For the first butterfly, it was the right place at the right time.
An alfalfa or sulfur butterfly (Colias eurytheme) fluttered into our pollinator garden in Vacaville to sip some nectar from a Mexican sunflower (Tithonia rotundifolia). It lingered for several minutes.
But on another day, several miles away, an alfalfa butterfly wandered into a rural nursery, and splat! Nailed by a yellow sticky trap, which is used to lure, trap, monitor and detect insect pests.
Second butterfly: wrong place at the wrong time.
"There are four to seven generations per year of alfalfa caterpillar, and each generation is closely synchronized with the hay-cutting cycle so that the caterpillar pupates before cutting occurs," according to the UC Statewide Integrated Pest Management Program (UC IPM) website. "Caterpillar populations usually result from a flight of butterflies into the field when the alfalfa is less than 6 inches tall. Extremely large numbers of adults migrating between fields are often present from June to September in the Central Valley and from May to October in the southern desert."
UC IPM points out that factors contributing to economically significant caterpillar numbers are:
- Slow and uneven growth of the crop
- Lack of natural enemies
- Hyperparasites (other parasitoid wasps attacking the natural enemy wasps reducing their numbers)
- Hot, dry weather.
Butterfly guru Art Shapiro, UC Davis distinguished professor of evolution and ecology, says 2020 proved to be a major outbreak year for the alfalfa butterfly in the Sacramento, Yolo and Solano counties. (See butterfly invasion in the Aug. 28, 2020 Bug Squad blog).
Ever seen one in a sticky trap? Often you'll see assorted--and tiny--flies, gnats, beetles, leafminers, psylids and the like. So a yellow butterfly in a yellow sticky trap really stands out.
My first thought was "Wow! Haven't seen a Polistes dominula nest for years!" (The last one I saw was hanging out on the lip of a trash can in a UC Davis parking lot; it vanished the next day.)
And the second thought: #wasplove," a hashtag coined on Twitter by Amy Toth of Iowa State University.
Back in May of 2015, Toth, now an associate professor in the Department of Ecology, Evolution and Organismal Biology and the Department of Entomology, delivered a presentation on wasps at a seminar hosted by the University of California, Davis. As her website indicates, she's interested in the mechanisms and evolution of insect sociality, using paper wasps and honey bees as model systems. Current research projects involve de novo sequencing of paper wasp genomes and transcriptomes, comparative genomic analysis of Hymenoptera, genomic and epigenetic mechanisms regulating caste evolution, and the influences of nutrition and viruses on honey bee behavior and health.
Toth holds a doctorate from the University of Illinois at Urbana–Champaign, where she studied with Gene Robinson, and also did postdoctoral work with Christina Grozinger at Pennsylvania State University.
Wasps are pollinators and they attack pests of agricultural crops, Toth told the Department of Entomology and Nematology at her seminar.
However, many folks we know just aren't fond of wasps. They're unwelcome guests in their yard, patio or picnic. See the information on "Yellowjackets and Other Social Wasps" on the UC Statewide Integrated Pest Management Program website, which includes "Preferring to live in or near orchards or vineyards, they (paper wasps) hang their paper nests in protected areas, such as under eaves, in attics, or under tree branches or vines. Each nest hangs like an open umbrella from a pedicel (stalk) and has open cells that can be seen from beneath the nest. Sometimes white, legless, grublike larvae can be seen from below. Paper wasp nests rarely exceed the size of an outstretched hand, and populations vary between 15 to 200 individuals. Most species are relatively unaggressive, but they can be a problem when they nest over doorways or in other areas of human activity such as fruit trees."
We remember asking Toth to list what she loves about wasps.
Here's her list, as posted earlier on a Bug Squad blog:
1. They are pollinators
2. They contribute to biocontrol of lepidopteran pests in gardens and on decorative plants
3. They have been shown to carry yeasts to winemaking grapes that may be important contributors to the fermentation process and wonderful flavors in wine!
4. They are the only known insect (Polistes fuscatus) that can recognize each other as individuals by their faces.
5. They are devoted mothers that will dote on their young all day long for weeks, defending their families with fury.
6. Their social behavior, in my opinion, is the most human-like of any insect. They know each other as individuals, and are great cooperators overall, but there is an undercurrent of selfishness to their behavior, manifest in nearly constant passive-aggressive interactions between individuals.
7. They are artists. They make perfect hexagonal nest cells out of paper, which they make themselves out of tree bark + saliva.
8. They are extremely intelligent. They're predators, architects, good navigators, and great learners. Among insects, they have large brains, especially the mushroom bodies (learning/memory and cognition area of insect brain).
9. They are beautiful, complex, and fascinating creatures!
And my No. 10: they are quite photogenic.
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You're not thinking of root-knot nematodes, major pests of potatoes.
But potato growers and nematologists are.
So are the editors of the scientific journal, Nature Plants. Their current edition showcases research on root-knot nematodes by Washington State University (WSU) scientists Lei Zhang and Cynthia Gleason, and a commentary by UC Davis nematologist Shahid Siddique and colleague Clarissa Hiltl of the University of Bonn, Germany.
“Plant-parasitic nematodes are among the world's most destructive plant pathogens, causing estimated annual losses of $8 billion to U.S. growers and of nearly $78 billion worldwide," according to Siddique, an assistant professor in the UC Davis Department of Entomology and Nematology.
“Most current control methods rely on chemical nematicides, but their use is increasingly limited due to environmental concerns," Siddique and Hiltl wrote in their News and Views column, New Allies to Fight Worms.
They commented that the WSU scientists' proposed alternative pest management strategy--naturally occurring molecules or plant elicitor peptides (Peps)—shows promise: “Engineering a naturally occurring rhizobacterium to deliver Peps to the plant root system offers a new opportunity in integrated pest management.”
It's better to build up the host plant's immune system rather than directly target the pathogen with chemical nematicides which “are highly toxic and have negative effects on the ecosystem," Siddique told us.
The root-knot nematode Meloidogyne chitwoodi is a noted pest of potato production in the Pacific Northwest. Idaho leads the nation in commercial potato production, followed by Washington. Oregon ranks fourth. California, which ranks eighth, grows potatoes year around due to its unique geography and climate.
The WSU scientists demonstrated the effective use of Peps to combat root-knot nematodes in potato (Solanum tuberosum). They engineered a bacteria, Bacillus subtillis, to secrete the plant-defense elicitor peptide StPep1. They wrote that pre-treatment of potato roots “substantially reduced root galling, indicating that a bacterial secretion of a plant elicitor is an effective strategy for plant protection." (See article.)
“Besides chemical nematicides, methods of nematode management include the use of crop rotation, microbial biocontrol agents, cover crops, trap crops, soil solarization, fumigation and resistant plant varieties,” wrote Siddique and Hiltl. “However, several of these strategies are not effective or available for all crops. Nematicides are highly toxic, and their use is strictly limited due to environmental concerns. Resistant plants are often ineffective or unavailable. Microbial biocontrol agents have produced inconsistent results. In this context, the current work provides a new opportunity to manage plant-parasitic nematodes by combining two progressive strategies: the use of plant elicitors to enhance crop resistance to pathogens and the use of B. subtilis to deliver.”
According to the UC Statewide Integrated Pest Management Program (UC IPM), root-knot nematodes "usually cause distinctive swellings, called galls, on the roots of affected plants. Infestations of these nematodes are fairly easy to recognize; dig up a few plants with symptoms, wash or gently tap the soil from the roots, and examine the roots for galls. The nematodes feed and develop within the galls, which can grow as large as 1 inch in diameter on some plants but usually are much smaller."
"Nematodes are too small to see without a microscope," UC IPM points out. "Often you become aware of a nematode problem by finding galled roots on a previous crop. However, you also can use a simple bioassay to detect root knot nematodes in garden soil. Melons seeded in pots in moist soil collected from the garden will develop visible galls on the roots in about 3 weeks when pots are kept at about 80ºF if root knot nematodes are present. As a comparison, melons planted in heat-sterilized soil won't develop galls."
Let's hear it for biocontrol.
You've seen lady beetles, aka ladybugs, preying on aphids.
But have you seen an assassin bug attack a spotted cucumber beetle?
How about a crab spider munching on a stink bug?
All biocontrol, part of integrated pest management (IPM).
If you access the University of California Statewide Integrated Pest Management Program (UC IPM) website or more specifically, this page, you'll learn that "Integrated pest management, or IPM, is a process you can use to solve pest problems while minimizing risks to people and the environment. IPM can be used to manage all kinds of pests anywhere–in urban, agricultural, and wildland or natural areas."
Or, UC IPM's more in-depth definition:
"IPM is an ecosystem-based strategy that focuses on long-term prevention of pests or their damage through a combination of techniques such as biological control, habitat manipulation, modification of cultural practices, and use of resistant varieties. Pesticides are used only after monitoring indicates they are needed according to established guidelines, and treatments are made with the goal of removing only the target organism. Pest control materials are selected and applied in a manner that minimizes risks to human health, beneficial and nontarget organisms, and the environment."
Think of biocontrol as beneficial: "Biological control is the beneficial action of predators, parasites, pathogens, and competitors in controlling pests and their damage. Biological control provided by these living organisms (collectively called "natural enemies") is especially important for reducing the numbers of pest insects and mites, but biological control agents can also contribute to the control of weed, pathogen, nematode or vertebrate pests."--UC IPM
Yesterday we witnessed an incredible case of biocontrol in action.
At Bodega Bay's Doran Regional Park, Sonoma County, we spotted a great blue heron stepping stealthily through a thatch of ice plant in the Jetty campground. It was 6:30 in the morning. As campers slept in their recreational vehicles a few feet away, the great blue heron just kept stepping silently through the ice plant. One step. Another step. And another.
And then it happened. Its long sharp beak speared a rodent. Yes, they eat rodents. It crunched the body from head to toe, breaking the bones, and then swallowed it whole.
Not a pretty picture, but a simple case of biocontrol, compliments of a hungry heron.
Have you ever heard anyone say that when they see the larva of a lady beetle (aka ladybug, family Coccinellidae)?
Unfortunately, it's quite common among non-gardeners and non-insect enthusiasts.
The larvae of lady beetle are mostly black and look like tiny, spiny alligators, but they're beneficial insects just like the adult lady beetles. In the adult and larval stage, they're both predators that prey mainly on aphids, but they'll also eat thrips, spider mites, scale insects, and other soft-bodied insects.
An adult lady beetle can eat as many as 5000 aphids in its lifetime, scientists say. Who knows how many a larva can eat! Who's counting?
"Young lady beetle larvae usually pierce and suck the contents from their prey," according to the UC Statewide Integrated Pest Management Program's website. "Older larvae and adults chew and consume their entire prey. Larvae are active, elongate, have long legs, and resemble tiny alligators."
You've seen lady beetle jewelry and t-shirts and the like (check out the gift shop at the Bohart Museum of Entomology at UC Davis, located in Room 1124 of the Academic Surge Building on Crocker Lane), but the larvae? They aren't represented.
They're well represented in many gardens, however. In our garden, the adults and larvae are polishing off the oleander aphids on our milkweed plants.