Janna L Beckerman

Professor of Plant Pathology
Department of Botany
Area(s) of Interest: Ornamental and Fruit Diseases
Janna L Beckerman's website

25 articles by this author

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Summer rots continue to rear their ugly heads (Fig. 1). This year, we are even seeing them on late season apples like Evercrisp    (Fig 2) and GoldRush. On the plus side, we are seeing some level of control with all fungicides in our trials (data will be presented at the Indiana Hort Congress); unfortunately, on highly susceptible varieties like Honeycrisp, we need to do more research to figure out how to better control these pathogens. Treatments that provided reasonable control in Golden Delicious suffered 10 times more infections on Honeycrisp. Future research will examine the role of timing and fungicide choice on infection. As always, please contact me if you are seeing new problems, increasing severity of problems, or you can surprise me and tell me what a great year you had! As you can see, Jojen loved the harvest, and has decided like most children, that Honeycrisp and[Read More…]


Fruit rots continue to pose a problem for those of us in the wetter parts of the state. Frequent rains and warm temperatures really set the stage for bitter rot, black rot, white rot, and even brown rot. Any rain event that produced more than 2” of rain would remove the majority of fungicide, meaning that harvested fruit is going into the storage bin unprotected from these pathogens. If possible, a fungicide like Merivon or Pristine, with a zero day preharvest interval will provide protection in storage. However, fruit that may have looked clean at harvest could be infected, and any infected fruit will develop lesions over time. At this stage, damage control is limited to scouting bins, and removing infected fruit as it develops. Remember that postharvest applications of fungicide will not “cure” fruit that is already infected! Some key points to minimizing storage rots include: Using clean bins[Read More…]


In 1907, Thomas Burrill wrote that regarding bitter rot, “There was nothing to do but to helplessly submit to the inevitable.” However, he continued and stated “that what formerly seemed incomprehensible is easily understandable.” Some key points he touches on regarding the management of bitter rot are weather conditions and sanitation. Obviously, there is little that can be done about the weather. The bitter rot pathogen complex grows well in hot, wet weather.  I say complex because it turns out there are several different species of Colletotrichum causing this disease (or causing Glomerella leaf spot). In fact, even the complex is complex, with the previous delimitation of Colletotrichum gleosporioides and C. acutatum both now described as complexes consisting of several different species each! What is interesting, 110 years later is that little has changed by way of management options: “(1) cutting of and handpicking the cankers and old mummies; and[Read More…]


Russetting of the skin

Since 2012, apple powdery mildew(PM) has been part of new normal of apple growing in Indiana. As many of you remember (but would like to forget), 2012 was the year when much of the state lost the crop due to a late season freeze. This was then followed by one of the driest years on record. The loss of fruit resulted in many growers greatly reducing their fungicide applications, or using just captan or mancozeb, which, although effective against scab, are not effective against powdery mildew. This led to a build-up of PM inoculum, and continued management issues surrounding this problem. Powdery mildew symptoms can range from the subtle (Figure 1) to the incredibly obvious (Figure 2), and everything in between. As these Honeycrisp terminal buds break due to excessive rainfall, new growth is very susceptible to powdery mildew. Cover sprays should include either Pristine, Merivon or Luna Sensation, Sovran[Read More…]


It may seem like the worst is over, but apple growers should continue to be vigilant and apply fungicides even as we approach the end of the ascospore discharge period. Leaves are still highly susceptible to both primary and secondary apple scab infection until the terminal bud has set and the leaves have hardened off. Our cool, wet, crazy spring resulted in the late formation of primary scab lesions coupled with a long growth period, meaning more opportunity for scab infection. As a result growers that scouted earlier and found no scab may think their orchard is a lot ‘cleaner’ than it really is. Those hard-to-detect primary lesions can churn out 95,000 conidia per lesion! This makes it difficult to determine if the later lesions are late primary infections or actually secondary infections. Let’s face it: No one cares except the plant pathologists. Upshot: Scab control is really, really important[Read More…]


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Diagnosing Phytophthora crown rot is difficult. First examine the crown and rule out any type of mechanical damage, including rodent damage. Early symptoms of root and crown rot include delayed bud break, small leaves (often with leaf discoloration), and twig dieback. Bark discoloration, unthrifty growth, and premature leaf drop may occur later in the season (Fig. 2). Adding more nitrogen to trees symptomatic trees will actually worsen the problem! Later symptoms, particularly for collar rot, often resemble rootstock blight, caused by the fire blight bacterium. Water-soaked, red-brown blight often extends throughout the susceptible tissue.


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Wet weather continues to be a problem, not just for foliar disease, but root and crown rot, as well. Phytophthora root and crown rot is observed in wet spots: low-lying areas of orchards with heavy, poorly-drained soils. These pathogens can infect all fruit producing plants. Occurrence of this disease is sporadic and tied to wet weather, but unfortunately, is likely to occur wherever susceptible rootstock is planted on a poorly drained site. The disease is caused by members of the genus Phytophthora, a type of ‘water mold’ and not a ‘true fungus’(Fig. 1). Phytophthora species prefer cool, wet weather, like what we have been experiencing now. Phytophthoras can infect the roots, the crown and the graft union. Of these, collar rot is more lethal and can cause rapid tree death, especially if it is a small tree. In apples, Phytophthora crown rot is commonly observed on 3- to 8-year-old trees[Read More…]


Although not always possible, avoid planting in low-lying, flood prone areas. Control weeds around the trunk of apple trees, as many serve as alternate hosts for the crown rot fungus(especially nightshades). Reduce nitrogen application on young trees, and trees with excessive growth as they are more susceptible to crown rot. As there are different species of Phytophthora (like P. cambivora, P. cryptogea, and P. cactorum, to name a few!) resistance isn’t as straightforward as it might appear (See reference at end of this article). Bud. 9 and Emla provide the most reliable resistance in published studies. To slow lesion growth (canker) on partially girdled trees, expose the crown, scrape away infected bark and air dry. Remember to replace earth around trunks before winter. Right now, Aliette and phosphorous acid derivatives like Alude or Rampart can be sprayed on the foliage of non-bearing trees at 30 to 60 day intervals beginning[Read More…]


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The recent spate of cool, wet weather has left one organism happy, Venturia inaequalis, the fungus that causes apple scab. Most of the state just underwent an extreme scab period, and unfortunately, few of us could do anything about it because of the combination of rain and wind. The revised Mill’s table (from http://www.fruit.cornell.edu/tfabp/revmills.htm )identifies this period as taking anywhere from 8 up to 30 hours. Unfortunately, days of rain provide the perfect infection period. The kicker is the fact that infection develops really slowly under these cool, wet conditions. This means symptoms may not show up for another two to three weeks. At this point, everyone is thinking ‘Fungicide resistance!’, as opposed to what really happened—heavy rains that washed off any trace of fungicide, plus a long, cool wet infection period that delayed symptom development. Obviously, we are past the point of rescue sprays. Furthermore, for those of you[Read More…]


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Upticks in powdery mildew last year, plus a mild winter (which allows the fungus to overwinter in buds) set the stage for powdery mildew (Fig.3). Early season rains kept things at bay, but the recent change to drier weather while leaves continue to grow sets the stage for this disease. Powdery mildew is active during dry periods above 50 degrees and below 90, but happiest on dry, mild, spring days. Keep an eye on the most susceptible varieties (Jonathan, Baldwin, Ginger Gold, Ida Red, Cortland, Rome, Stayman Winesap…). We saw an uptick of PM on our Honeycrisps last year, so keep an eye on them, too! Remember that captan and mancozeb are not effective for controlling this disease, but DMI fungicides (Frac 3: Rally, Topguard, Indar, Inspire), strobilurins (Frac 11: Flint, Sovran), and 11+7 premixes (Pristine, Merivon, Luna Sensation) all are, and will help with rust and scab, assuming resistance[Read More…]