Tarsonemid Mites on New Guninea Impatiens - University of Maryland Extension
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Greenhouse TPM/IPM Report
Central Maryland Research and Education Center
Ellicott City, Maryland
February 12, 2020
From: Stanton Gill, Extension Specialist – IPM for Greenhouse and Nurseries, Central Maryland Research and
Education Center, University of Maryland Extension
Karen Rane, Extension Specialist, Director of the Plant Diagnostic Clinic, University of Maryland Extension
Andrew Ristvey, Extension Specialist, Wye Research and Education Center, University of Maryland Extension
Suzanne Klick, Technician, CMREC, University of Maryland Extension
Tarsonemid Mites on New Guninea Impatiens
By: Stanton Gill
We received in samples at the CMREC lab on Monday of New
Guinea impatiens with stunted tip growth that was gnarled
and twisted. Examination under a dissecting scope revealed
tarsonemid mites. Tarsonemid mites commonly found on New
Guinea impatiens are broad mites and cyclamen mites. These
mites are small, and it is hard to distinguish between the two
species unless there are eggs present since each has distinctive
patterns on the egg covering.
Broad mites and cyclamen mites belong to a family called
tarsonemid mites. These small, hard to see mites can wreak havoc
if you let them build up this early in the season. Tarsonemids
are microscopic — less than one-one hundredth of a millimeter
— and require a microscope to be seen, they tend to hide in the
curled tip growth of the plant and when you expose them to light, Use a microscope to detect tarsonemid
mites on plants
they move about to find another site for coverage on the plant.
Tarsonemid mites are not able to fly. Therefore, growers
will not be able to catch them on yellow sticky cards. You
should monitor plants individually, looking for curled
tip growth. As I mentioned, the mites are small and often
require a dissecting scope with at least 40X to see them.
For help with identification, Maryland growers can send
samples to the University of Maryland CMREC, 11975
Homewood Road, Ellicott City, MD 21042.
If the tarsonemid mites get established, make sure you
check gerbera daisy, ornamental sweet potato, and herb
crops for the presence of these mites. They can complete Feeding by broad mites causes distorted tip growth.
a life cycle in 2 weeks at this time of year, and females can lay 40 – 70 eggs. A small population can quickly
become a bigger problem.
If you bring in unrooted cuttings or even rooted cuttings, consider dipping them in 0.5% horticultural oil. We
have used Suffoil-X oil in the past with good success. We have had greenhouse operations with trolley systems
for hanging baskets in which the tarsonemid mites became established. The mites cannot fly, but they can drop
down from infested plants and drop onto the plants below.
For chemical control, we have used Pylon and Avid with good success. Akari, is a contact miticide from SePRO,
which contains the active ingredient fenpyroximate and has performed well in trials. For biological control of
these mites, I would suggest releasing Amblyseius cucumeris. We mentioned them in the last IPM alert for thrips
control. They also feed on tarsonemid mites. You can obtain these predators in breeding sachets or in loose fill
containers containing vermiculite/bran mixes with the mites, which can be distributed over the crop.
Producing Hyacinths in Water
By: Stanton Gill
This week the big market is Valentine’s Day, but Easter is just around the
corner on April 12. Mother’s Day is May 10, 2020. Nobody really cares about
Father’s Day, at least flower wise. Clever people have done their homework
and pre-chilled hyacinth bulbs for 9 weeks over the fall and winter. Then,
they put the bulbs in bulb water trays to develop roots. The hyacinth
bulbs are then moved into a glass vase to be sold for Valentine’s Day and
if you delay them enough for Easter this year. They rarely hold up as long
as Mother’s Day. I contacted Ko Klaver, Botanical Trading Company, to
comment on the water method of growing bulbs for forcing for holidays.
Here are his comments:
Mother’s Day is a lot longer storage of bulbs than mostly is done, so they
need to be prepped and then forced. The long storage is the tricky part to
keep them from sprouting. Other bulbs that might work like this could be
Alliums or Iris.
Growing hyacinths in water for
Tulips and hyacinth are done on water for 15-20 years now. It is a little late holiday markets
unless you planned out your plan of attack last fall but you can plan out
for next spring. If you planned this out have fun selling artsey looking plants in glass vases this Valentine and
Easter.
New Pesticides for Use on Field Hemp: Note that this list has to be approved by MDA.
In December 2019, EPA approved adding hemp to the use sites of 10 pesticides. Nine of the products are
biopesticides and one is a conventional pesticide. As EPA receives additional applications to amend product
labels to add use on hemp, the agency will process those applications on an ongoing basis and update this list.
See the list on the EPA website. These materials have to be approved by MDA before using in MD.
Mite on Elephant Ear Plants
By: Stanton Gill
A grower brought in a sample of elephant ears with mites. Sam
Bolton, Florida Dept. of Agric. and Consumer Services, identified it
as Tyrophagus sp. which feeds on mold in greenhouses. You might see
this mite on foliage if you are shipping in tropicals. If you are unsure
of the identification, Maryland growers can submit a sample to me to
identify.
A Tyrophagus sp. mite found on elephant ear plant
2
More on Biological Control of Thrips in Greenhouses
By: Stanton Gill
This is a follow-up to the last IPM Alert in which we talked about biological control of thrips. I asked Michael
Brownbridge of BioWorks Company to comment on where sachets of the predatory mites can be found and the
potential of using banker plants for pollen sources for the mites.
Here are Michael’s comments:
Koppert sells N. californicus in sachets, as does (I think) Bioline. Good idea to try banker plants, but probably
just as effective to apply pollen on to the crop. See Biobest’s system. As for what to use in the winter - depends
what you can get. Agree, re: using the cooler-tolerant andersoni if you can get it. Compare prices. I think you
can get these in sachets from Biobest, likely Koppert as well. As for their response on bankers, again, I would
lean towards using supplemental food in the crop. Sometimes, predators can do really well on the banker then
fail to leave. “Cushy life” there.
Stock plants. Seeing very good data for plants treated with ONgard 2-3 days before taking cuttings. It works as
a biostimulant, and the resulting cuttings root faster and produce vigorous plants more quickly. Hate to sound
like a walking ad, but I would not recommend using these materials if I was not convinced that they could help.
Chesapeake Green 2020
February 19 and 20, 2020
Location: Maritime Institute, Linthicum Heights, MD
Go to https://www.mnlga.org/chessie-2020 for schedule and registration information
Early registration ends February 3.
Innovative Lawn Care Conference
Addressing the New Montgomery County Pesticide Ban on Turf
Location: The Universities at Shady Grove, Gaithersburg, Maryland
Coordinating with Maryland’s Turf and Green Industry Associations
extension.umd.edu/ipm/conferences
The information given herein is supplied with the understanding that no discrimination is intended
and no endorsement by University of Maryland Extension is implied.
Read labels carefully before applying any pesticides.
Photographs are by Suzanne Klick and Stanton Gill unless stated otherwise.
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