Eradication of pink bollworm infesting cotton crops and high cotton yields can be achieved without insecticides by the new sterile release strategy released in journal Nature Biotechnology.

Bruce Tabashnik, head of entomology UA's College of Agriculture and Life Sciences is the research lead. Tabashnik is a pioneer in study of crop pests and has to his credit the discovery of first moth that evolved BT toxin resistance.

History of pink bollworm

Pink bollworm (Pectinophora gossypiella) infests the cotton fruit capsule at the caterpillar stage. They were first detected in 1917, when Arizona cotton industry suffered a huge 50% loss of cotton crop.

Bacillus thuringensis cotton or Bt cotton introduced from 1996 was capable of targeted destruction of pink bollworm caterpillars.

Bt cotton is planted with refuge patches of non-Bt cotton that allow breeding of pests. Inherent resistance of Bt cotton destroys most of pests.

The remaining few resistant ones are forced to mate with a large population of susceptible pests (maintained by the presence of refuge land) making sure inheritance of resistance occurs as a recessive trait. Hence hybrid off springs is also susceptible.

The main disadvantage of refuge crop treatment is its inability to eradicate pests. Tabashnik "Refuges are a way of managing pest populations, so you have to accept the permanent presence of the pest. You don't get rid of them. You maintain susceptibility by promoting survival of the susceptible insects."

Arizona's eradication program

This highly profitable eradication program sterilizes moths and uses them for mating with resistant varieties. Although non-Bt fields require extremely large numbers of sterile moths, planting Bt cotton makes this method very successful. This is the first attempt at combining Bt plantations with sterile release strategy.

Tabashnik "On the Bt cotton, pink bollworm survival is virtually zero. This makes it much easier to overwhelm the wild population." This method provides for use of otherwise refuge land, does not use broad spectrum insecticides and results in sustained long term pest control.

Within four years of introducing the eradication program in 2006, pink bollworm infestation dropped by 99.9%. Losses by bollworm infestation decreased dramatically from $18 million per year (1990-1995) to $ 172,000 (2006-2009).

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