I've noticed some of our young Napier grass are suffering from this blight on their leaves. One guy told me it was alphids but I don't think so. Does anyone have any ideas?

Might be a small beetle that sucks the juice from the leaf leaving a black to brown marks as that part of leaf dies

Napier grass is susceptible to many diseases. The spots are most likely a disease coming from sugarcane. Napier grass is also attacked by many fungal diseases; the most common being leaf spots caused by Helminthosporium sacchari (syn. Bipolaris sacchari), Helminthosporium ocellum and Pyricularia grisea. Also attacked by the bacterium, Pectobacterium carotovorum. Other diseases including Pseudo- Fiji Disease, chlorotic streak, a disease of sugarcane, and leaf mottle virus, and by nematodes (Aphelenchus avenae, Meloidogyne incognita acrita, M. javanica and Pratylenchus brachyurus).

 

In Africa, napier stunt diseases has destroyed many napier grass pastures.

https://www.sciencedirect.com/science/article/abs/pii/S0261219415000587

https://plantvillage.psu.edu/topics/napier-grass/infos

 

Over the years I have campaigned about the use of napier grass in Thailand. It is a very poor quality grass. There are far better grasses available that do not get any diseases. Species like Mulato II and Mombasa guinea grass. I fail to understand why farmers keep growing napier grass.

A brother-in-law just told me it is aphids. Time to get out the trusted organic insect deterrent.

37 minutes ago, bannork said:

A brother-in-law just told me it is aphids. Time to get out the trusted organic insect deterrent.

Definitely not aphids. I wouldn't even bother spraying with your organic insect deterrent. Just change the grass species. 

1 hour ago, Michael Hare said:

Definitely not aphids. I wouldn't even bother spraying with your organic insect deterrent. Just change the grass species. 

Too late for that at the moment, maybe next year. Most of the Napier is fine and the cows love it.

2 hours ago, bannork said:

A brother-in-law just told me it is aphids. Time to get out the trusted organic insect deterrent.

ISN'T

1 hour ago, bannork said:

Too late for that at the moment, maybe next year. Most of the Napier is fine and the cows love it.

They love it because they have no alternative. Do you have to put the napier grass through a chopper to get the cows to eat it? With other grasses you do not have to do this. Do the cows put on weight with eating just napier grass? You probably have to feed them concentrate as well. That is expensive.

https://www.lazada.co.th/products/azoxystrobin-25-wv-sc-100-i312010440-s556952640.html?exlaz=d_1:mm_150050845_51350205_2010350205::12:1498579383!58089999096!!!pla-296030489971!c!296030489971!556952640!134264193&gclid=EAIaIQobChMI-KvF5fPV6QIVAg4rCh3LmAEpEAYYAiABEgLvSPD_BwE

 

Get yourself some of that mate. Its also a growth enhancer.

9 hours ago, emilyarin said:

Might be a small beetle that sucks the juice from the leaf leaving a black to brown marks as that part of leaf dies

..beetle-juice..that rings a bell.

Could be rust, looks like it, common disease of grasses.

Not easily cured, but can be prevented by use of (spray) wettable sulphur.

I've got this or something like it in my Morning Glory.

2 hours ago, millymoopoo said:

Could be rust, looks like it, common disease of grasses.

Not easily cured, but can be prevented by use of (spray) wettable sulphur.

It is not Aphids ,more likely rust.

My Nappier gets it every year and most years we take 3 cuts, a year, it gets infected at the same growth stage as the op's, no need to do anything the crop will keep growing and the rust will disappear, they is very literal  detrimental effect on the crop yield ,no need to spray .

We have had our Nappier for 8yeras now we use it for silage ,feed it during the dry season, they were only one occasion when I think it did reduce the yield a small amount .

Michael H has a good point abut Nappier grass they are far better grasses out they for cattle ,if it needs chopping then it is past its best feed value ,breeding cattle getting feed over 50-60 day old Nappier plus rice straw ,will give you an infertility problem ,diet being  short of energy ,and probably minerals.needing to feed concentrate to make up for the energy shortfall.

This Sweet Israel Grass ,or better known as  Dwarf Nappier does have a protein of 21 % but at no older than 40 days old ,when its gets to 60 day old the  protein  soon drops.

We grow it because we have a very limited acreage ,we have made( not last year drought ) 10 ton of silage ,3 cuts  from 1 1/2 rie does us for most of the year      

Thank you everyone for all the interesting ideas, I'm gonna go with the rust theory, it doesn't seem to be a big problem, once the grass grows, and with this heavy rain, it's going beserk.

Apart from the Napier, I've got Sweet Israel and Ruzi, the latter I'm particularly fond of, such an attractive grass.

Mulato II is a much more attractive grass than Ruzi. Mulato II is a three way cross between ruzi, signal and brizantha. Superior drought resistance, greater protein levels and much higher dry matter levels and leaf content than ruzi grass. 

2 hours ago, Michael Hare said:

Mulato II is a much more attractive grass than Ruzi. Mulato II is a three way cross between ruzi, signal and brizantha. Superior drought resistance, greater protein levels and much higher dry matter levels and leaf content than ruzi grass. 

Is it too late to plant Mulato II this month?

 

5 hours ago, IsaanAussie said:

Is it too late to plant Mulato II this month?

 

No, as long as you have some rain it will still grow ,a few years ago we planted grass seed end of May and it still grew despite a 2 weeks without rain, 10 days after sowing the seed.

22 hours ago, IsaanAussie said:

Is it too late to plant Mulato II this month?

 

Mulato II can be planted throughout the wet season. But it becomes difficult from late July through to the end of September with:

1 Too much rain causing excessive soil moisture which can rot the seeds.

2 A lot of overcast, cloudy days, reducing radiation and slowing down seed emergence and growth.

 

Best time to sow is from May into early July.