- Author: Kathy Keatley Garvey
It's Arachtober and that means celebrating arachnids for the entire month of October.
Well, we ought to celebrate them year around, but October is THEIR month.
Let's especially applaud crab spiders when they prey on such agricultural pests as the lygus bug, also known as the "western tarnished plant bug." It's a member of the genus Lygus in the family Miridae and feeds on plants by piercing the plant tissues.
The lygus bug is easily distinguished by the triangular mark on its back.
The western tarnished plant bug (Lygus hesperus) is known as a very serious pest of cotton, strawberries and seed crops such as alfalfa, entomologists tell us. In California alone, the bug causes $30 million in damage to cotton plants each year, "and at least $40 million in losses to the state's strawberry industry," according to Wikipedia.
"Lygus bugs are one of the causes of irregularly shaped, cat-faced strawberries; another cause may be poor pollination, which results in small undeveloped seeds," says UC Statewide Integrated Pest Management Program (UC IPM) in its Pest Management Guidelines. "Lygus bugs damage fruit by puncturing individual seeds; this, in turn, stops development of the berry in the area surrounding the feeding site. Straw-colored seeds that are large and hollow are a good indication of lygus bug damage. Lygus bug damage is more of a problem in strawberry-growing areas where continuous fruit production occurs.
"Adults are about 0.25 inch (6 mm) long, oval, and rather flattened," UC IPM points out. "They are greenish or brownish and have reddish-brown markings on their wings."
So what happens when a crab spider nails a lygus bug?
The cheering section is loud.
- Author: Kathy Keatley Garvey
But agriculturists and scientists have.
The spotted-wing drosophila (SWD), Drosophila suzukii, is an agricultural pest that is super tiny.
It's approximately 2 to 4 millimeters in length with a wingspan of 5 to 6.5 millimeters. One millimeter is approximately 0.039 inches. There are 25.4 millimeters in 1 inch. So, the adult is about the size of a grain of sand, which can measure 0.5 to 2 mm in diameter.
SWD, native to southeast Asia and first discovered in California in 2008, lays its eggs in such soft-skinned, ripening fruits as strawberries, raspberries, cherries, blueberries, peaches, nectarines, apricot and grape.
In 2008, the first year of its discovery in California, the economic loss attributed to this pest amounted to $500 million. Latest statistics from 2015 indicate a $700 million national economic loss.
Lead author of the paper, “Transcriptome Analysis of Drosophila suzukii Reveals Molecular Mechanisms Conferring Pyrethroid and Spinosad Resistance,” is Christine Tabuloc, then a doctoral candidate and now a postdoctoral researcher working under the mentorship of Professors Chiu and Zalom.
"In this work, we leveraged high throughput sequencing to identify biomarkers of insecticide resistance in D. suzukii,” Tabuloc explained. “We found that different genes are responsible for resistance to different chemicals. Specifically, we found that genes involved in metabolism are highly expressed in flies resistant to pyrethroid insecticides. We also observed evidence of two different mechanisms of resistance in 2 lines generated from a single spinosad-resistant population. We found an increased expression of metabolic genes in one line and increased expression of cuticular genes in the other.”
Tabuloc added that “our work has enabled for the detection of resistance in California populations, and we are currently doing a nationwide screening to determine whether resistance is now present in other states. Currently, we are working with the Zalom lab to use the results of our assays to try and combat resistance. There are experiments in progress trying to increase the efficacy of insecticides by blocking some of the genes involved in resistance, such that the enzymes encoded by those genes have decreased function."
A giant in the entomological world, Zalom directed the UC Statewide Integrated Pest Management Program for 16 years. He is an Honorary Member of the Entomological Society of America (ESA), the highest ESA honor, and he served as its president in 2014.
“This work not only represents good science; it has very practical implications," Zalom said. He and Tabuloc presented results of the work at a special berry grower seminar on insecticide resistance organized by UC Agriculture and Natural Resources (UC ANR) Farm Advisor Mark Bolda, strawberry and caneberry farm advisor in Santa Cruz, Monterey and San Benito counties, Mark Bolda in Watsonville.
"The presentations were extremely well-received," Zalom noted. "The original program was targeted for about 1.5 hours, but the meeting extended to over three hours due to the extent of questions and great discussion that followed. Growers and their consultants are hungry for new information that they find interesting and potentially useful, and this work was clearly of interest to them.”
Said Bolda: “The research was top shelf and the need, of course, is very great. Some of the information that Frank and Christine presented has been put into immediate use in the industry.”
What most people don't know is that Bolda was the first to discover the pest in North America. That was in 2008.
"He asked me to come down to look at it and the problem...we weren't able to get an actual species identification until 2009!" Zalom said.
As the pest continues to spread throughout much of the country, anxious growers are worried about its increased resistance to pesticides. The UC Davis research team is alleviating that worry.
- Author: Kathy Keatley Garvey
That would include the larvae of Tuta absoluta, a South American tomato leafminer. In its adult stage, it's a moth in the family Gelechilidae. In its larval stage, it's a major agricultural pest.
Since 2008, it has invaded much of Europe, northern Africa, and the Middle East, according to a California Department of Food and Agriculture post.
It hasn't yet invaded the United States, but scientists say it has moved from South America as far north as Costa Rica.
The bug "is a serious and devastating pest of tomatoes, causing crop losses as high as 80 to 100% in areas where it is found," according to a Pest Alert article published by the UC Statewide Integrated Pest Management Program. "This insect bores into leaves, stems, flowers, and fruit, often leaving the fruit unmarketable and altering plant growth structure through destruction of stem apical buds or flower buds. To manage this insect, growers may be forced to greatly increase the number of insecticide applications to their tomato crops."
The article, by UC Davis scientists Kris Godfrey of the Contained Research Facility, and Frank Zalom and Joanna Chiu, both of the Department of Entomology and Nematology, points out that the "South American tomato leafminer spreads via commercial trade of plants and fruit infested with eggs, larvae, and pupae. The adult moths can fly, but it is not known if this movement contributes significantly to its spread. There are numerous regulations in place that should limit the spread of the South American tomato leafminer in imported commercial tomato plants and fruit. However, movement of fruit and plants by private individuals is not as strongly regulated."
Enter Kyle Lewald, a doctoral candidate in the laboratory of UC Davis molecular geneticist/physiologist Joanna Chiu. He will present his exit seminar on "Using Genomic Data to Understand and Prevent the Spread of Tuta absoluta" at 4:10 p.m., Wednesday, Feb. 22 in 122 Briggs and also on Zoom. The Zoom link:
https://ucdavis.zoom.us/j/95882849672.
Chiu, professor and vice chair, UC Davis Department of Entomology and Nematology, will introduce him.
"Tuta absoluta is a serious agricultural pest of tomato plants," Lewald says in his abstract. "While initially discovered in Peru, it has rapidly invaded tomato fields around the world over the past century, causing widespread damage to the industry. The recent affordability of whole genome sequencing of insects opens the door to a wide number of applications to understand and control this pest."
"Using long read sequencing, we produced and annotated a highly contiguous T. absoluta genome assembly," Lewald noted. "Sequencing of individuals collected across many locations in Latin America allowed us to investigate population structure and diversity levels, as well as identify divergence times and possible migration events occurring between regions. Understanding these historical events can be key to predicting and preventing future invasion events. We also used comparative genomics between morphologically similar gelechiid species to develop efficient molecular diagnostics, allowing field researchers and stakeholders to identify Tuta absoluta rapidly to support quarantine and treatment efforts."
Lewald, who holds a bachelor's degree in molecular and cell biology (2016) from UC Berkeley joined the Chiu lab in 2018.
The UC Davis Department of Entomology and Nematology's winter seminars are held on Wednesdays at 4:10 p.m. in 122 Briggs Hall. All are virtual. Urban landscape entomologist Emily Meineke, assistant professor, coordinates the seminars. (See schedule.) She may be reached at ekmeineke@ucdavis.edu for technical issues.
- Author: Kathy Keatley Garvey
It's a crazy world out there.
Now our beleaguered honey bee has a new foe: the Rasberry crazy ant, Paratrechina sp. nr. pubens.
The Rasberry crazy ant is driving Texans crazy.
A UC Davis entomologist sent me an Associated Press news story about how these crazy ants are wreaking havoc in Houston and are now spreading to about a dozen counties in the Lone Star State.
Some facts:
First, this ant, about the size of a grain of rice, is named for an exterminator named Tom Rasberry who spotted the exotic, invasive pest near Houston in 2002 and sounded the alarm.
Second, these ants are considered "crazy" because they don't march like well-disciplined soldiers in a parade but weave erratically like equally crazy cockroaches.
Third, they eat honey bees, which already have enough trouble dealing with colony collapse disorder, pests, diseases, pesticides, stress, malnutrition and global climate changes.
Honey bees need a crazy ant like they need a hole in their antenna or a mite on their thorax.
Entomologists at Texas A&M just posted an informational Web site about the pest, which they describe as "1/8 inch long and reddish-brown."
And with a big appetite.
Fact is, these hordes of crazy ants are ruining electronic equipment--like computers, I-Pods, printers, telephones and burglar alarms--and are damaging sewage pumps and gas and electricity meters. They basically consume just about everything in sight--from the unwanted red fire ants to the beneficial ladybugs and honey bees.
Today the ant is being considered "a serious agricultural pest" because it's encroaching on "livestock, hay bales and a few honey bee farms," according to Associated Press writer Linda Stewart Ball in her piece published Aug. 5.
The Texas Department of Agriculture and the U.S. Department of Agriculture want to declare the crazy an "agricultural pest," something they must first do to seek research funds.
"If killing honey bees does not put it in the ag pest category," Rasberry told the Associated Press writer Linda Stewart Ball in her Aug. 5 piece, "I don't know what does."
Where did it come from?
Perhaps from the Caribbean. It could have hitchiked a ride on a cargo ship. At any rate, it's here and spreading by billions and it's not going away. You'll want to read Tom Rasberry's blog about the crazy ants.
Houston, they have a problem.
And so may we.