Attack on the Aphids

There were so many aphids in the greenhouse it was almost embarrassing.  Remember the pictures of leaves covered in aphids?  It was about time I did something to stop them. 

Goodbye greens!  This cart full of plants contained the very worst of the aphids.  So they got thrown out in the blue dumpster.  (Usually I compost everything, but the road to the compost pile is too mushy to drive on right now.)

Luckily the aphid infestation is in the non-organic certified greenhouse.  So, we sprayed two types of pesticide (by 'we' I mean the farm manager did the spraying).  The cocktail contained one part Botanigaurd and one part Azatin.  

BotaniGaurd is a mycoinsecticide, meaning spores adhere to the host and produce enzymes that dissolve the hosts cuticle.  

Azatin is an insect growth regulator.  When an aphid (and many other insects, fish and aquatic invertibrates) comes in contact with the pesticide it interferes with with the organisms ability to molt, thus killing it.  This is a pretty typical kind of pesticide.

Next week I'll release two beneficial insects: ladybugs and parasitic wasps.  They will control the aphids on a long term basis.  (The picture above is neither of these.  It's just an ordinary wasp on goldenrod.  I don't take many insect pictures.)  I'll write about them in detail next week when they get released.

Attack of the aphids

Last week I announced that there are aphids in the greenhouse.  By now there are more, lots more and we have begun a three-pronged attack on them.  But first, it's important to know just who we are dealing with.

The foxglove aphid, Aulacorthum solani, has a huge range of host plants and can transmit 45 diseases, so it's pretty bad.  The adult aphids are 1.5-3 mm long and are dull green or brown.  Their antenna are longer than their body and have dark joints.  Their legs also have dark joints and their cornicles are dark at the ends.  The picture below (which I did not take) shows all these characteristics really well. 

Photo taken by Andrew Jensen (aka Aphidman)

They like to colonize deep in plants on tender, young leaves.  I definitely found this to be true.  See how gross the young spinach leaves look?  What really kept me up at night is the reproductive rate of these aphids.  In just THREE DAYS the population doubles in a 55 degree environment.  How could I sleep when I knew aphids were busy multiplying that fast?  Happily, we've started attacking the problem.  You can look forwards to the next installment of "Attack of the aphids."

Sources: AphidID, Jandricic et al., 2010, RIS

Two very cold greenhouses

Last Friday I went to check on the greens and see if they needed to be watered.  In the winter they don't need much water, so I don't go in as often.  When I went in the greens looked wilty - wilty? Even though it was below freezing outside?  Closer inspection showed the media was frozen on top and the greens were not wilted, but frozen.  Here's what happened in a temperature timeline:

Fall fuel use

While sifting through all the growth rate data I collected last fall, one thing I'm looking at is fuel use, and if using more fuel to speed up growth rate is cost effective. 

The greenhouses are heated by a furnace that blows hot air out (left).  They have a meter on them (right) that shows how many hours the blower has actually been blowing air out.  I record the number twice a week.  Since the meter is continuous I adjust the numbers to reflect the number of hours it was on for my particular experiment.  Oh-so-conveniently, the furnace uses one gallon of fuel every hour, so I also convert "hours" to "gallons."

The above chart shows total fuel use in each greenhouse.  Greenhouse one is heated to a 40 degree (F) minima and greenhouse two is heated to a 50 degree minima.  This doesn't mean that each greenhouse is at a constant temperature, it means the temperature will not fall below the given set point.  You can see this created a big difference in how much fuel was used. 

Since 'gallons of fuel' is a bit arbitrary to the non-greenhouse owner, lets attach monetary values (everyone understands dollar signs). So,

Greenhouse 1: 108gal x 3$/gal = $324

Greenhouse 2: 264gal x 3$/gal = $792

That is a big difference!  But is it economically worth it to heat the greenhouse to a higher temperature?  Will that make greens grow faster?  Or is it just throwing money down the drain?   That's what I'm working on figuring out (but haven't done so yet!).

* As usual, this data pertains only to our greenhouses this fall.  It is not complete and should not be used elsewhere.  If you are looking for data pertaining to winter greens growth, fuel use and temperature you'll just have to wait until I'm done with my thesis! *

New Years

Happy new years!  For the next few weeks the greenhouses are empty of greens.  (For those of you in New England you'll notice the picture below definitely was not taken this week!  I cleaned out the greenhouses before Christmas.)  I'll start planting again mid-January.  In the meantime I am moving numbers around, analyzing them and planning for the upcoming season.  The big question is what variety of spinach should I use to avoid downy mildew? 

The greenhouses

All the greens I grow are in these two identical greenhouses.  I think they were built before I was born.  This summer their plastic coverings were replaced.  Proper greenhouses have two layers of plastic covering them.  On these two the top layer is regular greenhouse plastic and the  bottom layer is fancy IR plastic with an anti-condensation coating. Air is blown through the two layers to help insulate the greenhouse from the outside.  It's like a big, clear, puffy coat for the greenhouse instead of just a raincoat.

                                           Which would you rather wear in the winter?

The heater and fans are controlled by a complicated control board (above right) which I only have to set once and then it does all the work.

At either end of the greenhouses are great big fans which turn on in a three step process if the temperature gets above 75 degrees.  (I also measure the light with the little box on a stick on the left and hourly temperature with the white boxes four benches down on the right.)

If the temperature is lower than 75 degrees two little fans (in the upper right hand corner above) are always on to circulate the air.  This is one way the powdery mildew spores got spread around.  Since one set of fans is always on, it is always noisy.  

Circulating the air is super important on hot and cool days.  Right now air circulation is very important for spreading hot air from the heater around.  Each greenhouse has one of these propane heaters.  Hot air blows out the round part on the right.  On cold days I stand right in front of it to warm up. 

Early morning at the greenhouse

Sometimes it still feels dark when I get to the greenhouse early in the morning.  The past few warm days have caused lovely fog over the fields, and wetlands.

Greenhouse temperature

Today is graph day!

This week I have been thinking about temperatures.  If you remember back to when I set up the temperature probes there would be thousands of temperature readings.  All that data in a giant, overwhelming spreadsheet taunting me because I am not so sure how to use it all.  While figuring that out I've been looking at just a few days at a time.  Kind of like snapshots.

The greenhouse temperature itself is a good place to start. 

Soil temperature in control treatments.

I realized after I made the above chart that I had used soil temperature data instead of air temperature.  See what having oodles of numbers in a huge spreadsheet does to me?

Below I graphed soil and air temperatures together.  You can see the treads I highlighted in the soil temperature graph can also be seen in the air.  The major difference is air temperatures are much more volatile.  They seem to jump up or down a few degrees each hour.  This could be due to cloud cover, or air movement from the fans.

Soil and air temperatures in control treatment.

*  This data represents five days in the greenhouse I am working in.  

Other greenhouses or high tunnels may have similar temperature trends but they will not be identical.  *

Germination trials: Correct labeling

As I've started writing it became apparent I needed to work on my terminology.  Perhaps this is not the sexiest topic, but it is important to correctly name the different components of an experiment.  That way if someone wants to replicate what you did they will know how.  Or, if they are reading the paper (you will someday publish) they will have a clue what you did without the aide of a colorful picture. 

Greenhouse:  The setting of all this experimentation.

Block:  Contains one of each treatment.  I have two blocks of six treatments.

Treatment:  You remember all the treatments right? They are the independent variable.

Sub-plot:  With in each treatment there are six sub-plots for each species.  We stuck the three species in one tray because it was convient.

Replicate:  Each individual seed.

Just how many seeds is all this?  If you could make bets with the bill Salmon P. Chase is on you would be in the right ballpark.

Seeds are sprouting!

Last week I did a second planting of lettuce, spinach and mizuna.  I spread the work over three days, so it was far more relaxed than the first planting.

Now, 12 days after being planted, lots of seeds are sprouting.  For each tray-full of seeds I record the day each seed sprouted in a table like this:

Like before the green cells are lettuce seeds, the orange are spinach and the blue are mizuna.  So far the seeds are sprouting in the order we thought they would - first mizuna, then lettuce and finally spinach.

Germination trials: measuring temperature

The big fancy data logger from onset.com

One of the major components to this first experiment looking at germination rate is measuring the temperature in each of the treatments.  Happily there are data loggers that continually do this for you.  We are using two models from Onset: a big fancy looking one and a plain box one.  The fancy one is more expensive and is water proof so if I spray it with a hose by accident it will be ok.  The smaller one isn't water proof so I installed it way up high where only the hose shouldn't reach.

The small not-so-fancy looking data logger from onset.com

Both data loggers support four temperature sensors.  For the germination trials we need two sensors per treatment for a total of 24 sensors on 6 data loggers.  The data loggers can be programmed to take a temperature reading at any interval you would like.  We are going to set them to measure the temperature every hour on the hour.  In one week there will be over 4,000 temperature readings!  All this data is downloaded into a software program from Hoboware.

The picture above shows how the data is displayed with Hoboware software.  Each line, or dotted line, shows a temperature probe over a five day period.  Hourly temperature readings can be scrolled through or exported to excel.  

Germination trials: low tunnel coverings

Once the PVC pipes were set up on the greenhouse benches it was time to cover them, creating mini-greenhouses.  This led to an introduction into the world of plasticulture.  Tons and tons of plastic is used to grow our food.  So much, that the word plasticulture is used to describe all the greenhouse coverings, drip irrigation, mulches, wind breaks, post harvest handling, marketing, and fertilization tools used to grow food crops.

There are a lot of different kinds, colors and weights of plastic to use when making a greenhouse, high tunnel or low tunnel.  Here are the four kinds of plastic we picked and one non-plastic treatment:

1. Sun Master 70% Opacity overwintering film

From it's name you can tell that not much light gets through this white polyethylene plastic.  It's the kind of plastic that is put over greenhouses or tunnels that house woody plants in the winter to keep temperatures within from fluctuating too much.  So, it should be "warm" inside which will promote seed germination, but it will not be good place for leafy plants to actually grow.

2. Sun Master Greenhouse Film 

This is the clear plastic that you would expect a greenhouse to be made out of.  It is 6mm thick polyethylene and allows a whopping 92% light transmission through.  So, this one should keep it "warm" inside as well as let plants grow because they will have some light.  (I say some light because all the layers of plastic add up.  If there are two layers of plastic on the greenhouse itself and one on the low tunnel only 78% of the available light can be transmitted through.  On a dark winter day that isn't much light.)

3. Agribon+ AG19 Row Cover

This is a agricultural fabric but it made from plastic as well.  Polyester and polypropylene strands are bonded together in a swirly random fashion resulting in the term "spunbonded".  This makes a cloth like covering that allows water through, but doesn't actually absorb water as a true cloth would.  Spunbonded fabric comes in a range of weights.  The one we're using allows an 85% light transmission and weighs 0.55 oz/yd.

4.  Clear plastic with holes in it

I haven't sourced this plastic so I don't know much about it yet.  It is far thinner than the other plastics we chose so presumably more light will be transmitted through.  It is also covered in holes which allows better air flow.

5. KEN-BAR agritape heat mats

These obviously are not a covering, but they are the final treatment in this experiment.  They still alter the plant's environment by keeping the soil and roots warm.  Heat mats come in all sorts of shapes and sizes.  This brand often is used by people who keep terrariums filled with snakes and other cold blooded animals that I wouldn't want to have for a pet.  Right now we have the heat mats set to be 40 degrees Fahrenheit at night.













6. Control

Every experiment needs a control.   I forgot to take a picture, so you'll just have to take my word for it that there is a bench with a bottom layer of plastic and nothing else.

Germination trials: building tunnels

If you remember step one of Experiment Number One is finish building the low tunnels.  These hoop-shaped structures on top of the greenhouse's benches will hopefully help raise the internal temperature by a few degrees to speed up seed germination (and maybe growth?).  What coverings we are testing will be the topic of a future post, this is all about construction of the low tunnels.

Simplicity and affordability were the constraints in building the tunnels.  We designed them to mimic low tunnel construction used outside: bended hoops covered with a layer of plastic.  Indoor construction on benches involves a few more parts, but they are commonly found things and are cheap. We used only these seven parts:

1/2" PVC pipe

1/2" metal brackets

tech-screws

snap clamps

binder clips

bike hooks

covering

The greenhouse benches are made of aluminum and are 10' x 4'.  So, the first step was screwing the brackets on using the tech-screws.  To ensure the pvc wouldn't wiggle it had to be placed in the bracket as it was being screw on.  

Each bench used three pieces of pvc: one for each end and a middle piece to keep the covering from sagging.  The coverings were attached to the pvc using 1/2" snap clamps from Johnny's.  These are the best and made building the tunnels really easy.  They come in four inch pieces because they are designed for outdoor use.  Since these low tunnels are not outside and blustery winter weather won't be an issue we cut each one into four smaller pieces.  From 40 snap clamps we ended with a big box of 160!

Each low tunnel was covered with three pieces of material.  Each end-piece was attached to the pvc with clamps and to the bench with binder clips.  (Since starting this project I now have binder clips in all of my pockets.)    The largest piece of material is pulled tight over the low tunnel and secured to the bench on only one side.  The other side is attached to a piece of pvc with more snap-clamps.  The weight of the pipe holds this side of the tunnel down and allows it to be easily rolled up.

To get the rolled up side to stay up I duct taped a bike hook to a snap clamp and put it on the central piece of pvc in the tunnel.  So far these have worked really well, although I am careful to unroll the tunnel side and not just let it drop in case the hook could puncture the covering.

Next up: low tunnel coverings!  

Greenhouse or tunnel?

High tunnel

looks like a typical greenhouse but is not heated.

Greenhouse

has a source of heat like propane.

Low tunnels

temporary structures that look like mini-greenhouses.  

Sides are held down with sand bags or dirt and have to be uncovered for harvesting.

low tunnels in the greenhouse

Temperature values used are from H. C. Wien's paper
"Use of low tunnels to improve plant growth in high tunnels"

Today we started setting up germination chambers on top of the existing greenhouse benches.  Really our germination chambers are just fancy low tunnels.  Low tunnels are simple hoop structures made from wire or PVC and covered with permeable fabric or plastic.  Their benefits are two-fold for organic and small farmers, they keep insects off plants and warm up the air.  We plan on using the increased temperature to our benefit.

If you put these low tunnels inside a greenhouse or high tunnel (unheated greenhouse) plants are even more insulated from the outside cold.  Our first trials using this arrangement will be looking at the temperature ranges using different materials as covers for the low tunnels.  Permeable fabrics, plastic sheeting and permeable plastic all have their benefits and drawbacks.