Is this leaf damage caused by gnats/fungus fly? And will a zap-light kill them?

[LancelBracken]

Hi all.

Check out this leaf damage. This is pretty bad but most of my plants have some of it. Does this look like damage caused by black fly / fungus gnats
? I have them in my grow tent and i squish at least 10 every time im in there but they always pop up. I would estimate the population at 3 per plant (and i have about 30 plants in there) but they are elusive and hard to catch.

Since squishing them isn't working, and they aren't in high enough numbers to warrant spraying with something, would one of those blue-zappy-light-things work if i stuck it in my grow tent? You know, the things you hang up that zap mosquitos. I want to fry these pricks!

Thanks!

Here's my latest grow log update if you want to see pics of all of the plants
http://www.thehotpepper.com/showpost.php?p=218993&postcount=10

 

[RichardK]

Adult fungus gnats cannot damage plants in any way, the larva eat fungus and plant roots, like if they are rotting.

That looks like a Calcium/Magnesium problem coupled with some type of pesticide or spray damage.

 

[LancelBracken]

oh! I see. They seem to like sitting on the leaves, i am paranoid they are sticking their suckers into them and feasting! Ahhh!

I haven't used any sprays or pesticides, so i guess it could be a deficiency! I've been giving them seaweed fertilizer but only at 1/3rd strength dose and once a month.

This might be a long shot... but could it be leaf necrosis? I have had them under 24 hour light for their entire life (~2.5months now). It's only a 130W CFL but still. Maybe i should put them down to 18/6 or 20/4.

 

[RichardK]

oh! I see. They seem to like sitting on the leaves, i am paranoid they are sticking their suckers into them and feasting! Ahhh!

I haven't used any sprays or pesticides, so i guess it could be a deficiency! I've been giving them seaweed fertilizer but only at 1/3rd strength dose and once a month.

This might be a long shot... but could it be leaf necrosis? I have had them under 24 hour light for their entire life (~2.5months now). It's only a 130W CFL but still. Maybe i should put them down to 18/6 or 20/4.

Switch to 14-15 hours, only seedlings benifit from 24 hour lighting.

If you leave them on too long, the heat will cause flower drop, that and you need fans blowing around, and if you can, one in a window blowing in, for the cool nighttime air.

Thrips can cause new growth to be necrotic, check inside the flower buds for very tiny elongated things crawling around, they are smaller than aphids.

 

[POTAWIE]

This might be a long shot... but could it be leaf necrosis? I have had them under 24 hour light for their entire life (~2.5months now). It's only a 130W CFL but still. Maybe i should put them down to 18/6 or 20/4.

There are a few threads here with info suggesting that around 20 hours is ideal after approx 5-7 weeks of 24 hour ligting
http://www.actahort.org/books/580/580_9.htm
"Optimal growth and yields of tomato and sweet pepper were obtained under photoperiods of 14 and 20 hours, respectively. Longer photoperiods did not further improve growth and yields and even decreased growth and yields in some cases. Although long term use of continuous light is detrimental to tomato and pepper plants, vegetative growth and fruit production of both species can be improved by short term use (5 to 7 weeks) of continuous lighting..."

And don't use the bug zappers, they only kill insect which are attracted to light like moths as well as some beneficial insects

 

[RichardK]

The best way to get rid of fungus gnats is to let the soil dry out, then water it later.