Vol. 20, No. 1, March 29, 2005

In this Issue
Tree fruit news
Apple thinning strategies 2005
Peach leaf curl
2005 Tree Fruit IPM School covered wide array of orchard pests
Other news
2005 Fruit insecticide registration update
EQIP offers fruit growers up to $5,500 per year for IPM practices
Southwest Michigan schedules Monday fruit IPM updates
Southwest Michigan regional report
Is winter over?

Apple thinning strategies 2005

Philip Schwallier
Clarksville Horticultural Experiment Station

Thinning in Michigan can be quite a challenge each year due to the variable weather conditions. No two years are alike and growers must adjust their thinning strategies to take in account the new set of climate variables, not to mention all the other factors that affect fruit set and thinning. Due to the considerable variations from year-to-year, it is best to plan an approach to thinning starting as early as possible. Be ready to put into practice alternate strategies as the conditions change.

First, consider starting early with thinning. Best fruit size and return bloom will result from early thinning. Second, consider multiple applications of thinners. Especially for difficult to thin varieties and those that have biannual tendencies, multiple thinning is more likely to get the job done. Third, pick weather conditions that favor a thinning response, such as warm temperatures and even cloudy conditions. When these conditions occur within the two or three days after a thinner application, usually a good thinning response follows. Fourth, consider using combinations of thinners and consider adding a new thinner, BA (benzylaenine) in your program.

BA is not compatible with NAA. There is a possibility that NAA could be used before or after BA, separating the two sprays by 5 to 10 days, but more research is needed on that type of treatment. BA has all these beneficial characteristics, but in some years has a reduced thinning effect right at petal fall and when thinning late on large fruitlets. After 15 mm stage, the fruitlets are setting and may not thin with BA in some years. In Michigan research trials in 2003, BA + Sevin thinned best from 10 to 15 mm. In 2004 trials, BA thinned best from petal fall to 8 mm. It is difficult to predict the best timing every year, but applying BA between 6 and 15 mm is the best target.

Start thinning early with a plan that starts at bloom. At different times during the thinning window there are different thinners to consider. It is difficult to apply blossom thinners in Michigan. Petal fall is when some growers start thinning every year. It is the first time that serious thinning is done in Michigan and some years work quite well. The traditional thinning time at the 10 mm stage is when most thinning gets accomplished. The 10 mm stage usually works quite well for Michigan growers, but the weather needs to cooperate as well to get results. Late thinning beyond 15 mm can be a hit or miss timing, but aggressive combinations will be helpful at that time.

ATS can be used to thin apples by damaging the flower parts before fertilization has occurred when it is applied early to an opening bloom. A 1 percent solution of ATS in water is the standard recommendation. Often times this application will cause mild thinning and follow-up thinning is needed.

Petal fall thinning is especially important to consider on difficult-to-thin varieties and those with the added problem of being a biannual variety, like Fuji. On difficult to thin varieties, consider a combination spray at petal fall of Sevin at 1 qt/100 + NAA at 5 to 10 ppm. An alternate combination could be Sevin at 1 qt/100 + BA at 50 to 100 ppm. BA would be the preferred combination on small-fruited varieties such as Gala. Small fruit varieties like Gala would get an extra size enhancement from the BA that it would not get from the NAA. BA enhances cell division, increasing the potential fruit size.

The 8 to 10 mm stage is the traditional thinning window and generally best success is achieved if weather conditions also favor a response. When poor cold weather occurs at this time, it emphasizes the need to not let a good weather condition at petal fall pass by.

If thinning for the first time at the 10 mm stage, consider combinations of thinner with Sevin. Use the higher end of rate combinations on difficult varieties and lesser combinations rates on thinner sensitive varieties. On the easy to thin varieties, combinations may be a bit strong. If thinning applications are late and fruitlets are getting large, then strengthen the combination and achieve the thinning that is needed.

Thinning can be effective if thinning is started early, aggressive combinations and rates are used and the thinners are applied at the beginning of a warming trend. Difficult varieties need multiple applications. Biannual varieties need aggressive strategies and early thinning. Under thinning one year will hurt two crop years. Chemically thinning successfully each year will save money and increase quality and production.

Mark Longstroth
District Extension Horticultural & Marketing Agent

Peach leaf curl is an important disease in Michigan, as it 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 to 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.

The Michigan State University Tree Fruit IPM School was held for the first time in two years to a crowd of 75 growers, consultants, Extension staff and chemical field representatives. The two and a half-day event was conducted at Kellogg Biological Station in Hickory Corners, Michigan. The 2005 School had a terrific line-up of speakers and topics that addressed the challenges of growing fruit in Michigan today: changing pesticide chemistries and pesticide regulations, new integrated pest management techniques, and the ever-shifting complex of orchard pests.

Two out-of-state speakers, Dr. Elizabeth Beers from Washington State University and Dr. Ken Johnson, Oregon State University, discussed several topics related to the Michigan industry. Dr. Beers introduced the mullein plant bug to school participants, as well as mite thresholds, injury timing, and potential biological control. Dr. Johnson discussed the environmental factors that drive the growth and spread of bacteria in orchards, focusing on fire blight. As his research centers around biological control of this disease, his presentations provided school attendees with information on fire blight resistance and soft product control tactics.

MSU specialists and Extension educators covered a wide range of tree fruit pests. Dr. George Sundin presented his latest findings about cherry leaf spot resistance, while Dr. Bill Shane discussed potential controls of the apple scab disease if resistance to conventional fungicides becomes widespread in Michigan. Codling moth, plum curculio, and cherry fruit fly were the insects of concern at this year’s school.

On Wednesday morning, Drs. George Bird, Mark Whalon, Jim Flore, and Larry Gut introduced the concept of functional ecology. This half-day session was an exciting cross-discipline project that focused on the whole orchard as an ecosystem.

As orchard management continues to evolve in the 21^st century, holding comprehensive workshops such as Tree Fruit IPM School will be an integral part of tackling new issues. By combining research, communication and innovation at this type of conference, Michigan’s fruit industry will continue to succeed in the coming years.

For more information or to be placed on a mailing list for brochures about future schools, please call the Northwest Michigan Horticultural Research Station at (231) 946-1510.

John Wise, Rufus Isaacs and Larry Gut
Entomology

This is a summary of insecticide/miticide label additions and corrections to the 2005 MSU Fruit Management Guide. Agri-chemical labels and regulations change quickly so use this information within the context of each compound's actual label.

Platinum (thiamethoxam) is a soil-applied insecticide that belongs to a new class of insecticides called neonicotinoids (thianicotinyl subclass). Platinum is registered for use in blueberries targeting aphids and leafhoppers. This product should be applied to moist soil in the blueberry root zone then followed with 0.5 to 1-inch of water to be properly translocated into the plant. Being a systemic material it has long residual inside the plant and is particularly effective on piercing/sucking insect pests with minimal negative impact on natural enemies.

Rimon (novaluron) is an insect growth regulator (IGR) insecticide that acts by disrupting the generation of chitin in the insect exoskeleton. This prevents normal development of the insect larval instars and, when in contact with eggs, suppressing embryo-genesis. Rimon has no direct activity on adult insects, but hatching of eggs laid by treated adults will be suppressed. Rimon is registered for use in apples for the control of codling moth. Rimon is safe on most beneficial insects and has a unique mode of action for resistance management purposes.

Codling moth (CM) granulosis virus is the common name for a naturally occurring and highly specific option for codling moth control. Each virus particle is contained within a protein occlusion body (OB). Viral OB's are very small. Indeed, over a trillion OB's are present in an ounce of formulated product. These tiny particles must be ingested by the CM larva to be effective, but it only takes a few to cause death. Upon ingestion, OB's are dissolved by the insect's alkaline gut lining, releasing the viral particles. The virus replicates itself within the gut cells and spreads to other organs, causing the larvae to melt into a mass of billions of viral OB's. With the new addition of Carpovirusine, there are currently three CM granulosis virus-based biological insecticides available for use by Michigan apple growers, including Cyd-X^® and Virosoft^CP4. Stored material should be kept refrigerated to ensure stability and potency. There are many options for incorporating virus into a CM management program. Codling moth granulosis virus products are compatible with most fungicides and insecticides sprayed in apple orchards. However, they should not be mixed with lime sulfur, Bt products or copper fungicides. Use of a buffer to neutralize the spray mix is recommended if the pH is above 9 or below 5.

Agri-Mek (avermectin) is newly registered on plums and prunes for the control of European red mite and two-spotted spider mite. The active ingredient is a by-product of a soil fungus that has insecticidal activity. Agri-Mek is a translaminar (locally systemic) insecticide, and when applied before leaf tissue is mature and it has long residual inside the foliage. The performance of this product is enhanced with the addition of 0.25% or 1 gal per acre of paraffinic spray oil (may increase risk of phytotoxicity) to effectively penetrate the leaf tissue. For best mite control, apply when mites first appear and before populations build beyond threshold.

David Epstein, Michael Brewer, and Joy Landis, MSU IPM Program; and Larry Elworth, Center for Agricultural Partnerships

Fruit growers looking for financial help with implementing IPM practices on their farms need to be aware of a financial incentives program available through the Natural Resources Conservation Service’s (NRCS) Environmental Quality Incentives Program (EQIP). Financial incentives of $60 per acre, not to exceed $5,500 per year, are currently available to Michigan fruit growers for the 2005 season. Incentive payments for IPM are available to address resource concerns on your farm. Weekly pest and beneficial monitoring, use of EPA approved “reduced risk” pesticides, use of pheromone mating disruption and other biologically-based control measures, use of reduced-risk technology (e.g. electronic sensing technology for sprayers), and the use of cultural control measures, such as the use of mulches and groundcovers are all IPM techniques that may help your pest management and protect soil, water, and air quality on the farm. This program also provides financial incentives for practices that aid erosion control, conservation of water resources, wildlife habitat protection and nutrient management.

If you have had little experience with the Farm Bill, NRCS or government conservation programs, taking advantage of these opportunities may seem challenging. Here are the four basic steps to accessing these funds:

Step One – Contact the nearest NRCS office and tell them you want to apply for EQIP
They will schedule a time for you to meet with NRCS staff to start your application. The information in your application will be kept confidential. As part of this initial step, the NRCS district conservationist or a conservation planner will help you fill out a pre-application form to see if you are eligible for the program. The pre-application form asks basic questions about your farm. You fill in your name, county and the date. Then you circle the correct answers to the seven questions on the form. Be sure to submit the pre-application form directly to the district conservationist as soon as possible, because the date of submission will be used as part of the selection process if more funds are requested than are available.

Step Two- Work with NRCS to complete a site-specific conservation plan for your farm
The district conservationist or a conservation planner working with the district conservationist will come to your farm to help you identify practices that are eligible for EQIP or similar programs. You and the planner will develop a plan outlining conservation practices to implement. The goal is to work together to design a plan that makes sense for your farm, both for resource conservation and maintaining farm production.

For your meeting you will want to have copies of:
§      Pest and nutrient management records from the past three years
§      A farm layout or aerial photo of the farm (Discuss with the conservationist whether you need to provide a map for the meeting or whether they can generate one.)
§      A list of areas where you have conservation concerns
§      A list of crops and rotation schedules, if applicable

The District Conservationist will help you identify practices that make sense for your farm and will help you identify which resources (such as soil, water, air, etc.) those practices will address. In doing so he or she will also help you determine whether your application is likely to have priority for funding under EQIP. As a general rule, growers who are able to apply multiple practices that improve more than one resource have a higher priority for funding.

Step Four - Submit the application to NRCS
Once you have completed and submitted your application to NRCS, it will be ranked with other applications in the state based on the number of points it has received. The NRCS district conservationist will contact you about whether or not your application is funded. If your application has been accepted, you will complete and sign a contract stating the payments and your obligations.

Al Gaus, Mark Longstroth, and Bill Shane

The southwest fruit MSU Extension educators have set the schedule for the 2005 Monday Afternoon Fruit IPM Meetings. Each meeting will review the current fruit pest situation in Southwest Michigan. The meetings will include hands-on displays of current pests of fruit and mini-lectures on various topics. Each week’s topic will change with the changing pest complex.

This year, these meetings will take place in two locations. In Berrien County, the meetings will be held at the Bjorge Fruit Acres Farm on the corner of Friday and Carmody Road, south of Coloma exit 39 on I-94. The other location will be in southern Allegan County at the Overhiser Fruit Stand on the corner of 109th Ave and 64th St. This is just east of the Pullman Exit 26 on I-196/US-31. The meeting time at both locations will be 5:00 to 6:30 PM. The dates and location are listed in the accompanying table. These dates are also listed on the Berrien County web site at: http://web1.msue.msu.edu/berrien/hort/mondaymeetings.htm

Mark Longstroth
Bill Shane
Al Gaus

There are still a few piles of snow in some areas of the Southwest region but it will all be gone soon. Soil moisture is excellent and soil temperatures are near 40°F. The last week has been dry and warmer with highs above freezing into the 40s. At this time our GDD accumulations are similar to and lower than 2001. 2005 and 2001 are the coolest springs in the last 10 years. A warm week would quickly bring us up to average for this early in the season.

Peach buds are swollen and growers should be applying peach leaf curl sprays. There are reports of some fruit bud loss over the winter to cold, but damage has not been fully assessed.

Cherry buds are swollen. Orchard defoliation last year was severe on tart cherries, but forced buds look good.

Plum buds are swollen.

Early apples are at silver tip. Some growers have applied copper.

Pear buds show little movement.

Small fruit
Blueberry fruit buds are beginning to swell. We have the potential for a good crop.

Grapes are dormant. Pruning cuts should begin to bleed this week with the warm weather.

Strawberries are beginning to green up in southern Berrien County and new leaves should begin to emerge soon.

Raspberries show little movement. Growers should be tipping summer raspberry canes. Growers are mowing fall raspberry fields.

Jeff Andresen
Agricultural Meteorology
Geography

Following abnormally mild temperatures during much of February, the development of a persistent upper air troughing pattern over eastern North America led to the onset of true winter weather over the Great Lakes region during the last week of the month. This resulted in below normal temperatures and periodic snowfall reported over much of the region during the majority of March. This pattern has recently been replaced with a more transient, quickly changing pattern with the passage of a series of weather disturbances and the at least temporary reintroduction of southerly winds and above normal temperatures. In summary, short- and medium-range forecast guidance calls for the formation of weak ridging across the region with some overall moderation in temperatures.

In the short range, an area of low pressure centered over the northern Great Plains Tuesday morning (March 29) will slowly approach and pass through northern sections of the Great Lakes region during the next 48 to 72 hours. With increasing southerly winds ahead of the system, maximum temperatures will reach the 60's in many areas of the state Tuesday and Wednesday. Some southern locations may approach the 70 degree mark Wednesday. Low temperatures will fall back into the 30's in most spots with some low 40's in the south. A cold/occluded front will move from west to east across Michigan late Wednesday into Thursday, bringing a good chance for showers and thunderstorms, mainly across the southern two-thirds of the state. Light rain or showers are more likely in northern sections. Due to strong upper air dynamics associated with the frontal passage, some of the storms may reach severe levels late Wednesday afternoon and early evening with the primary threats being strong winds and possibly hail. The threat for showers will continue Thursday and into Friday with some snow possible as well as colder air filters back into the region on northwesterly winds. Fair, dry, and cooler weather is expected for the second half of the weekend into early next week. More rain or snow is possible by the middle of next week. Temperatures by Friday and Saturday will fall back to highs in the upper 40's and low 50's with lows in the upper 20's to mid 30's.

As noted above, most recent medium range forecast guidance is hinting at a change of the upper air pattern that has persisted for the past few weeks with more southwesterly flow expected across the Upper Midwest during the next one to two weeks. The latest NOAA Climate Prediction Center 6-10 day outlook for April 3-7 calls for temperatures to range from near normal over most central and eastern sections of Michigan to above normal in the west. With the primary storm tracks remaining north and south of Michigan, drier than normal conditions are forecast for the forecast period. In the 8-14 day time frame covering April 5-11, temperatures are forecast to increase to above normal levels statewide. Precipitation totals during this period are forecast to range from below normal levels in eastern sections of the state to above normal in the west.