April

SIOS
STATEN ISLAND ORCHID SOCIETY
APRIL, 2011
Volume XXXIV, Issue 4
NEWSLETTER
OFFICERS
John Foley
President 718-996-1064
Frank Ariosta, M.D.
Vice President 732-564-0994
A Message from John
Amy Eli Trautwein
Co-Vice President 347-216-1574
I’m Back!
Colman Rutkin
Treasurer 718-816-0682
Carol Cammarano
Assistant Treasurer 718-948-6439
hat do I have to do to get out of this job?
Die?
Sharon Jaffee
Secretary 347-484-7518
OK. Let's get to business.
TRUSTEES
Ron Altman, D.D.S. 908-658-3055
Patrick and Carol Cammarano
718-948-6439
Gerry Cassella 718-698-3718
Dr. Olga Federico 718-987-0255
Michael Corace 718-375-3177
Cara Minucci 646-299-6888
Karen Silverman 718-356-4482
Roy Fox 718-816-8187
David O’Dell 718-966-6174
Amy Eli Trautwein 347-216-1574
April 30 & May 1st.
NEWSLETTER
Kathleen Ruoti, Editor
718-967-6158
[email protected]
CONTENTS
Message from the President ...1
Show Table March ...2
Longwood Gardens Show..3-4
Semi Hydro techniques ...5-6
Vanda Care article...7
Web Links...8
Potting Media article...9
Fungicides chart...10
Fungus Gnats article...11
The SIOS meets on the
3rd Tuesday of each month at
7:00pm
All Saints Episcopal Church,
2329 Victory Blvd., SI, NY 10314
Happy
Spring
W
* * *
SNUG HARBOR...10 am till 4 pm.
SIOS Show BE THERE! Bring friends, enjoy
the Gardens and buy plants.
Cattleya skinnerii ---water color called “ Pride of
Costa Rica “ artist is from Montreal, Quebec
We will be in Bldg “P".
Dave needs your plants.
Set up will be Friday, April 29th after 3pm...call
Dave. It's always a fun and festive occasion.
Ivan Snyder will be our guest in May. He will
enlighten us on "Ascocendas"
Our June meeting will be our summer auction/Pot Luck Dinner.
You all know the drill. Bring food and money
and people.
I am happy to announce that "Back by popular
demand": this month's meeting will feature the
one and only Colman Rutkin.
Roots are on his agenda this time (a very important subject for plant growers).
THANKS AGAIN COLMAN!!!!!
We have a lot to talk about then, but that can't
happen unless you show up!
I'll be there.
So,
Till I see you all then,
Be Well and be Good!
~John
APRIL SPEAKER
Colman Rutkin will speak on the
topic of watering orchids.
Suggestions on watering mostly
cattleya types will be discussed
and there will be wonderful
pictures of roots.
ANNOUNCEMENT
SIOS MEMBERSHIP DUES
ARE DUE NOW
Dues ($20) can be paid at our
meeting or can be sent to me.
Colman Rutkin
129 Tysen Street
Staten Island, NY 10301
Please make check payable to SIOS..
APRIL, 2011
Page 2
SHOW TABLE TALLIES FOR MARCH
WINDOWSILL
Ed & Joan Grabowsky - 23
Amy Trautwein - 77
Roy & Gertrude Fox - 76
GREENHOUSE
Dave O'Dell - 84
Colman Rutkin - 29
Ron Altman - 10
LIGHTS
APRIL, 2011
SIOS Exhibit at Longwood Gardens
SIOS Display
Photos by Pat Cammarano
Page 3
APRIL, 2011
The SIOS Exhibit at
Longwood Gardens
Photos by Cara Minucci
Page 4
APRIL, 2011
Page 5
Amy sent me, for inclusion in the newsletter, a write-up of her growing techniques - most of it on
semi-hydro that she spoke about and showed everyone at last month’s meeting.
* * * * * * *
Orchids Experiments – or, How to be lazy and still have happy orchids
I’ve tried a variety of ways to grow orchids in an attempt to get them growing and even blooming with a minimum of effort
on my part. I make no guarantees for success (and have lost my share of plants), but I can say that I’ve had some surprising
sucsses and encourage you to experiment! The three techniques I showed at the last meeting were an epiweb automated watering system, semi-hydroponics, and a partial immersion system.
Epiweb Automated Watering System
My ‘growing tube’ is based on ideas found at http://www.epiweb.se/products.htm, also seen at
http://forum.theorchidsource.com/ubbthreads.php/galleries/183552/My_latest_growing_place.html. I got my supplies in various
places – the walls are ‘Ecoweb,’ which is the US-available variant of Epiweb, available at www.firstrays.com/ecoweb.htm, the
pump and tubing are from a fountain pump I got on Amazon.com, and the splash guard is just a large plant saucer with the middle
cut out. The pump is plugged into a timer (purchased at the local CVS, along with the chips bowl I use as the catch basin) which
activates the pump for 5 to 10 minutes every couple of hours during the day. I adjust the frequency as the day length and temperatures change. This has worked fairly well for plants that want more moisture, such as Masdevallias and other Pleurothallids.
Semi-hydroponics
‘Semi-hydroponics’ is a term coined by Ray Barker (www.firstrays.com), the guy who is most responsible for providing
information and supplies for this growing technique. Semi-hydro, or S/H, seems to have been independently discovered by various people, and there are a correspondingly large number of ways to go about it. The idea is simple – each orchid is planted in
organic medium placed in a pot with a reservoir. The medium must be able to wick the moisture up so that the roots from top to
bottom have access to some moisture, but it must also be open enough to provide air. Rather than a cycle of drying and rewetting, the roots are provided with a constant level of moisture and nutrients. If a dry cycle is needed, (for instance, if the plant needs
a winter dry rest) wait longer to refill the reservoir. Overwatering becomes impossible, and even if the grower forgets to water, the
medium will still hold some moisture for a while after the reservoir has emptied. While not a cure-all, semi-hydro can simplify orchid growing enormously.
continued on next page …..
APRIL, 2011
Page 6
Pots: A rule of thumb is to make the pots 1.5 times as high as they are wide, and to place two or three drainage holes approximately one inch up the side of the pots. A plant that likes more moisture can be potted with a deeper reservoir or a shallower
pot, while a plant that prefers to be drier can go into a taller pot, or have a smaller reservoir, and perhaps have extra holes punched in
the sides of the pots to increase circulation. Or use regular plastic pots and just place each pot in a saucer of water for the reservoir.
Pot Size: Because the medium will not break down, repotting shouldn’t be necessary until the orchid outgrows the pot. Because the medium wicks moisture at an even gradient, overpotting is not a problem in S/H. My only suggestion is that the pot should
be big enough that the plant’s roots will fit into the top third or half of the pot.
Media: Various forms of expanded clay aggregate have been used successfully (LECA, Aliflor, Hydroton, PrimeAgra, etc.)
and I also have had good luck with horticultural perlite, lava rock, and diatomite. It is important to rinse the media well before planting,
to make sure any salts or other chemicals, as well as fine grit, are removed. Media should be soaked in a large quantity of water for a
day or two, swishing it around occasionally, in order to remove as much of the fine dust as possible that could suffocate the roots. Be
careful not to breathe any of this dust! I sometimes throw in a few broken styrofoam peanuts to create air spaces, especially in larger
pots or for plants that might like it a bit more dry. A top layer of pebbles helps to keep perlite in place and will minimize evaporation.
(First Rays has a discussion of media, and there is also this site discussing perlite:
http://www.members.cox.net/lmlauman/osp/html/perlite1.html)
Repotting: As always, plants are more likely to respond well if they are repotted when new roots are getting started. Remove as much of the old, organic medium as possible without damaging the roots, and remove any dead roots. Dead, organic material could start rot in the moist atmosphere of an S/H pot! A brief soak in diluted Physan before repotting might also be a good idea.
An important tip for success is to keep the roots in the top third or top half of the pot when transplanting from traditional media into
S/H. Roots can adapt to the moister conditions, and even grow all the way into the reservoir, but roots can rot if they are placed into
too much moisture too fast! Monitor your newly planted orchid to make sure it is adjusting adequately to its new environment.
Watering: Ray suggests filling the pot all the way to the top of the medium with fertilized water and then letting it drain to the
level of the reservoir. Some people block the drainage holes to do this, while others set the pot into a tub of water. I, however, tend to
top off the reservoirs with a splash of water when I notice that they are low. Occasionally I do follow Ray’s directions, which I’m sure
are good for giving a better drink to the roots at the top of the pot where the wicking action does not carry as much moisture. Another
instruction is to flush the pot with clean, pure water once a month, to remove any possible salt buildup. I grow with S/H to minimize
effort, so this doesn’t often happen in my happy orchid home.
Fertilizing: Fertilizers stay in the reservoir, so keep it weak!
There are many online resources for more information about growing in S/H. Check out First Ray’s website, which also has
a discussion forum dedicated to semi-hydroponic orchid growing, or do a web search or visit an online orchid forum. I have been
growing some plants in semi-hydro since May 2002, and I would also be happy to answer questions!
Partial Immersion
I have also been growing in a variation of deep water culture, with the distinction that I will grow with only the ends of the
roots in constant or frequent immersion. Leaving the bottom of the basket or mount, or just one or two roots in a mounted plant, in a
quarter inch or so of water in the saucer often meets the water needs of the plant without the necessity on my part of dunking or
spraying the plant every day or so. Depending on the type of plant, most of the roots will be out of the water, or, if it is a plant that
prefers greater wetness, I will have more moss or tree fern around the roots which will bring more moisture to the root mass. I have
had great success with this with plants in the Sophronitis, Encyclia, Dendrobium, Holcoglossum, Cattleya, and other genera. This
method will risk rot, and faster breakdown of mounts and moss, so be prepared to remount or change moss more often than you
might if you were treating the plants more conventionally.
Venger’s has a website with information about deep water culture (http://www.usapatriotsamerica.com/culture/water.htm)
and I also found useful information by doing a search on water culture at the Orchid Board (http://www.orchidboard.com).
An overview of different culture methods can be found at http://www.rv-orchidworks.com/orchidtalk/articles/article-22.html.
I make no guarantees as to results, but venturing beyond the conventional pot or mount methods can, after some experimentation, make life easier and, at least in some cases, plants happier.
Amy Trautwein
APRIL, 2011
Page 7
VANDA CARE
Vanda
is one of many genera in the orchid family Orchidaceae. The name Vanda is derived from
the classical Indian language Sanskrit. Wild vandal orchids grow in northern Australia and Eastern
Asia, including India, Indonesia, the Philippines, New Guinea, southern China and the Himalaya region. The show from one Vanda spike can sometimes last up to eight weeks or more, and this is naturally a highly desirable treat in the floral industry. If you a Vanda plant with ideal Vanda orchid care, it
can bloom more than once a year.
Vanda orchid care - Medium
Many Vanda orchids are epiphytic, but you can also find lithophytic and terrestrial species. Finding out
which type of orchid you are keeping is recommended, since this will affect the recommended Vanda
orchid care. A coarse potting medium will usually work well, e.g. medium or coarse grade Fir bark.
Vanda orchid care - Temperature
The recommended day temperature for Vanda orchids is 75 - 85˚ F (24 - 29˚ C). If you want to provide your plant with ideal Vanda orchid care, you should lower the temperature to 65-75˚ F (18-24˚
C) during the night to mimic the conditions found in the natural Vanda orchid habitat. Healthy and
well established Vanda orchids can usually cope with occasional temperature extremes as long as they
are brief.
Vanda orchid care - Light
An important aspect of Vanda orchid care is providing your plant with sufficient amounts of light.
Vanda orchids need a lot of sun light, but should be protected from intense midday sun. Ideally place
your plant in a spot where it can enjoy full morning and afternoon sun while being shaded from 11 am
to 3 pm. Yellow leaves indicate overexposure to strong sunlight, while dark green leaves indicate that
your orchid needs more sun. Strive to keep the leaves light green.
APRIL, 2011
Page 8
Vanda orchid care - Watering
Epiphytic and lithophytic Vanda orchids are naturally very sensitive to over-watering, but the terrestrial species will also be hurt if you leave them “with their feet wet”. Always let the potting medium
dry out thoroughly before you water your Vanda orchids.
Vanda orchid care - Nutrients
Suitable Vanda orchid care that includes sufficient amounts of feeding can make your orchid bloom
more than once a year. Use a high nitrogen fertilizer (25-9-9) year round. For a normal strong fertilizer, one teaspoon a month will be enough. Ideally split up the dose and provide your orchid with several feedings instead of giving it all its food in one large serving.
Vanda orchid care - Repotting
Do not disturb your Vanda orchid by repotting it too often. Wait until the orchid has outgrown its old
pot before you repot. This will typically take 2-3 years during normal circumstances. In some cases,
the potting medium should however be exchanged immediately. Never let your Vanda orchid grow in a
potting medium that have gone sours and/or is unable to drain properly. Green mould and snow
mould is also a sign that should prompt instant repotting if you want to provide your plant with ideal
Vanda orchid care.
Anyone interested in receiving
the American Orchid Society
FREE eNewsletter,
please forward your email address to:
[email protected]
APRIL, 2011
Pat Cammarano sent me some great links of interesting orchid material
found on the web. The link to the repotting of the Tiger Orchid at the
BBG is especially interesting. Enjoy!
http://www.rv-orchidworks.com/orchidtalk/articles/article-31-12.html
This might be of interest to some of our new members.
On June 28, Aquatic House curator Dave Horak and members of the Horticulture staff repotted
BBG’s Grammatophyllum speciosum, commonly known as the tiger orchid. Considered to be
the world’s largest orchid species, the plant on display at BBG is a beautiful specimen weighing
approximately 300 pounds.
Use the link below to see the repotting of the
Tiger Orchid
http://www.bbg.org/news/repotting_tiger_orchid/
360 Degree Orchid Photography — A Step by Step Guide
http://www.lightandmatter.org/2011/general-photography-articles/360-degree-orchid-photography-astep-by-step-guide/
This may be of interest to some of our members.
http://www.rv-orchidworks.com/orchidtalk/articles/article-11-12.html
Some members might want to try Amy’s method of planting?
Page 9
APRIL, 2011
Page 10
Choosing Potting Media
The correct answer to that is that there isn't a single, best medium ! Instead, when choosing a medium,
one has to take a "holistic" approach and look at a variety of factors, including:The growing conditions the
plant prefers. The plant's water storage capabilities. How well does the plant take to repotting, that is, being
disturbed. What kind of conditions are you easily able to provide. How fastidious are you about watering
and feeding, or at least what are your capabilities. All of those factors should be considered when choosing
a medium, and should be reconsidered for each type of plant you grow.First of all, think about the conditions the plant experiences in nature (if it's a hybrid , think about the species in its breeding background,
especially recent ones). Right off the top we may be baffled, as orchids in nature usually have no potting
medium at all, but are epiphytes, living attached to the bark of host trees! Look a little closer though, at the
environment those roots, dangling in air, see. Water Supply: Is the plant from a rainforest, constantly
bathed in rain or fog? Is it instead exposed to seasonal monsoons followed by relatively dry periods, or does
it get typical, random rains such as seen in many temperate climates? Air Movement: Heavy and wet, cool
and buoyant, or parching, arid winds? Growing Location: Is the plant from a bog, where it constantly has
"wet feet," or is it in leaf litter on a forest floor, in a densely-leaved host tree, nestled in the detritus of fallen
leaves, or up at the top where the wind and sun dry it out rapidly? Typical Temperatures: Is the plant from a
hot, intermediate or cool environment? (The choice of medium can help you grow a plant that otherwise
might not do well in your environment.)
Next, let's looks at the plant's physical structure, and how it relates to the plant's water storage ability.Plant
Structure: Those with pseudobulbs can generally store water for longer periods of time than those without.
Take a close look at the leaves as well, before concluding your evaluation. Those plants having thin, straplike leaves, such as oncidium and cymbidium , will lose their stored water faster than those with shorter,
thick leaves, such as cattleyas. Plants that don't have pseudobulbs have in some cases developed thick,
fleshy leaves (phalaenopsis , for example) as their water storage scheme, but that's obviously not as effective
as pseudobulbs. Others that have neither pseudobulbs nor thick leaves, such as phragmipediiums, are going
to need a steady supply of moisture.
Root Structure is another important aspect in deciding on the medium. The factors to consider are the extent of root growth (long versus short, branched versus single), the thickness of the roots, particularly that
of the velamen layer. A very extensive root system suggests that the plant has to work hard for its water and
nutrition, so wants to gather as much as it can when it is available. By contrast, a short root system suggests
easy and/or frequent availability of them. Velamen - that layer of white that covers healthy roots - is actually dead tissue that acts as a sponge to rapidly absorb water and nutrients, so they can be passed onto the
plant. Thick velamen is generally found on plants that like to grab a lot of water, but prefer to have their
roots dry rapidly. Vandaceous plants are good examples. Don't take that to mean that roots with thin velamen like to stay moist - you need to couple that with the plant's storage structure, mentioned above. Oncidiums, for example, tend to have thin velamen on thin roots, but their root systems are quite extensive, and
they have pseudobulbs for storage, so they too, like to dry fairly rapidly. Phalaenopsis, with their minimal
storage capabilities, tend to have thick roots to add to the "reservoir," so do well in a damp, but not soppy
environment.
As to how well a plant tolerates repotting, that can generally be judged by the plant's growth rate, with slowgrowers being less tolerant of disturbance than others. Some plants, notably paphiopedilums, seem to actually enjoy repotting, often putting on a growth spurt immediately afterwards!Your growing conditions play a
most significant role in deciding on a medium. If you have no problem providing a constantly humid environment due to your climate or if you grow in a greenhouse, the moisture retention on the part of your media is less of a concern. Ambient temperatures play a role here, as well, as warmer temperatures tend to increase the evaporation of water, and along with the drying rate of the medium.
APRIL, 2011
Page 11
Choosing Potting Media continued...
Your personal tendencies, and how much time you can- or prefer to spend watering your plants is another
significant factor in choosing a medium. If you're a "busy bee" who likes to pamper your plants, then an
open medium that doesn't hold a lot of water may be a good choice. If, on the other hand, you have a large
collection and don't have time for such individual attention, or if you travel a lot on business, it might be
worth thinking in terms of a more stable moisture holding selection.OK, now that we have the background
behind us, it's time to look at the various media ingredients that are commonly available, and their specific
properties.
One of the more common media ingredients - used alone or in blends - is fir bark. Good quality bark is
getting harder and harder to find, but the stuff that is available is typically steamed to extract the resins that
could be toxic to your plants. The removal of that resin increases the water-holding capacity of the bark,
but also shortens the life of it. The irregular shape of the pieces of bark can lead to excess packing, which
may reduce the airflow to the root system. Fine grade is often used for small seedlings, and the coarser
grades for large plants. Before using bark, water it with boiling water to facilitate wetting, then let it cool.
Coconut husk chips (CHC), made from the pithy covering outside of the spherical, hard coconut shell, is
gaining popularity as a replacement for fir bark. It is readily available, relatively cheap, and wets and rewets
better than bark. It also tends to be more regular in shape - chunks or cubes as opposed to coarse flakes so facilitates better air flow throughout the root mass. CHC holds a lot more water than bark, so keep that
in mind when using it. It lasts considerably longer than bark as well, often going three years before decomposition becomes an issue, as opposed to a year for bark. A word of warning: despite claims otherwise,
most CHC has a fairly high salt content when you get it, so it pays to soak and rinse it several times prior to
use. Coconut husk fiber is the wiry result of stripping and shredding the interior of the coconut husk,
rather than chipping it. It is springy and flexible, and is often matted to form liners to hanging baskets, but
it can also be use straight as a medium for plants that really like to dry out fast. If fairly tightly compressed,
water will stay in pockets in the mass for a longer time period.Coir, sometimes called "Coco-Peat," is the
result of grinding the husk into coarse powder. It is often used as a substitute for peat moss in blends, but
can be used alone for seedlings that like to stay damp. Peat moss and its commercially available blends,
such as ProMix HP, are sometimes used in the so-called "mud mixes," which hold water really well. Like
coir, it can be blended with other ingredients to produce a good medium for terrestrial and semi-terrestrial
species. Osmunda fiber, the roots of a number of ferns from the genus Osmunda, used to be a staple in
the orchid-growing community, but it is now difficult to find a high quality fiber.. It is tough and springy,
and requires vertical alignment in the pot to ensure proper drainage. In almost totally ensures that the
plants' roots get all of the air they need, and as it decomposes, is an excellent source of nutrients, requiring
little or no supplementation via fertilizers. Tree fern fiber - the "trunks" of tropical tree ferns - has replaced most osmunda in orchid culture. It is very stiff and airy, and can be obtained as shredded fibers,
chunks or slabs. It has little moisture holding capacity, so aerates media blends very well. The slabs are often used for mounting plants directly. Redwood fiber, or "Palco Wool" as it is sometimes known, is a
light, fluffy wood fiber that does not decompose, and is added as a moisture-retention aid and as a means of
increasing the acidity of media blends. Sphagnum moss is pretty much a standard in the orchid growing
community, whether by itself or as a blend additive. Available in a wide range of quality - from the expensive New Zealand "Primo" and it's close-but-less-expensive counterparts from Chile, to some really lousy
stuff (short strands, no "fluff"), - the good stuff is a great medium for plants that love constant moisture.
Learning how to attain the proper packing density is a challenge, as it holds so much water that it can become sopping pretty easily. Generally, sphagnum becomes sour and in need of replacement in the 6- to 9month range, although that can be extended by blending it with charcoal.
APRIL, 2011
Page 12
Choosing Potting Media continued...
Hardwood charcoal is a very long-lasting medium ingredient having a moderate-to-low moisture holding capacity.
Many growers of vandaceous plants use the coarse grade as the sole medium. Some claim that the charcoal "sweetens"
the medium by absorbing some of the foul chemicals produced in the decomposition of other media components, or
excess salts from fertilizers. Perlite, often referred to as "sponge rock" for the coarser grades, is expanded volcanic
glass, and is a great aerator of blends, but still holds enough moisture to be a fairly good substrate for Semi-Hydroponic
culture. Pumice is similar in nature to perlite, but with a higher density and lower moisture-holding capacity. LECA,
standing for "Lightweight Expanded Clay Aggregate," is a general term for any number of more-or-less spherical terra
cotta pellets that were originally designed to be the aggregate in lightweight concrete formulations, but later diverted to
horticultural use. There are many brands available, including Aliflor, Hydroton, PrimeAgra and others, and they vary
greatly in their properties and applicability to orchid culture. Diatomite is calcined diatomaceous earth muds. It is
highly porous, and holds a tremendous amount of water. While it seems to be just too wet for Semi-Hydroponic culture,
it has seen good application by itself for pot culture for plants that appreciate a damp root environment.Read more
about Orchid Growing at the RVO OrchidTalk Orchid Forums.
APRIL, 2011
Page 13
APRIL, 2011
Continued from:
Page 14
Insect and Arthropod Pest Identification and Management Editor: Ronald Oetting
UGA/CAES/Griffin Campus Handout for Southeast Greenhouse Conference
FUNGUS GNATS AND SHORE FLIES
Description and Biology
Fungus gnat adults are flies, about 1/8-inch long, with long legs and long, thread-like antennae.They resemble mosquitoes
more than common flies. Fungus gnat wings are gray with a distinct, Y-shape in the vein near the tip. Adults are weak fliers, but they run rapidly on the medium surface or may remain motionless. Fungus gnat larvae live in the soil, which makes
them difficult to find. Larvae resemble worm-like maggots with no legs. They are translucent gray to white in color, about
1/4 inch long, and have a shiny black head. Fungus gnats have a life cycle consisting of an egg, 4 larval, a pupa, and an
adult stage. A generation can be completed on 20 to 28 days, depending on temperature. Females tend to fly around the
surface of the growing medium, and live approximately 7 to 10 days. Females deposit between 100 to 200 eggs into the
cracks and crevices of the growing medium. Eggs hatch into larvae in 4 to 7 days. Larval development requires from 8 to
20 days. The pupa stage lasts about 3 to 5 days.
Shore flies are found under similar environmental conditions, but they are more robust and stronger fliers than fungus gnat
adults are. Shore flies are shorter than fungus gnats, and are similar in size to fruit flies but they are black in color with dark
eyes, wings and legs. Shore flies have approximately five, tiny whitish spots on each wing. Both the antennae and legs are
short. The shore fly larvae is also a maggot and is approximately half the length of a fungus gnat larva and is fatter, being
more than one-third as wide as it is long. The shore fly larval head capsule has the same whitish color as the rest of the
body. Shore flies have a life cycle consisting of an egg, 3 larval, a pupa, and an adult stage. A generation can be completed
in 15 to 20 days, depending on temperature.
Fungus gnats and shore flies can infest a crop from either soil or algae within the greenhouse, from contaminated potting soil or transplants, or by flying short distances into the production area.
Feeding Damage and Symptoms
Fungus gnat larvae feed on plant roots and any organic matter in the growing medium. They tend to be found more in
growing medium containing peat moss or pine bark. Their feeding on roots can create sites for fungal infections and can
reduce the plants ability to take up water and nutrients from the growing medium. This may result in excessive moist conditions that may lead to more disease problems from soil-borne pathogens including Pythium spp. Tender plant stems and
leaves that contact the soil surface can be fed on by the fungus gnat larvae. In contrast, neither larvae nor adult shore flies
feed on plants. Damage caused by shore flies is primarily due to the excrement ("flyspecks") deposited.
Detection and Scouting
The best way to scout for fungus gnat adults is to use yellow sticky cards. These are similar to those used for detecting
adult thrips, whitefly and leafminer in greenhouses. For fungus gnat adults, yellow sticky cards can be placed horizontally
on the edge of pots or flats with the sticky side facing upward. The thread-like antennae and long legs are prominent characteristic features of adult fungus gnats stuck to sticky cards. For shorefly adults, place yellow sticky cards just above the
crop canopy. To determine the presence of fungus gnat larvae insert a ¼ inch raw potato wedge or stick into the growing
medium. Remove after 48 hours and count the number of fungus gnats on the potato.
Management
Cultural Control. Implementing proper cultural controls such as watering and fertility denies fungus gnats and shore flies
the conditions necessary for development, reduces the need for pesticides, and promotes healthier plants. Shore flies can
be controlled by managing algae, which is their primary food source. Both insects are more of a problem under excessive
moist conditions such as during propagation. Over wet conditions can develop quickly in a greenhouse during rainy, overcast weather, especially when automatic irrigation has not been reduced. Growing medium should be stored dry, and pots
and production areas must be well drained. Once regular scouting indicates that fungus gnats or shoreflies are likely to
cause a problem then chemical or biological measures may be appropriately implemented.
APRIL, 2011
Page 15
Sanitation. Remove weeds, old plant material, and old growing medium to reduce problems with fungus gnats
and shoreflies. Weeds growing underneath benches can create a moist environment that is conducive for fungus
gnat and shorefly development. Allow the potting medium to dry before watering also will reduce population
levels.
Chemical Control. Insecticides used for controlling fungus gnats can be applied as drenches to the pots (for larvae) or as sprays to foliage, pots, beds or other soil surfaces (for adults) as indicated by the label directions. Some
insecticides, such as Bacillus thuringiensis israelensis, cyromazine, diflubenzuron, fenoxycarb, kinoprene, and
pyriproxyfen work on the larvae stage when applied to the growing medium in pots and to the soil underneath
benches. These materials do not kill adults present during application or adults that develop from pupae present.
As a result, effects may seem disappointing for the first few days. Adulticides, such as the pyrethroids (i.e. bifenthrin and cyfluthrin), may be used in conjunction with products targeting the larvae. Insecticide applications for
fungus gnats should be made according to pest presence and the label instructions. Sometimes this results in applications at 10 to14 day intervals. Good resistance management practices dictate that classes of insecticides be
rotated, approximately every generation cycle or 3 weeks, depending on the temperature. Always follow pesticide
label directions.
Biological Control. Sometimes naturally-occurring, beneficial parasites or parasitoids may become established
and regulate fungus gnat populations. This frequently occurs when broad spectrum pesticides are not used in the
production area. Fungus gnat parasites are small, fragile wasps, much smaller than fungus gnats and may be seen
walking on the surface of growing medium. Commercially available biological control agents include the soil
predatory mite, Hypoaspis miles, and beneficial nematodes in the genus Steinernema.
. To be continued….
Topics to come in future newsletters are:
Whiteflies, Mealybugs, Scales, Lepidopterous Larvae, Caterpillars or Worms, Slugs and Snails, Pest Management
Strategies for Insects and Mites in Common Greenhouse Production.