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“THRIP - FRIEND OR FOE”

          Thrip are tiny insects, of the insect order Thysanoptera.  Most thrip can barely be seen by the naked eye, averaging only 1/15th to 1/25th of an inch in length.  Their wings are long and slender with close-set hairs on both borders.  These close-set wing hairs increases the lifting ability of the thrip in flight.  Most thrip species feed on plants, while other species are predatory, feeding on other thrip and small insects species.  Certain thrip species are essential for pollination of plants, especially of certain fruit varieties.

          Onion thrip (Thriops Tabaci) cause tremendous damage to onion crops across the United States.  It is estimated that onion fields infested with thrip cause from 7 to 35% yield loss.  The average yield loss is about 20%.  Thrip damage not only affects onion yields, but its storability as well.  The storability of the harvested onions can mean the difference between profit or loss to the farmer or processor.  If onions store well, the farmer and processor can wait until the market price is right before selling.

          The variety of the onions grown has a lot to do with its vulnerability to onion thrip.  Red onions in general are more susceptible to thrip damage than most of the white or yellow onion varieties.

          Onion thrip is a very interesting insect.  It does not simply insert its mouth parts into a leaf, or stem, like most sucking insects.  Thrip have a special part of their mouth that is shaped like a rasp. They work the rasp-like mouth part across the surface of the blade.  This action removes the top of the blade cell, thus the sap flows out of the opened area.  Thrip suck up the plant juices as they are released from the onion blade.  This type of feeding activity causes the onion blade to become very thin, and silvery white in appearance.  The higher the thrip infestation, the more damage there is to the onion crop.

          Onion thrip reproduce very rapidly.  Eggs take from 4 to 10 days to hatch.  The nymph that hatches begins to feed on the plant for about 5 days before going into the pupa stage.  They remain in the pupa stage for only four days before emerging as adult thrip, ready to start the cycle over again.  With such a short life cycle, the population of thrip can literally explode in a very short period of time.  There are generally 5 to 6 generations of thrip produced each growing season.

          Many different insecticides have been used to kill onion thrip over the years.  These insecticides have only been somewhat effective, as they only kill the thrip they come in contact with.  The thrip stay near the center of the plant where the foliage of the onion plant is tight, thus control using insecticides are limited.  Along with the fact of only limited kill, and the short life cycle of the thrip, control using insecticides is very difficult.  This frequent type of spray program may not be economically feasible for most farmers.  This type of program deals with the effect of the problem, not the cause.

          Another method being used to reduce or control onion thrip population is by the use of predatory insects that will feed on onion thrip.  The predators most commonly used for thrip are lacewings, convergent lady beetles, and minute pirate bugs.  Biological control of insect pests is relatively new in the United States.  There have been some successes using predatory insects in a contained environment, but it is hard to keep the released insects in a given field.  It may also be cost prohibitive to release enough predators to control the thrip in a given field.  Again, they are working with the effect, not the cause of the thrip problem.

          At Kozgro, Inc., we believe that the farmer needs to work with the soil as well as the plant to prevent a thrip infestation problem.  Kozgro’s organic fertilizer and plant food, AFB, helps to bring the sugar level up in the plant.  When the sugar level is high enough, the thrip will no longer feed on the plant.  Sucking and chewing insects, like thrip, excrete sugar, but are unable to digest it.  If the insect ingests too much sugar, it will develop symptoms similar to diarrhea and die.  Kozgro’s AFB creates a healthy vigorous plant that resists thrip damage.  At Kozgro, we deal with the cause of thrip infestation, not the effect of the infestation.

KOZGRO WORKS WITH NATURE - NOT AGAINST NATURE