Q&A with Erfan Vafaie, Entomologist
Erfan Vafaie currently works for the Texas A&M AgriLife Extension Service center based in Overton, Texas, helping growers adopt integrated pest management practices for insect pest management. He is originally from Canada, where he earned his undergraduate degree at Western University and his master’s in integrated pest management at Simon Fraser University. He has been living and working in East Texas since December 2013 and just completed his PhD through Texas A&M University, studying the use of two predators to manage whitefly populations in greenhouse poinsettias. Vafaie spends his days conducting research to determine how well (or not well) insecticides work against different pests; working on management strategies for new invasive pests; and providing resources, training, and education to growers on how to adopt timely and effective integrated pest management strategies.
World Tomato Society: Tell us a little about yourself and what you do.
Erfan Vafaie: Most of my research projects and work are listed on my website, Six-Legged Aggie, including a citizen science project aimed at collecting data on the attractiveness of commercially available flowering plants to different types of pollinators, strategies to manage a relatively new invasive insect (crapemyrtle bark scale), and biological control in greenhouse horticultural production. I also publish two fortnightly podcasts: Talking Bugs and Jolly Green Scientists. In the former, I interview entomologists and discuss some of their most recent research. In the latter, I cohost with a horticulturalist and we digest scientific and pop-sci articles related to the green industry. They are both fun and can be found on pretty much any podcast platform. Shameless plug!
WTS: What led you to entomology?
EV: Fame, fortune, and glamour! Well, not quite. Many entomologists interviewed on my podcast Talking Bugs did not consider entomology as a career from an early age. It’s often a career that people get intrigued with, usually in upper years in university, and the great number of opportunities keep them engaged. The story is similar for me as well. In the second and third years of my undergraduate degree, I took ecology and chemical ecology, instructed by Dr. Jeremy McNeil at Western University, where I first learned about how plants and insects can communicate with chemicals in the air. Dr. McNeil provided examples of what’s known as herbivore-induced plant volatiles (HIPVs), molecules that the plant releases when being eaten by an herbivore that is often used by predators to find suitable prey. In other words, the plant is recruiting predators, either advertently or inadvertently, to help defend itself! During those courses, I was not only completely fascinated with insects but also learned about their application for a very relevant and essential need: protecting agriculture. From then on, I had no difficulty finding summer jobs, part-time work, and other opportunities to pursue a career in entomology.
WTS: What is the most interesting thing you’ve learned during your research, studies, or career?
EV: Every few weeks, I learn something new in entomology that blows my mind. Insects are the most diverse organisms on the planet, so there’s no lack of surprises! Two subjects I find particularly fascinating are parasitic wasps and insect endosymbionts.
Parasitic wasps, also known as parasitoids, lay eggs on or inside another species. The offspring of the parasitic wasp must consume the other living species to continue its life cycle. Think of the movie Alien, but it’s fact instead of fiction, and it happens on very small scales in your backyard every day. Some examples of parasitoids include cicada killers, tarantula hawks, and cuckoo wasps. Most insects that have been described have one if not more parasitic wasp species that attack them, which has led some to think that parasitic wasps may be the most diverse animal group on the planet. It gets much more interesting when learning about how the parasitoid egg interacts with its non-mother host. In aphids, for example, the parasitoid egg releases proteins that convince the aphid that the parasitoid egg is just another aphid embryo, which ultimately ensures the parasitoid egg receives good nutrients inside the aphid’s body instead of being attacked by the immune system. Things get even more interesting when we talk about secondary parasitoids—a.k.a. hyperparasitoids—which lay eggs in or on parasitoids! There are even tertiary parasitoids! But we shan’t go further down that rabbit hole. I think you get the point.
Insect endosymbionts are bacteria that live inside insects and have a mutually beneficial relationship with their insect host. These bacteria can actually provide some beneficial characteristics to the insect, such as the ability to produce essential amino acids (Buchnera aphidicola), make all offspring in some parasitoids become asexual females (Wolbachia in Encarsia formosa), influence insecticide resistance (Wolbachia and Rickettsia), affect the plant’s ability to “recruit” predators, or even provide resistance toward some parasitic wasps (Hamiltonella defensa). These endosymbionts can be transferred between insects either through offspring (vertical transmission) or by some kind of contact, such as feeding on the same source (horizontal transmission). So, in some ways, you can have very rapid changes in characteristics, such as insecticide resistance, without typical natural selection processes. Changes can happen rapidly within a single generation of insects because the bacteria within them can be driving the change.
WTS: Got another interesting story to share?
EV: I had a really neat opportunity to go on a two-week project to English Guyana through the USDA USAID Farmer-to-Farmer Program. The purpose of this project is to provide some international expertise to local farmers. My entire first week was spent learning about farming practices, identifying the challenges they face, analyzing insects, and finding what kinds of resources they have available, such as insecticides, insect traps, and screening materials for excluding insects. I spent every second of the weekend analyzing photos, reading literature, and preparing presentations and training materials to deliver to the same growers during week two. It was a very intense but highly rewarding experience. Being able to work with and assist subsistence farmers was one of my strong motivations for going into this field, so it was a great opportunity. I wrote articles on a blog about my experience there.
WTS: Is there a certain insect that you have found commonly difficult to recognize or that’s often confused with another species?
EV: One of the most common misidentifications I get are ladybird beetle pupae and exuviae. Most people associate ladybird beetles—a.k.a. ladybugs—with the yellowish-to-red beetle with many to almost no black spots. Very few people recognize the immature stages of ladybird beetles, let alone the pupal stage, where they are transforming from the larvae to an adult. It also doesn’t help that ladybird beetles appear to pupate close together, making them seem like they are a group of pestiferous insects eating away at your plant! I get calls and emails asking me how to control these “pests” before even getting an ID. So, if you see these larvae or exuviae on your plants, they aren’t bad! They are actually good. Ladybird beetles are non-picky predators, feeding on many soft-bodied insects, such as aphids, mealybugs, and whiteflies. In general, the immature stages of insects are a bit trickier to identify than the mature stages. The University of Kentucky has an informative publication on some general characteristics of immature insects that can help one narrow them down to some general groups.
WTS: What signs indicate that there is a pest problem?
EV: In general, we consider that there’s a pest problem when the plant starts to show undesirable symptoms, such as leaves yellowing or curling, chewing damage, wilting, damaged fruit, or reduced yield. I specifically highlighted “undesirable,” because symptoms that we may consider problematic can be very context dependent: Are the tomatoes your livelihood or hobby? Without going into specifics about setting a threshold for when a pest can be considered problematic, it’s important to recognize some of the basic types of damage that insects cause, where the insects hide, and their general life cycle. Some of the main insect pests of tomatoes may include whiteflies, aphids, leaf-footed bugs, stink bugs, and caterpillars.
Whiteflies and aphids are both sucking insect pests, which cause a discoloration of the leaves. Some other insects, such as two-spotted spider mites and thrips, can cause similar damage, which can also occur on tomatoes in Texas. Whiteflies and aphids both produce honeydew as waste—a sticky, shiny substance that can often be seen on the topside of the leaves. Whiteflies have been swarming outside in large numbers since early October; however, pay attention to the undersides of leaves to see whether any offspring are actually being produced before panicking and spraying them. It’s also important to note that both whiteflies and aphids can vector viruses of tomato plants, and since neither aphids nor whiteflies adhere to social distancing regulations or wear masks, you may need to intervene with extreme population control measures if tomato plants start to show signs of viruses.
Leaf-footed bugs and stink bugs are also sucking insects, but they do not produce honeydew and are not soft-bodied like aphids and whiteflies. In addition to feeding on leaves, these insects will feed on buds and fruit, causing abortion, deformation, or damage to the actual tomato. In a small garden, these insects are best managed by handpicking and placing them in a bucket of soapy water or sticking them in the freezer.
Caterpillars cause chewing damage. Caterpillars known as cutworms will chew on the base of the stems, especially new transplants, making them topple and break at the bottom. These caterpillars are rather cryptic and nocturnal, making them hard to find during the day. Hornworms, on the other hand, are very large and easy to spot. Hornworms will chew parts of leaves, making symptoms rather obvious. Adult hornworms are commonly referred to as “hummingbird moths,” because their physical and behavioral characteristics resemble those of hummingbirds; so don’t consider them as your sworn enemy!
WTS: What general IPM practices can you recommend, especially for beginners?
EV: Begin by learning about the different kinds of insects you may expect to find on tomatoes, how to identify them, the kind of damage they cause, and how many you can tolerate on a tomato plant. Don’t worry about specific species names to start. General groupings, such as those mentioned above, are a good start! Search through extension resources—that is, add “extension” key term to a Google search—to find reputable sources. There are lots of websites that may claim “natural” or “holistic” information that aren’t always backed by research. Next, record some of the insects you actually see on your tomatoes. Don’t jump the gun on management at the first sign of the insect. Make observations about what happens with low insect densities over time. In some situations, the insect may be a pest that proliferates rapidly but then crashes as they compete with each other and get eaten by predators. In other scenarios, their numbers may not even increase because the predators are already there! Learn about the ecosystem in your own backyard and which insects become problematic without your intervention. [Editor’s note: You can also find this info on our webpage at (insert hyperlink).]
WTS: Are there plants that you recommend for intercropping with tomatoes to reduce pests?
EV: The idea of intercropping is to cultivate plants that will do one or more of the following: divert a specific pest from your crop of interest, attract predators or other beneficial insects, or act as a barrier to pest movement between rows of crops. To my knowledge, no silver bullet candidate has been found for intercropping with tomatoes; the pests and habitat context vary too much between different people’s gardens. In field tomato production, researchers were able to decrease whitefly populations when monoculture tomatoes were intercropped with either perennial peanuts or coriander. However, I wouldn’t bet any money on this intercropping method working effectively in anyone’s garden. In general, diverse plots with plants that are in bloom from the beginning to the end of the season can help by providing sources of pollen and nectar to promote predator and parasitoid populations.
WTS: Is there an insect you find to be particularly difficult to get rid of? Any tips or tricks you can recommend?
EV: Leaf-footed insects and stink bugs can be particularly difficult, especially because of their sheer size and apparent lack of predators (compared to smaller soft-bodied insects). In a small home garden setting, I typically suggest slipping on some gloves (if needed) and handpicking these insects into a bucket or container of soapy water. Just a few drops of soap can help break the surface tension of the liquid, making the insects actually drown rather than sit on top of it. Alternatively, you can place them in a lidded container and throw the container in the freezer. The cool temperatures in the freezer will put the insects to sleep and eventually kill them from ice formation. Just don’t leave them in there for weeks or you may cause disputes with any roommates or spouses that may occupy the same household.
WTS: What common mistakes have you seen that attract or worsen pest populations in a garden?
EV: Overuse or misuse of insecticides are probably the most common cause of secondary pest outbreaks. We usually go to insecticides for a quick solution to manage our pest problems; however, insecticides sometimes come with unintended consequences. For example, a study showed that a specific class of insecticide, when applied to tomatoes, can cause an increase in two-spotted spider mite populations by decreasing the tomatoes’ natural defenses. One of the most commonly used insecticides in home gardens with the active ingredient carbaryl is frequently cited as causing secondary pest outbreaks by killing many of the naturally occurring predators. For this reason, it’s very important to a) only apply pesticides when it’s really needed and b) use selective insecticides that have low residual toxicity to visiting predators or pollinators. Some examples include insecticidal oils and soaps. Gardeners should be aware that these products can cause plants to “burn” if applied during peak summer days and are most effective when they actually come in contact or cover soft-bodied insects.
WTS: What insect is your favorite to see around crops?
EV: I’m always delighted to find predators and parasitic wasps on plants. Watching them consuming prey makes me think of a mini-alien battle that is going on and being able to witness it is intriguing. One of the predators I’m particularly delighted to see is lacewing larvae. Their sickle-shaped mouthparts penetrate soft-bodied insects, inject digestive fluids in them, and suck them dry. Parasitoids are most easily spotted in their “mummy” stage—basically an empty husk of the host with the parasitoid transforming either within or under the said carcass. Mummies are usually a bit more inflated and quite different in color from the other aphids, so they are both easy and very rewarding to spot.
Lacewing larva consuming an aphid
WTS: Any other advice for gardeners—especially those growing tomatoes?
EV: The fruit, in my opinion, is only half of the “produce” you get from the plant. The other half is learning and gaining an appreciation for the insects that inhabit, feed on, and thrive by your plants being there. By cultivating an area, you are quite literally building gigantic trees from an insect’s perspective, terraforming their habitat to your liking. Remember that not all insects are going to completely destroy your plants and that every single insect has at least one, if not several, interesting facts to learn about them.