Janna L Beckerman

Professor of Plant Pathology
Department of Botany
Area(s) of Interest: Ornamental and Fruit Diseases
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Stone Fruit: At our orchard, we lost our stone fruit with the -20 degree F temperatures this winter. For those of you fortunate enough to have fruit, frequent and heavy rain present problems multiple problems, namely bacterial spot and brown rot. Three weeks before harvest, cease bacterial spot sprays, even though bacterial spot may continue to be an issue with this hot wet weather. You can still manage brown rot. To maintain and protect fruit, be sure to rotate chemistries by FRAC Code to minimize the risk of fungicide resistance. Some options to consider (choose one from each column and then choose a different column-do not repeat a column back to back, and always used the highest labeled rate).


Glomerella leaf blight seems to be rearing its ugly head. Symptoms include lesions with concentric rings in them that can grow together and give the leaf a blighted appearance (Fig. 1). Leaves may yellow and fall off (Fig. 2) and may appear like Golden Delicious necrotic leaf blotch on a variety of apple cultivars (Fig. 3). Before anyone panics, Glomerella is not a new pathogen, but the sexual state of a fungus that was first identified it its asexual state and was named Colletotrichum. Fungi known to infect apples and belonging to this group (genus) cause bitter rot. Previously, the bitter rot pathogens were divided into two species complexes: C. acutatum and C. gloeosporioides. Recent work in Kentucky found five different species of Colletotrichum associated with bitter rot: C. fioriniae, C. nymphaeae, C. siamense, C. theobromicola, and C. fructicola. The relationship between bitter rot and Glomerella leaf spot, if any, is not[Read More…]


Figure 1. The branch stub serves as a wound that enables a pathogen, in this case, Nectria spp., to infect. Photo by Janna Beckerman.

Diseases that affect the twigs, branches, and the main trunk of a tree are referred to as cankers or blights. Canker diseases  can be a serious problem in the orchard, vineyard, berry or bramble patch when they are not properly managed, and even when they are. All woody plants can be infected by canker pathogens. Cankers appear as a general sunken area of darkened tissue on the twigs or branches, often surrounding a branch stub(Fig. 1). Many canker pathogens produce perithecia, which contain sacs of spores (asci) that forcibly release the spores when the conditions are right. The perithecia are easy to find on the surface of the canker (Figure 2). As the canker grows, the twig or branch may become girdled, causing the wilting and death of the leaves past the point of infection on the tree. On stone fruit, this can cause gummosis, too (Fig. 3). What causes[Read More…]


Those of you lucky enough to still have a crop. Drier than usual weather means the risk of scab and bacterial diseases is low, but powdery mildew is higher. Although Rally and Topguard provide excellent control of powdery mildew, Flint extra, Luna Sensation and Merivon all provide excellent control of not only powdery mildew, but against scab and brown rot, should weather turn wet.  


Fig. 2. Juniper rust, specifically, cedar-hawthorn rust. Photo by Janna Beckerman.

From one of the coldest Aprils to one of the hottest Mays, what will June bring us? So far, apple scab has been less of a problem than usual, but powdery mildew seems to flying under the radar for many orchards. Keep your eyes out for the characteristic leaf curl (Fig.1). Varieties like Jonathan, JonaGold, Cortland, GingerGold and SunCrisp, are very susceptible. Due to the dry weather, many growers switched to a captozeb program, which is excellent against scab, but doesn’t do anything for powdery mildew, or very little against rust. Speaking of rust: Dry weather has delayed not only ascospore ejection of scab, but also those orange, gelatinous kooshballs of spores (Fig. 2). I don’t recall the last time I saw any telial spore horns (aka kooshballs) in June, but they were still going like gangbusters on June 1 here. For those in central Indiana to parts north, all[Read More…]


Fig. 3. Brown rot of plum. Photo by Steve Goodwin.

What??? Yes, thanks to the Return Bloom Fund and the Meigs Farm Team, we have a small planting of three varieties of plum: Early Shiro, Green Gage, and Ruby Queen. Did you know in Australia, some varieties are retailing at $15.90AU per kilogram (or $7.22 per pound)? Most Midwesterners only know those hard, tasteless things disguised as plums, hailing from California, and delivering only disappointment. Fresh plums not only taste good, but are good for you, regardless of variety—they are high in fiber and antioxidants. And let us not forget, plums are a principle component in ‘a warrior’s drink’. “NuqDaq ‘oH puchpa’’e’?” Although these plums will be used to study brown rot (Fig. 3), I hope I can convince a few of you that planting plums isn’t just good for the soul, but the bottom line. Live long and prosper!


rat-tail blooms

In case you blinked, we went from green tip to bloom in about three days, and by the time you read this, we will have passed through the blossom blight period. For most of the state, the late spring consisted of cool, dry weather that was not conducive to blight infection in the northern half of the state. The southern half of the state was only slightly more conducive for infection. This means that any strikes seen in the next few weeks probably came from damage from last year. Since last year was unusually wet, with a lot of susceptible rat-tail blooms, it is most likely that any fire blight infections observed as shoot and canker blight can trace their beginnings to rat-tail blooms of last year (Fig. 1). What to do now? Until a terminal bud has formed and growth has ceased, I do not recommend pruning out strikes[Read More…]


Please remember that it is the blossoms that are most susceptible to the bacteria; assuming that there are no rat-tail or autumn blossoms, and in the absence of a hail event, the probability of secondary infections in orchards is minimal. In the event that rat-tail blossoms are apparent and extensive, it is critical to prevent their infection. If fewer than 3 applications of streptomycin have been made during bloom, it can be used to protect these rat-tail blossoms as long as it is within 50 days to harvest (PHI) for apples and 30 days (PHI) for pears. Better still, if time and labor are available, removing the rattail blossoms by hand may be more sustainable. What to do next: “Based upon current information, growers need to distinguish between situations in which the disease is detected on blossom clusters, succulent shoots, or lateral branches, versus first detected on main branches and[Read More…]


apple fire blight blossom

Maryblyt 7.1 is now available for download at http://grapepathology.org/maryblyt For new growers: Maryblyt is a fire blight prediction model. Fire blight is caused by the bacterium Erwinia amylovora. It is one of the most destructive diseases of apple, pear, and quince worldwide (Fig. 1). There are five distinct phases associated with fire blight, and include blossom, canker, shoot, root, and trauma blight phases. However, only the blossom blight phase offers growers the opportunity to break the disease cycle. Today, blossom blight can be managed more successfully using disease forecasters such as Maryblyt. Maryblyt predicts fire blight infection events by identifying periods when weather conditions and tree phenology are suitable for infection, allowing growers to time antibiotic applications when they can be most effective. The current version is due to the efforts of Drs. Nita at Yoder at Virginia Tech. Maryblyt was originally developed by Dr. Paul W. Steiner, University of[Read More…]


Temperatures below -15°F generally kill powdery mildew infected buds. For those of you who had a milder winter, protecting susceptible varieties like Jonathan, Ida Red, Enterprise, Staymen, Granny Smith, and Ginger Gold, be sure to protect at tight cluster, pink, bloom, petal fall and first cover. Remember that fungicide protection is needed until terminal buds are set. As long as resistance isn’t an issue, Rally, Procure and Indar, are the most effective DMI fungicides; Merivon, Pristine, and Luna Sensation (7+11 fungicides) or Flint Extra, Flint, or Sovran (11).