With this issue we begin the 2002 publishing season for Michigan State University's Fruit CAT Alert newsletters. As we write, snow is forecasted for mid-Michigan, but like they say, "If you don't like Michigan's weather, wait a minute and it'll change."

Most of us are content that the state's fruit crops are moving slowly out of dormancy and are less likely to suffer from frost. Inside this issue, you'll find articles full of reminders and updates on starting the growing season with the best preventative measures in place. Will El Nino return and offer fresh weather challenges? Whatever the weather and pests may bring, throughout the season we'll be offering you the latest advice for fruit pest and crop management.

Watch for our next issue to be published April 9.

Abound (azoxystrobin) has received a supplemental label for use on blueberries, lingonberries, huckleberries, elderberries, gooseberries, currants, Juneberries, and salal. Azoxystrobin is a synthetic version of a fungitoxic compound naturally occurring in a small mushroom. It is considered a reduced-risk fungicide, has activity against a wide range of fungi, and has surface-systemic properties. Because of its favorable toxicological profile, Abound can be sprayed up to and including the day of harvest. Applications can be made by ground, air, or chemigation.

An application rate of 6.2-15.4 fl oz of product per acre is recommended on the label. A typical application rate would be more like 9-12 fl oz. The label recommends that applications begin prior to disease development and continue on a 7 to 14 day schedule. However, to reduce the chances of resistance development, Abound should not be applied more than three times per season, and no more than two times consecutively before alternating to a fungicide with a different mode of action. Integrating use of Abound with other disease management methods such as resistant varieties, removal of infested plant debris, and proper timing of irrigation, will also help reduce the risk of resistance development.

Small plot efficacy trials in blueberries in Michigan showed excellent control of anthracnose, moderate to good control of Phomopsis and mummy berry fruit infection, and poor control of mummy berry shoot strikes. From this data, it would seem that the best fit for the material might be in the period between pink bud and early fruit development. Because of anticipated anti-sporulant activities, Abound may also fit well as a late-season spray (aerially or ground-applied) to suppress anthracnose during harvest as well as late-season Phomopsis infections. More (on-farm) research is needed to confirm the best fit and use of this new disease-management tool.

All pheromone-monitoring systems are based on insect natural behavior. Have you ever wondered how a tiny flying moth can find a mate? Male moths find their mates based on chemical signals called pheromones, which are released by females. Scientists have taken advantage of this means of communication by engineering pheromone baited trapping systems. These provide an easy and reliable means of assessing seasonal occurrence and pest pressure in the orchard. The use of adult catches in traps to make treatment decisions or to time insecticide applications is fundamental to orchard scouting and integrated pest management.

Many factors affect the performance of trapping systems, and the usefulness of the information gathered. These factors are trap selection, trap placement and seasonal maintenance. Ignoring any one of these fundamentals will reduce the reliability of the whole trapping system.

Every trap is composed of three essential components. The design of the trap, the pheromone baited lure and the sticky surface needed to retain the moths. The three most commonly used traps are the wing, large delta and diamond traps. There are also many lures to choose from. The most commonly used lure is the red septa. Consult with manufacturers, suppliers or local extension service for information on choosing the appropriate trapping system for a particular pest species. We will provide details in upcoming issues of the Fruit CAT Alert.

Even if you select the right trap, if it is not maintained, disastrous decisions may be made. The effectiveness of the trap depends on maintaining the trap shape and the quality of the adhesive over the season. Two common problems with trap shape are failure to return side flaps to the upright position of the triangle trap, and not maintaining the proper entrance space in the wing trap after the traps are checked. Leaves, twigs, and moth scales can foul the adhesive bottom of traps over time. Each time traps are checked, debris and moths should be removed. The adhesive should be redistributed. A general guideline for replacing trap bottoms is at least once per generation, or when the surface has been fouled sufficiently to prevent routine capture. Lures should not be handled with bare hands. Gloves, sticks, or an instrument (with acetone dip) can be used, but whatever tool is chosen, pheromone cross contamination must be avoided. Replacement of lures for most species is between generations, except for codling moth, which may require more frequent changes. Check with the manufacturer for lure specific recommendations. Spent lures as well as new lure packaging must be removed from the orchard. A trap should never have more than one lure at a time.

Trap placement is a critical factor for optimizing trap performance. The key decisions are 1) how many traps to deploy, 2) where to place them in the orchard, and 3) location of the trap within the tree. Moth species vary in their response to pheromone lures; therefore the number of traps needed ranges from one to four per ten-acre block. The extremes can be represented by Oriental fruit moth at one trap per ten acres and codling moth at four traps per ten acres. The key considerations for effective trap placement within a block are 1) historical "hot spots," and 2) location relative to block perimeter. An area where moth catches from previous seasons were high, or a "hot spot," is a good place to locate a trap. A "hot spot" does not represent pest pressure in the whole orchard; thus traps should also be placed elsewhere. Avoid placing traps on the perimeter row. Instead place traps at least three to four rows in. Placing traps well within the orchard will increase the likelihood of capturing local moths, rather than your neighbors'.

The location of the trap within the tree is the third critical factor. A trap needs to be located where moth activity is greatest and placed in a way that allows moths easy access to the trap. For most insects the trap can be placed in the middle third of the canopy. Truck window height is not acceptable. The height that a trap is placed is especially important for codling moth. If traps are placed low in the canopy, too few moths will be captured to make an effective management decision. For monitoring codling moth in a pheromone-disrupted orchard, the trap needs to be placed in the upper third of the canopy.

Peach leaf curl has become an important disease in Michigan. This disease of peach and nectarine can defoliate 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 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. It is probably too late to use copper compounds in the southern peach growing regions. Warming temperatures will provide a treatment window before bud burst. Once leaves are infected there is no effective fungicide treatment.

The leaves are infected in the bud and once they 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 will reduce stress on the tree and increase the likelihood of a marketable crop. Severely infected trees should receive an increased ration of nitrogen fertilizer. This will help maintain vigor and help replace lost leaves.

Maintain the pH of orchard soils between 6.5 and 7.0 for optimum tree performance. When pH is too acidic (pH < 6.0), trees may not obtain adequate amounts of potassium (K), phosphorus (P), or Magnesium (Mg). When pH is extremely low (< 5.5), aluminum may build up to toxic levels and reduce overall tree health. Toxic manganese levels may accumulate in the bark of young apple twigs, causing "measles" where the bark splits and peals. Acidic soils may also aggravate bitter pit or Jonathan spot in apple orchards prone to these disorders.

Acidic orchard soils are common in Michigan and result primarily from the continued use of fertilizers containing ammonium-N, such as urea and ammonium nitrate. These materials are acid forming and gradually reduce soil pH. pH will decline most rapidly when high N rates are used on sandy, poorly buffered soils. As a rule, 1.8 pounds of lime is needed to neutralize the acidity in one pound of N supplied as ammonium nitrate or urea. Over a period of several years, N fertilizers can reduce pH to where lime is needed. If, for example, 50 lb N per acre is applied annually as urea, only 90 lb lime (50 x -1.8) would be required to counteract the added acidity. However, this acidity will reduce soil pH over time if lime is not used. Calcium nitrate differs from ammonium sources in that it may gradually increase pH.

Banding N under the tree row may speed soil acidification and cause pH gradients between the row middle and the herbicide strip. We sampled various apple and cherry orchards in northwest Michigan during 1999 and 2000, and observed the following average pH values in the accompanying table. The pH in the top foot of soil beneath the trees (weed-free strip) was quite acidic. This likely results from banded applications of N fertilizers. In contrast, the pH of the top foot in the row middles was neutral. This is a common situation in Michigan orchards.

Interestingly, we found that pH gradients were much smaller in trickle-irrigated orchards. Water from most Michigan wells contains high levels of alkalinity (dissolved lime), so irrigation tends to counteract the acidifying affects of N fertilizer. Orchard soils should be sampled every few years to monitor pH. Now is the time to apply lime if soils tests indicate a need.

Consider these four characteristics in choosing a lime: 1) calcium carbonate equivalent (neutralizing value); 2) particle size; 3) need for magnesium; and 4) cost and availability. Liming materials contain combinations of calcium carbonate (CaCO_3), magnesium carbonate (MgCO₃), and various impurities.

Calcium carbonate equivalent or neutralizing value (NV) describes how potent a material is relative to pure CaCO₃. The NV of agricultural lime usually ranges between 85 (less effective than CaCO₃) to 120 (more effective than CaCO₃). Lime recommendations given on soil test reports are for pure CaCO₃, so application rates may need to be adjusted up or down depending on the lime source.

The reaction rate of lime is particularly important in orchards, because lime cannot be incorporated into the soil. Often surface-applied lime may require one to three years to alter soil pH in the tree root zone. Particle size dictates how fast lime reacts; finely ground materials react quickest because their surface area is greatest. Sieve or particle size information should be available for all lime sold in Michigan. Results are expressed as the percentage of the lime passing through screens of different size. A #8 mesh has 2.4 mm holes, and particles not passing through this mesh are so big they should be considered zero percent effective. Mesh #60 is much finer (0.25 mm holes). Particles passing through # 8 but not #60 are considered to be 50 percent effective, while particles passing through #60 mesh are considered 100 percent effective. Finer ground materials react more quickly in soils but may be more dusty and hard to spread. The best materials contain only a small percentage larger than #60 mesh size.

If orchard soils are also short of magnesium (Mg), a lime containing MgCO₃ should be chosen. Dolomitic lime or "high-Mag" lime contains significant amounts of Mg. Dolomitic lime may be best if soils contain:

• Less than 35 ppm Mg,
• If potassium (K) represents a greater Percent of Bases than Mg, or
• If Mg represents less than three percent of the Total Bases.

Also, consider the availability and cost in choosing lime. The lowest priced lime may not be the best buy when NV and sieve analyses are considered. Use the NV to calculate the cost per ton of calcium carbonate equivalents. Then use the sieve analysis information. Consider the proportion larger than mesh size #8 as ineffective filler, and that between mesh sizes 8 and 60 as only 50 percent effective.

Pelletized lime is available in Michigan. Pelletized materials can be spread with most fertilizer spreaders alone or mixed with fertilizers. The NV is typically similar to agricultural limes, but since the products are pellets, the original material can be ground more finely without causing dust and application problems. For comparison, pelletized lime may cost $100 per ton, compared to perhaps $20 per ton for agricultural wet lime. Liming materials are also sold as lime suspensions (liquid lime, fluid lime). These products typically contain 50-75 percent lime, 25-50 percent water, and small amounts of clay or dispersing agents. Lime suspensions usually react quickly because the particles need to be very small to stay in suspension. These aqueous suspensions can also be spread uniformly without dust, and can be mixed with N or K fertilizer solutions. Drawbacks include the high cost per CaCO₃ equivalent, and the fact that less volume can be applied at one time; applications may need to be made more frequently and large pH changes are not possible. Perhaps the greatest disadvantage in orchards is the lack of appropriate application equipment.

At least two bi-products of manufacturing are sold as liming materials in Michigan. Dow-Lime is produced in the Ludington area and available through much of the state. This is a dolomitic (high Mg) lime that seems to react quickly in orchard soils. Monitor Sugar produces another lime material as a bi-product of sugar beet processing. This is a finely ground, high-Ca lime.

One difficulty with liming orchards is that the application equipment must fit between the tree rows. An additional complication exists in orchards where fertilizer has been banded under the trees, creating gradients in pH between the herbicide strip and the row middles as discussed previously. Lime also needs to be banded under the trees in these situations. One approach is to apply pelletized lime with fertilizer spreaders. At least one company (Stoltzfus, Morgantown, PA) manufactures a wet lime spreader that is narrow enough (60 inches) to fit between orchard rows.

Low pH can reduce the health and productivity of orchards. Apply lime when you know pH is too low; anytime of year is fine. Monitor soil pH every several years. Lime can take several years to adjust soil pH.

Spring frosts are a worry for all fruit growers. Radiation frosts occur when clear, calm conditions during the night allow the ground to cool by radiation to the sky. The cool soil chills the air above it lowering the air temperature. Cultivation is one measure that growers can do to increase soil temperatures during radiation frosts. Cover crops serve many valuable functions in fruit plantings such as reducing or preventing soil erosion, reducing soil compaction and allowing vehicle traffic over wet soils. Cover crops also shade the soil resulting in cooler soils during radiation frosts. Keeping the soil surface clean of vegetation allows it to absorb more heat during the day. Soils have a large heat capacity, so they can capture and store considerable heat during sunny days. This heat can maintain warmer air temperatures during cold nights. Weeds and sod insulate the soil surface from the sun. In addition, tall, unmowed cover crops raise the effective ground level, so even higher flower buds may be injured where there is a tall stand of grass or weeds.

Also important is the fact that wet or moist soils have a higher heat capacity than dry soils, and packed soils are able to absorb more heat than recently cultivated soils. This means that clean, moist and packed soil surfaces will absorb more radiant energy during the day, and protect from frost by releasing this heat during the night. In general, unmowed cover crops are cooler than mowed covers, which are cooler than loose cultivated soils. Packed bare soils are warmer than loose soils and wet soils are the warmest of all.

Moist packed soils can be as much as 5° F warmer than unmowed cover crops during radiation frosts. It is unlikely that such high increases in temperature are common, but I have seen noticeable differences in fruit set between orchards that were cultivated as opposed to those nearby where nothing was done to the cover crop. Cultivation is not for everyone, especially where the fruit planting is on uneven ground where soil erosion is a concern. Cultivation is more suited to flatter plantings where drainage or cold air out of the planting is not a major factor in the orchard.

The winter of 2001-2002 was generally mild. There were several heavy lake effect snow events but temperatures were generally mild. In March, there were several cold snaps with temperatures near zero. Warmer spring temperatures will arrive in April. The cold snaps have not caused serious damage to fruit. The southern areas of Berrien County are a week or more ahead of northern areas.

The beginning of growth was apparent in tree fruit last week. Rabbit and mouse damage is not as widespread as last year.

Peach flower buds are swollen. Some winter damage (10-25 percent) has been reported. Growers need to apply peach leaf curl sprays.

Cherries are at swollen bud.

Apples in Berrien County are at silver tip.

Grapes are dormant.

Strawberries are dormant.

Code-A-Phones in Southwest Michigan are now being updated. The Van Buren County Code-A-Phone is (616) 657-6380. The Berrien County Code-A-Phone is (616) 944-4126 ext. 1. The SWMREC Code-A-Phone is (616) 944-1477 ext. 4.

This past winter has truly been another one for the record books for SE Michigan. A late, mild fall last year contributed to a wonderful close of 2001 growing season. Fruit trees went into winter with a good crop of flower buds. Strawberries were mulched as late as anyone could remember, around Christmas time for many. Mild weather throughout the winter helped to maintain the large number of fruit buds that were formed last season. With the exception of a quick cool down that occurred on Saturday, March 9 where temperatures dropped close to 50 degrees in a matter of hours, the season has been very kind to us. Low temperatures recorded this winter have been in the range of -5 to 0 at most fruit farms.

In cutting flower buds over the last week it appears that there has been some slight or minor damage done to peach and sweet cherry flower buds, most likely from the March 9 rapid cold event. The extent of this flower bud damage to peach and sweet cherry is minor at this time, most likely in the range of 5 to 10 percent bud kill. Recall that we can have a tremendous amount of bud kill in most fruit crops and still have a full crop of fruit for the season. Apple buds seemed to have overwintered in great shape thus far.

Most fruit growers have actually welcomed this recent cold snap, as we want to avoid another early start to the spring season. So at this point in time, we are looking at an excellent crop of flower buds that appear to be primed and ready for 2002.

Soil moisture conditions appear to be adequate at this time. While many soils went into the fall on the wet side due to extensive moisture in the fall, most have dried out to a point that at this time we are at about normal moisture level.

Just a reminder that the Fruit Pest Management Code-A-Phone will be up and operating the first whole week of April with weekly updates throughout the spring. That phone number is 810-732-1005.

Stormy conditions continued across the state during early March with the passage of a series of low-pressure systems moving out of the southern Great Plains region. An unusually strong cold front crossed the state on March 9, bringing high winds and blizzard conditions to northern and western sections of the state, as well as power outages and property damage elsewhere (more on this event in an upcoming CAT Alert). Snowfall, both synoptic and lake effect, was heavy in most northern areas of the state with some seasonal totals nearing the 300-inch mark. As of March 26, snow depths of one to three feet or more were still common across Upper Michigan. For the state as a whole, precipitation was generally above normal, which kept soil moisture levels at relatively high levels. Given the widespread rains late last fall, the most recent NOAA Palmer Drought Index, a measure of long term water surpluses and deficits, puts all of the state of Michigan into "unusually moist" to "extremely moist" categories. This contrasts the "severe" to "extreme" drought conditions currently found in eastern seaboard and western mountain states. Besides soil moisture, the heavy precipitation last fall coupled with a more normal snowpack across the region should also help lake levels on the Great Lakes recover from the near record low values of the past year with increases of five to eight inches expected on the Michigan/Huron and Superior systems by this summer.

Looking ahead, upper air troughing is expected to persist across the region for at least the next week with a continuation of below normal temperatures likely. Highs will range from the upper 20's north to the 30's to mid-40's south through early next week.

The latest NOAA 6-10 day outlooks covering the period March 30 - April 3 calls for below normal temperatures and near normal precipitation totals. For the 8-14 day period (April 2-8), the model guidance suggests a gradual weakening of the trough feature over the region with temperatures moderating to normal to above normal levels. Precipitation during this period is forecast to remain at near normal levels. Given the jet stream change called for in the 8-14 day period, forecaster confidence is considered to be lower than normal.

In the long lead outlooks, all eyes are once again turning to the equatorial Pacific region, where warmer than normal ocean temperatures suggest the development of an El Nino event by this coming summer or fall. As a result, the current long lead outlooks are weighted heavily on the gradual development of a warm ENSO conditions later this year. Even so, the outlooks for the Great Lakes region are vague at best.

The most recent NOAA Climate Prediction Center outlook for April calls for the "climatology" scenario for temperature and precipitation, which translates to near equal odds of below-, near-, and above normal levels. The outlooks are the same (i.e. "climatology") for the April-June 3-month period continuing into the middle of the upcoming growing season. While the outlooks offer relatively little guidance in terms of the upcoming summer, the return of subsoil moisture levels to near or even above normal levels is a positive development with relatively low odds of a repeat of the drought conditions experienced by many growers in the state last year.