Thursday, June 27, 2013

Grasshoppers - Legends of Greatness & Evil

Legends of greatness and evil abound in the west.  When it comes to the 6-legged westerners there is no more storied creature than the grasshopper.  The stories of their swarms are epic and biblical – skies dark as night and crops devastated in moments.  The Hopi tell their children that the grasshopper will bite off the noses of those who disobey elders or violate taboos.  Other tribes claim that the grasshopper predicts bad weather or brings evil with it.  Even Aesop featured the grasshopper in his fable of the Grasshopper and the Ant – using the grasshopper as counterpoint to the industrious and hardworking ant.  Needless to say, the grasshopper doesn’t survive the harsh winter because of his summertime idleness and folly.

Grasshoppers present an obstacle for those of us who were taught to look for the best in every situation.  I’ve always felt that there isn’t much good that can be said about grasshoppers, but I’ve become curious about where they fit in the scheme of things and whether I need to change my attitude. 

It turns out there are more than 400 known species of grasshoppers in 17 states of the western U.S.  Only 2 dozen of these species are considered a pest.  Several species are considered as beneficial insects because they consume undesirable plants. The other grasshoppers are somewhat benign. 
Even the ‘bad guys’ have some good points:
  • As an herbivore, grasshoppers link plants to the rest of the ecosystem and his helps biodiversity.
  • Their droppings (frass) contribute nutrients by turning the plant material into fertilizer.
  • They are a food source for birds, spiders, lizards, and rodents.

However, as with all things in the garden, I’m looking for balance.  I think that there is enough vegetation to go around.  But I want those bad guys to exist outside my gardening perimeter.  I realize now that before I try to manage the grasshoppers in my patch, I need to identify what species I’ve got and determine whether they are actually harmful to my cultivated plants.  One excellent clearinghouse of identification guides is provided by the USDA and can be found at this link:

A little about their life cycles
Understanding the life cycle of a grasshopper can help you identify the species you have and to determine when treatments will be most effective.  Taking this step can save time and money.  Typically, grasshoppers emerge in late spring and remain active through autumn.  Treatment at any time will help, but to gain optimal control it is important to watch for them in their earliest, above soil stages. 

All grasshoppers begin life as an egg.  The eggs are laid in soil, in tight clustered pods and are usually well hidden in specific habitats.  The eggs begin to incubate immediately.  Depending upon the species, the embryos begin to develop and then based on environmental cues (temperature is a major cue) enter a state of diapause and cease growing until favorable incubation temperatures are reached.  Both the diapause and incubation inducing temperatures differ from species to species.

Generally temperatures between 50 oF and 55oF trigger development to restart.  Once optimal temperatures are reached grasshoppers continue to incubate in soil and will hatch as nymphs.  All grasshoppers develop through a process of gradual (simple) metamorphosis, there is no larval stage.  The hatched nymph looks like the adult except it is smaller, has no wings, fewer antennae segments, and only rudimentary genitalia.  Depending upon their species, as grasshoppers grow and develop they molt (shed) their outer skin 4 to 6 times during their nymphal (immature) life.

Control options
One way to keep grasshoppers away from the plants you don’t want them to consume is to provide some beneficial habitat in a place where you are happy for them to be.  An island of dense, native grasses and flowers is a great way to help keep them away from your more precious plants. 
When grasshopper populations exceed your tolerance, there are two natural and effective organic methods for controlling them. 
  • Nosema locustae - naturally occurring fungus that weakens and kills when eaten.
  • Beauveria bassiana - derived from naturally occuring fungi in the soil cause muscadine disease when consumed.
Nosema locustae is available under two labels:  Semaspore and NOLO Bait.  These products are effectively the same.  The Nosema locustae is embedded on flakes of bran that act as bait to the grasshopper.  Once consumed, the grasshopper develops a disease, is weakened, consumes less, and eventually dies.  In 2 – 4 weeks, 50% of the population will be dead.  It is most effective when grasshoppers are ½” – ¾” in size.  Nosema locustae is only fatal to grasshoppers and their close relatives such as crickets and mantids.

Beauveria bassiana is available as a liquid under two product names:  Mycotrol O and Botanigard ES.  It is available as a wettable powder as Botanigard 22WP.  This product causes white muscardine disease in a wide variety of pest insects including thrips, aphids, whitefly, psyllids, and fire ants.

When either of these products are applied, pay close attention to grassy areas of untilled ground, to southern slopes or any other location known as a grasshopper hatching bed.

While grasshoppers may be considered a scourge, they have some interesting and quirky behaviors.  I’d like to leave you with a few of these so you might see why they are quite fascinating:
  • Females lay eggs in holes that they dig with their abdomen.
  • Some grasshoppers spit a bitter, brown liquid as a defensive behavior - they may spit at you when you handle them.
  • Before molting, grasshoppers do not eat.
  • During molting, they swallow air to build pressure to break the cuticle of the old 'skin'.
  • Each grasshopper species has an individual song produced by rubbing or flicking the lower back legs on their forewings.
  • Some species have elaborate courtship routines performed by the males. Some include posing using wings and legs while others wave brilliantly colored wings to woo their mate.

In spite of their bad reputation, I can’t help but feel respect and some admiration for an insect that has achieved fame in so many cultures and breeds such fear and loathing in the hearts of gardeners and farmers everywhere.   But when it comes down to the battle for my plants – I am happy that there are control methods that won’t harm the good guys in my garden.

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