Category: Plant pathology

Dr. Alamgir Rahman began his position as Clemson’s Vegetable Pathologist specialist in late 2025. Before joining Clemson, he earned a PhD from Penn State University and then joined Corteva Agriscience as a Research Investigator and Discovery Fungicide Biologist, where he conducted projects on vegetables, cereals and small grain crops. At Clemson, Dr Rahman is eager to contribute significantly to the realm of vegetable pathology working alongside growers in South Carolina. The vegetable pathology program will focus on better understanding diseases of legumes, cucurbits, leafy greens and tomatoes. Dr. Rahman outlines below his research and extension plans at Clemson.

Dr. Alamgir Rahman, Clemson’s vegetable pathology specialists

“My program will begin in growers’ fields. In 2026, I will prioritize systematic pathogen scouting in lima bean, snap bean, cowpeas, pepper, kale, cucurbits, tomato, and watermelon production systems. These surveys will allow me to document disease incidence, collect representative pathogen isolates, and detect emerging or shifting populations.”, says Dr. Rahman, who also points out the additional research on the topic through molecular techniques. “Once collected, isolates will be purified and characterized in the laboratory using classical morphological approaches and molecular diagnostics. This process will establish a curated pathogen repository that will serve as the biological foundation for my long-term research program.”

“The flagship focus for 2026 will be anthracnose of lima bean, primarily caused by members of the Colletotrichum species complex, including C. truncatum, C. magnum, and C. lindemuthianum. Through scouting growers’ fields Collectotrichum symptomatic plant samples will be collected followed by pathogen isolation, characterization, fungicide sensitivity assays, and greenhouse-based pathogenicity tests to evaluate virulence diversity and cultivar response. By generating baseline EC₅₀ values and validating fungicide performance in plants, my research will aim to strengthen evidence-based management recommendations for growers while building foundational datasets for future genomic analyses.”

“In addition to lima bean, my research program will address several high-priority vegetable pathosystems. In leafy greens, I will investigate white mold of kale caused by Sclerotinia sclerotiorum, focusing on biosurveillance of pathogen airborne spore detection to make informed decision of fungicide applications. In solanaceous crops, I will examine the distribution and diversity of Phytophthora capsici on tomato, including mating type characterization and baseline sensitivity to oomycete-targeted chemistries. For cucurbits, I will monitor downy mildew outbreaks associated with Pseudoperonospora cubensis and evaluate cultivar susceptibility and preventative fungicide programs under greenhouse conditions. The primary objective will be to establish robust baseline datasets on pathogen diversity, fungicide sensitivity, and host–pathogen interactions. These data will directly inform Extension recommendations and will provide practical, science-based guidance to South Carolina growers. Looking ahead, the long-term vision of my program includes whole-genome sequencing, comparative genomics, and transcriptomic analyses to identify virulence determinants and track pathogen population dynamics. By linking phenotypic characterization with genomic insight, my research program will contribute to molecular diagnostic development, fungicide resistance monitoring, and effector-informed breeding strategies.”

“At PDREC, my Vegetable Pathology Lab will remain committed to delivering precise, impactful research supporting specialty crop producers while building the molecular and epidemiological framework needed to confront future disease challenges of vegetables of Southeast US.”

The combination of warmer temperatures and stress from dry conditions for rainfed fields is a reminder that if our fields have some history of stem rot/white mold disease (Figure 1), we can proactively protect them during our earlier fungicide applications. This can be as simple as adding tebuconazole in with the 45-day spray or coming in earlier 30/35 DAP with Elatus/Excalia/Lucento, or we may also consider swapping fungicides during latter applications for increased control. Not all fields need the extra attention, but it is a helpful tool at our disposal where we are looking for additional management. Likewise, earlier applications are less subject to canopy interference of spray penetration/ground deposition. Rain is our friend for many things including fungicide wash in, but its contribution rapidly drops off with increasing time after application. Two days after an application, rain will help some but is at that point more modest than monumental. Rain-in the day of application or a day after improves wash in, but this often comes at the expense of foliar leaf spot coverage/control. A persnickety predicament, or rather, a reminder of fine tuning one way or another. If we are coming due for an application where soil disease control is a priority and we can wait a day to two/three days to take advantage of a coming rain we can consider doing so, keeping in mind the suggestive rather than absolute nature of forecasts. This is more helpful later in the season when canopy size is larger. However, an application without rain is better than no application at all. We cannot wait indefinitely to take advantage of a possible rainfall, and we do well to keep in mind the importance of effective leaf spot management at the same time, as both our soil and foliar diseases are best managed in a preventative rather than reactive manner.

From work across eleven experiments conducted from 2015 to 2023 evaluating the efficacy of several different fungicides for stem rot/white mold control, maximum label rates of benzovindiflupyr plus azoxystrobin (Elatus) and inpyrfluxam (Excalis) were estimated as conferring the greatest returns over the chlorothalonil-only control (Bravo-only).

Control efficacy of maximum labeled rates of flutolanil (Convoy) and prothioconazole plus tebuconazole (Provost Silver) were also effective in managing this disease. While an application of tebuconazole alone for soil disease control was among the most efficient in terms of % stem rot control per fungicide product application cost, that active ingredient also conferred the least total amount of control at its maximum label rate. This makes tebuconazole an important and efficient fungicide to keep in our overall disease management programs, but other fungicides or tank mix combinations are capable of providing greater control where we could benefit from it due to specific fields having a history of increased white mold disease pressure, weather conditions during the year favoring its development, or application windows preceding a timely rain or irrigation allowing us to capitalize on increased efficacy.