Leek Moth

The best part about an online magazine, is that they send you emails only if you want them.  And in the case of Saveur, I get tasty recipes to try on a regular basis.  Last week, a number of recipes for a Summer Vegetarian Feast filled my email inbox.  One was a delicious leek and zucchini galette, combining great flavor and seasonality.

There are leeks growing alongside my onions in some fields.  Some of the growers I work with have a few different Allium species growing including garlic and leek.  These crops could be subject to leek moth infestation, but leek moth is currently only known in certain areas of New York and Canada (in North America).  An invasive species from Europe, leek moth,  Acrolepiopsis assectella, is a small, brown to black moth with yellow-green caterpillars.  The pupae are small cocoons with a distinct lacy casing.

Adult Leek Moth courtesy of AgroAtlas

Leek moth pupal casing

Leek moth damage include mining and perforations in the leaf, with window-paning damage where the caterpillar has not eaten all the way through all layers of the leaf tissue.

Leek moth damage

While there are no chemical treatments yet in New York, cultural treatments such as crop rotation, row covers, and removing vegetative debris at the end of the season are recommended.  In Canada, a parasitoid wasp  Diadromus pulchellus was released as a biological control agent as part of an integrated pest management approach to control leek moth.  Perhaps that may be an option for leek moth control here as well.

 

Ashes to Ashes

Emerald Ash Borer is now in Western New York!  If you remember my first Who’s Who post, the Emerald Ash Borer is a new invasive species that infests ash trees.  This is what the insect looks like:

Read more about the recent infestation here.  And remember:

Thrips counting

This past week I’ve been out in the field a lot, looking at a lot of onions.  And good news for the growers, I haven’t found very many thrips.  In integrative pest management, counting and sampling has quite an important role.  Courses of action are based on thresholds established for certain pests and certain crops.  These are economic thresholds and economic injury levels.

The economic injury level (EIL) is defined as the lowest pest population density that will cause economic damage.  If a pest populations reaches the EIL, economic damage will be sustained.  To prevent such damage, action can be taken at the determined economic threshold (ET).  The ET is the point at which action should be taken to prevent further damage, and prevent pest densities from reaching the EIL.  The ET is also called the action threshold, which is more descriptive.  More information about EILs and ETs can be found here.

In New York State, the ET for onion thrips is 3 thrips per green leaf.  When sampling, it is important to examine multiple plants in different areas of the field.  Some growers sample up to 50 plants to evaluate thrips populations  The calculation to determine whether or not the ET has been reached is:

(# of thrips counted)/(# of leaves counted)

Of course, it is also important to assess damage, for thrips as well as other pest species.  For onion thrips on onion, this is the characteristic damage:

Different growers have differing levels of acceptable damage, depending on whether it is direct or indirect damage, or may have different thresholds at different points in the season.  To spray or not to spray, that may still be the question.

One ray of sunshine

We’ve gotten a lot of wet weather the past few weeks which has greatly affected the vegetable growers in the region.  Soil preparations and field plantings have been delayed, putting everything a couple weeks behind schedule.  With the delays in crop host establishment, it seems like pests may also be delayed in the colonizing of crop fields.  One way of determining whether this is the case is to use degree day models.

In pest management, degree days are a measure of heat which can be used to track development or manage insect pests.  Organisms have development temperature thresholds, below and above which development is arrested.  For example, with San Jose scales Quadraspidiotus perniciosus the lower threshold is 51ºF and the upper threshold is 90º.  As long as the ambient temperature is between these two thresholds, San Jose scales continue to develop.  For onion thrips, the lower threshold is 52.7ºF.

Degree days are the accumulated product of time and temperature between temperature thresholds.  One degree days is one 24 hour period in which the temperature is one degree above the lower development threshold.  Of course, temperature varies throughout a 24 hour period in field situations. This is taken into account when constructing a degree day model.  Degree days can also be accumulated throughout a growing season, which is how emergence predictions are calculated.

In the simplest model, the equation for a degree day calculation for one 24 hour period looks something like this:

(min temp +max temp)/2 – (min threshold)

Summing the above term for the number of days would give you the degree day accumulation.  Other calculations model temperature fluctuation in more complicated ways, which may provide closer estimates of actual degree days accumulated.

So let’s check on onion thrips in Elba, NY.  Cornell has degree day information here, with 147.6 degree days accumulated since Jan 1.  This calculation is based on 50ºF as the minimum threshold.  The UC IPM site states 140.4 degree day accumulations are necessary for egg development.  Given that onion thrips have a slightly higher threshold than the Cornell model, they’re not hatching.  In Penn Yan, degree day accumulation is 182.0.  Slightly higher, which is better for onion thrips.  But on account of the rain, which demolishes thrips populations, I still didn’t see any thrips out and about when I was in the field yesterday.  So until we get some sun and it warms up, I may just be sitting pretty.

Funions

As a graduate student writing about entomology and agriculture, it’s inevitable that my own research will come up.  So I would like to share a little bit about what I do, especially as I begin my first field season.

My research interests are focused on sustainable pest management of agricultural systems, specifically biological control of insect pests.  Currently I’m working on management of onion thrips in onion production systems of New York.  Onions are one of the most valuable vegetable crops in the state, grossing $45 million in 2009.  Most of the crop is grown for fresh market or storage, indicating a low tolerance for insect damage that reduce bulb size, quality, or both.

Onion thrips (Thrips tabaci) are a major pest in New York onion production.  They hide in leaf folds and feed on green leaves, reducing photosynthetic capacity of the plant and overall yield. Furthermore, onion thrips can can transmit Iris yellow spot vitus (IYSV) a Tospovirus which can further damage plants and cause complete yield loss.

Photo courtesy of Thrips of California

Current management practices rely heavily on foliar broad spectrum insecticide sprays with multiple sprays per season to control onion thrips.  However, efficiency may not be adequate as thrips often hide between leaves, protecting themselves from spray droplets.  Furthermore, the possibility of insecticide resistance development is high due to the nature of thrips reproduction.  Newer selective insecticides have shown to be effective in thrips management and fortunately may be compatible with biological control agents such as predators and parasitoids.

I’m interested in natural enemies that may potentially impact thrips populations.  This season, I am lucky to have multiple research sites with a mix of growers to complete my research.  I’m so excited to be doing field work out in the sunshine!

Who’s Who #1

For those of you who can’t make it through the whole post, the answer is… Insect 2- the Emerald Ash Borer!  If you see this little beetle crawling around, please see this site to report your sighting to the appropriate contact.  Now, on to the other critters!

Insect 1

Photo courtesy of Philip Rose

This particular specimen from Thailand is commonly known as the Jewel Beetle, in the family Buprestidae. Individuals in this family are commonly known as the metallic wood borers and are known for their iridescent color.  The coloration is not pigment, but rather structural coloration that will not fade with time.  As such, they are often used as adornments and frequently collected.  There are 53 genera of Buprestidae in North America, but not all shiny green buprestids are of concern!

Insect 2

Photo courtesy of Insect Images

This is who you should be looking for!  If you see this critter running around, head the other way!  No, not really.  Make sure to report your suspicion to the appropriate Cooperative Extension office found here under “Contact Info.”

This is the Emerald Ash Borer (EAB), Agrilus planipennis Fairmaire.  Like Insect 1, this is another beetle (order Coleoptera) in the Buprestidae family.  One of the distinguishing characteristics of the EAB is its elongate and cylindrical shape, unlike the other Buprestids.  They are bright metallic green, occasionally with reddish or bronze tones as well.  They are usually around 10mm in size.

This particular species is a concern because it is an introduced species from Asia causing damage to ash trees in Eastern North America.  Severe infestations cause branch dieback and can eventually kill the tree in just a few years. Biological control agents have been explored, concentrating primarily on parasitoid wasps.  Research is currently still being conducted and these biological control agents are still being evaluated for efficacy.  For more information about the state of native bio control agents see here.  For bio control agents native to Asia see here.  Pathogenic fungi and nematodes are also being considered.  Currently, the best preventative measure is to reduce the movement of infested material, including moving firewood.

Insect 3

Photo courtesy of Wisconsin Butterflies

The six spotted tiger beetle Cincindela sexguttata is a beetle in the family Cicindelidae and are found all over the world.  These beetles are aggressive predators that run really really fast.  One of their identifying characteristics is their protruding eyes, that classic “bug-eyed” look.  While found in similar regions as the EAB, it’s long legs and protruding eyes help to identify it is not of concern.

Insect 4

Photo Courtesy of Flicker

This is the red-legged buprestid beetle, Buprestis rufipes. While in the same family of beetles as the EAB, the yellow markings are a good way to distinguish between the two species.

Long post after a long onion-planting day…whoo! More on that later.  Thanks for sticking around!

Potato potata

It seems an auspicious time when I come across extremely similar recipes on two different food blogs that I follow…especially when they’re crispy potato roasts from The Bitten Word and Smitten Kitchen. And my office mate was just talking about home made potato chips. Good thing I’m making dinner for the house tomorrow.

With all this talk about potatoes, how could I not mention the devastatingly cute Colorado Potato Beetle and all the havoc it’s wrecked over the years.

Leptinotarsa decemlineata is a beetle native to North America that originally fed on other Solanaceous plants.  It’s primary host is the cultivated potato, but also does damage to tomato and eggplant crops.  The potato beetle is multivoltine, having several generations per growing season.  Because of this, early management of the pest is key to minimizing loss.  While chemical control is perhaps the most common management strategy, the development of resistance to insecticides is increasing in many populations.  Other non-chemical controls are equally important in managing this pest, which might include changing crop planting times, applying mulches, or lining trenches in the periphery of the field to reduce early season colonization of the pest.  At home, physically removing adults or egg masses can be an effective way of managing the problem.

Until next time, I leave you with delicious preparations of potatoes, so versatile!

Potato au gratin

Twice baked potatoes

Potato salad

And if that weren’t enough, there’s always potato-origin beverages….  Happy Slope Day 2011!