Apple Thinning |
Apple thinning is always a difficult but necessary orchard management practice that needs to be done annually. Apple trees have the ability to set heavy crops even with moderate budset. These trees will need thinning. Even light budset trees will often need thinning to break up clusters or remove the poor quality fruit that often sets on one-year-old wood. The budset now present in Michigan apple orchards is somewhat variable. Some blocks have an abundant number of buds and will require aggressive thinning. There are some blocks where the budset is light and will only need moderate thinning. Here are some key points to consider. First, all thinners work best when the temperature after a thinner application is warm to hot. Maximum temperatures in the upper 70's and lower 80's (degrees F) are excellent temperatures for thinners to work. Try to apply thinners at the beginning of a forecasted warming trend. Second, thinning early promotes return bloom and promotes increased fruit size. On difficult to thin varieties consider applying the first thinners at the petal fall stage. Most years' fruitlets at the petal fall stage are less responsive to thinning. Usually, it is very difficult to over-thin apple at petal fall, but this is the time when some thinning can occur. Petal fall thinning will reduce the fruit set early, promote return bloom and allow plenty of time for follow-up thinning later if needed. Biennial varieties thinned early will have increased return bloom the next year. Third, consider aggressive combinations of thinners when thinning in the traditional 8 to 12 mm stage especially where all fruitset factors are positive. If bloom is heavy, strong, uninjured by frost, and weather conditions have favored bee activity and pollination, aggressive thinning will be needed. Only aggressive combinations will thin a heavyset crop. This year a new thinner, MaxCel, has been labeled from Valent Bio-Sciences. Its active ingredient is a cytokinin (6-BA). Exilis is already labeled and is another 6-BA product. These new products will give growers an additional thinning tool with some additional approaches to apple varieties that are sensitive to or non-responsive to other traditional. MaxCel and Exilis are gentle thinners, that is, they thin without the harsh stress to leaves and fruitlets that can occur with other thinners. They tend to increase cell division and, therefore, provide additional increase in final fruit size. They are dose dependent; that is, if the concentration or dose applied is increased, the thinning response increases. This will allow growers the choice of using lower mild rates or higher aggressive rates. If aggressive thinning is desired, simply increase the rate of the 6-BA. When 6-BA is used in combination with Sevin, it is an aggressive thinner. Use moderate rates of 6-BA, around 75 to 100 ppm plus Sevin to get moderate to aggressive thinning on varieties that are moderate to thin. On easy to thin varieties, lower the rate of 6-BA or use thinners alone, not in combinations. On difficult to thin varieties, increase the 6-BA rate used in combinations. To summarize, thin early, at the beginning of a forecasted warming trend and use aggressive rates. Consider combination of materials to get moderate and aggressive thinning when needed. The new thinner, 6-BA is a welcome additional tool in our thinners toolbox. It appears that this year's crop has the potential to be normal to above normal. It will need thinning. |
Peach leaf curl |
Peach leaf curl has become an important disease in Michigan. This disease can defoliate peach and nectarine trees. Infections take place in the spring as the buds open. The fungus infects peach buds from bud swell to bud opening under wet conditions. Air temperatures between 50°F and 70°F are ideal. Rain or dew moves spores into the opening bud allowing the infection of young tissue. Prolonged cool, wet periods during bud burst can result in severe infections. Effective controls include Bravo, Ziram, Ferbam (Carbamate) and copper compounds. Copper compounds have the benefit of providing some suppression of bacterial spot as well. Early spring applications at or before bud break are effective in controlling this disease. Later applications can reduce the severity of the disease. Peach growers in Berrien County are putting on their copper sprays now. Once leaves are infected there is no effective fungicide treatment. The leaves are infected in the bud. Once the leaves have emerged they are not susceptible to infection. Infected leaves become thick and crinkled, turning orange or red. When the fungus sporulates, the leaves become powdery with spores. Infected leaves will eventually fall off. The tree will grow new leaves. Peach leaf curl weakens the tree by removing leaves during early growth. This reduces the size of the remaining fruit. Heavy fruit thinning reduces stress on the tree and increases the likelihood of a marketable crop. Severely infected trees should receive an increased ration of nitrogen fertilizer. This will help the tree replace lost leaves and maintain vigor. |
Vineyard IPM training workshop |
Effective management of vineyards requires a thorough knowledge of how to identify, sample, and respond to a range of different pests and disorders that can affect vines. The Grape Team at Michigan State University has recently developed some new printed and electronic training materials for grape growers. These were designed to assist with vineyard scouting, and are part of an increased effort to deliver IPM information to the Michigan grape industry. Another component of this program is to provide an annual workshop that will train growers, scouts, consultants, and others on using these new resources, and will provide other new information that can help with making pest management decisions. This year's workshop will be held on April 13, and will provide a mix of hands-on training and presentations on monitoring and managing pests in Michigan vineyards. The topics covered will include scouting for diseases, weeds, insects, and vine disorders; biological control agents; using MSU's new grape website; weed identification; diagnostic services; and the latest label changes and new registrations of pest control products. Presentations and workshops will be led by speakers from MSU research, Extension, and diagnostic services. Advance registration for this meeting is $10 (April 6 deadline), and is $15 on the day. The registration fee covers lunch and the workshop materials. To register early, send a check made payable to Michigan State University to: Steve Van Timmeren, Trevor Nichols Research Complex, Fennville, MI, by April 6. This will help with planning our seating and lunch. The workshop will be held in the new Angus J. Howitt IPM Training Room at the Trevor Nichols Research Complex. This research and extension center is on M89 at 62nd Street. It is four miles west of Fennville, opposite the turn to Fenn Valley winery. For more information on the meeting contact Steve Van Timmeren at (269) 561-5040. Restricted Use Pesticide credits will be available, and this meeting is open to anyone interested in keeping their vineyard management programs up to date. |
New this spring for grape growers
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Michigan State University has been working with the National Grape Cooperative and the Michigan Wine Industry to bring you a new resource for integrated vineyard management. Visit http://www.grapes.msu.edu/ The new web site is funded by Project GREEEN and hosted by the MSU IPM Program. |
2004 Fruit agrichemical update information |
This is a summary of pesticide label additions and corrections to the 2004 MSU Fruit Management Guide. Agrichemical labels and regulations change quickly, so use this information within the context of each compound's actual label. Corrections to Fruit Management
Guide 2004 Michigan State University Extension Bulletin E-154 Page 21 - Capture 2EC not labeled for use in strawberry. Page 21 - Pyramite 60WP is being renamed
as Nexter Page 52 - Assail 70WP has a PHI of 7 days, REI of 12 hours, and the EPA registration # is 264-609. Page 53 - Calypso 480 SC has a PHI of 30 days and REI of 12 hours. Insecticide additions, label changes, restriction
New labeled insecticide
descriptions Actara (thiamethoxam) belongs to a new class of insecticides called neonicotinoids (thianicotinyl subclass). It is registered for control of several pests of stone fruits. The translaminar (locally systemic) nature of Actara provides for an extended residual inside the plant, making it particularly effective on piercing/sucking insect pests such as leafhoppers and aphids. It is effective against leafhoppers at rates of 2.0 to 2.75 ounces, aphids at moderate rates of 3.0 to 4.0 ounces per acre, and plum curculio and cherry fruit fly at rates of 4.5 to 5.5 ounces per acre. Because most of Actara's surface residue is quickly absorbed into the plant, negative impact on natural enemies is minimized. Restrictions for use of Actara in stone fruit include an REI of 12 hours, a Preharvest Interval of 14 days and a maximum usage of 8 ounces (0.125 lb AI) per acre during one growing season. Zeal (etoxazole) is a growth regulator miticide labeled for use in pome fruits and strawberries for the control of mites. Zeal is primarily active against major tetranychid mites (spider mites and red mites) in the egg and larval stages of growth, providing control ranging from eight weeks to full season depending on mite pressure, the extent of tree vegetative growth, and predator mite populations. Zeal controls susceptible mites by inhibiting the molting process through disruption of the cell membrane. Since Zeal's activity depends upon mite development, control may not be observable for several days. Etoxazole exhibits pronounced translaminar movement in plant leaves, enhancing activity when the pest is located on the undersides of leaves. Zeal is not known to have risk of cross-resistance with other currently registered miticides. Zeal is restricted to one application per acre per season. CYD-X (codling moth granulosis virus) CYD-X is a biological insecticide that is specific to codling moth. The active ingredient is a virus that is lethal to codling moth larvae when ingested. It may take several days to cause mortality. CYD-X should be applied in sufficient water for thorough coverage of the tree canopy. Do not tank mix with lime sulfur, copper, or Bt products. The REI is 4 hours and the product may be applied up to and including the day of harvest. |
Fruit Crop Pest Management available |
The new Category 1C manual,
Fruit Crop Pest Management, is now available though the Michigan
State Extension bulletin office (517-353-6740). This is a completely
rewritten manual and has a new bulletin number - E-2891. It may
be ordered though the bulletin office website at: The new retail cost of this manual is $13.00. The manual is also available for FREE at the MSU
Pesticide Education web site at: |
Spanish Core certification manual available |
A Spanish version of the Michigan pesticide core
manual is now available through the MSU Extension Bulletin Office
for $15.00 as E-2195SP, Manual Basico de Entrenamiento para Aplicadores
de Pesticidas. This manual was edited by individuals speaking
several different Spanish dialects, so there is more consensus in
the translation. The manual is also available FREE on the MSU Pesticide
Education web site at: More Spanish resources from the
US government |
New DVD teaches how to scout apple orchards |
Apple growers have a new tool for teaching or updating scouting skills. This spring, Michigan State University Extension is introducing a new video in DVD format, A Practical Guide for Scouting Apple Orchards. The 90-minute DVD is divided into 21 modules covering topics from choosing a weather monitoring system to discussions on degree-day models and monitoring primary disease and insect pests. The DVD can be viewed in one sitting, but is designed more for those who want to learn about specific topics at any point during the growing season by simply choosing the desired tracks from the DVD menu. The DVD can be purchased through the MSU Extension
Bulletin office and some local Extension offices. Call 517-353-7640
or order on the Internet at: http://web2.msue.msu.edu/bulletins/
The DVD was produced with funds from the USDA with
additional support provided by the Michigan Apple Apple Committee,
MSU IPM Program, MSU Extension, the Michigan Agricultural Experiment
Station and Project GREEEN. |
Regional reports |
1 - Southwest |
Weather Development of the fruit buds has just begun and growers are monitoring bud development and critical temperatures for bud stages. No hard frosts are forecast for the upcoming week. Cool weather with a chance of showers is forecast this week. This means infection periods for some fruit diseases.
Tree fruit Peaches are at swollen bud. For growers in the southern areas of the district, the time to spray for peach leaf curl has past. For most cherries, the swollen buds are at green side. Some areas are probably in water bud when the developing fruit buds are susceptible to frosts and are damaged by temperatures in the low 20s. Copper sprays to damaged fruit buds can reduce bacterial canker in cherries. Copper should be applied to sweet cherries before bud burst. European plum buds are swelling. In the South they are at white side. Japanese plum buds are bursting. Apples are generally at silver tip but green tissue is showing in early varieties in Van Buren and Berrien counties. Growers should be applying copper sprays for early scab protection and to suppress fireblight later in the season. Check the apple scab infection table on page 43 in the 2004 Michigan Fruit Management Guide. Growers should pay close attention to the new table during the early scab season when temperatures are low. Pear buds are beginning to swell. In the South the swollen buds have scale separation. Small fruit Grapes are generally dormant and show little bleeding from pruning cuts. In Van Buren County a few buds are at scale crack. Strawberries are pushing out new leaves but the flowers are still in the ground. Raspberries are at green tip. Now is the time for lime sulfur applications to burn out anthracnose lesions on overwintering canes. Growers are tipping summer raspberries. Cranberries are dormant. Miscellaneous |
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3 - Grand Rapids Area |
Tree fruit There is some rabbit damage being seen in apples around the district. We had a great deal of snow cover for much of the winter and the rabbits will feed on the lower limbs of apple as they sit on top of the snow. Our snowfall amount was average for the winter, but it never melted much in between snowfall events, which led to a good foot or two on the ground through much of the winter months. Dormant lime-sulfur applications are being made to peaches at this time. The Ridge area Code-A-Phone is operational. The number is 616-451-8065. Meeting announcement |
Some considerations when purchasing your own weather equipment |
Given the strong dependence of many IPM activities on weather, there are a number of reasons for monitoring conditions yourself. Perhaps most important is the fact that many weather variables are highly variable across space, and are best measured where they are to be used. There are many options when it comes to weather monitoring, so before you spend money or time on a new system, ask these critical questions to find equipment that is most economical and suitable for your needs. System considerations Sensor accuracy. Sensor costs increase quickly for sensors with high accuracy. For many IPM applications, research-grade measurements are not necessary. Robustness. Will the system perform when I really need it? Get a company's previous track record or advice from professionals. Simplicity. Simplicity can sometimes be an asset when under other time constraints. Number of variables measured. Do I need more than precipitation and temperature? Multiple sensors may require a larger, more expensive datalogger. Degree of automation. How often can I afford to take observations? The method of telemetry. How do you plan to retrieve the data? Options include everything from a manual read of the sensor recorded on paper to radio, telephone, direct RS232 link to a personal computer, or even satellite. In general, the greater the complexity and sophistication of the system, the greater the cost. Similar to tools and other purchases, there is a rule-of-thumb that applies here: "You get what you pay for." Remember this especially if you are looking for a system that needs to be working properly during many seasons of use. Other options beyond buying Deployment In deciding where to place your instruments, a rule-of-thumb is that the station should be at least four times the height of the closest obstruction and away from any large paved areas. Keep grass and weeds near the station trimmed. Also consider the effects of microclimate. Microclimate refers to time-averaged weather conditions over distances of less than half a mile, and includes climate effects from the orchard level down to the microscopic level. Endless combinations of characteristics such as crop canopy structure, topography, and soil type can create unique microclimates. Solar heating and airflow are the most significant factors determining the microclimate in a particular area. For example, locations within or very close to vegetation acting as a windbreak tend to be warmer and more humid than locations in the open. Low-lying basin-shaped areas tend to be prone to cold temperatures during the growing season since cold air ponds there after moving from surrounding areas. Besides serving as a location for a frost alarm for the first location to reach the freezing mark on a frosty night, these sites should generally be avoided for siting IPM instruments. Try to select an area that
is: § Relatively flat, to minimize the impact of cold air drainage or forced turbulence around topographical obstacles; § Easily accessible to you night and day; and § Close enough to an orchard to place a leaf wetness sensor if one is available with your system. In choosing a site to meet your needs, remember that it may be virtually impossible to meet all of these criteria. Try to minimize the number of overall potential problems. Temperature and precipitation For placement of temperature sensors in the field, there is one special rule. Never allow the sensor to be directly exposed to the sun or open sky, as such exposure can lead to erroneous or misleading measurements. If at all possible, use a screened or ventilated shield or enclosure if one is available for this purpose. By convention, the sensor should be placed at a height 5 to 6 feet above the ground surface. Avoid installation near paved areas, on walls of buildings or other artificial heat sources, or near low places where water tends to pond after rain. Relative humidity and leaf
wetness The first issue is what type of sensor to choose. Options range from a rope wick connected to a mechanical recorder to an electronic grid plate across which resistance can be measured. For simplicity and automation, many users choose an electronic grid. Some users prefer to have the sensor professionally coated with a latex paint. Paint causes the sensor to be physically more representative of a plant leaf and tends to spread out any water droplets over the surface, making the painted grid generally more sensitive to dew formation. For leaf wetting events associated with rainfall, painted and unpainted grids respond similarly. Placement of your leaf wetness sensor in the field may vary greatly depending on crop and disease. In contrast to other meteorological measurements that are taken in more open locations, the best bet with leaf wetness sensors is placement within the plant canopy. While there is no standard, some plant pathologists recommend placement in an apple canopy on the north side of the tree above the first scaffold about midway between the tree trunk and the drip line. Past research indicates a consistent response with the plate sloped at a 20-degree angle downwards towards the north. Upkeep and maintenance Some commercial sources
of weather instruments and equipment
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