Today was a Monarch Kind of Day...in Vacaville.
When Art Shapiro, UC Davis distinguished professor of evolution and ecology, searched for butterfly species today at one of his field sites--Gates Canyon in Vacaville--he spotted not one, but two monarchs.
He spotted them separately, both near the bottom of the Brazelton property, and recorded "Two Danaus plexippus: one large, fresh-looking male; one small, unfresh-looking female."
Shapiro, who maintains a research website, Art's Butterfly World (he's monitored the butterfly population in central California since 1972), knows just how scarce monarchs are this year.
Yes, they are. In the fall of 2016, we'd see seven or eight monarchs at a time flutter in for nectar or lay eggs on our milkweed in our Vacaville pollinator garden. This year they're as scarce as the proverbial hen's teeth. However, over the last two weeks, they're starting to appear, one sighting at a time, one monarch a day. They are mostly huge, fresh-looking males seeking nectar from our patch of Mexican sunflowers (Tithonia). A few are females that head over to the tropical milkweed or Tithonia. Solo sightings.
But today was a Monarch Kind of Day.
Around noon, two monarchs arrived at the same time and they both sipped nectar from the Tithonia at the same time. In tandem. Inches away.
It was a Monarch Kind of Day.
The insect, a native of Asia, was first detected in the United States (Palm Beach County, Florida) in 1998, and California (San Diego County) in 2008. HLB, the bacterial disease that it transmits, was first detected in Florida in 2005, and in California (Hacienda Heights, Los Angeles County), 2012.
“The ACP has the potential to establish itself throughout California wherever citrus is grown,” according to the California Department of Food and Agriculture (CDFA).
Now an international team of scientists, led by chemical ecologist Walter Leal of the University of California, Davis, has discovered a new lure or male attractant that's more efficient and effective than the current trap surveillance system of yellow sticky traps.
“Our newly discovered lure captures an average of three times more ACP than the current trapping system, the sticky yellow traps,” said Leal, a distinguished professor in the Department of Molecular and Cell Biology and a former chair of the Department of Entomology and Nematology. “And it works in areas with low population densities. This is particularly important in California, because HLB is already established in urban areas and, therefore, trap surveillance systems are at a premium.”
The research, “Laboratory and Field Evaluation of Acetic Acid-Based Lures for Male Asian Citrus Psyllid, Diaphorina citri, is published today (Sept. 9) in Scientific Reports. It can be accessed free online at https://www.nature.com/articles/s41598-019-49469-3.
The 16-member team, which includes scientists from Brazil and Costa Rica and Benjamin Lehan of California State Polytechnic University, Pomona, wrote in their abstract: “Lures are much needed for improving ACP trapping systems for monitoring populations and surveillance. Previously, we have identified acetic acid as a putative sex pheromone and measured formic acid- and propionic acid-elicited robust electroantennographic responses. We have now thoroughly examined in indoor behavioral assays (4-way olfactometer) and field tests the feasibility of these three semiochemicals as potential lures for trapping ACP. Formic acid, acetic acid, and propionic acid at appropriate doses are male-specific attractants and suitable lures for ACP traps, but they do not act synergistically.”
“An acetic acid-based homemade lure, prepared by impregnating the attractant in a polymer, was active for a day,” they wrote. “A newly developed slow-release formulation had equal performance but lasted longer, thus leading to an important improvement in ACP trap capture at low population densities.”
“The disease has ravaged the citrus industry in China and Brazil,” said Leal, a native of Brazil. “In Brazil, about one-fourth of the citrus trees in the state of São Paulo has been eradicated since 2004 as part of an HLB control strategy. Florida has also sustained severe losses.
Now the disease threatens California's citrus growers “Of note, 1,100 findings of HLB in urban, but not in commercial orchards, suggest that the disease is already established in urban areas in California,” the scientists wrote. “Monitoring ACP populations is essential for integrated vector management and, more importantly, for surveillance. One of the challenges for abatement personnel in areas of low ACP densities is to capture the vector to determine infection status so that control strategies can be implemented before HLB is spread. Therefore, the development of trapping systems is at a premium, particularly the discovery of lures for enhancing ACP captures in areas of low populations.”
Earlier, an international team of scientists led by Leal identified the sex pheromone of the Asian citrus psyllid. Leal, a fellow of the Entomological Society of America and the Entomological Society of Brazil, announced the discovery, encompassing six years of research, at the 10th Annual Brazilian Meeting of Chemical Ecology in Sao Paulo in December 2017. (See Bug Squad blog)
Pheromones and other semiochemicals are widely used in agriculture and medical entomology. “Growers use them as lures in trapping systems for monitoring and surveillance, as well as for strategies for controlling populations, such as mating disruption and attraction-and-kill systems,” Leal noted.
In response to the ACP invasion in California, the CDFA has launched an extensive monitoring program to track the distribution of the insect and disease. They check yellow sticky traps in both residential areas and commercial citrus groves, and also test psyllids and leaf samples for the presence of the pathogen.
Survey methods for ACP include visual inspections; sweep netting, and placement of yellow sticky traps in trees in citrus nurseries, commercial citrus-producing areas and residential properties throughout the state, according to the CDFA. They also place sticky traps in California fruit packing houses, specialty markets, retail stores and airports that receive such produce from areas known to be infested with ACP.
CDFA has set up a hotline at (1-800-491-1899) for residents to report suspicious insects or disease symptoms in their citrus trees.
What are the odds?
Here you are, standing in the garden section of a home improvement store, and you select a tropical milkweed to purchase. You place it on the ground and admire the brilliant yellow blossoms and luxurious green foliage. It's the best of the best. Just as you're about to pick it up and place it in a cart, a monarch lands on it and begins laying eggs.
What are the odds?
That happened to us around Wednesday noon, Sept. 4 in Vacaville as we were purchasing an end-of-the-season Asclepias curassavica.
Most likely, the plant had been in the nursery since last spring, as it was root-bound. We took it home, replanted it in a larger pot, and set it in the sun. Milkweeds like full sun. And monarchs go where their host plant is, whether it be in the wild, in your backyard, in your city park, or in a garden section of your local home improvement store.
Hopefully, the monarch eggs will hatch and this tropical milkweed will yield some caterpillars, chrysalids and adults.
Ironically, we found a monarch laying eggs in the garden section of a home improvement store!
Said entomologist David James of Washington State University, Pullman, who researches migratory monarchs: "That's an amazing story...selecting your milkweed and then having a female come over and deposit a few eggs for you!"
As an aside, as we were purchasing the milkweed, I casually asked the clerk at the check-out line "Have you seen any monarchs here?"
"Not in HERE," she said, surprised I would ask such a question. She tallied up the sale as "Mama Monarch" fluttered around her nursery, unnoticed, laying the next generation.
Curiously enough, a family member recorded a monarch laying eggs in the garden section of that same store the day before. About the same time. Maybe the same monarch. (See YouTube video)
Butterfly guru Art Shapiro, UC Davis distinguished professor of evolution and ecology, who has monitored all butterfly populations in the central valley for more than four decades and publishes his research on a website, says that “this is the biggest milkweed year in northern and central California in living memory. Speciosa is up to 5' tall and some fascicularis almost as big, and both are covered with both genera of Lygaeids (milkweed bugs), plus both oleander and gray aphids. But Monarchs only showed up here about two weeks ago! Lots of milkweed, no Monarchs to use it. I have seen 10 Monarchs in 2019 and have not seen a wild larva since 2017, and I am afield 260 days a year.”
Sometimes life just isn't fair. Entomologist Lynn Kimsey, director of the Bohart Museum of Entomology and professor of entomology at UC Davis, commented “Weirder and weirder. They still haven't found MY milkweed.”
When we last left Ms. Mantis, a female Stagmomantis limbata residing in our verbena patch, she was munching on a honey bee.
A successful ambush stalker, she was.
But not always.
Her plan to take down a duskywing butterfly, genus Erynnis, didn't go so well.
The butterfly, foraging on the blossoms, touches down near the predator, unaware of the trouble that could lie ahead.
The predator and the prey. The skillful hunter and the unsuspecting prey. Ms. Mantis is poised, ready to strike. The butterfly flutters away in the nick of time.
It will live to forage another day.
The mantis? It will live to hunt another day.
They manage to find us, don't they? Even when we're doing our best to try to avoid them!
It's not so well-known that mosquitoes, both male and female, frequent plants to feed on nectar for energy.
And now UC Davis chemical ecologist Walter Leal and scientists Fangfang Zen and Pingxi Xu of the Leal lab have discovered that the odorant receptors from the southern house mosquito, Culex quinquefasciatus, and the yellow fever mosquito Aedes aegypti, are sensitive to floral compounds.
The manuscript: "Odorant Receptors from Culex quinquefasciatus and Aedes aegypti Sensitive to Floral Compounds."
The team, led by Leal, a distinguished professor in the Department of Molecular and Cellular Biology and a former chair of the UC Davis Department of Entomology, cloned the genes of several odorant receptors from the mosquitoes and tested them, using egg cells of Xenopus toads. They exposed the cloned receptors to different scent chemicals.
"We are delighted to find out how mosquitoes smell plant-derived compounds and are repelled by them," Leal said. "These findings may lead to the discovery of better repellents from natural sources."
"Mosquitoes rely heavily on the olfactory system to find a host for a bloodmeal, plants for a source of energy and suitable sites for oviposition," the scientists explained in their abstract. "Here, we examined a cluster of 8 odorant receptors (ORs), which includes one OR, CquiOR1, previously identified to be sensitive to plant-derived compounds. We cloned 5 ORs from Culex quinquefasciatus and 2 ORs from Aedes aegypti, ie, CquiOR2, CquiOR4, CquiOR5, CquiOR84, CquiOR85, AaegOR14, and AaegOR15 and then deorphanized these receptors using the Xenopus oocyte recording system and a large panel of odorants. 2-Phenylethanol, phenethyl formate, and phenethyl propionate were the best ligands for CquiOR4 somewhat resembling the profile of AaegOR15, which gave the strongest responses to phenethyl propionate, phenethyl formate, and acetophenone. In contrast, the best ligands for CquiOR5 were linalool, PMD, and linalool oxide. CquiOR4 was predominantly expressed in antennae of nonblood fed female mosquitoes, with transcript levels significantly reduced after a blood meal. 2-Phenylethanol showed repellency activity comparable to that of DEET at 1%. RNAi experiments suggest that at least in part 2-phenylethanol-elicited repellency is mediated by CquiOR4 activation."
Meanwhile, Leal is gearing up for the 2019 Entomological Society of America (ESA) meeting in St. Louis, Mo., where he will deliver the Founders' Memorial Award Lecture on “Tom Eisner — An Incorrigible Entomophile and Innovator Par Excellence,” at the awards breakfast on Tuesday, Nov. 19.
ESA officials selected Leal, an ESA fellow and internationally recognized chemical ecologist, for the global honor. Leal is the first UC Davis scientist selected to present the Founders' Memorial Lecture, although medical entomologist Shirley Luckhart of the University of Idaho, formerly of UC Davis, delivered the lecture in 2018.
The 7000-member ESA is the world's largest organization serving the professional and scientific needs of entomologists and people in related disciplines. ESA, founded in 1889, is headquartered in Annapolis, Md.