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Downy mildew of watermelon has been observed on watermelon in Knox County in southwestern Indiana. Downy mildew of cucurbits has also been reported in southwestern Michigan on the Indiana border and central Missouri. All cucurbit growers in Indiana should be scouting and managing for downy mildew. The organism that causes downy mildew of cucurbits doesn’t overwinter in Indiana because it requires living plant tissues. That means that the fungus-like organism that causes downy mildew has to be blown in every year. It is common for downy mildew to start the season in the Gulf States and migrate north with the cucurbit crops. Downy mildew apparently overwinters in northern Michigan/southern Ontario in greenhouses where cucumbers are grown year-round. Therefore, downy mildew is often found in Michigan before it is found in Indiana. On pumpkin and cucumber, downy mildew causes angular yellow lesions on leaves (Figure 1). Lesions on cantaloupe and watermelon tend to be diffuse[Read More…]

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Greenhouse and Indoor Hydroponics Workshop  Date: September 5, 2019 8:00 am-3:00 pm Location: Pfendler Hall- PFEN 241, Purdue University, 715 W State St. West Lafayette, IN 47907 You will learn about best varieties, nutrient recipes, production systems, artificial lighting and temperature needs for hydroponic lettuce produced in greenhouses and indoors. Attendees will tour our latest state-of-the-art greenhouse and indoor hydroponic facilities and experience many hands-on activities. Registration fee is $15. Register here https://tinyurl.com/yxm5ttb9 Northwest Indiana Food Council 2019 FarmHop: Local Farm Tour Date: September 21, 2019, 9 to 4 pm Central Time Location: Valparaiso or Gary, IN Valparaiso, IN departure – This widely diverse tour will take you to a lively family farm with nearly 600 egg-laying chickens; an organic tilapia farm; a biodynamic farm producing vegetables, fruits, and flowers; and a homestead with incredible diversity including fruit production, heritage breed animals, and value-added products. Gary, IN departure – See[Read More…]

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Even the climate models are confused by this year’s weather.  When the August monthly outlook was released (July 31st; national Climate Prediction Center) it showed significant confidence that August would have below-normal temperatures and below-normal precipitation.  However, the shorter-range outlooks (that update daily) the last few days, seem to contradict that prediction.    Whether it is the 6-10-day (August 20-24), the 8-14-day (August 22-28; Figures 1 & 2) or the 3-4-week experimental outlooks (August 25 – September 7), all are predicting significant confidence for above-normal temperatures and precipitation. Given the recent development of drought conditions across the state, these climate predictions (particularly for precipitation) are strongly desired! Will those climate outlooks verify? The current 7-day quantitative precipitation forecast is indicating very little precipitation over the next seven days. That is slightly below normal for this time of the year in Indiana (Figure 3 & 4).  It is a roller coaster ride,[Read More…]

Plectosporium lesions on pumpkin fruit are less common.

Recently, I have had a few phone calls about Plectosporium blight on pumpkins. This disease can be difficult to describe in words. However, once observed, Plectosporium blight is easy to remember. Therefore, this article will include photos of the disease. Lesions of Plectosporium blight are most often observed on the stems of affected plants. The lesions are small and irregularly shaped. The lesions often coalesce to form a scabby area (Figure 1 and 2). When the handle of the pumpkin is affected, the marketability of the pumpkin is affected. In severe cases, the pumpkin itself may have lesions of Plectosporium blight.     Plectosporium blight lesions on fruit may be confused with bacterial spot. However, bacterial spot lesions are usually larger than Plectosporium blight lesions and do not coalesce over large areas like Plectosporium blight. This disease may be managed through a combination of cultural and fungicide treatments. Crop rotations[Read More…]

Although unusual in Indiana, powdery mildew can cause infections on watermelon fruit as seen here.

While cantaloupe and pumpkin growers are used to combating powdery mildew in Indiana, watermelon growers may not be familiar with the disease. Occasionally, I observe this disease on watermelon as well. If left uncontrolled, this disease can cause loss of foliage, loss of yield and lower quality fruit. This article will discuss the biology and management of powdery mildew of cucurbits with an emphasis on watermelon. While powdery mildew often causes a white talc-like growth on either side of the leaf, on watermelon the symptom may show up as a chlorotic lesion on the upper side of the leaf (Figure 1).  The talc-like growth on the lower side of the leaf may be more idiffuclut to observe than on other hosts. Occasionally, powdery mildew may be observed on watermelon fruit (Figure 2). This article https://vegcropshotline.org/powdery-mildew-symptoms-vs-variegated-leaves/ has additional information about powdery mildew symptoms. The fungus that causes powdery mildew, Podosphaera xanthii,[Read More…]

whiteflies on cucumber leaf.

Here in Indiana, whitefly problems are rare, but when encountered it is most often in protected ag production (greenhouse or high tunnel) and less often in the field. However, this is the time of year that you may be seeing them in either environment. Whiteflies are not true flies, but rather Hemipteran insects, more closely related to aphids and plant hoppers. They are sap sucking insects that feed on the phloem of the plant, making them efficient vectors of plant pathogens. Whiteflies produce honeydew secretions which can attract other insects or host the growth of sooty mold on infested leaves. There are two main species of whiteflies that may be encountered in Indiana: the greenhouse whitefly (Trialeurodes vaporariorum) and the sweetpotato whitefly (Bemisia tabaci; Figure 1). They can be distinguished by the way in which they hold their wings when at rest on the plant: sweetpotato whiteflies hold their wings[Read More…]

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Please welcome Dr. Laura Ingwell as she continues her experience in the Department of Entomology as an Assistant Professor in Horticulture Entomology. Laura received her Bachelor of Science in Biology from the University of Wisconsin-Milwaukee in 2006. She received her Masters of Science in Ecology from the University of Rhode Island in 2009 and her PhD in Entomology from the University of Idaho in 2014. Prior to her new faculty position, Laura has been a Postdoctoral Associate in the Department of Entomology since 2014. Laura is a member of the Indiana Small Farm Conference Committee where she is working to engage with diverse small farmers by providing educational sessions to improve production and facilitate conversations around increasing diversity in agriculture. Dr. Ingwell’s research has focused on managing insect pests and insect transmitted pathogens in high tunnel cucumber, cantaloupe and tomato production and investigating the impacts of pesticide use on pollinator[Read More…]

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Welcome to Dr. Elizabeth Long as she returns to the Purdue Department of Entomology family as our second hire in Horticulture Entomology. Elizabeth received her Bachelors of Science in Biological Sciences from North Carolina State University in 2007 and obtained her PhD in Plant, Insect and Microbial Sciences from the University of Missouri in 2013. Elizabeth previously was a Post Doctoral Associate in our department from 2013-2016. Elizabeth has spent the last three years as an Assistant Professor in the Department of Entomology at The Ohio State University. Her research has centered around three key themes: (1) addressing the consequences of human-mediated change to the environment for ecosystem services and function, (2) building our understanding of the impacts of biodiversity loss, and (3) evaluating the unintended impacts of agricultural management on non-target organisms in agroecosystems and surrounding areas. Elizabeth looks forward to engaging with horticultural crop producers in Indiana.

Bacterial spot can cause mostly light colored angular lesions on pumpkin leaves.

I have observed this disease in scattered commercial pumpkin and squash fields across Indiana. Symptoms: Bacterial spot causes ⅛-¼ inch angular leaf lesions that are white to light brown in color (Figure 1). These leaf lesions may be accompanied by yellowing (chlorosis). The more important symptom are the lesions on fruit that are scabby to raised, round and a light brown in color. These lesions are often less than ⅛ inch in diameter and do not extend into the surface of the fruit. However, lesions may become secondarily infected in which case lesions can become an inch or more in diameter. Such lesions may grow into the flesh of the fruit (Figure 2). Any type of fruit lesion can ruin the marketability of the fruit. Biology: Leaf lesions, while unimportant economically, are important in diagnosing bacterial spot before fruit is present. This head start allows growers to begin preventive measures.[Read More…]

Southern rust pustules on corn leaf, and chlorosis on the underside of the leaves. Pustules generally form and erupt on upper surface. (Photo Credit: A. Sisson, Iowa State University

This article is modified from Darcy Telenko’s article about field corn in a recent Purdue Pest and Crop newsletter. Southern rust of corn is normally a disease of tropical areas. During summer months, however, the fungus which causes southern rust, Puccinia polysora, may move into Indiana or other Midwestern states.  Southern rust has officially been confirmed in Posey and Vigo County. If you think you have this disease contact me or submit a sample to the PPDL https://ag.purdue.edu/btny/ppdl/Pages/Submit-A-Sample.aspx Southern rust pustules generally tend to occur on the upper surface of the leaf, and produce chlorotic symptoms on the underside of the leaf (Figure 1). These pustules rupture the leaf surface and are orange to tan in color. They are circular to oval in shape. We are seeing a lot of common rust as well and both diseases could be present on a leaf. Common rust will form pustules on both sides[Read More…]

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