Posts Tagged: maggot
What's a Picnic Without Bugs?
What's a picnic without bugs? Well, it wouldn't be a picnic at all! The UC Davis Department of...
Stick insects, aka walking sticks, will be part of the Bohart Museum of Entomology's petting zoo in a pop-up tent at Briggs Hall during the UC Davis Picnic Day. The Bohart Museum headquarters in the Academic Surge Building will be closed on Picnic Day. The pop-up tent will showcase butterflies, bees and other specimens. (Photo by Kathy Keatley Garvey)
Forensic entomologist Robert "Bob" Kimsey will staff the "Dr. Death" booth in 122 Briggs Hall. (Photo by Kathy Keatley Garvey)
Maggot art is among the popular activities at Briggs Hall during the annual UC Davis Picnic Day. Artists dip maggots in water-based, non-toxic paint. (Photo by Kathy Keatley Garvey)
Run, roaches, run! Cockroach races are an integral part of the "bug" activities at Briggs Hall during the UC Davis Picnic Day. (Photo by Kathy Keatley Garvey)
What’s with all of the trash bugs this season?
I have received a handful of calls this season with concerns about “trash bugs,” a catch all term for various soil invertebrates. These soil invertebrates include root maggots, springtails, bulb mites, and symphylans, all which will happily feed on decomposing plant debris, i.e., trash. If given the opportunity, trash bugs will feed on seedlings and transplants, but high pressure can usually be avoided by allowing plant debris to fully breakdown before planting the next crop. A long enough pause between plant debris and seedlings acts as a sort of field-level host-free period, allowing trash bug populations to drop before planting.
Why does it feel like we have more trash bugs this season?
We had an unseasonably cool, wet spring. Under these conditions, crop debris from the fall was breaking down much slower than usual. With the compressed start to the season, folks have been eager to plant into fields as soon as possible, so many were likely planting into fields with higher-than-optimal plant debris.
By mid-April, daily temperatures were starting to get more back to normal, so why are we still dealing with more trash bugs? From talking with a handful of growers and PCAs, the slow start to the season has set back the whole planting schedule. To try and bring things back to schedule as close as possible, folks are still pushing the limit on how quickly they turn around fields for the next crop. A perfect storm for trash bug pressure.
Which trash bug am I dealing with?
A diverse group of pests can cause stunting and stand loss, so accurate pest ID is critical for successful management.
Root Maggots (seedcorn maggots or cabbage maggots, Delia spp.)
Root maggots are the larvae of small grey flies. The adult flies are commonly caught on sticky cards that are deployed for monitoring thrips and aphids.
Seedcorn maggot, Delia platura, seems to be the primary culprit that I have come across that is stunting brassicas. Seedcorn maggots tend to hit fields within a week or two after planting, causing patchy stands and stunted seedlings. Closely related cabbage maggots tend to hit fields a few weeks after planting and can continue to cause damage as plants mature.
To scout for root maggots, pull up stunted plants (see picture #1 below) and check roots for small, yellowish-white maggots (less than ¼ of an inch long). They can be easy to miss when they're all tangled up in the roots (picture #2). If scouting is delayed, you may also find the brown pupa (picture #3). With seedcorn maggots, timing a reactive control (i.e., insecticide application) can be tricky since the damage may go unnoticed until the maggots have already pupated and left the field.
From left to right: #1 broccoli stunting caused by root maggot feeding; #2 maggot tangled up in the roots of a broccoli plant; #3 root maggot pupa found next to a stunted broccoli plant. |
Springtails and soil mites
Pest springtails and soil mites are trickier to identify, since non-pest species are common in healthy soils. The one species of springtail that has been identified as an occasional pest of lettuce and brassicas is Protaphorura fimata, while the main pest mites are bulb mites (Rhizoglyphus spp., Tyrophagus spp.). Both P. fimata and bulb mites are small and whiteish while non-pest species are often larger and more colorful.
Clockwise from top left; Protaphorura fimata, the springtail species that can be a pest (Photo Credit: Shimat Joseph, previous UC IPM Advisor); non-pest springtails (note that these springtails are more colorful and have long antennae); a predatory soil mite (not a pest); and two bulb mites (Photo Credit: Jack Kelly Clark, UC IPM). |
Symphylans
Symphylans look like small (less than ½ an inch), white centipedes. Since symphylans are fast and mobile, you will be more likely to catch symphylans in action if you dig around stunted plants that are near healthy looking plants. If you readily find symphylans just by digging, the symphylan pressure is probably high enough to cause economic damage.
Lower symphylan densities can be harder to observe, so you may want to try bait-trapping with potato or beet wedges if you suspect symphylans but cannot find any by digging around stunted plants. The bait-trapping method can also be used to scout for springtails.
For more on the identification, scouting, and management of these pests, be sure to reference the UC IPM Pest Management Guidelines:
https://ipm.ucanr.edu/agriculture/cole-crops/
https://ipm.ucanr.edu/agriculture/lettuce/
Related blog posts from past entomology advisors:
Root maggots:
https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=9804
https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=4301
Symphylans:
https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=18819
Springtails:
https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=16769
Bulb Mites:
https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=13271
/table>Bohart Museum of Entomology Open House: Magnificent Maggot Art!
Ever created Maggot Art? You pick up a maggot with a forceps, dip it into a non-toxic, water-based...
Maggot Art at the Bohart Museum of Entomology open house. Tools of the trade: maggots, water-based and non-toxic paint, paint containers, forceps, and white paper. (Photo by Kathy Keatley Garvey)
Isaiah Hu, 4, of Davis, works on his Maggot Art creation, while his mother, Lisa Hu (next to him) and Bohart Museum associate Kat Taylor, a UC Davis entomology major, watch. Lisa is a 2011 graduate (DVM) of the UC Davis School of Veterinary Medicine. (Photo by Kathy Keatley Garvey)
Maggot Art underway; it begins with picking up a maggot with a forceps. (Photo by Kathy Keatley Garvey)
Bohart Museum volunteer Kat Taylor, a UC Davis freshman majoring in entomology, shows her Maggot Art. (Photo by Kathy Keatley Garvey)
The Art of Maggot Art
They came, they saw, they participated. Youngsters--and the young at heart--headed over to Briggs...
UC Davis entomologists, first-year doctoral students Abigail Lehner (front) of the Neal Williams lab, and Iris Quayle of the Jason Bond lab, staff the Maggot Art table at Briggs Hall. (Photo by Kathy Keatley Garvey)
UC Davis doctoral student Iris Quayle of the Jason Bond lab supervises the Maggot Art project, as young artists dip maggots into water-based, non-toxic paint. (Photo by Kathy Keatley Garvey)
Watson Owens, 2, of Carmichael, watches a maggot crawl on his Maggot Art project. His father, Sean Owens, is a UC Davis alumnus. (Photo by Kathy Keatley Garvey)
Winter Owens, 5, of Carmichael, displays her Maggot Art masterpiece. (Photo by Kathy Keatley Garvey)
Maggot Art drying on a bulletin board in Briggs Hall, UC Davis campus. Soon they will be ready to take home. (Photo by Kathy Keatley Garvey)
Maggot Art at UC Davis Picnic Day: Just Me and My Maggot
Do you like to blend science with art, or is there a budding young artist in your family? Then you...
So many colors to choose from! A young artist working on his Maggot Art. (Photo by Kathy Keatley Garvey)
Hands reach for more maggots. (Photo by Kathy Keatley Garvey)
A work of art: Maggot Art being done at a UC Davis Picnic Day. (Photo by Kathy Keatley Garvey)