Archive for April, 2011

Integrated Pest Management

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.

Insect attack

As many of you may know, not all insects are bad. In fact, some are actually quite beneficial. The groups I’m referring to are predators and parasitoids. These kinds of insects help maintain population balance in natural ecosystems. In agricultural systems, they can help suppress and manage pest populations and prevent outbreaks.

Predatory insects are the carnivores of the insect world, feeding on other insects and animals. Common predators include ladybugs, hover flies, and mantises. Arachnids, like spiders, are also great predators. My current favorite are predacious diving beetles in the family Dytiscidae. Specifically, the pair of sunburst diving beetles Thermonectus marmoratus (order Coleoptera) I have swimming around in the tank on my desk.

Photo from Arthropoda

In explaining parasitoids, I must also differentiate between parasites. So I’ll start with the latter. Parasites are organisms, in this case insects, that feed on other organisms and depend on them for survival. They complete their reproductive cycle on the host without killing it. Lice are parasites for example. Their host specificity can vary from humans, cows, or birds in some cases. In contrast, parasitoids feed on other organisms and complete their reproductive cycle while killing their host. Many parasitoids include wasps or flies. A majority of parasitoids have specific hosts but some are generalist parasitoids and can use different host species. Parasitoids lay their egg(s) in their host, and the immature parasitoids develop within the live host. As parasitoids continues to develop, it slowly kills the host.  For the record, it’s one of my pet peeves when the terms “parasite” and “parasitoid” are used interchangeably.  They’re similar, but really not the same.

Photo courtesy of University of Florida Entomology

This video was shown in one of my classes.  From National Geographic, it’s a clip about parasitic wasps called “Body Invaders.”  Fascinating, and a little gruesome.

Latex lovers

So the title of this post is a little misleading I have to admit.  I wouldn’t say these insects particularly love latex, but the words tolerate and sequester come to mind.  With the alternatives being avoid, succumb to, die from…not the most pleasant options.

In the title, I’m referring to the common milkweed plant Asclepias syriaca and its associated herbivores. What a group they are!

Photo courtesy of Folks Butterfly Farm

Milkweed is particularly known for its chemical defenses against herbivory, producing latex and cardenolides for protection.  Usually, these compounds are toxic to insect herbivores.  But, as always in the insect world, there are exceptions.  A handful of insects are specialists on milkweed, feeding on one or a few species because they have evolved a mechanism to overcome the plant defense.  For a full list of specialist herbivores, see here.  The most common milkweed associated insects I see around here include monarch butterflies, the common milkweed beetle, and the small milkweed bug.  But I haven’t been looking very closely.

Photo courtesy of Rhode Island Bugs

Notice the striking color of the beetle, bug, and butterfly.  Their bright coloration is known as aposematic coloration, or warning coloring.  They’re telling predators, “I’m not very good to eat.”  Monarchs, in particular, sequester the toxic cardenolides as caterpillars and butterflies.  The result?  Birds spew their last meal.

The thing I’d like to introduce is the amazing monarch migration across North America.  These butterflies overwinter in lower latitudes as adults, congregating in Monterey, California and Michoacán, Mexico.  Given that we just had (hopefully the last) snow in Ithaca, maybe I should go to Mexico too!

Photo courtesy of Wanderlust Images

For more about this awesome migration and ways to tag and get involved, see here.

Cycle of life

The last few posts have been a little heavy on the policy side so I thought it would be good to write more about bugs. That is part of the reason I’m here anyway.  Today’s post will be a bit more technical, but hopefully not more boring.

Most insects exhibit one of two kinds of life cycle: hemimetaboly or holometaboly.

Hemimetabolous insects include true bugs, grasshoppers and crickets, mantises, dragonflies and damselflies, cockroaches, and termites to name a few.  The “hemi” refers to the simple type of development or metamorphosis.  In this case, the immature insects look very similar to the adults.  Most often, immature insects are called nymphs. Below, we have nymphal (L) and adult (R) bugs (Order: Hemiptera).  They look like milkweed bugs, perhaps Lygaeus kalmii.

Photo courtesy of Wikipedia

Holometabolous insects include beetles, flies, bees, wasps, ants, butterflies, and moths (and several others).  Theirs is a complete metamorphosis with the following stages: egg, larva, pupa, adult.  There can be several laraval stages as the insects grow.  Typically, the immature larva look nothing like the adult stage.  Likewise, the pupal stage varies in appearance and similarity to larva or adult.  Larval moths and butterflies are most often known as caterpillars.  Below is the life stage cycle of monarch butterflies, Danaus plexippus  (Order: Lepidoptera), who also feed on milkweed.  More on these specialist feeders to come.

Photo courtesy of Laurie Williams

Understanding the development of insects is imperative to appropriate management and control by biologically based strategies, as well as chemical or cultural strategies.  Happy Earth Day everyone!

Save science education!

While researching some interesting bugs for Expanding Your Horizons, I came across this great educational project engaging young scientists and teaching them about vernal pools.

It’s an inspiration to see environmental outreach and science education working together to encourage a new generation of citizen and research scientists.

So when I heard that the NSF GK-12 program (National Science Foundation Graduate Fellows for Science, Technology, Engineering, and Mathematics (STEM) in K-12 Education) has been cancelled due to cuts in the 2012 budget, I couldn’t be more disappointed.  An article published in Science describes reasoning for and reaction to this decision.  It’s a large program, and an impactful one at that.  Not only is it beneficial for K-12 classrooms, it is valuable experience for graduate students like myself.  Suffice it to say that many, many people are upset.

If you want to add to the discussion and dissent, I encourage you to write to save GK-12 and support opportunities for science education.