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.
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!
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
And if that weren’t enough, there’s always potato-origin beverages…. Happy Slope Day 2011!
There has been and continues to be a lot of discussion regarding genetically modified organisms (GMOs) or genetic engineering (GE). While there are many things that fall under this category, I’m going to stick to food crops (which is an expansive category in itself).
This is what I’m not interested in.
Although it looks pretty cool, and might entice children who are picky eaters to try something nutritious, I find the blue hue of strawberries completely unnecessary and unnatural. It looks radioactive and reminds me of Teenage Mutant Ninja Turtles. (Speaking of which, who thought it was a good idea to let kids pal around with teenaged mutant turtles who were ninjas and took orders from a sewer rat? That said, I loved that cartoon.)
What intrigues me is the possibility of using genetic engineering to reduce the use of pesticides, reduce environmental impact, and help create a more sustainable agricultural system for the future. The blue strawberry above is an example of one kind of genetically engineering a transgenic crop. An arctic flounder gene coding for an antifreeze protein was introduced to strawberry to help protect the crop against frost. In theory, it seems like a pretty good idea to protect crops. But I’m curious to hear the reasoning for using a fish protein in contrast to a cold-hardy plant from the tundra regions of the world.
Another hot commodity in the Frankenfoods debate is Bt corn. Bacillus thuringiensis is a bacteria currently used in organic agriculture as an insecticide for particular crops. Different strains of Bt are effective against different kinds of pests which means not all pests are susceptible to the insecticide. The bacteria produces proteins which disrupt the gut membrane of insects, causing pests to stop feeding. Currently, Bt has been genetically engineered into certain field crops like corn, soy, and potatoes. Instead of the pest coming into contact naturally with the bacteria, the plant continuously produces the protein toxic to insects. This dramatically reduces the insecticides necessary to control pests, as is the case with Bt corn and the European Corn Borer. But it’s important to keep in mind that all the concerns about insecticide resistance and resistance management still exists for Bt crops.
Photo courtesy of Iowa State Entomology
Genetic engineering is not a cure or a method. It’s merely a tool that might assist with production and the promotion of sustainable agriculture. It is equally important that we proceed with caution and concern for social and cultural values. It’s a complex issue that has no singular answer. And that seems to be my answer for everything.
For more information, Harvest of Fear was a televised report by NOVA and Frontline exploring this issue. The report can be viewed on YouTube by clicking here. The Future of Food was a documentary on the same issue produced by Deborah Koons Garcia.
Integrated pest management, or IPM, relies on biological, cultural, and chemical methods to manage pests in agriculture and in your community. It is neither conventional pest management, nor organic management. Instead, it draws on the best of both, and uses many other tools and resources available.
Biological control focuses on using living organisms to suppress the population of a pest organism in an effort to reduce damage below a threshold. Such control organisms may be other insects which include predatory insects or parasitoids. Other biological control agents might be bacteria, fungi, or nematodes.
These control efforts include physical barriers like mosquito nets or row covers as well as traditional practices such as crop rotation or intercropping. Field sanitation, the removal of diseased plants or pest refuge, is also considered under cultural control.
Chemical control includes using pesticides judiciously to manage pest, but also manage for pesticide resistance. Considering the mode of action, or how the pesticide kills the pest, is an important aspect of chemical control.
IPM is an ecological approach to pest prevention, observation, and intervention. It is a tool that can be tailored to grower needs and resources for practical pest management while reflecting biological, social, and economic understandings of the system.
There was some buzz a while back about the funding and future of the New York State IPM program. Thanks to public support, the state budget has allocated monies to continue supporting the agricultural and community programs. The power of people is incredible.