Fruit Pest News Volume 12, No

Fruit Pest News Volume 12, No. 5 July 26, 2011 Entomology and Plant Pathology Department, University of Tennessee In This Issue: 1. Strawberry Growers: New Rules for Fumigation Now in Effect 2. Manzate on Pepper 3. Bitter Rot of Apple 4. Apple Alternaria Blotch Moves West 5. Lightning Injury in Tomato 1. Strawberry Growers: New Rules for Fumigation Now in Effect Growers who plan to use standard fumigants will need to follow the new regu- lations for worker and bystander protection released by EPA in December 2010. These include requirements for a detailed Fumigant Management Plan (FMP) and for worker training. Even those who have fumigation done by cus- tom work will need fumigation plans specific to their farm and the day of fumigation. You can access EPA’s templates for the FMP’s at the EPA web site by googling “fumigants toolbox.” Much of the FMP can actually be filled out ahead of time, to save you time on the day of fumigation. The FMP must be available for inspectors, emergency personnel, or handlers and kept on file for two years. Other tasks needed to prepare for the new rules: Before the FMP can be completed, the requirements found in it will have to be satisfied. At least two workers (handlers) involved in the fumigation will need to have appropriate respirators and to have completed respirator medical clearance and fit testing. Figure 1. The Fumigant Toolbox, from EPA’s Your physician may use the form found at http://www.ncstrawberry.org/docs/ web site. Each label represents a link that pro- Respirator%20Medical%20Clearance%20Questionnaire.pdf to qualify you for fit vides you with information on that topic. testing. Information on respirators can be found at http://63.234.227.130/SLTC/ etools/respiratory/index.html. Also, the size of the buffer zones will need to be determined, and signs prepared for posting. Refer to the EPA web site for requirements. You will need to secure an air monitoring meter for escaped gas, and handlers will need to be assigned tasks and trained in those tasks. Do I really want to do this? You need to ask yourself if you really need to fumigate. If fumigation sounds as if it’s more trouble than it’s worth any more, you first need to how much it’s worth. I hope you have left some untreated areas in crops, for comparison. That’s the only way you will ever know. Many Tennessee farms probably do not need soil fumigation, because we do not have many of the soil-borne problems found in the coastal plains soils. And with recent advances in strawberry herbicides, we have answers to most weed problems other than nutsedge. New ground and rotated ground probably do not need fumigation. It has been shown that crop rotation can be as effective as methyl bromide. Unfortunately, not everyone can rotate their strawberries. If this applies to you, and you think you may have soil-borne disease problems, you may wish to consider alternative methods of control such as solarization, mustard seed meal, or molasses. The latter is a method recently published by the USDA that works by encouraging beneficial soil microorganisms. (SB) 2. Manzate on Pepper If you have not heard, the long-awaited supplemental label for mancozeb on peppers has arrived. Manzate Pro-Stik received a supplemental label in April for pepper, lettuce, broccoli and cabbage. These crops were EBDC “orphans” when maneb registrations were dropped a year and a half ago. EBDC’s are the only products that will enhance the activity of copper against bacterial diseases, which are of particular importance to pepper. Manzate is distributed by United Phosphorus, Inc. (UPI), which acquired the rights from Dupont. The pepper rate is 1.6-3.2 lb/A, with a 7-day preharvest interval. For bacterial spot control, tank mix with a full rate of a fixed copper product. (SB) Figure 2. Bacterial spot of pepper 3. Bitter Rot of Apple Bitter rot is the most potentially explosive of the apple fruit rot diseases, and I have recently received reports of severe cases (Figure 3) and difficulty with control. The disease can move so rapidly because infection can occur in as little as 5 hours of wetting at 79-82 F, and spore production is so prolific. Fruit re- main susceptible right up until harvest. Identification. Bitter rot is recognized by round, sunken lesions on the fruit. When very young fruit are infected, the lesions ap- pear as tiny gray-brown flecks. Later infections begin as small, round, slightly sunken areas that are light to dark brown in color. As the lesions enlarge, concentric rings of spores or their fruiting bodies form around the center (Figure 4). Decay lesions extend in a cone-shaped pattern toward the core, observed by cutting the apple in half through the decayed area. This V- shaped lesion distinguishes bitter rot from white rot, which has Figure 3. Apple bitter rot tends to be explosive in hot, a cylindrical decayed area. rainy weather. Photo courtesy of Paul Hart. Cultural control. Control efforts are aided if trees are well-pruned and air circulation is good in the orchard. The removal of excess growth improves drying conditions and penetration of sprays into the canopy. Try to prevent the buildup of inoculum by removing overwintered mummified fruit, if feasible, or even diseased fruit during the growing season. Leaving fire-blighted shoots on the trees can increase fruit rot problems, because the fungi can colonize them. Do not allow prunings to pile up near the orchard. Prunings can be left on the orchard floor if they are chopped with a rotary or flail mower, which removes the bark on which the fungus can reproduce. Monitoring bitter rot. Inspect the trees each week, beginning in early June. Highly susceptible varieties include Golden Delicious, Fuji, Arkan- sas Black, Granny Smith, Empire, and Yellow Newton. Almost as susceptible are Gala, Stayman, Jonagold, Jonathan, Grimes Golden, Ginger Gold, and Braeburn. Among the least susceptible are Delicious, Rome Beauty, and Winesap, but no variety has a high level of resistance. Figure 4. Concentric rings are often If bitter rot is seen increasing, a change in the control program may be visible in bitter rot lesions. needed. The needed change may be in the tree training and other cultural practices mentioned above. Or it may be in the spray program. The spray interval may need to be shortened, the fungicide choice may need to change (a bitter rot fungicide should be used in each cover spray), or the application method may need adjustments. Chemical control. Where bitter rot is a problem, cover sprays should be applied at 10- to 14-day intervals, using 10-day intervals during rainy periods. The need for fungicidal protection against bitter rot is greatest from midseason until harvest, although some fruit infection can occur as early as petal fall. Captan, Ziram, Pristine, and Flint are the best bitter rot materials, and should be used at full rate where problems with bitter rot are expected. Strobilurins such as Pristine and Flint can only be used four times per season, col- lectively or individually. The addition of Topsin M to Captan or Ziram helps with control of sooty blotch and flyspeck, as well as white rot and black rot. Research has shown that calcium reduces growth of the causal fungus and applying this element reduces bitter rot incidence. Tank mixing calcium nitrate or calcium chloride with the fungicide products should improve control. Do not apply calcium chloride if temps are over 85 degrees. Also, the use of surfactants in sprays intended for control of diseases of the fruit is very important. (SB) 4. Apple Alternaria Blotch Moves West Alternaria blotch, caused by Alternaria mali, has moved from East TN to Middle TN in recent years, the most recent case on the grounds of the Ellington Agri- cultural Center in Nashville. Leaf spots are brown, becoming ash gray (Figure 5). Lesions can resemble frogeye leaf spot, but can be distinguished by their distribution within the canopy. Alternaria blotch is usually uniformly distributed throughout the tree, while frogeye is usually clumped and associated with mummified fruit or dead wood. Alternaria blotch severity is aggravated by mites. Alternaria blotch affects many varieties, but is most severe on Delicious and varieties with Delicious parentage, such as Empire. Loss of half of the leaves in a block is not unusual. This disease tends to be more of a problem at the higher elevations of the state, and where mites are at high levels. It is very important to maintain mites below 10 per leaf in orchards with a history of Alternaria in order to minimize defoliation. Shredding leaves or applications Figure 5. Alternaria blotch of apple. of urea to leaves just before or after leaf fall may reduce the inoculum. The stro- bilurin fungicides Pristine, Flint, and Sovran have shown good activity on the disease when applied in a sequence of three sprays. The guidelines for use of these fungicide were determined in orchards with a history of the disease, and sprays were initiated around mid-June, while disease incidence was rather low. (SB) 5. Lightning Injury in Tomato Plants in tomato fields struck by lightning will exhibit flattened stems (Figure 6) and dry pith, separated into disks (Figure 7) or hollow. Plants within the stricken area of the field may or may not be dead; some will show little effect. Figure 6. Flattened stem of tomato, caused by a Figure 7. Dry, disked pith in stems of a tomato lightning strike.

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