Beneficial Biological Controls and working toward a chemical free greenhouse
I have been looking forward to the post since last year, once it was determined that our pilot program in biological control of insect pests was a success. I can happily say that we have reduced chemical use in the greenhouse by about 95% or greater within only a years time. As it happened last year we were a bit behind the eight ball when we started and we were not starting with a clean space, but now, this year we were ready in time and met all of this season’s plants with the appropriate methods.
Now while we are still getting the hang of the system, it does seem to be working again this year, and the problems we have seen so far have been checkable by quick response. I realize already that this is beginning to sound very abstract and rambling, so maybe it is time for a brief refresher.
Historical Pest Control
In the past we have relied on a variety of insecticides and fungicides to finish the plants in our greenhouse to a successful point prior to your taking them home. We did this as part of the Integrated Pest Management (IPM) program which we are still involved in, which constitutes a weekly scouting of the greenhouse space to determine what pests there are, if any, and whether or not we have reached a critical point in which we would need to treat with chemicals.
In order to do this we would stay after closing hours and certified applicators would use expensive equipment, with expensive chemicals on expensive time to solve the problem. If successful treatment resulted in a clean plant we could be happy, but as you may have heard many of the pests that we have begun to encounter in the industry have become resistant to the chemicals that are available to use. This is due in part to a limited number of chemicals that are considered safe for the environment and the people using them and the fact that each time a pest is hit with those same limited chemicals it can gain some resistance to them. The old adage “What doesn’t kill them makes them stronger” is completely accurate for the insect pests in our greenhouse.
The Pests We Focus On
In our spring and summer greenhouses there are a few pests we focus on and a few more that are peripheral nuisances we are concerned with. Aphids are the insect you are probably most familiar with as a home gardener. The tiny and bulbous insects spend nearly as much time creating offspring as they do devouring plants and being vectors for disease. There are a few hardcore chemicals which work on aphids, as well as some certified organic compounds like insecticidal soap. This insecticidal soap is a great option for control in your home garden as it is safe and effective. In our greenhouse we are going a different route as these chemicals would conceivably harm some of the beneficial insects we have cultivated as well.
Thrips are the other insect we are investing a lot of energy in preventing. You have probably never seen one of these tiny flying insects, but in fact it is one of the pests that creates the largest problem for the flowering plant industry. Thrips live in the soil and on the plants in their larval and nymph stages, and once they reach adulthood they can fly to a great distance. They feed on the pollen and plant matter in many of our most popular plants, often leaving a damaged leaf or a shriveled and misshapen flower and failing buds. The threat of thrips has actually been the impetus behind many growers in our area to go toward a biological controls as thrips in the U.S. were resistant to the chemicals that used to work on them within a year of those insecticides being approved for use here. This is due to the increasing globalization of horticulture and plants that used to be propagated locally were now coming from further and further away, sometimes infested with pests that were already resistant to the strongest chemicals.
We have a history of fungus gnats and shore fly as well, which up to this point have never been much of a threat to us, or more so, we have never done anything about them. The more we learn about the intricacies of how biological systems work together the more we find that it is pretty likely they are the causes for some of the diseases we do get from time to time.
The last pest we fight most regularly is not an insect at all, but a bevy of fungi. Botrytis, Powdery Mildew, Phytophthora are just a few of the nemeses we face in the greenhouse. They thrive in humid and warm locations and can take out a single plant or a houseful in a matter of days. We do most of our fungus fighting through ventilation and clean growing practices, which has been made easier in our newest greenhouses with their multiple options for air movement and moisture removal. But we still need to consider chemical fungicides a possible and useful tool to combat breakouts.
Our Present Biological Program
We have been working with BioBest, an international company based in Belgium and Canada that specializes in biological pest controls. We have close contact with their sales and advice departments, to the point that they will probably soon tire of our questions, if they weren’t also really into their product.
What we have set up is a combined effort of primarily defensive protection and when necessary a directed offensive. We treat every plant cutting or seedling that comes into the farm with preemptive beneficials, and we treat every space that will house plants with healthy doses of both predatory and parasitic creatures.
This is one of the most fun control methods we are employing, mostly due to its existence above a microscopic level. So many of these controls take place on such a tiny scale one really needs to suspend disbelief and hope they are working. But with aphids it is all real and in your face. In fact to combat aphids we go to the extreme step of bringing the enemy into our home. Ok that sounds absurd, but what we do is create a breeding program for cereal aphids, which we raise on barley plants throughout the greenhouses. The thing about cereal aphids is that they don’t care about the majority of the ornamental plants that we raise in our houses, except for a few fancy grasses. They are however similar enough to the green peach aphid which is one of our greatest foes. This is where a miniscule wasp, about the size of a small mosquito come in.
The colemani wasp places its egg in a living aphid, in which it grows and turns the aphid into a mummy, or incubator for the pupal wasp. This leaves a once green aphid an empty brown hull once the young wasps cuts its way out and proceeds to parasitize countless other aphids. The reason we offer these “banker plants” lush with cereal aphids is to insure that the thousands of wasps we release into the greenhouses have a host for their eggs in case there are not enough actual pest aphids present in the growing space.
These colonies will keep themselves populated throughout the spring so that there are several generations of young wasps hatching to seek out new hosts for their young. So when you see a pot of grass hanging low with sticky aphids and honeydew, actually be relieved that we know and we are doing it on purpose. Those ugly baskets are chemical free gold in our greenhouses.
While these tiny colemani wasps will parasitize more than 40 types of aphids they do not go after the many types of long-legged aphids that we also are confronted with, like the foxglove or potato aphid.
This is where we got into trouble last year as we didn’t realize quickly enough that we needed to be aware of the type of aphid infestation we were under. Now we know that to combat these other aphid types we can’t set up banker plants of parasitoids but instead need hungry predators. A slightly larger wasp, called ervi, is a tireless carnivore of potato aphid and we have recently released some in the big greenhouse just to clean up the edges.
Predators are not as dependable at finding their prey so it is helpful if they can be placed in the heat of the problem, being ever hungry they move on quickly if the food isn’t right in front of them. We last year also had little colonies of midges hanging out in styrofoam cups around the greenhouse. We so far this year have not had a need to introduce these little aphidoletes, but they can be brought in if we encounter an infestation. Watch the video below to see one of our own colemani ravaging a barley blade, or click the link at the top of this section to watch one actually parasitizing aphids on BioBest’s website. Theirs is a little less out of focus.
So as I said, thrips are one of our greatest pests, though you wouldn’t be able to tell this spring. We have invested a lot of energy, thought, and money in keeping their numbers in check this year and it is paying off. The first method we employ is a healthy bath. This bath is spa-like in a way, if you enjoy spas that let you soak in millions of microscopic worms. Or nematodes to be more exact.
Steinernema feltiae nematodes are a natural predator of fungus gnat larvae, but also an avid consumer of thrips at all stages except for the egg. We dip every plant that comes to us as a transplant in a suspension of 50 million nematodes in 12 gallons of water. This deposits nematodes on the foliage and in the soil of the incoming seedlings giving them ample opportunity to parasitize any existing thrips on the plants. When we have a likelihood of infestation, I am able to treat an afflicted crop with a spot treatment of nematodes through our Dosatron, a fertilizing and chemigating machine. If performed on a cloudy day or in the evening the extended time that the foliage stays wet allows the nematodes to get their business done. This has proven to keep our incoming plants clean and our self-raised ones healthy too.
We apply a multiple of mites to the greenhouses as well in the control of thrips. Mites are tiny arachnids which can cause all sorts of problems in your life. Dust mites are responsible for many Americans’ allergies and spotted spider mites are one of the major vegetable crop pests we fight in the fields. However there are some types of mites that can be extremely beneficial. We apply hypoaspis miles to each of our greenhouses at the start of spring. This mite feeds on both fungus gnat and thrip larvae, and does wonders to cut down on populations that may have overwintered in the greenhouses.
You will never see hypoaspis miles in action, but know they are there. Who you will meet are the pair of mites in our paper sachets. These paper pouches have been applied to nearly every hanging pot, flat of bedding plants, and container on the farm. Last year we applied small spoonfuls of bran and mites to each plant,and this year in an effort to standardize and streamline the process we have gone with a system that has the two types of mite already contained in a single pack. One is a feeder, one a food source, and bran, a food source for the feed mite all combine in a sawdust like mixture inside the paper sachet which has a small hole in one side. From this hole about 25-50% of the cucumeris mites will emerge to seek out thrips on their host plant. The rest remain in the pouch feeding and breeding more predatory mites to exit over the next 8 to 13 weeks.
When you take your hanging plant or Impatiens flat home and you notice this paper pouch laying on the soil you can do a number of things. 1. Use it, the pouch will continue to provide insect protection for your plant for up to 13 weeks from the date printed on it, enjoy the added punch of protection to your home garden. 2. Toss it out. Hand it to us at the register, or throw it away when you get home. 3. Let it do its thing into oblivion. The pouch is all paper and the contents are 100% natural so let those mites work their magic and don’t give them a second thought. The sachet should biodegrade over time in the garden. So there you go, set it and forget it.
This year, in exciting bug land news, we had a possibly serious thrip infestation in our early crop of fuchsia hangers. These thrips could have damaged and created disfigured blooms on your mother’s favorite Mom’s Day Gift, had we not brought in the big guns. And by big guns, I mean cannons. And by cannons I am alluding to the Pirates, or Pirate Bugs, or orius insidiosus.
Yeah, we had a lot of fun releasing these swashbuckling little bandits on the situation. And lo and behold, they worked! Within a week we went from scouting up to 10 thrips a day on one sticky card to 1 or less. Hopefully we never find their treasure chest with all those carcasses.
We also introduce atheta coriaria into the greenhouses in early spring. These are also known as predatory or rove beetles. They are fast to dig into the soil where they will travel far and wide seeking larvae of shore fly and thrips to feed on. Just a final and additional step in making sure our pest problems are kept in check.
We are taking advantage of our chemical free proclivities to reduce the amount of chemically based fungicides we need to use in the greenhouse as well. As a companion to our nematode system of treating all incoming plants we have included the product know as Rootshield in all of our suspensions and as a post transplant drench. This is actually a beneficial fungus that latches on to the roots of the target plant. This plant then thrives as the root locked fungus prevents other harmful fungi and mildews from breaking into the root system at a later date. The fungus comes as a powder, and smells like toasted mushrooms in a way.
Open for business
So it has taken me a few weeks to compile this article, and in that time we have opened for the spring season. So you may have had a chance to see some of this program in action. What I can say so far is that we have for the first time in my memory opened without having used any chemical insecticides whatsoever. This is a great and positive step and I hope you enjoy the efforts we have made in this respect, to reduce the amount of chemical in our greenhouses, and ultimately at your home. This is still a flexible and growing program so if you have questions about it or want to express your thoughts, please feel free to stop in and ask us about it. I am just about to the point where I can speak with some knowledge on it, so I am happy to talk to you about it. Thanks a lot for your interest and get down here soon to check out these super clean and super healthy plants for your garden.