CactiGuide.com

Hello,

I usually check my succulents on a daily basis and since 4-5 days I started to see some really small larvae on a windowsill where some pots are. They were not directly under the pot, but rather under the teracotta plate which the pot sits in. At first there was only tiny white larvae, but now it is mostly really small flies (see picture). They appear to be of a reddish/rusty color. Not more than 1-2 mm in lenght.

From your experience can you tell me what it is ? I already am a little bit worried, but should I be even more or no ?

Again, thanks for your help !

These are usually sciara (mushroom) flies. I'm led to believe that the flies do not eat once they have emerged from the pupae. The larvae are not usually a problem to adult plants, but are devastating to seedlings.

I find that the low cost aerosol cans of domestic fly spray kill them very effectively.

Steve

I just had larva eat about 40 seedlings :'( but never had a problem with my adults

I usually have this insect in my cactus seeds pots, lead to destroy the roots and the seedling death, is there any recommendations to avoid it ? do you think spraying Malathion on seeds pots could help ? and do you think Malathion is safe for seedlings ??

Malathion applied as a soil drench works. Some plants are sensitive to it, such as some Crassulas, but I couldn't find anything about Cacti. In an emergency it might be worth the risk, but unless the label specifically lists it for that use I'd be reluctant to use it.

Prevention is best. Thoroughly sanitize the medium by baking or microwaving it. The larvae primarily live on decaying organic matter, so your seedling mix should contain little if any organic matter - peat-based mixes are especially attractive to the gnats. Most Cactus seedlings can be grown for many months sealed in baggies or other clear containers, giving the insects no access. Water only from below after you do take them out, let the surface dry out between waterings (if the plants are far enough along to tolerate this). I use a sprayer bottle to apply a measured amount of water at the bottom of each pot.

I'd just like to mention an amazing trick I read in one of the Epiphyllum Society of America's Bulletin a few years ago and that was to crush up 1/4 - 1/2 of a mosquito dunks into a watering can leave it 24hrs give it a swish around and then use it to water your plants, it works brilliantly! I put one in my water butt (water barrel to Americans) every month or so and since then I've never had any!


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