Poinsettias are well suited for integrated crop management programs because the plants fill greenhouse space from late summer through fall.
Integrated crop management (ICM) is an effective and environmentally sound strategy that controls insects and implements the use of beneficial control agents along with compatible insecticides. Poinsettias are a good crop for ICM programs because the plants generally dominate the greenhouse space from late summer through fall. This allows growers to focus on specific pests and control strategies.
Most ICM programs implement a detailed and proactive approach that relies on regular scouting, monitoring and identification of insect pests. While implementing an ICM program is challenging, the advantages include less time spent applying insecticides and no re-entry interval issues.
The keys to a successful ICM program include:
- Identifying pests early and accurately.
- Monitoring and releasing beneficial organisms as needed.
- Isolating and treating “hot spots" before a problem spreads.
- Developing realistic threshold pest levels. Most growers view insect threshold levels as those that are below an economically damaging level that customers will accept.
Trialing an ICM program
Heartland Growers in Westfield, Ind., implemented an ICM program on its poinsettia crop during the summer/fall 2009. The company, which has 24 acres of production, grows poinsettias primarily for chain and home improvement stores. The target pests that were monitored and controlled were whiteflies, thrips, fungus gnats and shore flies.
ICM strategies were implemented in 60,000 square feet during propagation and later as plants were moved into production greenhouses for finishing. The propagation area consisted of benches on porous concrete and asphalt floors with overhead misting. The finishing areas consisted of either flood irrigation on cement floors or drip irrigation on asphalt floors.
Poinsettias grown in 6½- to 7-inch and 10-inch pots were used in the trial. Plants in 6½- to 7-inch pots were direct stuck and rooted into their final containers and then moved into a greenhouse for finishing. Cuttings for the 10-inch crop were rooted in Oasis foam cubes and later transplanted into the finished containers.
Beneficial control releases
Plants were monitored several times per week for both insect pests and establishment of beneficial control agents. Beneficials were released based on the information collected from scouting and monitoring (Table 1).
The following releases were used in the trial program:
- Exhibitline sf: Week 29, 31 (propagation area)
- Hypoline m: Week 33 (propagation area)
- Amblyline cu: Week 34 (propagation area)
- Staphyline c: Week 34, 37 (propagation area) and Week 40, 44 (finishing area)
- Eretline e: Week 34, 37 (propagation area) and Week 40, 41, 44 (finishing area)
- Swirskiline as: Week 40 (finishing area)
Minimal insect damage
Heartland Growers’ ICM program worked well in controlling the targeted pests. The poinsettia crop had very good overall quality with very few losses related to insect damage.
Because of the high moisture level, gravel/dirt floors and warm conditions in the propagation area, fungus gnats were the predominant pest. The fungus gnat levels spiked a few weeks after cuttings were stuck, but decreased as the beneficials became established. Shore flies followed a similar trend, but were not nearly as prevalent as the fungus gnats and did not pose a major concern.
It was determined that for future crops the greenhouse sanitation program should be improved, including eliminating standing water on the floors. Also, populations of Atheta coriara and Hypoaspis miles should be established throughout the growing season. Regular applications of Steinernema feltia should be made to gravel and dirt floors to reduce fungus gnat and shore fly larvae feeding areas and to decrease pest numbers.
Heartland Growers set a relative threshold level of 3 for whitefly and thrips and 5 for fungus gnat/shore fly. The pest population trends were similar in the propagation area, except that fungus gnat levels were significantly lower (the area that had cement flood floors).
After week 39, the levels of all pests, including fungus gnats, were below the threshold levels. Whitefly and thrips spiked slightly in week 39 (still in relatively low numbers), but were controlled during the remainder of the production cycle.
Upon analysis, much of the overall cost of the ICM program was in the propagation area and was related to fungus gnat control (Table 2).
In evaluating relative insect pressure, growers at Heartland Growers felt the whitefly pressure in 2009 was relatively low compared to past seasons. This may have contributed to the success of control. Comparing whitefly counts in the ICM program areas versus other areas where conventional chemical controls were used, the ICM greenhouses showed slightly better control. It was determined that the majority of the ICM program costs were associated with the propagation area. A better sanitation program in the propagation area would dramatically reduce pest numbers and ICM costs.
Harvey Lang is technical services representative, (303) 898-7850; firstname.lastname@example.org, and Paul Winski is technical services specialist, (281) 620-4624, Syngenta Flowers Inc.