Greenhouse TPM/IPM Bi-Weekly Report Central Maryland Research and Education Center Ellicott City, Maryland

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1 Greenhouse TPM/IPM Bi-Weekly Report Central Maryland Research and Education Center Ellicott City, Maryland August 9, 2013 From: Stanton Gill, Extension Specialist IPM for Greenhouse and Nurseries, Central Maryland Research and Education Center, University of Maryland Extension Karen Rane, Extension Specialist, Director of the Plant Diagnostic Clinic, University of Maryland Extension Andrew Ristvey, Extension Specialist, Wye Research and Education Center, University of Maryland Extension Suzanne Klick, Technician, CMREC, University of Maryland Extension August 6, 2013 Cut Flower Tour Highlights Long Season Statice: On August 6, 2013, we conducted tours of two cut flower operations on the Eastern Shore. We started at Long Season Statice in Salisbury, MD which is owned by Ron and Sharon Peterman. They bought the land 18 years ago and Ron grows annuals, perennials and woody plants on five acres creating as long of a production season as possible. He sells to three local florists. Ron gave a tour of the farm highlighting plants grown and equipment used. Ron modifies his equipment based on his specific needs. For instance, he uses a waterwheel from a planter to dibble holes in the plastic. Tuberose is a crop that he can start earlier in the season under perforated plastic in low tunnels. The plants bloom earlier compared to ones not under this plastic. There is no need to raise the sides. Ron referred to it as a poor man s high tunnel.

2 Ron highlighted this Hypearls series hypericum that he started about 3 years ago at previous cut flower programs. The one he is growing produces lovely, deep peach to reddish fruit. Marigold Narai Orange and Babuda Gold are good for cutting and have much less of the typical marigold scent than other cultivars. Before leaving for the next farm, University of Maryland Extension Specialists, David Clement and Stanton Gill, provided information on diseases and insects that may show up on cut flower crops and how to control them. In the afternoon, we headed to Seaberry Farm in Federalsburg, MD, where after lunch Chuck Schuster talked about weed issues that crop up in cut flower production and how to control them. Then, we toured Seaberry Farm. Seaberry Farm: Richard and Wenfei Uva produce tree fruit, annuals, perennials and woody plants for cut stems on 36 acres. There are also five full-time employees who work on the farm. One of their specialty fruits is the beach plum which is native to the Eastern seaboard and is sold to wineries Figs are grown for their fruit and the foliage is used as greens in arrangements and jam makers in the region. Their focus is shifting more to cut flower sales. Wenfei offers full service floral design for weddings and other events. They also sell at farmers markets. Changes to their crops include expanding their dahlia production to two acres. Richard has found Karma Naomi to be the most productive burgundy. The other cultivars grown at Seaberry Farm are not in the Karma group. Beach plum is one of their specialty fruits They force woodies such as quince and forsythia in one of their greenhouses. Other woody cuts include hydrangea, viburnum, hollies and lilac.

3 Greenhouses Who Dare to Use Biological Control While attending the OFA meetings in Ohio I had the opportunity to hear three greenhouses growers talk about how they are adopting biological control at their operations. It was rather refreshing since we have been trying to get greenhouse growers to adopt more biological control since the mid 1990s. The cost of chemicals has skyrocketed, pest resistance is becoming more troublesome, and the restrictions have made chemical applications less attractive to many growers. I am relaying the successes of these greenhouse operations so more growers will begin to consider a biological approach to controlling insects and diseases in greenhouses. The three greenhouses that presented on use of biological control were Barlow Flower Farm, of New York, Dickman Greenhouses of New Jersey and Longfellow Greenhouses of Maine. Each greenhouse made the commitment to use biological control to deal with insect and disease problems. Each used scouting as the mainstay of their program. Each flat of plug plants that arrive at their greenhouses is inspected for insects and diseases and rejected if there is a problem. Each greenhouse would then make up a solution of beneficial nematodes, Steinernema feltiae, and 4 ounces of wettable powder BotaniGard (Beauveria bassiana) in 15 gallons of water, and RootShield (Trichoderma for root disease control). A plug tray of plants was submersed in the solution. They can treat between flats before they have used up 15 gallons of solution. In most cases, they come back in 4-6 weeks after transplanting and applying RootShield a second time. The nematodes and BotaniGard were to deal with any thrips pupating in the soil. They also release rove beetles into the greenhouse to control fungus gnat and shore fly larvae. We had set up a biological control project 5 years ago with Catoctin Mountain Growers where we released rove beetles over an 8 week period with three releases. These releases were made in the spring season of 2010 and it reduced shoreflies and fungus gnat populations fairly well. Catoctin Mountain Growers still uses these rove beetle releases in their plug production area where it is kept very moist. In the three greenhouses in the OFA presentations the managers started Pepper Purple Flash plants in February or March to serve as banker plants on which to release the predatory Orius insidious in late March to early April. The Orius arrive in lots of 100 adults per container (cost is around $40 per 100) which they apply at the rate of 5 Orius (minute pirate bugs) on each of 20 plants. Since Orius is a little pricey, the idea is to get them to reproduce on banker plants so you can keep your order for more Orius limited. Orius will feed on the pollen of the peppers, and then lay eggs into the foliage. The nymphs feed on pollen until thrips are present. Orius adults migrate through the greenhouse looking for thrips on which to feed. The great thing about Orius is that they will feed on 1st and 2nd instar nymphs and adult thrips. They use between 5-10 banker plants of the flash peppers per acre of growing area. All three operations felt this approach has given them good levels of control of thrips and felt the use of the Orius was worthwhile. They also release the predatory mites Amblyseius cucumeris, in sachets of 50 mites each, applying at the rate one sachet on each hanging basket. For the flats of plants they obtain the mites in dispenser bottles and sprinkle grain with the predatory mites onto trays of plants at 5-10 mites per square meter. The predatory mites feed on the 1st instar stages of thrips. The combination of the predatory mites and Orius releases has been used successfully for two of the growers for the last 5 years. The third grower had been using this method for the last 3 years with success. One of the growers comes back with a soil drench application of beneficial nematodes to kill any thrips pupating in the soil and to kill fungus gnats. For aphid control, each of the operations is using banker plants, growing oats or barley in a 6 8 pot. You can obtain a bag of oats or barley from a farm supply store. Two weeks after the oats are potted, the bird cherry oat aphid is introduced onto the oat plants. This aphid species feeds just on monocots such as grains and grasses and should not become a problem in the greenhouse on bedding plants. The bird cherry oat aphids are kept in a net covered cage so that it excludes predatory wasps. If the wasp gets to the bird cherry oat aphid too soon your population of aphids will be wiped out, and you will have to buy more bird cherry oat aphids from a

4 biological supply house. The objective is to build up the bird cherry oat aphid population on the banker plants so there will be a good population as a food source for the release of predatory wasps on the plants. One of the growers did not build a netted cage and instead used two layers of hair netting stretched over the pots to screen out the predatory wasps until the bird cherry oat aphid population was large enough. The banker plants were ready 2 3 weeks after the release of bird cherry oat aphids and have enough aphids present that they can be moved into the greenhouse growing area. The growers are using 5-10 plants per acre of growing area. A parasitic wasp, Aphidius colemani, is released onto each banker plant. The adult female wasp stings the bird cherry aphid and lays an egg inside the aphid s body. The wasp larvae kills the aphid and swells it body often changing the aphid a tan brown color. An adult wasp emerges from the dead aphid and will search the greenhouse for green peach aphids and melon aphids in which to lay eggs. The growers continue to produce additional oat or barley banker plants with bird cherry oat aphids and repeat the process of placing out the banker plants among their greenhouse Netted cage for barley plants at Sharp Farm crops so they have a source of aphids to increase their population on. If you develop a problem with potato aphid or foxglove aphids then you will have to release another predatory wasp called Aphidsius ervi. We at the University of Maryland Extension can help you identify the aphid species so you can decide which predatory wasp to purchase from a biological supply house. A general predator of aphids that can be used is Aphidoletes aphidimyza. This is a gall midge insect and the female will lay eggs near an aphid colony. The hatching larvae pierce the body of aphids and suck out the liquid contents of the aphid sucking them dry. The midge is used against fast building populations of aphids. The manager at Longfellow Greenhouse in Maine used a plastic bucket that they cut a hole into the lid and they place the pupae of the A. aphidimyza inside it. The wasps are protected, and when they pupate can emerge through the hole in the lid. They move the bucket around the greenhouse to where they have rapidly building aphid populations. If fungus gnats build up in wet springs like 2013 then beneficial nematodes are applied as a drench, making sure to remove any screening if an injector is used. Each of these greenhouse operations commented that their workers were happier since they stopped applying fungicides and insecticides regularly in the greenhouses and several have really got actively involved in the benefical releases. So far, this approach has worked for these three diverse greenhouse operations in various parts of the northeast. It might be time for you to consider working toward a biological control program. We have conducted various biological control trials in Maryland greenhouses. If you are thinking that you would like to try biological control and want to work with us in 2014 let us know. Fungus Gnats in Poinsettia and Pansy Crops Fungus gnats and shoreflies both thrive in the damp, moist greenhouse environment. With the recent rain and cloud cover it is moist in greenhouses right now. The best thing you can do is keep the crop on the dry side to keep fungus gnats and shoreflies in check. Fungus Gnat Damage: Fungus gnats are most damaging to seedlings, newly rooted cuttings and young plants. Poinsettias are still rooting out in the pots and are easily damaged. Young pansy plants are also susceptible. Keep pansies dry for fungus gnat control and to keep plants from stretching. Fungus gnat larvae injury caused by feeding on tender young roots provides an entryway for pathogens. Plants with succulent stems, such as poinsettias, are especially prone to injury and suffer serious losses. As the young feeder roots and stems are

5 damaged, affected plants wilt. Leaves may turn yellow and drop. In laboratory studies, adult fungus gnats carried spores of Pythium, Botrytis, Verticillium, Fusarium and Thielaviopsis as they moved from plant to plant. Spores have also been found in their droppings when on the very dry side. Monitoring: The abundance of fungus gnats in the greenhouse is typically monitored by counting the numbers of adults attracted to yellow sticky cards. Sticky cards indirectly estimate the abundance of damaging fungus gnat larvae in the plant pots. This method has traditionally been used because removing the soil from pots to extract larvae is impractical. Placing freshly cut slices of potato on the soil surface attracts larvae to the surface and allows estimation of larval abundance in a plant pot without destroying the plant. The numbers of larvae attracted to potato slices gives a much more accurate estimate of larval populations than do adult numbers on sticky cards. Using Entompathogenic Nematodes: Steinernema feltiae provides excellent control of fungus gnats. In trials we have conducted over the years we have found plants treated with this nematode control of larvae comparable to plants treated with kinoprene (EnstarII), Gnatrol (Bacillus thuringiensis israeliensis), Steinernema carpocapsae (All strain), or a water control. Insect Growth Regulators: Insect growth regulators (IGR s) are most effective against the young developing larvae of fungus gnats and shore flies and will have no direct activity against adults. Commercially available IGR s include Azatin XL, Aza-Direct, Ornazin, Citation, Distance and Enstar II. Please note that the Adept label reads: Warning: Exceeding label rates, volumes or number of applications of Adept can cause serious foliar injury to crops, particularly to poinsettias, hibiscus and Reiger Begonias. Do not apply Adept to poinsettias, hibiscus and Reiger Begonia. Other Treatment Options: DuraGuard ME is a microencapsulated product that may be used for both larvae and adults. The neonictotindoids Safari (dinotefurnon), Flagship (thiamethoxam), Marathon (imidacloprid) and Tristar (acetamiprid) are labeled for fungus gnat larvae. Pylon has contact and stomach activity against fungus gnat larvae. November 7, Greenhouse Seminar at Chesapeake College Mark your calendar for November 7th. The University of Maryland Extension and the Maryland Greenhouse Growers Association are developing a one-day seminar on greenhouse topics. We have asked Maryland greenhouse growers and industry experts that are experienced in growing tougher to grow greenhouse crops to share some of their secrets how to produce quality plants. Several growers are moving fertility management to lower rates of nitrogen and potassium and higher rates of micronutrients. This produces better quality plants with lower fertilizer inputs. Dr. Cari Peters of Peter s Lab will talk about this method at the conference. There will also speakers talking about new markets to investigate. We will send out the schedule in a future report when it is finalized. The information given herein is supplied with the understanding that no discrimination is intended and no endorsement by University of Maryland Extension is implied. Read labels carefully before applying any pesticides. Photographs are by Suzanne Klick and Stanton Gill unless stated otherwise. University of Maryland Extension programs are open to all citizens without regard to race, color, gender, disability, religion, age, sexual orientation, marital or parental status, or national origin.