If you're a gardener, you're aware that nematodes are "microscopic, eel-like roundworms" and that "most troublesome species in the garden are those that live and feed within plant roots most of their lives and those that live freely in the soil and feed on plant roots," according to the UC Integrated Pest Management Program website on nematodes.
If you attended the ninth annual UC Davis Biodiversity Museum Day, you learned hands-on information from nematologists Christopher Pagan and Corwin Parker, doctoral students who study with major professor Steve Nadler, professor and chair of the UC Davis Department of Entomology and Nematology.
Pagan and Parker held forth at their display in the Academic Surge Building, where they fielded questions about nematodes and showed specimens to the visitors. The nematode collection was one of 13 museums or collections featured at the Biodiversity Museum Day, always held the Saturday of Presidents' Weekend.
Many visitors asked what nematodes are, they related.
Other common questions asked:
- Do I have nematode parasites?
- How dangerous are nematode parasites/can they kill you?
- How long do they live?
- How many species ofode are there?
- Are soil nematodes good or bad for my garden?
Parker shared some of the answers:
Do I have nematode parasites?
Probably not unless you've been traveling a lot. The most common nematode parasite of humans in the US is pinworm which most children get, but not adults. Worldwide however, hundreds of millions of people are infested with parasites including Ascaris, hookworm, and whipworm.
How dangerous are nematode parasites/can they kill you?
Nematode parasites are usually relatively benign unless you have a lot of them. Potentially fatal exceptions do exist, such as zoonotic infections of rat lungworm and raccoon roundworm, but those are rare.
How long do nematodes live?
It depends on the species and life history. Parasitic nematodes can live for a long time, while most free-living nematodes have relatively short lifespans. Some nematodes that live in harsh environments such as deserts can extend their lives by going into a state of suspended animation until environmental conditions are optimal.
How many species of nematode are there?
More than 30,000 described species, but it's estimated there are more than 1 million total.
Are soil nematodes good or bad for my garden?
Most soil nematodes are neutral to beneficial for your garden. They're an integral part of the soil ecosystem and help with nutrient cycling, and some kill of root-feeding insects. There are some plant-parasitic nematodes, but most don't cause significant damage.
UC Davis Biodiversity Museum Day
In addition to the nematode collection, the UC Davis Department of Entomology and Nematology showcased the Bohart Museum of Entomology and the Häagen-Dazs Honey Bee Haven. Other participating museums or collections at this year's Biodiversity Museum Day: the Botanical Conservatory, Arboretum and Public Garden, California Raptor Center, Museum of Wildlife and Fish Biology, Paleontology Collection, Phaff Yeast Culture Collection, Viticulture and Enology Culture Collection, Anthropology Museum, Center for Plant Diversity, and Marine Invertebrate Collection.
If you missed it, calendar the 10th anniversary Biodiversity Museum Day in 2021. The event always takes place the Saturday of Presidents' Day Weekend.
Sounds like a great story, right?
Make that great cookies.
They weren't there to present their research on nematodes, aquatic insects or pollinators. They were there to enjoy some camaraderie at the UC Davis Department of Entomology and Nematology's holiday party, and...drum roll...they won the top prizes in the cookie contest.
- Best chocolate cookie: Aquatic entomologist Sharon Lawler, professor, UC Davis Department of Entomology and Nematology, for her recipe, "Dirty Drunk Snowballs"
- Best non-chocolate cookie: Nematologist Steve Nadler, professor and chair, UC Davis Department of Entomology and Nematology, for his Internet-modified recipe, "Cranberry Orange Cookies"
- Best decorated cookie: Community ecologist Rachel Vannette, assistant professor, UC Davis Department of Entomology and Nematology, for her "Stamped Citrus Shortbread" recipe from the New York Times
William Tuck, academic personnel specialist in the Phoenix Cluster, which serves the Department of Entomology and Nematology and the Department of Plant Pathology, coordinated the event and awarded $25 Amazon gift cards to the winners.
The proof of the pudding? Empty containers.
Want to make the recipes? They shared!
Dirty Drunk Snowballs
By Sharon Lawler
1 box Trader Joe's Mini Dark Chocolate Mint Stars
1/4 cup dark rum (white rum or bourbon will also work)
1/4 cup confectioner's sugar
Grind up the cookies in a food processor or blender until pretty fine but with some texture left. Stir enough dark rum so that the crumbs hold together well, but stop before it gets soggy. Let the mix sit for 15 minutes or so. Sift the confectioner's sugar into a bowl. Roll the mix into small balls, and then roll them in the confectioner's sugar.
Cranberry Orange Cookies
By Steve Nadler
1 cup unsalted butter, softened
1 cup granular white sugar
1/2 cup brown sugar (packed)
1-1/2 teaspoons grated orange zest
5 tablespoons orange juice
2-1/2 cups all-purpose flour
1/2 teaspoon baking soda
1/2 teaspoon salt
2 cups orange-flavored dried cranberries (Trader Joe's)
1-1/2 cups confectioner's sugar
- Use a food processor to chop the dried cranberries
- Preheat oven to 375 degrees F.
- In a large bowl, blend together the butter, white granular sugar, and brown sugar until smooth.
- Whisk the egg in a small bowl, then mix into the large bowl.
- Add 1 teaspoon of orange zest and 2 tablespoons of orange juice into the large bowl and mix.
- In a separate bowl, mix together the flour, baking soda, and salt.
- Stir the flour mixture from step 6 into the large bowl.
- Mix in the chopped cranberries, working to distribute them evenly.
- Drop cookie dough mixture (rounded tablespoon) on ungreased cookie sheets. Space them 2 inches apart.
- Bake for about 12 minutes in the preheated oven (375 F). The edges will begin to turn golden brown when ready.
- Remove cookies from sheets and cool on wire racks.
- In bowl, mix 1/2 teaspoon orange zest, 3 tablespoons of orange juice, and the confectioner's sugar until smooth. Brush on the tops of the cooled cookies. Let dry.
By Rachel Vannette
Recipe from New York Times
For the Cookies
- 2 cups/255 grams all-purpose flour, plus more as needed
- ⅓ cup/45 grams cornstarch
- ½ teaspoon kosher salt
- 1 cup/225 grams unsalted butter (2 sticks), softened
- ½ cup/100 grams granulated sugar
- 1 orange (preferably tangelo)
- 1 lemon
- ½ teaspoon vanilla extract
- ½ teaspoon lemon extract
- ¾ cup/75 grams sifted confectioners' sugar
- 1 tablespoon melted butter
- 1 tablespoon fresh orange juice, plus more as needed
For the Glaze:
- 3/4 cup/75 grams sifted confectioners' sugar
- 1 tablespoon melted butter
- 1 tablespoon fresh orange juice, plus more as needed
- Prepare the cookies: Add flour, cornstarch and salt to a medium bowl, and whisk to combine. Set aside.
- Combine butter and granulated sugar in the bowl of a stand mixer fitted with the paddle attachment. Zest half the orange and half the lemon directly into the bowl. Reserve the lemon and orange for the glaze. Cream the butter mixture on medium-high speed until light and fluffy, 2 to 3 minutes. Add vanilla and lemon extracts and beat on medium speed until well combined, scraping the bowl a few times as needed.
- Add the flour mixture to the butter mixture and beat on low speed just until combined. Scrape the bowl and fold a few times to make sure everything is well combined. Wrap dough in plastic wrap, flatten into a disk, and chill until firm, at least 1 hour, and up to 3 days.
- Heat oven to 350 degrees. Cut dough in half and let one piece warm up for 30 minutes if it has chilled longer than an hour. Return the other half to the refrigerator. Portion the dough into pieces roughly the size of walnuts (a scant 2 tablespoons/about 35 grams), then roll each piece into a ball between your hands. One at a time, dip a ball of dough into flour and set on work surface. If dough balls soften too much, return them to the refrigerator to firm up for a few minutes. You want it cool, but malleable. Dip cookie stamp in flour, and press down on the ball of dough until it is about 1/4-inch thick. Remove stamp. (If dough sticks to stamp, carefully peel it off. Don't worry about excess flour as you will brush it off after chilling.) Trim the edges using a 2-inch cookie cutter, and transfer dough rounds to 2 parchment- or silicone mat-lined baking sheets, arranging them about 1 1/2 inches apart. Repeat with remaining dough.
- Once you have stamped out all the cookies, knead together the scraps to make a few more. Chill in the freezer until very firm, about 10 minutes. When cold, brush off any excess flour with a dry pastry brush.
- Bake until cookies just start to turn golden underneath, 12 to 14 minutes, switching the baking sheets from front to back and top to bottom halfway through baking time.
- Make the glaze while the cookies bake: Zest the remaining skin from the reserved lemon and orange into a small bowl. Add the confectioners' sugar, butter and orange juice and whisk until smooth. If glaze is too thick, add more orange juice. If it is too thin, add more confectioners' sugar. It should be the consistency of thin custard.
- Let the cookies cool for a few minutes on the baking sheets, and transfer to a wire rack set over a parchment- or wax paper-lined baking sheet. Pick up a cookie, and using the back of a small spoon, spread a generous teaspoon of glaze on a cookie, letting any excess drip onto the next cookie. Repeat until all the cookies are glazed. Cool completely. Cookies will keep in an airtight container at room temperature for up to 1 week.
The U.S. Department of Agriculture's (USDA) Agricultural Research Service (ARS) and Pheronym, a company in Alachua, Fla., that develops and produces nematode pheromones, have announced plans to send nematodes (small round worms) to the International Space Station as early as this year.
The news, announced Feb. 20 on the ARS website, may have been overlooked by many ("What's a nematode?") but not by nematologists and other scientists.
The headline: "Starship Nematode."
"The mission represents a look into the future where food crops will be grown in space," according to writer Sharon Dunham. "The goal is to develop environmentally friendly methods for space travel that are not harmful to humans," she wrote. "This will be the first biological control experiment in space."
She went on to relate that experiment will "test the movement and infection behavior of beneficial nematodes (also called entomopathogenic nematodes or EPNs) that control a wide array of insect pests in agriculture." ARS research entomologist, David Shapiro-Ilan at the Fruit and Tree Nut Research Station in Byron, Ga., is co-project director of the experiment.
Nematodes, Dunham said, are "environmentally friendly alternatives to broad spectrum chemical insecticides and are also safe to humans and other nontarget organisms. One fascinating aspect of the EPN biology is that the nematodes kill their insect pest hosts with the aid of symbiotic bacteria that are carried in the nematode gut."
Nathan Augustus Cobb (1859-1932), the "father of nematology in the United States," had this to say about a world without nematodes.
"In short, if all the matter in the universe except the nematodes were swept away, our world would still be dimly recognizable, and if, as disembodied spirits, we could then investigate it, we should find its mountains, hills, vales, rivers, lakes, and oceans represented by a film of nematodes. The location of towns would be decipherable, since for every massing of human beings, there would be a corresponding massing of certain nematodes. Trees would still stand in ghostly rows representing our streets and highways. The location of the various plants and animals would still be decipherable, and, had we sufficient knowledge, in many cases even their species could be determined by an examination of their erstwhile nematode parasites."
In fact, nematodes seem totally destructible.
Congratulations to the world's top 10 entomology departments, as listed today (April 3) in the long-awaited Times Higher Education's Center for World University Rankings.
The rankings show the University of Florida's Department of Entomology and Nematology as No. 1.
In California, the University of California, Riverside, is ranked No. 2, and UC Davis, No. 7. That's not a national statistic, but a global one. Kudos!
- University of Florida, 100 score
- University of California, Riverside, 95.23
- Cornell University, 91.95
- Kansas State University, 91.29
- North Carolina State University, 90.88
- Michigan State University, 90.74
- University of California, Davis, 89.88
- University of Georgia, 88.98
- Nanjing Agricultural University, China, 86.74
- University of São Paulo in Brazil, 86.74
The departments were scored in five peformance areas: Teaching (the learning environment); research (volume, income and reputation); citations (research influence); international outlook (staff students and research) and industry outcome (knowledge transfer). View the World University Rankings methodology here.
The UC Davis Department of Entomology and Nematology, based in Briggs Hall, is led by chair Steve Nadler and vice chair Joanna Chiu.
Interested in insect science? Be sure to visit the UC Davis Department of Entomology and Nematology's displays at the 103rd annual campuswide Picnic Day on Saturday, April 22. Last year thousands of visitors flocked to Briggs Hall; Bohart Museum of Entomology, home of nearly eight million insect specimens; and the Sciences Laboratory Building (nematology display). Here's what the department did last year. More information pending!
And it's an enemy to be reckoned with, Extension apiculturist Eric Mussen told students in the UC Davis "Biology of Parasitism" class, taught by forensic entomologist Robert Kimsey and nematologist Steve Nadler, Department of Entomology and Nematology.
Guest-lecturing at a special session held at the Harry H. Laidlaw Jr. Honey Bee Research Facility, UC Davis, Mussen talked about the varroa mite--its history, biology, damage and control methods--and then opened several hives at the apiary.
The Varroa destructor, a native of Asia, is now found in hives throughout the world except in Australia. It was first detected in the United States in 1987.
The eight-legged reddish-brown parasite, about 1–1.8 mm long and 1.5–2 mm wide, is a blood sucker that's difficult to control, Mussen said. Mites transmit viruses (there are now some 22 named RNA viruses) that can wipe out a hive. A familiar mite-transmitted disease that beekeepers see is DWV or Deformed Wing Virus. Mites are also known lowering the protein level of a bee's blood, and reducing its weight and life span.
Mussen said that mites spread from colony to colony by phoresy (animal-to-animal transport). They ride on flying drones (males) and adult worker bees (females). They also spread changing hosts on flowers.
"A mite enters a honey bee cell just before or during the time it is being capped," Mussen said. "It feeds on older larva or prepupa. Sixty hours later, the mite lays its first egg. The egg will hatch in about 24 hours."
"The number and release of offspring depend on the length of the pupal stage. The queen is pupa for 8.5 days (no mites). The worker is pupa for 12.5 days (1.3 mites) and the drone is pupa for 14.7 days (3 or 4 mites)," he said. Thus, due to the longer time required for drone development, drone pupae get the worst of it.
"When maturing, the newly emerged mites climb onto adult bees and feed by puncturing the intersegmental membranes and sucking the bee blood," Mussen related. "Often these are nurse bees that stay around the brood nest. Sometimes the hosts are drones and older foragers that are flying from the hive every day. Eventually the new mite climbs off the nurse bee onto a comb in the brood nest and enters a cell. The reproductive cycle starts and within 6 days, 44 percent of the young mites have moved into the brood cells; within 12 days, 69 percent of the mites are in the brood cells; and within 24 days, 90 percent of the mite are in the brood cells."
"If there is no brood, the mite has to feed on adult bee blood every six days or so to remain alive," Mussen said. "Mite life expectancy in summer is around 60 days; bees about 42 days. Mite life expectancy in the winter is up to 9 months; bees about six months."
Mussen also discussed how to detect mite infestations through non-chemical and chemical methods, and listed chemical treatments being used throughout the nation. Mites are developing resistance to a few chemical treatments, he pointed out. And, some of the chemical treatments not only kill the mites, but damage or kill the queen and the brood.
Beekeepers who try to go organic, figuring that "if the bees can't make it on their own--if they're not fit--let them die" are really doing a disservice to neighboring beekeepers, Mussen said. The mite will overrun a colony and then infest other colonies.
Public Enemy No. 1--definitely a force to be reckoned with.