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 Post subject: Aphids + root issues
PostPosted: Sep 12th, '20, 14:09 
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Hello, recently i let some lettuce outgrow their usual schedule for harvest as our restaurant (farm produce is primarily for use in our restaurant) has lower than usual business.

Noticed that there is now a lot of black spots on the older leaves which i suspect are aphids but would like to have some confirmation before i embark on a suitable plan to mitigate them.

In addition, newer plants in the system seems to have shorter roots now, so am also wondering if I have a potassium / magnesium deficiency?

All seemed good just a few weeks ago but started facing these issues after demand couldnt keep up with the supply. I have since removed all the older plants in the system. Also its the monsoon season where I am so not sure if the rainfall has got anything to do with issues facing now.

Any help / advise will be greatly appreciated.


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 Post subject: Re: Aphids + root issues
PostPosted: Sep 12th, '20, 21:39 
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Doesn't look like aphids to me. I think you might have a couple of things going on and probably due to a combination of rain and high temps. I think the black spots are probably due to a fungus but I also notice that you have some rough patches (light brown stippled areas - kind of look like sandpaper was rubbed across the area) that look like they might be damage from spider mites. Spider mites are really tough to see so you might need a magnifier of some sort and then you'll need to look at the leaf underside since that's where most of them will be. You can also brush the underside of the leaf surface over a piece of white paper, some will fall off and the paper makes them easier to see.

The moldy looking parts could also be frass, mold, mites, their eggs or a combination of things... the last of the pictures is the one showing the most of what I think is mite damage.

I'm not sure what to tell you about the roots. They are short but otherwise they look healthy. Hope this helps.


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 Post subject: Re: Aphids + root issues
PostPosted: Sep 12th, '20, 22:40 
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Thank you for your reply. I have added a close up picture. Based on your experience, is it spider mites?

How do I get rid of them if where I am i cant find beneficial insects such as ladybugs or green lacewings easily?


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 Post subject: Re: Aphids + root issues
PostPosted: Sep 12th, '20, 22:45 
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Oh and regarding potential fungi problem, did trying spraying baking soda with a few drops of dish washing liquid foliarly but doesnt seem to help.

Mostly the older leaves are affected but its getting quite widespread in the system so short of a full restart which for obvious reasons one may not be keen on (besides, will still face the same problem in future), any ideas how to tackle the source of the problem?


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 Post subject: Re: Aphids + root issues
PostPosted: Sep 14th, '20, 03:17 
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They don't look like spider mites, the body seems too elongated (although there are lots of different spider mites). Can't get a good enough focus on any of these to tell you what they are for certain but they look like they might be young thrips. Usually these are more of a problem on flowers. If they are thrips, this is one creature that I haven't had to deal with yet so I'm not sure what would work on them (predatory mites are one possible option; neem oil might work and would work on other pests but you have to be careful because of the fish). The black spots on the leaves could be associated with their frass or eggs so removing the critters would help with those as well. For any black spotting on lettuce that aren't associated with these critters you need to reduce splashing on the leaves or improve air circulation. If you aren't able to do either of these because it's weather related then I suggest removing infected tissue to reduce the amount of infectious material. With fungal infections usually the black areas are mold spores and this is one way they spread.

See if you can get a better photo. I'm not sure I'll be able to tell what they are but maybe someone else will :thumbright:

ps - forgot to mention that springtails are common in AP and look a lot like thrips so if these launch themselves (springtails don't fly but some thrips can) when you try to go after them that's probably what they are. Sprintails can cause damage but they are more of a detritovore so they usually aren't a problem unless you get huge numbers.


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