Though undetectable for the human eye, mites create major costs for papaya growers who currently rely on pesticides to control the crop-damaging pest.

To tackle this tiny, yet expensive intruder, researchers from Universidad Autónoma in Chiapas, Mexico are studying alternative methods of biological pest control.

Lead investigator, Dr. Martha Elena De Coss Flores, spoke with www.freshfruitportal.com about the the team's efforts to address this increasingly significant crop concern.

"Before mites were secondary, but now they are a main pest and are a concern for producers. This is because the crop depends 100% on chemicals and pesticides. The pests become more resistant, and the natural controls and predators are destroyed," she said.

"We propose using alternative methods of biological control to diminish chemical use and damage to the environment."

She explained that the tropical mite Polyphagotarsonemus latus damages plant health by interfering with photosynthesis. The pest may go unnoticed until producers observe a reduction in foliage and fruit loss.

"There are other mites like Tetranychus where damage is done to the leaf stomata. The mites' toxins close off the stomata from the leaves and that prevents exchange of gases, leading to a decrease in photosynthesis and production."

To avoid pesticide use, De Coss Flores described a naturally occurring fungus that has shown pest-control potential.

"When we talk about biological control, we are talking about the Beauveria bassiana fungus, which transmits white muscardine disease. The fungus is found in all of the world's soils and is used in many countries as a biological pesticide," she said.

"Per hectare you only need two 300-gram bags with a proper proportion of conidia to combate Tetranycchus urrticae. You can also use this for spider mites."

At US$4.50 a bag, this option is considered one of the most economical control measures.

Another option is a "trap crop" using the Tepary bean to attract mites.

"This bean is preferred to attract mites, which can be used for trapping with excellent results. The most recognized farmers in the region can diminish acaricide applications up to 75% in green houses," she said.

"For me this is a promising plant that we have in our country. It also attracts white flies which carry Polyphagotarsonemus latus with them."

She also mentioned banker plants which, as the name implies, serve as a bank for predators and parasites.

"If we introduce a predator, we can lower the mite population. This way we can preserve the natural predator population as a bio-control agent," she said.

In Chiapas, some producers use poinsettias as "banker" plants and have reported great results.

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