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Insect pests, plant diseases and integrated pest management


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Anybody know what is doing this to my young mango leaves? It seems to happen at night but I haven't managed to spot the culprit. The cut leaves are not even eaten, just left lying around on the ground. Vandalism!

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I haven't seen this in mango, but I would suspect a cutworm or leaf cutter bee. If it's happening at night, a cutworm is the most likely suspect. 

 

https://en.wikipedia.org/wiki/Cutworm

 

https://www.gardeningknowhow.com/plant-problems/pests/insects/leaf-cutter-bees.htm

 

Go out at night and look for pest activity, inspect the stems and under side of leaves closely with a flashlight, to try and get a positive identification. 

 

Since your tree appears to be in seedling stage and not a fruit producer yet, you could use a chemical insecticide barrier application, like the pyrethroid "bifenthrin", active ingredient in Chaindrite Stedfast 30SC. 

 

An organic approach would be to spray the foliage and drench the soil with a neem seed extract product, Azadirachtin concentrate, a repellent and reproductive disruptor . And/or a soil treatment (where cutworm larvae may reside during day) of Metarhizium, or Beauveria, entomopathogenic fungi that attack the pest insect's cuticle. 

 

But there is also the wait and see approach, because the tree will not likely be killed, the insect pest will pass the feeding stage of it's life cycle and the tree will re-foliate and outgrow the susceptible stage of growth. Avoid high NPK chemical fertilizers that stimulate excessive vegetative growth which is tender and attractive to pests. Enrich the soil with compost, and complete organic fertilizer. 

 

Don

Chaindrite Stedfast 30 SC.jpg

Metarhizium anisopliae225.jpg

Aza.jpg

Beauveria (2018_05_25 14_55_25 UTC).jpg

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Thanks for that. Cutworms of some kind sound quite possible and could explain why they just let the leaves drop to the ground (to eat later). They’ve taken all the young leaves off this sapling but they have appeared on other young mango trees. Next time it happens I’ll have a more careful look at night and maybe try a physical barrier around the stem like a ring of outward-facing sticky tape as a first line of defence.

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