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| Fruit Crop Advisory Team Alert newsletter | ||||
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| Vol. 22, No. 7, May 22, 2007 |
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| In this issue Tree fruit news  Cidadas expected to emerge in Berrien, Cass, St. Joseph counties Prowl® formulation now labeled for bearing fruit trees Gibberellic acid on cherries TNRC trapline data: American plum borerSmall fruit news Blossom blight in blueberries Bloom is a critical time for control of Botrytis gray mold in strawberriesOther news Management of glyphosate-resistant horseweed (marestail) Enviro-weather tip: GDD accumulations Regional reports Weather news |
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| Cidadas expected to emerge in Berrien, Cass, St. Joseph counties An emergence of Brood XIII of the 17-year periodical cicada is expected in southwest Michigan in the next few weeks (view photo). This is an emergence of a different brood than we had a few years back, and is only expected in southwestern Michigan. These are not migratory insects like locusts, and will not be flying in swarms. They could be in high abundance, and will be loud if they emerge in high numbers. Cicadas prefer woody plants for their egglaying, and are of minimal risk to mature vineyards. Most injury in mature vineyards can be tolerated because most oviposition occurs distal to the clusters, and injured shoots will be pruned off later. Some simple scouting with eyes and ears will verify whether they are in vineyards, and it will be easy to detect these loud insects. There is some risk in young orchards and in young vineyards where growers are trying to establish the tree and vine shape. This is the information posted at a reliable website from Virginia Tech, where they experience this more regularly in their winegrapes: young vines are subject to severe injury, with females using even the trunks as oviposition sites. Ovipositon may occur at multiple sites on one shoot or young trunk; affected areas become weak and will break easily (Eggs in the shoots may be seen on dissection of the injured material). Such young vineyards should be protected. |
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If high abundance of cicadas is detected inside vineyards and cicadas are found laying eggs into stems, then Sevin, Imidan or any of the pyrethroids will be highly effective. |
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| Prowl® formulation now labeled for bearing fruit trees Prowl®, active ingredient pendimethalin, is a selective residual herbicide from BASF Corporation useful for the control of annual grasses and certain broadleaf weeds, such as kochia and lambsquarter. Prowl®, a preemergent herbicide, has been seen as a lower cost alternative to Surflan (oryzalin), but up to now has not been available for bearing fruit plantings. The older EC formulation, Prowl® 3.3 EC, has been joined by Prowl® H20, a water-based formulation available since 2005. Prowl® H20 has recently received a supplemental label that allows application to pome and stone fruit (see table). This supplemental label expires December 31, 2008 and is currently not applicable to New York and California. Also, as mentioned in the May 8, 2007 issue of the Fruit Crop Advisory Team Alert, Prowl® H20 has also been labeled for carrots, peppers, tomatoes and strawberries for the same time period. Table 1. Prowl® H20 herbicide may be applied to the following fruit-bearing trees
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| Gibberellic acid on cherries Cherries have natural tendency to produce “blind wood.” This phenomenon is associated with the flower bud formation on the young wood, so after the harvest we are left with long bear spots with no spurs. Research done by MSU’s Dr. John Bukovac, showed that it is possible to manipulate the flower bud formation in favor of spur development by applying gibberellic acid. When do we apply gibberellic acid? If you used to go by the calendar, the general recommendation is to apply the spray three to four weeks after full bloom. Perhaps, a more accurate timing would be when you have five to seven fully developed leaves on terminal growth. Mature trees Gibberellic acid (GA) will induce spur development, thus reduce “blind wood” formation and provide greater bearing capacity. How much gibberellic acid you need to a use will be the function of the tree vigor. High vigor requires a low rate; low vigor demands higher rate. Material: Pro - Gibb 4% - commercial form of gibberellic acid. Rate: General recommendation is 10 - 25 ppm. 10 ppm = 4 oz. / 100 gallons of water 15 ppm = 6 oz. / 100 gallons of water 20 ppm = 8 oz. / 100 gallons of water 25 ppm = 10 oz./ 100 gallons of water How to apply Gibberellic acid should be applied in 50-150 gallons in water. For best results, apply gibberellic acid when the temperature is 70ºF or above. At lower temperatures, the uptake has not been adequate, and the applications were less successful. Dr. Bukovac has found that use of surfactants can yield various results; it shows no effect to some effect to over-response with phytotoxicity. Silicon-based surfactant caused phytotoxicity. In conclusion, do not use surfactants! Young, non-bearing trees In the environment where the trees are mechanically harvested, it is particularly important to insure good vegetative growth in the first few years following planting. Well-developed trees with a strong framework, will be able to provide uniform and plentiful bearing capacity. That is why the trees are not allowed to produce fruit in the first five to seven. By spraying gibberellic acid in high concentration (100 ppm or 40oz in 100 gallons of water) over the given span of years, there are very few flower buds, with most of the buds being converted into vegetative buds clustered in spurs along the shoots. Timing of the application on the young trees, is the same as for the mature trees. The difference is in the concentration of gibberellic acid applied. To insure almost no flowers, use 100 ppm or 40 oz. of Pro - Gibb 4 percent in 100 gallons of water. If tree vigor is low, a second application, three weeks following the first one, may be helpful. Two applications of 50 ppm about two weeks apart are more effective than one application of 100 ppm. Do not treat more than twice in one year. Bringing young trees into bearing Following the early years of high concentration sprays of gibberellic acid, it is essential to bring trees into full bearing, gradually. If the plan calls for getting the trees into bearing in the eighth year after planting, in the fifth year concentration of gibberellic acid sprays should drop from 100 ppm to 75 ppm, in the sixth year there is a need for further concentration reduction to 50 ppm, in the seventh year concentration is down to 30 ppm. After this gradual “introduction” into production, the program for gibberellic acid should follow the outline proposed for trees in full production. Following this protocol, trees are allowed to produce in increments that are higher from year to year. As the concentration of gibberellic acid decreases, the yield increases. If the concentration of gibberellic acid is allowed to suddenly drop from 100 ppm to 25 ppm or 15 ppm, that would lead to fruit oversetting, overcropping and stunting the growth. Application timing is the same as for the mature trees: once there are five to seven fully expended leaves on terminal growth. Caution: Do not spray gibberellic acid on the trees in the year of planting! |
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| Blossom blight in blueberries Blighted flower clusters were seen at low levels in several blueberry fields. In most cases, the blighted clusters looked like they were caused by Phomopsis, which is characterized by a dark brown discoloration of the twig that bears the flower cluster (photos 1, 2). Initially, the brown lesion is ¼-½ inch long, but can expand to several inches in length in a couple of weeks and can kill additional flower clusters on that same twig. Eventually, the lesion will stop growing and the blighted blossoms will fall off. The causal fungus, Phomopsis vaccinii, overwinters in dead twigs and canes, and in the spring infects the flower clusters, aided by long wetness periods and possibly by frost injury. In some cases, it also appears that the fungus infects flower buds in the summer or early fall and overwinters in live buds. In the spring, the fungus will become active again and kill the bud followed by invasion of the twig. These types of infections are characterized by a dead flower bud surrounded by a brown lesion, while nearby buds would have developed normally. In Michigan, at least four different pathogens can cause blossom blight: Phomopsis vaccinii (Phomopsis twig blight), Monilinia vaccinii-corymbosi (mummy berry flower strikes), Botrytis cinerea (Botrytis blossom blight), and Colletotrichum acutatum (anthracnose). Just by looking at a blighted blossom, it may be difficult to identify the causal agent unless fungal growth is present, so it is a good idea to inspect the cluster with a hand lens or magnifying glass. In the case of mummy berry flower strikes, a layer of gray powdery spores is present, but restricted to the flower stem or cluster stem (photo 3). In general, flower strikes are much less common than shoot strikes, so it is unlikely to have flower strikes without shoot strikes. Spores produced on flower strikes behave similarly to those produced on shoot strikes and infect the stigmas of recently opened flowers. Botrytis blossom blight, caused by Botrytis cinerea, may occur during or after very wet and cool weather and is characterized by fluffy grayish brown spores that are present all over the blossoms (photo 4). Often, leaves and twigs are also showing blight symptoms. Considering the relatively warm and dry weather conditions we’ve had so far, Botrytis is not a likely cause of the blossom blight currently observed in blueberry fields in Michigan. Anthracnose blossom blight looks a lot like Phomopsis twig blight and does not have very diagnostic features to distinguish it from Phomopsis. Incubation in the laboratory is necessary to identify the causal agent. To scout for blossom blight, walk several rows in a blueberry field and scan the bushes for symptoms. When you find any, inspect the flower clusters for twig lesions and fungal sporulation and possible presence of insects or insect frass. To quantify disease severity and changes over time, pick five random bushes and record the number of blighted blossoms per bush every one to two weeks. Record numbers of blighted blossoms, type of sporulation, and average lesion length of twig lesions. For control of further blossom blight or twig blight infections, a fungicide spray may be needed if rainy weather is in the forecast. A spray of Topsin M + Captan (or Ziram), Indar + Captan (or Ziram), or Pristine would work well against most causes of blossom blight at this time. |
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| Bloom is a critical time for control of Botrytis gray mold in strawberries Botrytis gray mold, caused by the fungus Botrytis cinerea, is one of the most important fruit rot diseases affecting strawberries. Typical symptoms include a spreading brown rot and fuzzy gray mold on ripening berries. Wet weather and moderate temperatures are conducive to development of this disease. The bloom period is the most important time for control of gray mold, since primary infections take place almost exclusively through the blossoms. The infections then remain dormant until the berries start to ripen. As gray mold develops on infected berries, these become sources of inoculum secondary infections of adjacent berries. Ripe and overripe berries in particular, are very susceptible and gray mold can spread rapidly at that time. The gray mold fungus overwinters on old leaves and plant debris and can sporulate profusely on dead and decaying plant material. The spores are airborne and are usually plentiful in strawberry fields. If the bloom period is dry or good fungicide coverage is maintained, incidence of gray mold at harvest will be low. However, if primary infections get established, it will be harder to control the disease both before and after harvest. Where possible, remove sporulating berries from the field and destroy them to limit inoculum availability. During picking, avoid handling infected berries, since spores can be transferred on hands to healthy berries. Timely harvesting and rapid post-harvest cooling, may also help to reduce losses to Botrytis gray mold. There are a number of excellent fungicide choices for gray mold control in strawberries: Switch (cyprodinil and fludioxonil) and Pristine (pyraclostrobin and boscalid) provide excellent control; both have two different active ingredients - one of which is systemic - which broadens their spectrum of activity. Pristine also provides outstanding control of fungal leaf spots and anthracnose fruit rot. Elevate (fenhexamid) is a locally systemic fungicide with good to excellent activity against gray mold. Captevate is a pre-mix of captan and fenhexamid and has a broader spectrum of activity than Elevate alone, as it also protects against anthracnose and leaf spots. Scala (pyrimethanil) is a newer fungicide labeled for Botrytis gray mold control in strawberries and is similar to one of the active ingredients in Switch. With respect to older fungicides, a tank-mix of Topsin M (thiophate-methyl) and Captan (captan) has good activity against a broad spectrum of fungi, including gray mold. Adding Kocide (copper hydroxide) or Cuprofix (basic copper sulfate) can help tackle angular leaf spot as well. Thiram (thiram) is a broad-spectrum fungicide with fairly good efficacy against gray mold as well but is strictly a protectant. Just as a reminder: Cabrio (pyraclostrobin) and Abound (azoxystrobin) are not suitable for gray mold control, but are effective against anthracnose and other fruit rot and leaf spot diseases. All fungicides mentioned above have a 0-day pre-harvest interval, except Topsin M (1 day), Scala (1 day) and Thiram (3 days). Copper products have a 24-hour re-entry interval. Remember to alternate fungicides in different fungicide classes for resistance management purposes. A table showing fungicide classes is available in the MSU Fruit Management Guide (E-154) at http://web1.msue.msu.edu/epubs/pestpubs/E154/4-Fungicides.pdf. |
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| Management of glyphosate-resistant horseweed (marestail) In the May 3, 2007 Field Crop CAT Alert, Steve Gower with MSU Diagnostic Services reported the first confirmation of glyphosate-resistant horseweed (or marestail) in Michigan. Steve has been actively screening weed samples for glyphosate-resistance over the last five years. We have been extremely lucky in Michigan, because of all of the samples that Steve had tested over the years none had been confirmed glyphosate-resistant until now. Glyphosate-resistant weeds are not new to the United States. Currently, there are seven different weed species that are resistant to glyphosate. In fact, the first weed was a horseweed (marestail) population that was confirmed glyphosate-resistant in 2000 in Delaware. Since this first discovery, glyphosate-resistant horseweed has been found in 15 states with Michigan now being added as number 16. Our diverse cropping systems, I believe has helped us slow down the development of glyphosate-resistant weeds. However, now that we have resistance, there are several steps we need to do to manage resistant weeds and to further reduce the spread of glyphosate-resistance. The horseweed population that was confirmed glyphosate-resistant was from a Christmas tree plantation in Mason County, Michigan. Repeated use of glyphosate to control weeds in this plantation was the main cause in the development of resistance. If resistance can be found in Mason county, it may be present in other counties in Michigan. Possible other areas where we may have glyphosate-resistant horseweed are counties where no-till crop production is high and glyphosate is used exclusively for weed control. While resistance may not yet be present, following the practice of continuous glyphosate use without other weed control strategies will most likely lead to the development of glyphosate-resistance. So, how do we slow down the development of glyphosate-resistant weeds? Diversity is the key. Whether it is diversity in tillage, herbicide use or cropping systems, diversity is one of the main strategies to slowing down the development of glyphosate-resistant weeds. Here are six main strategies that should be followed to help reduce the development of glyphosate-resistant weeds.
Many of the strategies that are used to reduce the development of glyphosate-resistance can also be used to manage glyphosate-resistant weeds. However, unlike other weeds, even if you follow the strategies to reduce the development of glyphosate-resistant weeds you may find glyphosate-resistant horseweed in your fields. The main reason for this is that horseweed seed is wind-blown and can blow in from other sources. In fact, a recent paper in Weed Science strongly suggests that horseweed seeds can enter the planetary boundary layer, where long-range transport is possible. In addition, we also have several horseweed populations in Michigan that are resistant to ALS-inhibitors. Key principles to horseweed management
For more information and specific herbicide recommendations there is a fact sheet on Controlling Horseweed on page 167 in E-434, 2007 Weed Control Guide for Field Crops. Also visit www.glyphosateweedscrops.org to view a regional bulletin on the biology and management of horseweed. |
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| Enviro-weather tip: GDD accumulations Use weather summaries at www.enviroweather.msu.edu that include growing degree-days (GDD) to get GDD accumulations for the entire year-to-date. The summary automatically generates a report showing data from April 1 first through the current date. Even though the report begins April 1, the GDDs are calculated from January 1. To get a report that includes all dates or any number of consecutive days between January 1 and the current date, use the “Change date range” option near the top of the page. Remember, all GDDs on these reports are calculated from January 1. To get a report that calculates GDD accumulations after a certain date, click on “More data from MAWN for this station.” Near the bottom of the MAWN page is a drop down menu for “Select Data Type”, click on the arrow and select “Growing degree-day data”. Options for methods and dates will appear on the screen. Enviro-weather generally uses the Baskerville-Emin (BE) method for calculating GDD. You can select one or all four methods for your report. Then select the starting date and ending date of your interest. When you click on “generate report,” you will get a report that begins accumulating GDDs at your start date and continues accumulation through your end date. |
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| Regional reports 1 -- Southwest Mark Longstroth Bill Shane Greg Vlaming Weather Last week’s weather was variable. Monday, May 14 and Tuesday were hot with highs near 80. A cold front moved through the region on Wednesday with thunderstorms and the overnight rain. Precipitation totals were about a third to a half inch of water. Soils are still dry. There was a long enough wetting period 17-19 hours at 50ºF to be a concern for apple scab and cherry leaf spot. A fire blight infection was possible, but unlikely due to cool conditions following the rain. Cool weather most of the week ended with scattered frost on Friday morning. Scattered storms crossed the region Saturday and Monday, but not all areas received precipitation. The forecast is for hot weather with lows in the near 50’s and highs near 80 for the next two days. Thunderstorms are possible Thursday followed by cooler temperatures with highs in the 60s and 70s.
Tree fruit The May 16 rain was an infection period for apple scab and cherry leaf spot. Plum curculio egg laying scars have been found in stone fruit. Plum curculio activity should return with warmer temperatures. Oriental fruit moth catch in pheromone traps is down. Oriental fruit moth, Biofix was April 21 at 230 GDD at SWMREC. The end of egg hatch should be about 646 GDD base 45 after biofix so the end of egg hatch will be about 975 GDD base 45. We are catching American plum borer and lesser peach tree borer. Peach fruit are 18 mm in diameter and growers are hand thinning. We are finding shoot flagging from Oriental fruit moth larvae feeding in the shoot tips. We are about two-thirds of the way through egg hatch. Peach leaf curl is scarce this year. Growers should protect susceptible varieties from peach mildew or rusty spot. This disease needs a wetting period to begin spore release, but does not need continuous wetting for infection. Tarnished plant bug and plum curculio damage can be found on fruit. Pheromone disruption of lesser peach tree borer also suppresses greater peach tree borer. This tactic works best in large homogeneous blocks. Tart cherry fruit are 12 mm in diameter and pit hardening is nearly complete. The crop is light and very variable. Fruit set is spotty within the orchard and between orchards. Plum curculio egg laying should increase with the warm weather. The May 15 rain was a light infection period for cherry leaf spot. Sweet cherries are 12 mm in diameter and the pits are hard. Growers need to protect against plum curculio. Sweet cherries should be protected from brown rot from bloom until harvest, and the possibility of warm wet rains exist this week. Plum fruit are about 14 mm in diameter. Growers should be protecting against plum curculio black knot and brown rot. Apple fruits are 12 to 18 mm in diameter. Growers are spray thinning. Many blocks do not need thinning. Blossom blight symptoms of fire blight appeared Monday, May 21. These symptoms are from the May 9 infection. Apple scab symptoms can also be found from the May 9 infection. The Enviroweather website is forecasting that all the apple scab spores are mature, but growers should maintain fungicide protection through the next good rain. Plum curculio will be attacking fruit during this warm period. Oriental fruit moth is still being caught in pheromone traps. Egg hatch should continue for several more weeks. Codling moths began flying May 5, and were biofixed on Wednesday, May 9 in some locations, but the flight has been very spotty, light and variable. It is not necessary to treat orchards without a sustained flight of moths. Growers should not be applying codling moth controls if they have not recorded a sustained flight of moths. It is entirely possible that many orchards have not had a sustained flight because of the cool evening temperatures. We are catching obilquebanded leafroller moths in pheromone traps. European red mites and rosy apple aphids are out, and growers and scouts should be looking for sap feeding spotted tentiform leafminers and the first mines. Pear fruit are 15 mm in diameter. Pear psylla nymphs are feeding in the axils of leaves. Pear blister mite symptoms have appeared. Pear scab is similar to apple scab, and pear scab symptoms should appear this week as with apple scab. A good scab program usually controls Fabraea leaf spot, but the infection period lasts longer than pear scab. Small fruit Blueberries are at petal fall and bees are active. Both cranberry and cherry fruitworms were reported caught in pheromone traps. Treatment for these pests is focused immediately after bloom after bees have been removed. Obilquebanded leafroller larvae are feeding on fruit buds. Many fields have shoots that lack many leaves, but have lots of fruit. Bluecrop and some other varieties are showing this symptom. The shoots affected are generally older shoots with short shoots from last year. In some cases, the leaf buds immediately below the flower buds were killed by the Easter freeze. In other cases, it appears the few leaf buds remained after the flower buds formed. Vigorous shoots with good growth do not show this symptom. Little can be done to force new leaf growth at this time. In severely affected fields, growers should remove shoots that have a large number of fruit and very few leaves as the fruit on these shoots will not size. By removing excess fruit, now growers can reduce stress and maintain good fruit size at harvest. It is likely that severely stressed shoots will not have marketable fruit and will dieback this winter. See the Blueberry IPM Newsletter at the MSU Blueberry Site. Grapes: Concord shoots are about 12 to 16 inches long and flower clusters are separating in the bunch. Vinifera shoots are 6 to 8 inches long. Wild grapes bloom has begun, and bloom could begin later this week depending on the weather. Growers are applying the last prebloom disease control materials. Phomopsis lesions were found on grape leaves and shoots. Grape berry moths are still being trapped. Treatment should be timed for the end of bloom. We expect to see rose chafer soon. Check the MSU http://www.grapes.msu.edu website for scouting updates. Strawberries are at full bloom. Given the dry conditions growers should be irrigating and applying bloom fungicides. Summer raspberry bloom has begun. Fall raspberry shoots are about 12 inches high. Orange rust has been reported. Cranberry buds are elongating. Now is the time for the first fungicide treatment. Miscellaneous Soils are still dry and growers should irrigate if they can. This springs plantings are leafing out and would benefit from irrigation. The Van Buren County MSU Extension Office has moved. The new phone number for the Paw Paw Extension Office is 657-8213. The new Code-A-Phone number is 657-8217. The next Monday Fruit Update meeting will be Monday June 4, 5:00 PM, at the Fruit Acres Farm in Berrien County. There will be no Monday Update meeting on May 28, Memorial Day. There are RUP credits available for the Monday Fruit Updates meetings. |
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| 2 -- Southeast Bob Tritten Weather Rainfall last Tuesday, May 15 evening and Wednesday brought another round of apple scab and fireblight infections to most apple growers in east Michigan. There were also several reports of pea-sized hail in many of the imbedded thundershowers that ripped through the region. High winds also caused some leaf tearing in many of our fruit crops. Our season is still running about three to five days ahead of normal. Most areas received about 0.5 inch of rain with the severe weather of last Tuesday evening and Wednesday, however there were several farms that reported rainfalls in the range of 1 to 2 inches from that single event. With this rainfall, soil moisture supplies have been adequate across the region. Planting is now wrapped up for tree and small fruits. Pruning is moving along quite nicely in peaches. Southeast Michigan Growing Degree Day Totals for March 1 to May 21
Tree fruits Apples are mostly at 13 mm to 15 mm in the southern part of the region and 12 mm in the Flint area. Red Delicious are currently at 8 mm to 9 mm in the Flint area. We have an excellent amount of new growth this year in apples, as well as most of our tree fruits. Apple size is now in the thinning window range, and many growers have begun to apply thinners. Thinning is going to need to be done on a block by block and variety by variety basis, as there is little consistency across farms in terms of apple crop load. Red Delicious is the one exception; there is a heavy crop load at this time. There are some blocks that will not require chemical thinning at this time. There is still a bit of a spread in the fruit sizes however, with Ida’s having the larger size at 14 mm, and Spy’s are just now at fruit set. However, even in the Northern Spy’s, fruit is starting to differentiate in terms of early drop and others that appear to be set. New pests reported in apples over the last week included; codling moth trap catch and plum curculio adults being found on trees, as well as egg laying. Later this week, I expect to see good codling moth numbers being caught in traps, more abundant plum curculio sightings, and the first emergence of mullen bug. Codling moth trap catches have been very low thus far this year at most farms across the region. Most farms have numbers in the range of two to four per trap, only a few farms have been biofixed. Codling moth emergence is not as consistent as it normally is. Plum curculio was seen mid to late last week in most tree fruits, including apples. As of late last week, I also began to see some fruit scarring/egg laying injury. Plum curculio numbers are lower compared to most years. Oriental fruit moth trap catches have been very high across the region, with some in the range of 140-160 per trap. Tarnished plant bugs were seen last week in apples, however their numbers were very low. Potato leafhopper were seen at one farm, however it may have been an isolated sighting, as it was only one event. Larvae from the following insects were seen last week in fairly low numbers; obliquebanded leafroller, redbanded leafroller, green fruitworm, and climbing cutworm. Rosy apple aphid numbers have been high in a few blocks, however they are under control at most farms. Green aphids also continue to be seen, however their numbers have been fairly low. Mite hatch continues, however there are very low levels of mites in apples this year. There are a good number of predators being seen this spring, with adult lady beetles being in more abundance last week. The only reduction of predators is in mite predators, which most likely have not had enough food to maintain their existence in the last week or so. Apple scab spore discharge continues with each rain event, with a good spore release with the rain event of last Tuesday and Wednesday. I’m not calling an end to primary apple scab season at this time. I’ve seen very few apple scab lesions, however I would expect to see more show up late this weekend from last Tuesday’s and Wednesday’s rain event. Fireblight strikes are starting to be seen as of this morning. Most growers have applied two to three sprays of antibiotic for fireblight control. There is still some ragtag bloom in some blocks, so growers need to be vigilant to make sure that they are covered late in the fireblight season. There has been a fair amount of streptomycin burn observed in orchards over the late week. Pears are mostly at 11 mm to 12 mm in size, with a thinning crop as we move through springtime. Pear psylla adult flight continues, with an abundant egg hatch. Peaches are at shuck split for Red Haven. There have been several cases where European red mites have been seen in peaches, more heavily than in apples this year. Tarnished plant bugs have also been seen in a few peach blocks. Shuck split sprays are being applied at this time. Sweet cherries continue to put on a fair amount of new growth, with fruit continuing to size nicely at 13 mm to 14 mm. There is only about a 30 to 40 percent of a crop this year across the region. Bacterial spot continues to be seen on foliage. Plum curculio has been seen in sweet cherries. Tart cherries are mostly at 12 mm, with 40 percent of a crop. Plums are mostly at 9 mm to 10 mm in size. There has been a fair amount of fruit drop over this last week. Bacterial spot continues to be seen affecting the foliage. Small fruits Most strawberry farms have frost protected two to four times this season. There were two marginal frost events on the morning of May 18 and May 21. Strawberry clipper feeding injury has become more evident over the last week, as more strawberries have come into bloom. I’m also seeing low populations of tarnished plant bug on strawberries. Many growers are controlling both of these pests at this time. Grey mold fungicide sprays have been applied to strawberries at most farms. Raspberries continue to put on new growth, with fall red raspberries now being about 12 to 15 inches in length. Flower buds are visible now on summer red raspberries. I am not seeing any pest problems on either crop. Blueberries remain at full bloom for most of the main season varieties, and are at early petal fall for some of the early fruiting types. I continue to see a few mummyberry shoot strikes, however at very low levels compared to most years. I am concerned about the lack of foliage development in many blueberry plantings across the region. It appears that the early leaf buds or emerging leaves were damaged in the Easter freeze event. We’ll see what another couple of weeks bring in terms of more of a normal looking crop of leaves on blueberries. Petal fall is an important time for insect control in blueberries, and watch for that development over the next week or so in most plantings. Grapes have put on about 15 inches of new growth and are looking fairly normal at this time. I expect to see this bloom in about a week to 10 days. |
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| 3 -- Grand Rapids Area Phil Schwallier Amy Irish-Brown Carol Garcia-Salazar Tree fruit Tree growth has been consistently normal for all tree fruit crops. Apples are mostly at petalfall, with a few varieties still holding some bloom, mostly on one-year-old wood. Shoot growth in apples is at about 5 or 6 inches for most varieties. Weather conditions during bloom this year were wonderful with much bee activity and lots of nice sunny weather. Some thinning of early varieties has begun. Weed spraying and orchard mowing is also being done where there is time. Apple scab should be at 100 percent spore maturity now, but only 80 percent of those spores are most likely discharged at this time. We’ll need several more rain events to discharge them all. Primary scab fungicide rates are still very important. The last apple scab infection was from the rains on May 15 – a light infection. Some early symptoms of blossom blight infection started to be seen on Monday, May 21, just the initial wilting of tissue in blocks with high fire blight pressure. With the very warm temperatures predicted for this week, blossom blight symptoms will probably be easy to see in the next day or two. A regional biofix for Oriental fruit moth was set for the Grand Rapids area on May 10. Adult numbers have consistently been increasing in traps over the last 10 days, and we should be nearing peak adult activity this week. Flagging of peaches and other stone fruit shoots should be seen at any time, and cover sprays are recommended. A regional biofix for codling moth has been difficult to set this season because trap numbers have been all over the board, even in the same blocks. I am shooting for a middle of the road date for biofix and going with May 20. Keep in mind that it is best to biofix for your own blocks and trap catches. May 20 might be too late or too early for a few blocks, but it should work for the majority of acres around Grand Rapids. It’s always best to set a biofix for your individual blocks and not run with the regional biofix. This season might be a good example of why that is true. Many growers are getting started with petalfall applications, targeting aphids, leafminer, mites and plum curculio. Apple grain aphid can still be found in low to normal numbers. Rosy apple aphids are being found, as individuals and in colonies. European red mites are becoming much easier to find, and adults can now be found, but no new egg laying yet. The warm weather this week could really drive red mite populations. Spotted tentiform leafminer adults are still flying, but decreasing in number, and sap feeders can now be found. Plum curculio have been actively making ovipositioning scars in plums, cherries and peaches. Plum curculio activity in apples could be seen at anytime this week, especially with the very warm nights that are predicted for the next few days. Also, there are a lot of small apple fruits at a favorable size for plum curculio egg laying. Small fruit Blueberries in West Central Michigan are in bloom. Early varieties are in petal fall and late season varieties are in 50 percent to full bloom. As of May 22, Growing Degree Days (GDD, base 50 °F) accumulation in west central Michigan is around 350 ± 20 with an average daily accumulation of 10 GDD. Accumulated rainfall for the last 7 days ranges from 0.25 to 0.50 inches. Fruitworm activity is increasing with both cherry fruit worm (CFW) and cranberry fruitworm actively flying. We detected the first emergences seven days ago, but because the cold weather all activity stopped for several days. However, during the weekend we trapped up to 26 cranberry fruitworm moths in a single trap located around Pullman, MI. So, we expect that in 130-140 GDD base 50 we may see the first cranberry fruitworm oviposition in that area. We are finding shoot strike damage in those fields that neglected the first fungicide applications. Shoot strike is damage is more abundant in areas near to wooden areas. Another observation is that in some fields with limited irrigation or no irrigation at all, we can see older cane with plenty of flowers but no leaves. Fruit on those canes will not mature, and the best advice is to remove them completely to allow new shoots to replace these older canes (see photo). |
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| 4 -- West Central Mira Danilovich Last week, cool weather was prevalent. Daily highs were mainly in the 60’s with couple of days into the 70’s. Lows were generally into the 40’s, with the exception of May 18, when they dropped below freezing. The lowest temperature of 29.9ºF was registered in Ludington followed by 30.9ºF in Hart and 30.7ºF in Manistee/Bear Lake. Except for some low-lying areas and frost pockets, this event did not cause widespread damage. There were several rainfalls this past week accounting for slightly more than 0.5 inches of accumulation. Apples have set heavy crop. Fruit size is from 9-11 mm min early bloomers to petal fall. Pears are about 10mm in diameter. Peaches are in shuck split to out of shuck with the fruit size about 8-10mm. Plums are out of shuck and about 5mm in diameter. Tart cherries are in shuck split. Sweet cherries are about 10-12 mm in diameter. West Central Michigan Growing Degree Day Totals since March 1-May 21
Tree fruit The rain of May 15, resulted in moderate apple scab infections in Ludington and Manistee/Bear Lake areas and low infection in Hart. Four subsequent rains did not develop into infection events, but did induce spore discharge. Currently, we have 99 percent mature spores. It will take a few more rains to flush them out. Until then, we are still in primary infection period. Scab lesions from previous infections could be found on occasion. Most of the commercial blocks are clean. Rain event on May 15, resulted in fireblight infection in the Hart area. The northern parts of the district were colder preventing the onset of infection. There are no reports of oozing cankers or blossom blight symptoms. There was moderate cherry leaf spot infection on May 15 in the northern parts of the district (Manistee and Mason Counties), and no infection called for the Hart area. Cherry leaf spot lesions on spur leaves have been reported for the Hart area. It appears that they are the product of the very first infection for this season. No other reports about similar finds elsewhere in the district. Insect activity is on the rise. Codling moth numbers are still relatively low averaging from one to four moths per trap. There are some exceptions where there is extremely high pressure resulting in 20-30 moth catches per trap. These blocks will have to be managed on the individual basis. American plum borer catches have gone up significantly. Scouts have reported first catch of lesser peachtree borer on May 19. Oriental fruit moth catches are still high and up since last week. Degree-day model is calling for treatment by the second part of next week. Redbanded leafroller numbers have dropped significantly. Obliquebanded leafroller larvae are about 1 inch long and found sporadically in low numbers. Yesterday, fresh plum curculio stings were found on sweet cherries for the first time. Miscellaneous First round of apple thinners is being applied on early blooming varieties to take advantage of their optimum size and excellent weather conditions forecasted for the next two to three days. We are expecting to have great thinning response. Cherries have natural tendency to produce “blind wood”. This phenomenon is associated with the flower bud formation on the one-year wood, so after the harvest we are left with long bear shoots with no spurs. Research has shown that by using gibberellic acid at proper timing, these natural tendencies could be manipulated resulting in spur formation. Best timing is three to four weeks after the full bloom, or, perhaps more accurate, once we have five to seven fully developed leaves. Currently, there are four to five fully developed leaves. Applications should start this week. |
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| 5 -- Northwest Nikki Rothwell Duke Elsner Growing degree day accumulations at NWMHRS GDD42 526 GDD50 244 Growth stages at NWMHRS (5/14/07—8:00am) As apples are still in bloom in the region, fire blight continues to be a concern. The fire blight model is forecasting EIP’s over 100 for Wednesday and Thursday; however, these predictions may change as the forecasts are adjusted. The last apple scab infection period at the NWMHRS began on Friday, May 18 at midnight and continued until Sunday, May 20 at 9:00 AM; the infection period was recorded as moderate. Only the Elk Rapids and Old Mission stations also reported apple scab infection periods; however, these were considered low infections. For apple insects, we have seen codling moth flying at the NWMHRS, Old Mission Peninsula and in Benzie County. Spotted tentiform leafminer and aphids are still out in apples this week. Although we had some rain this past weekend, we had cool enough temperatures that we did not accumulate enough wetting hours to cause a cherry leaf spot infection, but we were close in some locations. For example, here at the NWMHRS, we needed a minimum of 25 wetting hours at our weekend temperatures to have a cherry leaf spot infection, and we accumulated 23 hours. Other stations in the northwest had similar situations. However, growers should keep covered with Bravo in tarts, as most orchards are not through shuck split at this time. Bravo is not an option for many sweet cherries in the region because sweets are beyond shuck split. In the entomology block here at the NWMHRS, we have seen plum curculio egg laying scars in the sweet cherries. We have also seen green fruitworm damage in that same block. Growers should be monitoring plum curculio, especially in “hot spots” at this time. Plum curculio will really be moving, if we have the temperatures they are predicting. Most sweet cherries are at the vulnerable stage of attack for plum curculio, and growers should be considering an insecticide application at this time. American plum borer trap counts remain high this week with over 22 moths per trap. Small fruit In grapes, most vinifera cultivars have 1-2 inch shoots with clusters visible. Climbing cutworm and flea beetle injury should no longer be a concern. No potato leafhoppers have been seen yet. Powdery mildew remains the principle concern at this time. |
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| Weather news Jeff Andresen A warm front moving northward through the Great Lakes region Tuesday, May 22, will lead to a few days of summer-like weather in Michigan. Look for high temperatures to increase from the 70's to near 80 Tuesday to the mid 70's to mid 80's Wednesday and Thursday. Some southern areas of the state may approach 90EF Thursday. Low temperatures will rise from the 50's Wednesday morning, to a range from the mid 50's north to low 60's south Thursday. A cold front is forecast to move west to east across the state beginning Thursday afternoon, which will lead to the next chance for rainfall. Numerous showers and thunderstorms are expected as the front passes through the state. Cooler and dry weather is expected again Friday statewide, but another frontal system approaching from the west will lead to a chance for more showers and thunderstorms Saturday and Sunday. Temperatures this weekend will fall back to below normal levels, with highs in the 60's north to low 70's south, and lows generally in the 40's to low 50's. Further ahead, medium range forecast guidance suggests, the gradual formation of an upper air troughing feature across western sections of United States during the 6-10 and 8-14 day time frames. The official NOAA 6‑10 day and 8-14 day outlooks for the May 27-31 and May 29-June 4, both call for above normal mean temperatures statewide. The outlooks also forecast normal to above normal precipitation totals across the state for both time frames. As has been the case recently, forecaster confidence in these outlooks is considered lower than normal for the season given inconsistency in some of the forecast guidance. |
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