Herbicide damage, papaya, Not stated

There were a number of comments:

• It could be the phytotoxicity of the herbicide. Perhaps irrigate the soil to dilute the effect of the Roundup.
• Carica papaya is sensitive to many herbicides. The sensitivity depends oil type (clayish or sandy or rocky) and the age of the plants. Papaya has a shallow root system, and death can occur in 8-14 days. Do not forget that papaya are prone to root rots caused by oomycetes, and especially so in times of heavy rains.
• It is important to differentiate between the normal growth of papaya and herbicide damage:
  • look at the youngest leaves; if they show curling and chlorosis, then this a sign of herbicide drift.
  • yellowing of older leaves is normal, often a flush of yellow (young) leaves will occur and produce a leaf drop at the same time.
  • papaya are very susceptible to glyphosate while the trunks are still green. Once they have hardened they can tolerate spray on the trunks (but not on green trunk or foliage).
  • you should continue to manage the trees as normal providing nutrients, pest and disease control and irrigation.
• If Roundup was sprayed after rain it is unlikely that it was carried into the soil to cause toxicity via the roots – it tends to disintegrate very quickly in soil in any event. The options are:
  • the plants are suffering from Roundup drift onto the young plants or from waterlogging.
  • drift damage can easily happen if the plants are very small with leaves close to the ground. Without knowing how tall your plants are you will have to make a judgement on that.
  • it is likely you are seeing the effects of waterlogging as a result of the heavy rain. That is more likely to show up as yellowing of the lower leaves – Roundup injury is more likely to show a more general yellowing of the whole plant.
  • trying adding some nitrogenous fertiliser to help the plants recover.