When we first started farming we thought we didn’t have pests. Either they hadn’t found us yet, or we hadn’t found them because we didn’t know what we were looking for. Now we scout weekly in the greenhouses from late winter through spring to make sure we catch problems before they get out of hand, paying special attention to the crops we know are most susceptible. We look for any pest or disease issues, documenting trouble areas and our plan of action. We have yellow sticky cards to help diagnose problems, but it is best just to get our faces down in the crops to check. We also train our staff to be on the lookout as they are harvesting.

 

pest_control_in_greenhouse_flowers


Greenhouse production, especially heated winter production, has required some extra attention to bugs. While out in the field pests may have gone dormant for the winter, in the greenhouse there are still crevices for them to hide in, or they may reemerge sooner than outdoors. The problem is that sometimes it is too cold for native beneficial insects to be active, so we choose to introduce them into our greenhouse production by ordering in beneficial insects.


Our hope is to not have to use any sprays for pest control, relying on the beneficials to help control any pest problems. With the greenhouses closed often more in winter, we are more likely to be able to keep the good guys in there to do their job. Here is the program we have established, getting beneficials every two weeks December- May, so that we can be proactive rather than reactive.

sticky cards in greenhouse flowers

Yellow sticky cards are placed throughout the cut-flower greenhouse to help with pest monitoring. All photos courtesy of Sunny Meadows Flower Farm.

 

Aphids
Aphids are a big problem for us with greenhouse production; heated or unheated, they love it all. They are sap suckers that leave a nasty residue on the plants, and they multiply fast. Some varieties are even born pregnant, so their population can explode in a short amount of time. Green peach aphids are one of the main pests, living on the foliage underneath the leaves where it is hard to get spray coverage. These can be on almost anything, but problem crops we’ve found are ranunculus and anemones, snapdragons, and spinach too.


Foxglove aphids are another variety that gives us trouble. They can be identified by the dark spots on their backsides. These guys love freesia and our new growing venture, cymbidium orchids. We have some magnifying glasses so we can look at the aphids closer, to figure out what our best plan of attack is based on the species of aphid we are dealing with. We focus much of our IPM practices on aphid control- using Aphidius colemani (a parasitic wasp), lady beetles, and lacewings.


The Aphidius wasps come in a little vial and are about the size of small ants. Their job is to lay their eggs in the body of the aphid so that when they hatch, their larvae eat the aphid from the inside out. Sounds gruesome, but nothing is more satisfying than finding the aphid mummies they leave behind when they have done their job. What they are doing is similar to what parasitic wasps do with tomato hornworms, if you’ve ever seen parasitized dead ones with those white cocoons on their backs. The problem is that they only work on a few species of aphid- green peach, cotton, and melon aphids. That is why we also use lady beetles, to be sure we are targeting the foxglove aphid population (or any other aphid that may be in the greenhouse- chrysanthemum, hedera ivy, etc.).


The lady beetles need a drink when they show up, so be sure to spray them down with water before releasing, otherwise they will just cluster on the nearest water source. These guys do a good job unless they run out of things to eat, then they will leave the greenhouse. Lady beetles are multi-purpose, not just for aphids. Since lady beetles don’t discriminate about what they eat, they could potentially be eating other beneficials, but the benefits far outweigh the consequences. They are a little costlier than other options, but will give you more instant gratification.


Lacewings are a multi-purpose beneficial whose larvae eat mainly aphids, but they also eat mealybugs, scale, thrips, spider mites, and small caterpillars. They come on a card full of eggs, which we place throughout each house or we will concentrate them in a hot spot if we are having an outbreak. We grew ivies in hanging baskets for cuttings, and the foliage attracted lots of pests. So we cut the lacewing cards in half and put a piece in each basket.

ranunculus scoutingMarcus Davis inspects ranunculus ‘LaBelle Champagne’ at Sunny Meadows. Ranunculus is one of the crops scouted often for aphids.  Once the blooms are open, spraying will damage the petals, so being proactive by scouting and utilizing IPM helps control pests.

Thrips
Western Flower Thrips are the kind we deal with in our area. They love snapdragons and freesia, but they can also affect anemones and lisianthus, and, I’m sure, others. These little buggers are real tiny and are reddish brown. They lay their eggs into plant tissue, leaving blooms and/or foliage looking spotted. To scout for these pests, use a white piece of paper and tap on the plant to see if any fall off onto the paper and wiggle around. On freesia, they seem to get the foliage when it has started to grow, so sometimes you can see spotty leaves from the mosaic virus that they carry. Thrips live down in the bloom which means spraying with anything organic that requires making contact with the pest may not be that effective. That’s why we chose to use IPM methods instead of spraying.


Cucumeris are a mite that come in bran, in what looks like a parmesan cheese shaker. These little no-see-ums infect the thrips larvae so are best applied preventatively. We focus mainly on the snapdragons and freesia, but make sure we get one full shaker applied every two weeks in our 30 x 96 greenhouses. We rotate the container as we shake them out to evenly distribute them, making sure none stick to the sides of the container. Since we have been using cucumeris, we haven’t had to use any sprays against thrips. This is important because spinosad, one of the few organic spray options, is overused and not properly rotated in the fight against thripsThey can build up resistance if you are going the chemical route, organic or not.

Fungus gnats
Fungus gnat larvae will eat bulbs and the roots of anything we are propagating, causing rot. If we are trying to root geraniums, salvia, or dahlias, or are sprouting ranunculus or anemones in soil and aren’t seeing roots, fungus gnat larvae is probably to blame. Sometimes they feed on the surface, but many are in the soil as well. The adults congregate where there are wet spots, and they really like it underneath row cover in our unheated spaces.


Opening the row covers on sunny days when the sides are up helps dry out the soil and release the cloud of fungus gnats. Keeping everything drier, especially during winter production, has really decreased our fungus gnat problems. If there is any algae buildup on flats, you can also attract shoreflies. These behave similarly to fungus gnats, but are a little larger and their flight pattern is more like a fly than a gnat.


For these we apply a nematode to the soil. It looks like a wet powder when it comes, and you add water to make it spreadable. We have used a nematode hose-end sprayer before, but we found it difficult to measure how much is being applied, so we just use a watering can for application. Make sure whatever you use doesn’t have a filter in the spout otherwise it will filter out all the good guys. First the nematode solution is mixed in a bucket at the suggested rate and then put into the can for even application throughout the greenhouse soil. This solution is also usable on potted plants by applying some in each pot.


Another beneficial insect we use for fungus gnats are Dalotia, or rove beetles. These guys are double trouble as they eat thrips larvae, and they also eat fungus gnat larvae. They come in soil and need to be watered when they arrive, like the lady beetles. Put them in wet spots or fungus gnat trouble areas. 

dalotia

Dalotia, or rove beetles, help control fungus gnats and thrips.


Other beneficials
Whiteflies are annoying flying insects that really like our geraniums and salvia, or anything that is in the ground for a long time and could get a woody stem. They lay their eggs on the underside of the foliage and are sap suckers. You’ll notice them flying around while you are harvesting. Encarsia is a beneficial insect that helps control whiteflies. They come on a little card with eggs on it that gets placed down below the canopy of the foliage. They feed on the whitefly scales under the leaves and also lay their eggs in them.


Praying mantises we mainly use outside. We will go through in the spring and collect egg cases before mowing down any unkempt areas. They like brambles, rose hips, and goldenrod to lay their egg cases on. They start out as a foam of eggs that hardens for the winter and have hundreds of little babies that hatch out in the spring. They are the size of small ants when they come out, and it’s fun to watch them grow through the season, ending the year slow as dinosaurs and in their final stage of life with wings or as pregnant mamas. You can also buy praying mantis egg cases to apply in areas that don’t have them. Some of these methods work in outdoor production as well, but we don’t have as much experience with outdoor releasing. Beneficial insects are more likely to fly away, but it may be after they have done their job at the trouble spot. All of our beneficial insects come from IPM Labs in New York, but there are other companies that sell them as well.


Remember that nature doesn’t really want to completely wipe out another species, so they control the pests, but they won’t go away altogether. That’s why scouting and IPM have to be put into place together, like a system of checks and balances to be sure you are applying the right things at the right rates. Now if they could only find something that is a predator to cucumber beetles, we’d be set!


Gretel and Steve Adams own Sunny Meadows Flower Farm in Columbus, OH. Contact them directly to schedule their consultation services which can be tailored to fit your business or personal flower farming needs. [email protected]