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.
May 2013.A memeber from a country not stated, planted 100 papaya trees. Everything was fine until a few days of heavy rains. After the heavy rains, the ground was sprayed with Roundup (glyphosate). A few days later, the lower leaves were yellowing. Can anyone tell whether the rain caused this or the spraying. Is there anything that can be done for these trees.
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.