Leptoxyphium, an Unusual Sooty Mold

Ornamental sweetpotato leaves with sooty mold at the petiole/blade junction

The sooty mold Leptoxyphium on the underside of an ornamental sweetpotato leaf

This blog is going to be a bit more technical than many of my posts, but I hope you'll find it interesting. A recent sample of ornamantal sweetpotato leaves from a greenhouse showed dark fungal growth at the top of the petiole and on the upper and lower surface of the leaf, just at the point of petiole attachment. The colonies could be scraped off easily, which is typical of sooty molds. The fungus was sporulating freely, with conidia (asexual spores) produced in drops of liquid at the tops of dark synnemata (tiny columns of fungal hyphae).

Synnemata of Leptoxyphium sp. on sweetpotato leaf

Top of a synnema of Leptoxyphium, at 400x

Using Seifert & Okada's key to synnematous hyphomycete genera in the 2011 book "The Genera of Hyphomycetes", the identification was made to the genus Leptoxyphium. The name means "slender sword" in English, possibly referring to the shape of the synnemata, but it is interesting that there are also awl-shaped (subulate) cells around the fringe of the spore-bearing area. This genus is also described on pp. 777-782 of Stanley Hughes's 1976 paper "Sooty Molds" (Mycologia 68(4): 693-820). Leptoxyphium species are a tropical to subtropical sooty molds, and rather unusual in that they often grow in association with glands and glandular trichomes of plants, rather than on insect honeydew. The good news for the greenhouse producer is that while it is an asethetic issue, this fungus is not going to harm the plants.

Meet Our New Vegetable Pathologist

Hello, my name is Lina Quesada (pronounced Lena Kesada in case you were wondering). On March 1st of 2013 I joined the Department of Plant Pathology at North Carolina State University as an Assistant Professor and Extension Specialist for vegetable pathology. I am originally from Bogota, Colombia (not Columbia!) and came to the US in 2006 to work on late blight of potato at the Ohio State University.

Shortly after that I moved to Lansing, Michigan and started a PhD in Plant Pathology at Michigan State University working with Phytophthora capsici, an important pathogen of cucurbits and solanaceous crops. While working on my PhD I fell in love with the boy in the lab next door and married him on 2010, the same year I finished my PhD.

I stayed at MSU and did a postdoc working on cucurbit downy mildew and bacterial canker of tomato. After that I did another postdoc working on corn postharvest diseases caused by Fusarium, a soilborne pathogen that can also affect sweetpotatoes and vegetables. My husband and I moved to NC a few weeks ago and have really enjoyed this beautiful state and its kind people. I am very excited to be here and have the opportunity to work with the clinic and all of you during the next few years to address challenges you have with vegetable diseases. If you need to contact me my information can be found here.  You can follow me on Twitter, Facebook or LinkedIN if you wish and I am in the process of making a lab website that will be posted to the link I just provided to quickly disseminate any findings or materials produced by my program.

The New Bug Guy

Hello everyone! My name is Matt Bertone and I am the new entomologist for the Plant Disease & Insect Clinic. I will be taking over for the now-retired Dave Stephan, a great entomologist with years of encyclopedic knowledge who will not be easily replaced. I do hope to follow in his footsteps, however, and to learn as much as I can about the insects and other animals that affect the daily lives of North Carolinians. But first, let me tell you a little bit about myself.

I was born up North (don’t hold it against me) and lived most of my formative years in Pennsylvania. From a young age I was obsessed with the natural world (see below photo). It started with the usuals like dinosaurs and such, but quickly turned into a passion for insects, spiders and other creepy-crawlers¹. They were so strange and diverse that there was always something amazing to learn.

Only the nerdiest kids know how to draw
a microscope in kindergarten.

After high school I entered college at Salisbury University on the Eastern Shore of Maryland. I had a great time there and took as many zoology courses as I could. There I met many great scientists and was introduced to research studies and continuing to graduate school. I was not aware of the universities that had entomology programs and applied to NCSU on a whim after seeing one of my colleague’s certificates from the department. After applying I was very happy to be accepted and had no idea how wonderful the area, school and people were going to be.

In 2001 I started my master’s work on dung beetles (Scarabaeidae & Geotrupidae) inhabiting cattle pastures in the Piedmont (Salisbury, NC) and coastal plains (Goldsboro, NC) under the advisement of Dr. Wes Watson. The project was great. I was introduced to a charismatic group of insects, researching their seasonality, abundance and diversity, and performing experiments to show how they help fertilize different soils. I was also happy to participate in extension work, since teaching in any format is another passion of mine.

A rolling dung beetle (Melanocanthon bispinatus)
from North Carolina.

In 2004 I began my PhD work under Dr. Brian Wiegmann on the evolution of true flies (Diptera), one of the most underappreciated – yet extremely diverse – groups of animals. I used genetics to see how different groups of the more “primitive” flies, like mosquitoes and midges, were related to one another. It was eye opening to learn the things flies do and I could (and may well in the future) go on and on about them. Needless to say, I found another group to love².

The elephant mosquito (Toxorhynchites), a large and distinctively blue fly, 

is one of the few beneficial mosquitoes. Larvae eat other mosquito larvae and adults do not bite. This male was sucking goldenrod nectar in Garner, North Carolina.

Following my degrees I have worked on various projects including a computer-readable glossary for the anatomy of wasps, bees and ants (Hymenoptera) and a citizen science project on the arthropods (insects, spiders and relatives) that are found in Triangle homes (a project through NCSU and the NC Museum of Natural Sciences).

Now I’m here in the clinic! I am very excited to help people find out what little leggy things are on their plants, eating their crops, and inside their homes. Please feel free to send photos or specimens to the clinic. I will do my best to get an ID, so that a specialist can recommend the proper action. All said, I hope to serve science and the citizens of North Carolina well in this position!

Other facts about me:

• I am a huge (literally and figuratively) insect geek, competing in many insect quiz bowls (Linnaean Games) during my time at NCSU
• I am an avid insect macrophotographer (my Flickr) and graphic designer
• I enjoy music, movies, games and cooking
• Last but certainly not least, I have an amazing wife and daughter, and a baby on the way (as well as two dogs)

¹ I also love reptiles, amphibians, fish, and many other groups of organisms (even plants!)
² I highly suggest anyone interested in flies read Harold Oldroyd’s captivating tales in The Natural History of Flies – it is very easy to read except for some scientific names (which you can just pretend are like the variously named creatures from Tolkien or Dr. Seuss!)