Integrated Crop Management for Greenhouse Bedding Plants with Emphasis on Biological Control

Final Report for FNE93-003

Project Type: Farmer
Funds awarded in 1993: $1,199.00
Projected End Date: 12/31/1993
Region: Northeast
State: Massachusetts
Project Leader:
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Project Information


We have 28,000 sq. feet of greenhouse under plastic. Of that 5,000 sq feet of geraniums was used for the SARE Project. Stock plants arrived during November and grown in greenhouse #12. Cuttings were taken from those plants during January. To supplement our cuttings additional rooted cuttings were purchased and placed in greenhouse #12 until they were potted. Greenhouse P-2 was opened up when P-1 was filled. Once geraniums were potted and moved to P-1 and P-2, greenhouse 12 was used for a different crop.

Plants were planted in PX-2 Progro and fertilizer regularly with 175 ppm, 15-16-17 commercial fertilizer.

Yellow sticky traps were used for monitoring flying pests, which turned out to be mostly fungus gnats and some thrips and shoreflies. Sticky traps were changed each week to 10 and number of insects were recorded. In addition, plants were inspected regularly for insects and root rot disease. Fungus gnats, shoreflies and thrips were found on plants.

We began the season by cleaning up the greenhouses of weeds and debris. We cleaned the benches and walls with Triathlon to kill any algae, since fungus gnats and shoreflies feed on algae. Since root rot had been a problem in previous years we used the fungicide Banrot as a soil drench on stock plants and on newly planted plants. Fungus gnat adults showed up in high numbers right from the beginning and rooted cuttings that were purchased, arrived with high numbers of larvae.

We made 4 applications of parasitic nematodes, numbers did not go down. We also tried using two applications of Steinernema Feltaw, sold as Scanmask which was supposed to be more effective. After learning more about parasitic nematodes, we wondered if the soil had dried out too much after application causing them to die or perhaps we may have applied them through a nozzle opening too small. By the middle of January, greenhouse 12 was very infested with fungus gnat adults and larvae and plants began to die. Out of 2,718 cuttings taken, less than 50%, 1110 were salvaged and potted up to be placed in greenhouses P-1 and P-2. After plants were potted we used Gnatrol every 3 days to break the life cycle. Numbers of fungus gnats dropped a little in some areas until infested cuttings were placed in P-1, then the card count went up again. At this tie, the potted plants were large.

Although, adult numbers were still high on sticky cards, few larvae were seen in the pots. We believe adults were coming from the infested cuttings. During April we tried Grub Buster, a combination of two parasitic nematodes. During this time trips began to show up on the sticky cards. We removed unnecessary flowers and treated with Resmethrin.

The reduced the number of thrips. Finally at the end of the season, we tried Azatin, a new neem product and let the plants dry a little more. The decreased the numbers although we had finished keeping track of card counts. Plants were sold beginning May 15th.

In the fall, we will clean our the greenhouse that had thrips and let it freeze for the winter. I will be using Triathlon to kill algae on benches and plastic sides.

In the spring, we plan to continue to monitor pests using sticky traps and foliage inspection. We also plan to use Gnatrol or a predatory mite at the very beginning of the season before infestation gets out of control. We also plan to do a better job of watering, so plants don't stay excessively moist or dry. Cuttings will be checked on arrival for fungus gnats and treated immediately. Infestations were very high on purchased cuttings before we realized it.


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  • Tina Smith


Participation Summary
Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.