Introduction Biological Control in Roses has been attempted for many years in Europe and North America. Results have ranged from fair to poor, despite active research on the part of growers and researchers. Recent research has shown the devastating effect of burning sulphur on parasitoids. This research confirms the Biological Control industries’ strong belief that the burning of sulphur is not complementary to the use of Biological Controls, especially in the case of Encarsia.
Planting out Fungus gnats are an economical pest. The larvae effectively prune the fine, new root hairs, reducing the growth rate of the plant and its’ vigor. For roses grown in loose soil such as coco fiber, Hypoaspis miles or, if allowed, Gaeolaelaps gillespiei, (now collectively referred to as Hm), should be applied to each pot at the time of planting. The rate should be 10 per pot, or 250 per square meter, whichever is less.
In an established crop, Atheta coriaria should be added for control at a rate of 0.1 per square meter, just once. Crop Management The use of Monitoring/Trapping/Banking plants is essential in Rose production. The typical host plants are;
* Eggplant, for general use. Eggplant is considerably more attractive than Roses, to most pests. The eggplant should be used at a rate of at least 1 for every 1000 square meters. They should be grown in the main aisle of the house so that they can be easily accessed.
* Bush Beans, for general use. Bush Beans are very attractive to Spider Mites, Whitefly and Thrips. In the case of Spider Mites, they show damage only a few days after initial contact, effectively becoming an “early warning system”. Bush Beans should be placed in strategic locations, such as near heating pipes and perimeter walls. They can also be used in temporary locations, such as hot spots, to dilute the pest pressure and become banking plants for future dispersal with a persimilis application.
* “Hero” Marigolds, for Thrip management. In Potted Roses, this technique is indispensible. Providing flowering targets will actually draw the Thrips out of the Roses, on to the Marigolds. The Marigolds should have high levels of A. cucumeris maintained on them, as well as high levels of Hm in the soil, to handle pupating Thrips. In cut Roses, this technique also has some merit, especially during the summer, when Thrip pressure is highest. In clean houses, they serve as monitoring devices, alerting you to an arrival of a pest. As the pest level builds up, the pest can be physically removed, in the case of whitefly, they can be vacuumed daily using a “dust buster” type unit.
Once trapping becomes unreasonable, the plants can be turned into banker plants by focusing the release of Biological Controls at the eggplant. These “banker plants” can generate large amounts of beneficial insects, while continuing to attract the pests out of the roses.
Extreme care must be taken to avoid spreading the crawling pests, such as spider mite. Employee movement is a major method of spider mite dispersal. Employees should enter a mite infested area last, then leave directly. The coveralls should either be sprayed down with soapy water, or frozen overnight. I have seen air hoses work well for blowing mites off of employees.
European cut Rose houses tend to be one variety only. In North America, most houses, if not all of them, grow as many varieties as they can. Experience as shown us that some varieties are more susceptible to various pests than others. A log book should be kept to note when and where the various pests occur.
There is some indication that fungicides are having a negative impact on some Biological Controls, especially Encarsia. Always attempt to complete your fungicide treatments before the application of the Beneficials. Also, please attempt to correlate pest increases with fungicide treatments about 1 month prior. This will help us determine if, and if so, which fungicides are having a negative impact.
 
Spider Mite Employees should be trained to spot spider mites and use a flagging system to identify their location. The section affected with mites should become the last section visited during the day.
Amblyseius fallacis should be used throughout the greenhouse, preventatively, at a rate of 2 mites per square meter, just once, for the life of the plant. The fallacis will control all known species of spider mite and will not interfere with the Phytoseiulus persimilis which should be directly applied to the hot spots. The typical release rate is 1 to 100 (predator to pest), for control within 2 weeks.
When a hot spot is discovered, push a Bean seed into the affected pot or pots, or, bring in a pre-grown Bean plant. The Spider Mites will move onto the Beans, if they are 2 Spotted, and take some of the pressure off the Roses. Pp should them be added to the Beans to create a Banking system. If the Banking system is active, leaves can be harvested from it and used elsewhere in the Greenhouse, in other hot spots. Whitefly Whitefly is an insidious pest. It only takes a few females, laying 300 eggs, to create a significant outbreak. The illumination of burning Sulphur has helped with Whitefly control, but, Roses still remain one of the toughest crops in which to manage Whitefly. This is due to the density of the foliage and possibly negative interactions with fungicides.  Based on our observations, we suspect that fungicide sprays are significantly impairing Encarsia performance.
If a Whitefly hot spot develops, the honey dew tends to repel the small parasitoids, such as Encarsia. These hot spots are the Whitefly’s offensive strategy, and are best dealt with, by applying Delphastus catalinae, preventatively. Dc is a small Beetle that specializes in Whitefly. The adult actually prefers eggs, so, once released in a hot spot, they will tend to migrate throughout the crop, attacking future potential hot spots. Dc should be applied monthly, at a rate of 0.1 Beetles per square meter. In severe cases, the rate should be doubled by introducing 0.1 every two weeks.
Extreme hot spots should either be chemically treated, or, alternatively, a concentrated release of Aphidoletes can be employed, by directly releasing at the site, up to 1000 midges per square meter, just once.
 
Aphid Aphids can cause considerable damage in roses. During aphid season, weekly releases of Aphidoletes aphidimyza should be made at a rate of 3000 per hectare (0.3 per square meter). Aphidoletes control and eliminate all species of aphids. They are excellent flyers and can find even just one aphid rapidly. If there is a high aphid population, care must be taken to release the preventative Aphidoletes in a “neutral” location, away from known aphid hot spots. This will force the Aphidoletes to disperse. The hot spots should be directly treated with additional Aphidoletes and Aphidius matricariae, a parasitic wasp.
The eggplant will help considerably with aphid control. Eggplants will attract many of the incoming Aphids, seen as winged Aphids. Thrip The problem of thrips in roses has drastically been reduced since debudding has become popular. Thrips still can come in a big way, and can cause considerable damage, but they won’t persist in the crop if all of the flower buds are removed from the house and Hm is present in the root zone, interrupting thrip pupation.
Amblyseius cucumeris works well on roses, feeding on the first and second instar larvae. One application of cucumeris per month will maintain a constant level in the crop. Release rates are dependant on the level of contamination, ranging from 100 to 1000 per square meter. Slow release bags can also be used, but care must be taken to ensure that the bags are removed after 6 weeks to prevent the bran mite from causing damage in the buds.
Strategically placed, flowering “Hero” Marigolds have been very effective Trapping plants for Thrips. During periods of significant Thrips, Marigolds should be placed throughout the house. Keep the Marigolds “topped up” with Hm in the soil and Ac on the leaves. If the plant becomes overwhelmed with Thrips, carefully place the plant in a plastic bag and remove it from the house.
Yellow or Blue sticky traps should have a cotton ball placed on them to absorb Vanilla or Almond Extract. These aromatic compounds can be very attractive to Thrips, and can increase trapping by a factor of 10. Summary Few crops are as difficult to manage pests in as Roses. The protected environment tends to hold out many natural enemies, such as Orius, as do the frequent fungicide treatments.
Most people don’t appreciated how much leaf surface area is present in this crop, so, as a general rule, release rates are frequently too low. Because of this, Roses must be managed with a strong preventative program. Fallacis for mites, Encarsia and Delphastus for Whitefly, and Aphidoletes for Aphids, all of these biological controls must be “fresh” product in order to ensure effective searching.
The use of Monitoring/Trapping/Banking plants will have a significant payback and will reduce the cost of monitoring.
Cucumeris in the crop against Thrips has an added value, as they are effective Spider Mite preventers, and also feed on Whitefly eggs if Thrips are not present.
All of the above mentioned Biological Controls are compatible with each other. Care must be taken if you wish to substitute any of them with alternate products.
Please also note that all of these strategies are based on our “fresh” non-refrigerated products. These release rates and application strategies will not work if you choose to use anybody else’s products. Please use their guide-lines for their products.