Facts for Fancy Fruit 07-02 Crop conditions: Severe overnight cold temperatures covered the entire state on April 6-8, with minimums of 20- 25 common and some reports of mid-teens. This caused widespread damage to most fruit crops (see following story). Although there is some variation, we predict the state losses to be: 50% of apples, 100% of peaches, 70% of grapes, and 70% of blueberries The freeze has affected crops beyond Indiana. Most states across the Midwest from Arkansas and Missouri and as far East as Virginia and North Carolina have had crops severely damaged. The northern tier of states seemed to have experiences slightly less damage as their crops were not as far along in development. A primer on cold damage: Generally plants are most tolerant of the cold when they are fully dormant. As they develop in the spring, they lose cold hardiness. This is especially true of flower buds. For example, when apple buds are at half-inch green, a temperature of 23F is unlikely to cause much damage, whereas the same temperature at pink or beyond will cause severe damage. Since the risk of cold temperatures is higher early in the spring, crops that develop and bloom early (such as apricot, sweet cherry, peach) are more likely to be damaged than later flowering crops like apple. This is the primary reason that damage from the recent cold was more severe in more southern areas of the state. While the minimum temperatures were fairly similar across the state, crops in southern areas were more developed and therefore more damaged by the cold. Tables showing damaging temperatures at different stages of development for the major fruit crops are included in the Commercial Tree Fruit Spray Guide. Bear in mind that these temperature damage thresholds are general guides because many factors can influence the amount of damage that results from a certain minimum temperature. These other factors include the duration of cold temperatures, stage of crop development, crop genetics, ground cover, soil water content, wind and previous crop load. Most of these tables were developed for radiative frost events, when critical temperatures are reached for a short time. They may not be accurate for this advective freeze event where temperatures were below critical levels for several hours on successive days. A quick word of warning: even if your crops are still looking OK, we still have a couple of weeks during which another frost could hit us. (Hirst and Bordelon) Spring temperatures: The damage from the recent freeze was due as much to warm temperatures in early March as to the recent low temperatures. Letās look at an example of a northern, central and southern Indiana site. Northern Indiana The minimum daily temperature in Plymouth was much warmer than average for about 10 days at the end of March. This pushed crop development along rapidly. Minimum temperatures from April 5-11 were below average. Lows were 20 F on April 7 and 8. The reason crop development was so advanced can be easily seen from the graph of growing degree days (GDD) starting on March 1. Over the last 3 years, the average growing degree day accumulation at this point was 44, but this year weāve had 103 GDD. Normally we donāt reach 100 GDD (enough to cause bud break) in this area until early May. Central Indiana Three weeks of temperatures well above normal during late March and into early April led to rapid early season development. Minimum temperatures dropped by 20 degrees from April 3 to April 4 and have stayed low ever since. Three nights with lows of 23 F were experienced on April 6- 8. From March 1, about 3 times as many GDD were accumulated as usual (176 compared with 66). This region normally achieves 100 GDD in late April. Southern Indiana About 3 weeks of temperatures 10-20 degrees above normal were experienced from Mid March to early April. Lows were 25 F on April 7 and 8, but given the advanced stage of crop development, this was cold enough to cause a lot of damage. Once again, GDD were well above the average of the last 3 years. This year we have accumulated 239 GDD compared with and average of 108 GDD. As we see from all the above, conditions were much warmer starting on March 20 and lasting 2-3 weeks, This was enough time to advance plant development well beyond a normal year. Based on normal GDD accumulation, this year is about 3 weeks ahead. Thatās the main reason that plants were so vulnerable when the cold snap arrived. (Hirst and Bordelon) Evaluating freeze damage in apples: It is relatively easy to assess damage to apple flowers. Collect flowers and slice them longitudinally (lengthwise). Any browning of the flower parts, usually most obvious at the base of the flower, indicated the flower has been killed. Browning can been seen with the unaided eye although use of a hand lens may make the job a little easier. The most susceptible flower tissues are the pistils. These are the long thread- like structures in the middle of the flower. For fruit set to occur, compatible pollen must land on the end of the pistil and grow down to the ovule to fertilize the eggs and set seed. Pollen cannot grow on dead pistils, so even if the ovaries of the flowers are still alive, there is no way they can be fertilized. Flower of Pink Lady apple, showing dead pistils in the center of the flower. (Hirst) Evaluating freeze damage in grapes and berry crops: Itās still too early to know for sure what the full extent of the damage from the Easter weekend cold event. We havenāt had enough warm weather these past 10 days for plants to continue developing. As with apples (see story above) itās relatively easy to slice open some flowers and evaluate whether they are healthy or not. Grape buds are similar, except those that were damaged are now dry and crumbly. Weāve taken some blueberry cuttings into the lab and forced them. It appears that a few flowers are undamaged. Grapes that were are bud break or beyond are clearly damaged. The amount of production possible on secondary buds wonāt be known until buds break and an estimate of cluster numbers can be made. Even then, it wonāt be until after bloom before we know for sure how much crop to expect. On later budding varieties, that were less than full swell stage, we expect a normal crop. Damage is not evident at this time. But that is only a limited number of varieties in the Lafayette area. Most commercial growers are further south and they were more advanced, so we expect the impact more damage, even to later budding varieties. Brambles also appear heavily damaged in the Lafayette area. Some were damaged by sub-zero temperatures in February. Those that escaped winter injury developed buds that were damaged in the recent freeze. The leaves were killed, but it appears that the shoots are still alive and may continue to develop. So there may be a small crop on some brambles. Strawberries have suffered damage to exposed leaves and buds, but most plantings were not yet in bloom. It appears that some growers will have a reasonably good crop. (Bordelon) Pest management strategies following the freeze: In grapes we suggest growers continue to make early fungicide applications to control Phomopsis, even if they donāt know how much crop to expect. Those early applications of mancozeb or captan are relatively inexpensive, and are critical to controlling the rachis infections on clusters. Both will also control early black rot and downy mildew infections. A decision about the how to proceed the rest of the year can be made after an estimate of crop is made. On blueberries, applications of captan or CapEvate should help reduce invasion of damaged shoot tissue by Botrytis and Phomopsis shoot blight. If a reasonable amount of flowers have survived the freeze, then a normal spray program to control fruit rots and fruit insects should be followed. A complete recommendation is listed in the Midwest Commercial Small Fruit and Grape Spray Guide (http://www.hort.purdue.edu/hort/ext/sfg/default.html) (Bordelon) Officials Working to Determine Damage to Indiana Fruit Crop: Indiana State Department of Agriculture Director Andy Miller tells Inside INdiana Business that the state is working with members of the U.S. Department of Agriculture (USDA) to determine just how much of the state's fruit crop has been damaged by the recent cold weather. Miller says USDA field offices are trying to document and quantify the losses to the peach and apple crops. Source: Inside Indiana Business (insideindianabusiness.com) Reporting crop damage: All Indiana fruit growers that experienced damage from the recent freeze should contact their USDA-FSA office regarding crop losses, even if not currently covered by crop insurance. The reason to notify FSA is that they are making an evaluation and informing the Indiana Department of Agriculture about the extent of the losses. The Department of Agriculture can then request a declaration of disaster be issued. They can best describe what type of relief may be available to you and can also tell you about existing programs for next year such as the new grape insurance products being offered. Please stay tuned to our next issue for implications for growers with or without crop insurance. Chateau WDG Herbicide for Strawberries: From Ohio Fruit ICM News Vol. 11 (10) by Dr. Doug Doohan, State Specialist, Dept. of Hort and Crop Science, The Ohio State University. Valent recently received EPA approval for Chateau WDG herbicide on strawberry. Chateau is good news, but berry growers need to proceed with a degree of caution as we all learn more about just how this product fits into matted-row and plasticulture systems in the north. The supplemental label for Chateau (EPA Regn # 59639-119) authorizes Pre-Transplant applications to new plantings, late-fall or early-spring applications to established dormant plantings, and shielded sprayer applications to row middles once the crop emerges from dormancy. Reading between the lines (if its not obvious), Chateau burns non-dormant strawberry leaves and fruits, thus the need for caution. This registration is one that calls for some careful on- farm grower experimentation while we work out the crop safety considerations. Right now the early-spring application is the one of greatest current interest to growers as well as the one of greatest concern because of potential for crop injury. Regardless, Iāve already consulted with one who intends to use Chateau on his established fields because of severe weed problems. If this applies to you, listen up. If your weed problem justifies it, apply Chateau as soon as you remove the mulch. The longer mulch is left on the crop, the more sensitive-new- growth will be developed. Delaying Chateau application after mulch removal will further the development of new growth, all of which will be burnt off by the herbicide. Donāt be surprised if your field temporarily looks like you sprayed with Gramoxone, but donāt despair. Based on experience in research plots with similar herbicides such as Goal and Blazer the crop will quickly recover and within a couple of weeks you will not likely be able to tell the difference between sprayed and unsprayed areas. In trials with Goal applications immediately after mulch-removal, crop-yield was unaffected although earliness was delayed by 2 or 3 days. Chateau is also registered Pre-Transplant. The supplemental label states that Pre-Transplant should only be used when berry plants are transplanted into plastic mulch. However, Valent Company representatives have told me that is incorrect, and Pre-Transplant applications are safe to standard matted-row plantings on bare ground as well. Regardless of matted-row or plasticulture system, Chateau must be applied 30 days before planting. Chateau is applied at 3 oz/A and is primarily a soil- active, residual herbicide, meaning it mainly controls weeds during emergence and control of sensitive weeds is extended for several weeks following application. Premergence control of a wide-spectrum of broadleaf weeds can be expected including pigweeds, mustards, jimsonweed and nightshades, lambsquarters, marestail, mallow, and chickweed. Some emerged broadleaf weeds will be suppressed and control will be improved by including crop oil concentrate at 1% or non ionic surfactant at 0.25% of final spray volume. Potential users of Chateau should obtain a supplemental label, as the strawberry use is not yet listed on the Section 3 label. The supplemental label can be obtained on the Internet at the Valent Web Site (http://www.valent.com/), or from crop-protection dealers. Managing diseases on Apples and Pears: In 2007, fruit growers throughout the entire Midwest have experienced one of the worst spring freezes in over 30 years. This disease note is intended to provide information that will aid fruit tree growers in developing a disease management program for freeze damaged trees that will not bear a crop this year. A program for trees such as these needs to be as economical (cheap) as possible, due to the lack of income from the trees this year; however, it must provide an acceptable level of disease control. Despite the potential loss of crops, disease management, particularly for fire blight, and apple scab is of the utmost importance right now. Although results arenāt yet in on the state of this yearās crop, improper management of trees from this point on can profoundly affect future harvests. Freeze injury, much like hail injury, results in damage to young and succulent shoots and leaves, providing a means for the fire blight bacterium to cause shoot blight. Two predictive programs for fire blight (Cougar Blight and MaryBlite) should be useful in monitoring the potential for infection by the fire blight bacterium. Even if low potential for infection is predicted, you may wish to protect some of the most susceptible varieties, like Fuji, Gala, and Ida Red (For a list of susceptibility see the new Extension Brief Disease Susceptibility of Common Apple Cultivars, at http://www.ces.purdue.edu/extmedia/BP/BP-132-W.pdf especially if these are grafted on M.26 and M.9 rootstocks. Streptomycin or a low rate of copper (0.2 -0.6 lb of metallic copper/acre depending on tree row volume) should provide protection against fire blight. Keep in mind that copper can cause injury on some varieties, and application should occur after the temperatures are above 50 degrees F to prevent phytotoxicity. Suggested coppers include Cuprofix, Kocide, or C-O-C-S. Turner Sutton, at North Carolina State University reports using the 0.2 and 0.4 lb rates on Golden Delicious during the summer without any problem. If you think you might have a crop on a copper sensitive variety, use streptomycin if you are concerned about possible injury. Should you still have a crop, based upon regional weather forecasts, you should plan on applying streptomycin prior to anticipated rain and warm weather during bloom and on rat-tail bloom (abnormally late flowers after normal bloom). According to the prevailing wisdom, dead flowers that donāt fall off are not good hosts for the fire blight bacterium. However, any escaped side blossoms, later developing blossoms, or ćrat tailä blooms that are still alive can become infected. Continue monitoring until bloom is over, and apply streptomycin as needed, not to exceed four applications per season. Information and simple directions as to how to use Cougarblight to assess your risk of infection can be found at: http://www.ncw.wsu.edu/treefruit/fireblight/2000f.htm If your orchard has a history of fire blight, I would strongly encourage you to consider applying Apogee (Prohexadione-Ca). Apogee is a growth regulator that does not directly kill the fire blight bacterium, but reduces shoot growth, thereby increasing plant resistance by reducing host vigor. Apogee suppresses apple shoot growth when applied near petal fall as a single spray, or as several applications over time. Apple response to Apogee depends upon the cultivar, timing, rate of application, crop load, and even geographical location. Regardless of this variability, Apogee remains the best management tool available for controlling the shoot blight phase of fire blight that growers may be faced with after a freeze. For use recommendations and rates for Apogee, see the ćMidwest Tree Fruit Spray Guideä. Despite the potential or real loss of crop, it is imperative to maintain a least a minimum spray program to control important diseases such as apple scab, powdery mildew and (where applicable) cedar apple rust. Failure to do so will result in defoliated trees that fail to produce next year, or may not survive next winter. In addition, non sprayed trees will result in the build up of scab inoculum in the orchard. This will be an additional problem to face next year and may threaten the production of future crops. Normally, the greatest risk of scab would be right now, from pink to bloom. However, nothing is normal about this year. For these reasons, I am recommending: * EDBC fungicide (3 lb/acre) program through bloom. Alternate with copper or sulfur from first cover on to remain under label limits. Remember to stay within the 21.0 lb/acre/season limit for your EBDCs. I like the EBDCs as they also protect against bitter rot, black rot and white rot. Use this schedule if cedar-apple rust is a particular problem. * Alternatively, Captan can be used earlier in the season for good scab control instead of the EBDCs, but provides no control of rust or powdery mildew. * NOTE: Do not use Captan (any formulation) in combination with or closely following or in alternation with wettable sulfur products, or oil. Sulfur sensitive varieties of apples such as Red Delicious, Staymen, and Baldwin, can suffer severe injury and defoliation. Captan 50 WP has a 64 lb limit per acre per year. For those that have lost crops: Copper (0.2 ö 0.6 lb metallic copper per acre based on tree row volume) + sulfur (6-30 lb/acre depending on product and formulation) every 10-14 days between now until the first week in June, or later depending upon weather conditions. In summer cover sprays, this treatment could be applied on a 14 to 21 day schedule (10 to 14 days if excessively wet) to help control secondary scab. Suggested sulfur formulations include Thiolux, Microthiol Disperss, or Microfine Wettable sulfur. This spray program protects against scab and mildew. Remember, copper can russet fruit, and should not be used if you want to use your crop for anything except cider. Do not use sulfur if temperatures are going to exceed 90 degrees F, or drying conditions are extremely poor. Do not use sulfur or copper within two weeks of an oil application. Neither of these programs is going to provide complete scab control but should reduce leaf infections. Organic trials in both Michigan and North Carolina regularly apply 6 lbs of sulfur per treatment without any reported phytotoxicity due to temperature. If it turns considerably wetter, or if powdery mildew is particularly bad, you may wish to consider applying a sterol inhibitor like Nova, or Rubigan; or a strobilurin like Flint, Sovran, or Pristine prior to second cover. Due to cost, and the potential of no return on investment, I am recommending against using these fungicides for growers experiencing significant loss. It simply is not cost effective in the absence of a crop, nor worth risking the development of resistance. Managing Diseases on Stone Fruits: With stone fruit crop loss approaching 100% throughout most of the state, management must focus on protecting foliage to ensure a good potential crop for next year, while reducing over wintering spore loads. Captan at the 1.3 lb/ 100 gallon rate should sufficiently control brown rot twig blight, scab on peaches and cherry leaf spot. If the season is excessively wet, higher rates of captan may be required. Captan will not control powdery mildew. Wettable sulfur at the 6 lb per 100 gallon rate is probably the least expensive material you can use and provides excellent control of powdery mildew of all stone fruit, and should aid in controlling brown rot twig blight, and peach scab. Bacterial spot on peach, particularly if the weather is wet in late June and July, may warrant applications of Flame Out (Oxytetracycline) or Mycoshield.