. The worst of all, we do not yet know what causes it!
The symptom seems to be for bees simply to disappear. That is why initially peopled called it disappearing disease (or fall dwindle disease). A colony with 30,000 bees checked one week ago – apparently healthy with lots of honey and pollen – suddenly has nothing, or a handful of bees with a queen left, but with lots of food and many frames of capped brood left. Very few dead bees are found inside the hive or near the entrance. Strangely, wax moths, small hive beetles, and robbing bees are slow in moving into such newly abandoned colonies – two to three weeks later – while normally they move into defenseless colonies right away.
I just attended an emergency conference in
It seems almond growers in California, who need about half
of the bees in the country (about 1.2 million colonies) did not have an obvious
shortage of bees for pollination, but they did see a $15-25 per colony increase
in price. Blueberry growers in
Even though
Here are the instructions for finding a beekeeper at my web site, http://cyberbee.msu.edu
1) Type in the URL (cyberbee.msu.edu) on your browser window.
2) Click “beebase” on the left menu
3) You will see (421 beekeepers registered now).
4) Click “2. For any beekeepers providing pollination services” in the “Search Information from the Databases” window.
5) Put your mouse on the second window (area code), and change it to the method you want to search (either area code, county, last name or zip code), and type the corresponding criteria in the “for” window. For example enter “517” here if you selected area code or “48824” if you entered zip code, etc.
6) Then click “search”
7) You should see information listed, including beekeepers name, address, phone # and email address and how many colonies they have.
Give them a call and you are all set. Good luck with your pollination!
June 14 from 6:00 - 9:00 PM
Northwest Horticultural
Research Station
This workshop is designed for pesticide applicators working
with nurseries, greenhouses, vegetables, floral, forest and other small acreage
settings. Dr. John Grande, Snyder Research Farm,
Two core recertification credits for commercial and private applicators have been applied for. The cost is $5. The rest of the program expense is sponsored by a North Region Project GREEEN grant.
To register, send check for $5 to Roberta Dow,
Last week temperatures were cool with lows in the 40s. Monday and Tuesday (April 23-24) were nice with highs near 70. Wednesday and Thursday (April 25-26) were cold and rainy with highs near 50. The last two days have been warm and pleasant with highs climbing into the 60s on Sunday, April 29. We accumulated between one to two inches of rain. Soils are moist. Scattered thunderstorms brought scattered light hail Monday. This week’s forecast is for cooler, dry weather with lows in the 40s and highs near 60. Warmer temperatures are forecast for the weekend.
|
Grapes, from April 1
|
|||
|
Location |
GDD 42 |
GDD 45 |
GDD 50 |
GDD 50 |
|
426 |
334 |
215 |
117 |
|
|
477 |
384 |
258 |
138 |
|
|
346 |
266 |
164 |
84 |
|
Plant growth and
insect activity are moving quickly with warmer temperatures. Reports of damage
to fruit plantings from the Easter freeze continue to come in. The two days of
rain on Wednesday and Thursday (April 25 and 26) were cold (about 47ºF) but
long enough (40 to 65 hours) to be an infection period for many diseases.
Peach bloom is ending. We should have a good assessment of the peach crop as it
emerges form the shuck in the next few weeks. Oriental fruit moth adults
are being caught in good numbers in pheromone traps. Biofix was Saturday, April
21 at 230 GDD at SWMREC. Pesticide sprays are targeted for 150 to 200 GDD base
45 after Biofix; this timing would be this weekend. The first generation of tarnished
plant bug adults has been seen in trees during warm weather. Last week’s rains
could have caused brown rot infections (48 hours at 50F for infection).
Tart cherries are at petal fall and bloom is ending. Copper would be a good material to
use to reduce bacterial canker from the cold rain last week. Growers with
little, if any, crop may want to use copper as their primary cherry leaf spot
material and to reduce their fungicide costs and maintain a healthy leaf canopy
for as long as possible. There was a report of a tart cherry orchard severely
damaged by winter cold with many dead trees. This occurred because the orchard
was defoliated last July and did not withstand the February cold snap with
temperatures below zero.
Sweet cherries are at petal fall. Copper is phytotoxic to sweet cherries and should not
be used. Growers should protect against brown rot. Sweet cherries are
susceptible to brown rot at all times.
In plums, European plums are in the shuck. Growers should be
protecting against black knot
and brown rot. There was also a report of a plum orchard severely damaged by
winter cold with many dead trees.
Apples are blooming. Growers should begin to assess their crop in preparation
for thinning sprays soon. Signs of powdery mildew can be found in apples. Last
week’s rain was a heavy apple scab infection and symptoms should appear next
week. Symptoms from the April 4 infection should be appearing now. We are
updating our Code-A-Phones with fire blight conditions. The
rain was too cold for fire blight and this week will be too cool for the
disease. Warmer conditions on the weekend may pose a risk. Now is the time to
apply Apogee sprays to reduce fire blight and control vegetative growth. Growers
can also check for apple scab and fire blight at the Enviroweather website: http://www.enviroweather.msu.edu/.
Oriental fruit moth is
being caught in good numbers in pheromone traps. Biofix was Saturday, April 21
at 230 GDD at SWMREC. Pesticide sprays are targeted from 150 to 200 GDD base 45
after Biofix; this timing would be this weekend.
Pears are at petal fall. Pear scab is similar to apple scab and pear scab
symptoms should appear next week as with apple scab.
Blueberries are at pink bud. In many fields, there is a heavy set of fruit buds. Mummyberry mushrooms are out, so last week’s rain was probably an infection period. Growers should check the new Blueberry IPM Newsletter at the MSU Blueberry Site. No cranberry or cherry fruit worms have been caught yet and scouts should be setting out pheromone traps for these pests.
For grapes,
Strawberries are at white bud. Wild strawberries have begun to bloom.
Fall raspberries are putting up new shoots. Summer raspberries are leafing out and some flower buds are visible in some fields. Some varieties were severely affected by the Easter cold snap. Blackberries were severely damaged by winter cold (early February) and the Easter freeze. Advanced shoots were damaged or killed, but new growth is emerging.
Cranberries are beginning to green up on the edges of the beds and buds are beginning to swell.
Currents and gooseberries are blooming.
The next Monday Fruit Update
meeting will be Monday, May, 5:00 PM,
at the Fruit Acres Farm in
It seems as if our stop and go season has continued over the last week. We’ve had four days of cool weather with few, if any degree day accumulations, and then a few relatively warm days with a good number of degree day accumulations. Our season is still running about three to five days ahead of normal in terms of degree day totals, but based on phenology of flowering, we are about a week ahead of normal.
The region received between a 0.5 and 1.75 inches of rain over the last week, with most farms receiving around a 1 inch. While this rain did slow up tree planting and other field work, as of yesterday many growers were back at it again.
I am pleasantly surprised to see the amount of bloom in most of our tree fruits over the last several days. It appears that the Easter freeze event was not as dramatic as what we had originally thought. While there is still significant damage in sweet cherries and some in tart cherries, at this point in time it appears that overall we have a pretty good crop of tree fruit. The notable exception would be peaches that in many areas, with the exception of Romeo, are very thin this season. Look for more details on the Easter freeze event later in this report.
|
|
|||
|
Location |
GDD42 |
GDD45 |
GDD50 |
|
Commerce ( |
358 |
269 |
162 |
|
Emmett (St Clair) |
317 |
236 |
139 |
|
|
354 |
265 |
161 |
|
Lapeer (Lapeer) |
348 |
262 |
160 |
|
|
400 |
307 |
192 |
|
Romeo ( |
346 |
259 |
158 |
Apples have moved
along quite fast in the last few days, with most varieties being at bloom or
near bloom in the south and in the
Most growers had an apple scab infection late last week on April 28, with most of the reporting stations having a high infection. Symptoms from this event should start to show up mid- to late next week. I have not seen any apple scab lesions. I continue to get apple scab spore discharge with each rain event.
For the most part, it appears that we have an excellent crop of apples coming along this year. In cutting flower buds since the Easter freeze event, it was apparent that there was damage in individual blocks and varieties; however that varied from block to block across most farms. Even in blocks that appeared to have a good percent of flower bud loss, it now appears that we have a crop of bloom. In some blocks that were over cropped last year, there is also a notable lack of bloom. I feel that this is due more to over cropping in the 2006 season as opposed to loss from the Easter freeze event.
Pears are at king bloom, with a good crop of pears coming along. Pear psylla adults were seen yesterday in much higher numbers than last week. Egg laying has been going on for several weeks. Egg hatch occurred as of this morning.
Peaches are at full bloom where we have a crop. The color of the bloom is off a bit this year at many blocks. There are also a good number of blocks that have an extensive amount of flower bud kil, primarily due to cold events in January and February. In blocks where there is a full crop of peaches, growers can go ahead and prune normally. In blocks where there is heavy bud damage, this may be an opportunity to bring the height of peaches down to more of a manageable level. Also in these blocks of peaches without a crop, I would encourage growers to cut back their fertility program for the season.
Sweet cherries are at bloom to early petal fall. It appears that most farms have about 50 to 60 percent of a crop of sweet cherries at this time. This is a crop that I think was affected most from the Easter freeze event. It may be a good recommendation to apply copper to reduce bacterial canker in blocks that have a poor crop this year.
Tart cherries are at bloom for the most part, however there is a fair amount of delayed bloom that may have been injured from the frost and freeze event. At this time, it appears that we have about 60 percent of a tart cherry crop.
Plums are at full bloom, with the exception of early flowering types, which are at early petal fall.
Strawberry flower trusses have started to emerge from the ground. See the strawberry nutrition article in this issue for details on the extra nutrition recommendation this year.
Raspberries continue to rebound from the Easter freeze event. Many of the leaf buds, which were at green tip at that time, were burned off. There may be some delayed Easter freeze injury on summer red raspberries, which will show up as they begin to fruit. Fall red raspberries are at 2 to 3 inches of new growth. Most of this new growth has reemerged since the growth that was present at the Easter freeze was burned to the ground. This may delay harvest of fall red raspberries by a few days this fall – time will tell.
Blueberries are at pink for earlier flowering types. It appears that there was much less damage to flower buds than I originally predicted.
Grapes are at bud
burst for
Growth over the last week has been more normal due to some average or slightly above average temperatures. Apples are at open cluster to pink stage depending on the variety. There are a few king blooms open on early varieties like Ginger Golds and Ida Reds.
Sweet cherries are mostly in full bloom. Peaches are blooming also.
As we get closer to bloom, freeze damage to apples still doesn’t appear to be
extensive. There are some varieties and some blocks with more damage than
others, but overall, the apple crop from the
Now that we know more about the crop load, ground applied fertilizer applications are beginning. Growers are also adding foliar nutrients to their regular cover sprays to boost bud health. Tree planting is ongoing.
Apple scab has
had two infection periods over the past week for all areas around
With bloom coming on, apple growers will need to think about adding a mildewcide in the tank for powdery mildew in the next week or so for those varieties that are susceptible to it.
Brown rot sprays on sweet cherries and peaches in bloom should be applied – these rainy days during bloom will promote brown rot at harvest time.
Oriental fruit moth should begin flying at anytime, but no reports of activity at this time. Apple grain aphid can be found, but in relatively low numbers for this time of year. Rosey apple aphids are being found in low numbers in non-sprayed blocks and should be present in commercial blocks as well. Green fruitworms are flying. Overwintering European red mite eggs are still very difficult to find at this time, but there have been some reports of early red mite activity in known hot spot areas. Spotted tentiform leafminer adults should start flying at any time, especially with some warmer nighttime temperatures. Climbing cutworm damage to buds could be seen at any time.
Pink sprays are going on in commercial apple blocks where warranted. There is still time to get them on in later blooming varieties, but be sure you are aware of neighboring blocks that may have bees set out already.
Blueberries in
west central
So far, insect pest activity is non-existent due to the prevailing low temperatures, but we need to remind growers that it is time to install cherry and cranberry fruit worm pheromone traps. At this time, it is critical that traps be monitored twice a week to be able to detect the beginning of the moth flight and to time our pest scouting activities. In the past we have observed that cranberry fruitworm eggs appeared 120-130 GDD (base 50 °F) after the beginning of the moth flight. Therefore, if we are going to use GDD to predict the fruitworm activity detection of the beginning of moth flight is critical.
The weather has been nice and seasonable. We had quite a spread of temperature, from mid 40’s to the 70’s. Nightly temperatures were in low to mid 40’s with the exception of Saturday and Sunday night (April 28-30) when the temperatures dropped down into the mid30’s. Some low-lying areas might have had some frost. In the past seven days there were four rain events. It appears that the heaviest precipitation was in the southern parts of the district, then diminishing as it progressed north. The combinations of moisture and warmer temperatures have stimulated vegetation development.
Apples are in various stages of phenological development depending on the variety. Idareds are in pink. Red Delicious is in open cluster, Jonagolds are showing early pink king blossom and McIntosh is in early pink, etc.
Pears are in open cluster showing early white blossoms. If the warmer temperatures continue, I would expect them to start opening flowers in a couple of days. No doubt they will be in full bloom by the end of the week.
Peaches are in full bloom.
Plums are starting to bloom.
Tart cherries are just starting to open their flowers.
Sweet cherries are in full bloom.
|
Location |
DD42 |
DD45 |
DD50 |
Rainfall last week |
Rainfall since 4/1 |
|
Hart |
283 |
212 |
126 |
0.99 |
2.52 |
|
Ludington |
275 |
205 |
120 |
0.85 |
2.58 |
|
Manistee |
274 |
207 |
122 |
0.9 |
2.28 |
Rain on April 26-27 in combination with heavy fog that
lasted most of the day on April 27 provided favorable conditions for a heavy apple scab infection period in the
whole district. As predicted, another wave of precipitation rolled into the
area yesterday late afternoon. At the time of this report we have had an
ongoing wetting for more than 12 hours. By 10:00 AM (on May 1), all the
requirements will be satisfied for low infection. Spore discharge has been
increasing. At this time there are about 40 percent mature spores with
estimated 14 percent discharged. Rapid green tissue development must be taken
into consideration when deciding on spray options. Best control will be
achieved by using a combination of materials that would have a component
capable of providing post infection, curative action. Captan or one of the EBDC
fungicides in combination with Vangard could be one such option. Vangard is
pre-bloom material that works better under cooler conditions and, given the
current weather conditions, it could make a good fit. Vangard is a protectant
with some after-infection capability if applied at full label-recommended rate up
to 48 hours post infection. Other possibilities would be strobilurins (
Leaves are unfolding indicating a need for protection from cherry leaf spot. Last year this area
had quite a few blocks with very heavy disease presence causing early
defoliation. The inoculum presence is heavy and vigilant approach and
aggressive control is necessary to avoid a repeat of last year’s performance.
The current rain event has not yet reached the 20 hours of wetting necessary to
trigger infection. According to the forecast, rain will stay over the west
central part of the state over most of the day and expending into tomorrow
morning indicating that the first infection of the season is imminent. Young
leaves are at the highest risk. Spray options include, but are not limited to,
Bravo, Indar and Pristine. Bravo is excellent cherry leaf spot material that will
extend the protection against blossom brown rot. It is a very good fit at this
time due to label restrictions allowing it to be used only up to the point of
shuck split. Some of the other options are Indar with excellent ratings against
leaf spot and blossom brown rot and Pristine that provides excellent control
for leaf spot and powdery mildew.
Plums are susceptible to
leaf spot infections. Conditions are favoring disease development requiring
protection at this time. Spray options are Elevate, Bravo, Rovral, Vangard,
Orbit, Pristine, Captan and Topsin-M.
As stated in the last week’s report, now is the prime time for brown
rot/blossom blight, bacterial leaf spot and black knot requiring full attention
and prompt control.
Insects are still relatively quiet. Very few European red mite eggs have been observed. Pear psylla is the only one showing significant activity. No reports of oriental fruit moth flight yet, though I would expect to have a catch this week. There are very few spotted tentiform leafminers in the orchards at this time.
GDD42 253
GDD50 102
Last week, April brought in its usual showers, and we look forward to the start of May with warmer and dry weather, except for Tuesday, May 1 in the morning.
Growth
Stages at NWMHRS (4/30/07—8:00 AM)
Apples: Tight cluster.
Pears:
Sweet cherries:
Hedelfingen are at bud burst; Golds are at early white bud; Napoleon are at 10
percent bloom.
Tart cherries: Montmorency are at bud burst; Balaton are at late bud burst.
Apricot: petal fall.
Grapes: Chardonnay are at early bud swell.
Warm weekend weather is moving the trees along. In pears, we are at late green cluster for
Not too much to report in the insect world, except for low levels of two-spotted spider mites and green apple aphids. We have seen a few blocks with lots of apple rust mites. We have not seen any European red mite eggs. We have also trapped a few (about 10) spotted tentiform leafminers at the research station. We have a new experiment in place to investigate plum curculio overwintering and spring migration, and we have observed movement in the weevil population this past week in our emergence traps. In other words, plum curculio are up and moving. However, primary migration into the orchard occurs for up to six weeks after bloom, with the biggest flush of movement happening up to 14 days after petal fall. This movement indicates the beginning of migration.
With the wet weather of last week, all eight weather
stations reported wetting events that resulted in a low to moderate apple scab
infections. As of Tuesday morning, May 1, the
For grapes, a few climbing cutworms have been seen at the NWMHRS vineyard, but they were not feeding on buds; some were seen feeding on the bleeding sap from pruning cuts. Numbers were relatively low, about 1 per 70 vines. Growers should be scouting vineyards for symptoms and signs of last year’s powdery mildew infections, making notes on relative levels of overwintering powdery mildew on canes. If dormant sprays are planned for powdery mildew control, these need to go on soon.
Upper air ridging and high pressure will move into the
Medium range forecast guidance is currently in good
agreement suggesting a continuation of upper air troughing across the western
Further ahead, the new