Karin, I looked at your metal tray. i think you could find something more cost effective that would work better for your plan. I think that thin metal will have a short life span, and needs drainage holes or things will drown. One suggestion is a company called Anderson that makes tree band pots for grafting,etc. They make a square tray 5 inches deep with good bottom drainage. It is injection molded plastic that should last for several seasons or more depending on the UV exposure. I have built a table with treated lumber and plywood and drapped in a rubber liner. I added a edge board around the border to make a very large 48"x32 foot tray. This entire surface could be filled with soil. i pitched it in one direction so the excess water will run off. I have been growing in a greenhouse for about 14 years now. Those ants and aphids still give me problems during certain seasons. They seem to find ways around impediments. Some growers shut their house up tight in the middle of the summer for a few days and cook everthing so you can start fresh. During the spring when lady bugs are going strong, as well as aphids, I go around collecting there eggs layed on leaves outside the greenhouse, and bring them to the greenhouse crops to hatch. Once these hatch they will do a lot of damage to aphid populations. I have had some success with release of ladybugs, but they are generally not happy staying in a greenhouse and fly away soon. They will surpress aphids and if aphids are in high numbers lay there eggs in infested areas, before they start their migration. Unfortunatly with beneficials you are not able to soap if you expect them to do their job, so it is a difficult thing to figure out if you should stick with soaps sprays, or hope the beneficials take off. It will work well certain times of the year before the season gets too warm. I have also had natural populations of parasitic wasps build up, so keep an eye open to that as well. They can be purchased, but because they have to be overnighted shiped, they are too expensive. If you see leaves with mummified aphids remove it from your crop but keep it in the greenhouse. this will allow the wasps to hatch out and seek out new aphids. Good Luck

ants MILK aphids for honeydew.. on the leaves.. not in the soil ... [and actually.. they sweat it.. and the ants eat it .. its a sugar source meaning they really dont have little milking stools..e tc.. lol] the words used also also include herding ... i am sure.. you probably also saw farming them.. but no.. they dont plant them in the ground... lol in fact.. ants.. are how i usually find aphid infested plants ... when i notice a plethora of marchers going up and down plants ... if you disturb an any colony ... and presuming you dont have any of the southern bad ants... they will be gone in hours... and you move on with life... when i run across this.. i just do a little more disturbing.. and come back in a day or two.. and finish whatever i was trying to accomplish ... its not really a situation.. where i feel i need to eradicate them ... [unless they are coming in the house.. then its all out warfare ....] ken

Or scales (look just like they sound) may be on stem or around the leaf vein where it connects to the stem. Like woohooman said, they are there for a reason. I've only see them when aphids or scales have been present (let's me know time for a misting of neem oil!). Good luck!

Not all ants like aphids but more than one species of ant likes various species of aphids. The aphids have to show up first. Nearby ants then detect the honeydew liquid secreted by the aphids; this is what the ants are interested in as a food source. Ants do not raise aphids, but they may discourage other insects that would eat the aphids, so they are more of a protector than a farmer. Ants can crawl on plants for a number of reasons. If there are aphids on your plants they will be on the newest growth; curled or distorted growth occurs if the aphids are numerous. Spraying with a hard stream of water or using insecticidal oils or soaps are common ways of controlling aphids. Tanglefoot applied to the base of a plant can reduce ants from climbing up. This post was edited by larry_gene on Thu, Jul 24, 14 at 0:33