A network that helps people worldwide obtain rapid advice and information on crop protection, including the identification and management of plant pests.
PestNet is a network that helps people worldwide obtain rapid advice and information on crop protection, including the identification and management of plant pests. It started in 1999. Anyone with an interest in plant protection is welcome to join. PestNet is free and is moderated, ensuring that messages are confined to plant protection.
A condition of taro in Niue showed signs of nutrient deficiency and/or fungal disease and members were asked to comment. No insect pest or disease was found on the plant. Later, the entire plantation was affected.Questions were asked about:
The growing regime of this plant.
Was it very dry a couple of months ago?
How long ago was it planted?
Was it the only one in the field with such symptoms?
Are tiny eriophyoid mites present?
In response, Niue replied:
The taro suckers were planted during the time of rain.
The plant is only 4-months’ old.
When the suckers were prepared for planting the small corm was snipped off and planted. That is why no corm is present, but there are a lot of roots.
There was no sign of nematode affecting the roots, i.e., a lack of swellings or half dead brownish roots. In fact, the roots are perfectly healthy.
If the mites cannot be seen with the naked eye, that could be a possibility.
Sometimes, mite attack is secondary to the plant being under stress. However, there seems to be little corms and may suggest a root problem – possibly nematodes or a pathogen. If the latter, Pythium is a likely candidate. If this fungus is to blame, the roots are often brown, and even on those that are still white, the small side or feeder roots are decayed. All this can best be seen by washing the roots to remove soil and then looking at them in water. But if Pythium was the cause, the leaves should show signs of wilt, and those in the photo are erect.It was asked whether the youngest leaves are unusually small. If so, this could be a sign of Pythium infection; however a small leaf symptoms could also be causd by Taro badnavirus or Dasheen mosaic virus.The photos were forwarded to the Plant Diagnostic and Advisory Service, CABi Bioscience. The response was: Foliage symptoms such as interveinal necrosis and marginal scorching suggest a nutritional problem perhaps as a result of poor root efficiency. The root system looks poor in two of the photos so this could be the ‘root’ cause(!). Need to examine roots to get any idea of what if, anything, is the problem on them.