Overview:

Ornamentals don’t have the luxury to wait while the Biological Controls achieve a balance in the crop. Pests such as Spider Mites cause economic damage almost immediately. Pests such as Aphids and Thrips can carry viruses. And wholesale purchasers won’t accept any level of noticeable pests.

The traditional Biological Controls and their strategies need some level of pest to be present, in order to establish and be present.

At Applied Bio-nomics we have found that fresh beneficial insects and mites perform better and faster. We have, as a result, minimized or eliminated the storage of the products where there is a degradation in quality and performance over time. These “fresh” products fly farther, live longer, lay more eggs, and are actually smarter than the stored product available elsewhere. The result is that “fresh” beneficials are capable of prevention of pests at low, regular introductions.

As always, the movement of people in the greenhouse is a major form of dispersal of the crawling pests, such as spider mites. Whenever possible, restrict the movement of people, or pets, in known hot spots. Enter the hot spots last and then directly leave. Coveralls should be frozen overnight or washed each day, especially for the people that worked in a known infested area.

Prior to Propagation:

The house should be thoroughly cleaned. Walls, floors, posts, wires etc should be washed with soap or another suitable cleaning product. Whitefly and Aphids will persist in cool greenhouses for well over 1 month without any plant material available, but they will be killed with a thorough cleanup.

If the house has a history of spider mites, they will be hiding in the ground around the posts and the walls. An introduction of Hypoaspis miles (25 mites per square foot, more if high levels of spider mites were present) at each post and along the walls will help kill the overwintering spider mites. This only needs to be done once, as subsequent usage of Hm will maintain year after year establishment.

At Propagation:

Because fungus gnats can have a significant impact on the rate of growth of your plants, it is essential that they are controlled immediately. Apply Hypoaspis miles or Gaeolaelaps gillespiei (if permitted) (both will now be referred to as Hm) at a rate of 250 per square meter.

Skipping plants can work in clean houses, as the Hm will disperse themselves quite well. A recommended technique is to broadcast them over the finished crop using a “whirlybird” hand spreader.

Within one week apply nematodes at the recommended rate. This application will have two effects; first, they will kill some of the fungus gnat larvae and second, they will act as a food source for the Hm, which will help them disperse into the entire crop and establish.
If there is a very high count of fungus gnats you should consider altering the soil mix slightly, as even subtle variations in the soil mix will have significant impact on whether or not the fungus gnats will explode in population. Also, the wetter the soil, the more likely the Fungus Gnats will be a problem. Raw potato slices should be used to monitor the relative numbers and stages of the fungus gnat larvae. Try placing a slice of potato on the soil surface for a known time (usually overnight). The fungus gnat larvae are attracted to the potato and, when lifted, will give you a relative count. Repeated monitoring for the same duration of exposure will give you an indication whether the problem is getting better or worse. If the soil is loose, Atheta coriaria, the Rove beetle should also be applied at 0.1 to 1.0 per square meter, just once. If you are using humidity tents, increase the rate of Atheta and cut the rate of Hm in half.

If the crop is susceptible to whitefly, apply Encarsia at a rate of 0.25 per square meter if no whitefly is detected. At one to two whitefly per yellow card per week, increase rate to 1 per square meter. See below; Whitefly Strategy Overview.

Aphid prevention can be achieved by introducing Aphidoletes aphidimyza at a rate of 3,000 to 6,000 per hectare per week. They should be released away from any know aphid hot spots, usually in the same place each week, which will force them to disperse and seek out new infections. Any known hot spots should be dealt with directly, releasing about 100 adults from the shipping container at each hot spot.

Early Season (Indoors):

Spider mites should be watched carefully, as the damage is permanent. Preventative releases of A. fallacis in the granular carrier, at a rate of 1 mite per square meter should be made on all plants that are prone to Spider Mites, after the plants have been removed from any humidifying chamber. For houses that have a history of spider mites, bean plants should be grown around the walls and touching table legs. The beans will attract the spider mites and show damage very quickly, which will help with monitoring. Once spider mites are present, apply P. persimilis to the beans at an approximate ratio of 1 to 100. The bush beans will become bankers, releasing persimilis up, onto the tables for as long as the spider mites survive. In most cases, this will be a long time, as the spider mites come out of hibernation over a very long period of time. Bean leaves that display a ratio of 1 to 10 (persimilis to spider mites) can be picked and used to treat remote infestations. Feltiella may volunteer in a cool season crop, but their habit of pupating on the plant leaves may cause more problems. If the spider mites are under control, it is unlikely that Feltiella will populate the crop.

Whitefly must never be given a chance to increase. A count of over 2 whitefly per week on the yellow sticky cards should be reacted to immediately. Rates of Encarsia should go up to 4 per square meter per week and Delphastus catalinae should be introduced at a minimum of 100 per hectare every two weeks, until the counts are brought back in line. If the leaves become sticky with honeydew, the parasitoids movement becomes impaired. Delphastus releases should be increased up to 5,000 per hectare if control is at stake. The use of Bush Bean or Eggplant, strategically located along the aisles at a rate of 4 to 6 per hectare, will help draw the whitefly out of the crop. See below; Whitefly Strategy Overview.

Aphids are best managed preventatively. Begin weekly or bi-weekly introductions of Aphidoletes aphidimyza about 1 week before you traditionally begin to see Aphids, at a rate of 0.3 midges per square meter. If Aphids are already present or the temperatures are below 15 C on average, introduce Aphidius matricariae at 0.05 wasps per square meter, bi-weekly, or, if permitted Micromus variegatus, the Brown Lacewing, at 0.05 per square meter, monthly.

Thrips can show up at any time. Catching them early is essential to prevent damage. Alternating some blue sticky cards with the standard yellow ones will make it easier for you to see them quickly, as only Thrips consider the blue cards as evenly as the yellow cards. Card placement is critical with Thrips. The cards must not be more than ½ inch above the canopy, as Thrips don’t soar. High mounted cards will give you a false sense of security, and only catch Whitefly, Aphids and Fungus Gnats. Work done by Margaret Skinner and Michael Brownbridge at U of Vermont has shown that the yellow “Hero” strain of Marigold is a very effective Thrips Trapping plant. The showy yellow flowers are much more attractive to Thrips than your crop. The Marigolds should have high levels of Hm in the soil and be very heavily inoculated with A. cucumeris. If the Marigolds become over-run with Thrips, remove them carefully and put a new plant in its place. From what I have seen of this system, I think every grower should be planting a flat of these Marigolds every few weeks, throughout the year. The effect they can have in a greenhouse is nothing short of amazing.

Summer Season (Indoors):

In crops that are susceptible to Spider Mites, Bush Beans should be interspersed throughout the crop at a rate of 1 plant for every 50 square meters. The persimilis should be placed low on the treated plants as they instinctively move upwards. A ratio of 1 persimilis to 100 spider mites will achieve control in 2 weeks. As the humidity drops in the house, any volunteering Feltiella will disappear. Stethorus punctillum should be released at a rate of 500 per hectare every 2 weeks. The Stethorus are not intimidated by low humidity and high temperature. See below; Spider Mite Strategy Overview.

Whitefly should be under control based on the preventative releases. Any weekly count of over 2 whitefly per card should immediately be responded to by doubling the rate of Encarsia. Delphastus catalinae will remove very large numbers of whitefly eggs and can be used to reduce outbreaks. If Bemisia are present, Delphastus should be released every two weeks at a rate of 1,000 to 5,000 per hectare, depending on level of infestation. In extremely hot situations (over 30 Celsius) whitefly adults will only live for a few days (instead of months) and will not lay eggs. See below; Whitefly Strategy Overview.

Aphid prevention should be maintained. If Aphid hot spots begin developing, double the preventative rate and direct release extra Aa into the hot spots at a rate of 1 midge to every 100 Aphids. See below; Aphid Strategy Overview.

If you didn’t start the Marigolds earlier, you must start them now. There is no chemical that will manage a Thrip infestation currently and any attempt to use a chemical will only screw up the other systems. Sticky traps can have a significant effect on the population of adult Thrips, especially if they are enhanced by adding Vanilla (thank you Pierre) and/or Almond extracts. The easiest way to apply the liquid is to stick a cotton ball to the cards (thank you John) and then drop onto the ball. Vanilla can increase the trapping efficiency of the cards by a factor of 10. All of your plants that are invaded by Thrips should have Ac applied, every 3 weeks, at a rate of 200 mites per square meter. The Hm, already in the soil will also have a significant effect.

Late Season (Indoors):
This is the most important time of the year for spider mites. What you do at this time will determine how bad the next year will be. Every effort should be made to eliminate all of the spider mites before the beginning of September. Once the day-length begins to noticeably decrease and the evening temperatures drop, the spider mites begin diapausing. In a diapause state, spider mites are more resistant to chemicals and are not as attractive to the beneficials. If chemicals should be used, it would be at this time.

If the whitefly is not in good control, it will begin to runaway in the fall. Adding trap Eggplants will help if the plants are vacuumed daily. Adding parasites beyond 6 per square meter will have very little effect, as there are just too many Whitefly and the stickiness of the honeydew will begin to impair the movement of all of the parasitoids. Delphastus will continue to work at very high whitefly densities but their impact will not be quickly seen, as they will graze on the eggs and the adult whitefly will live on for months.

Aphids must be in good control going into the fall as the Aa will stop cycling due to diapause. Preventative releases will still work, as they are not being asked to cycle. As the temperatures drop Aphidius should be substituted for the Aa.

Planting into the field:
As soon as the plants are set out, release Hm at a rate of 10 to 20 liters per acre. Hm will establish permanently and will control Fungus Gnats, Springtails, over wintering Spider Mites and soil pupating Thrips, to name a few pests.

Early Season (Outdoors):

Spider mites can be prevented and chronic infestations can be cured by the release of A.fallacis. A general release rate of 10,000 per acre should be modified so that 5,000 are evenly dispersed and the other 5,000 used directly on infested plants or susceptible ones. This is usually a “one-time” introduction, as the fallacis will establish and persist in the plants for years.

Mid-Season (Outdoors):
Overhead watering helps prevent spider mite establishment. When many growers began switching to drip irrigation, they found the spider mite problems increased. P. persimilis should be used for serious 2 spotted spider mite problems. Stethorus punctillum beetles will also work very well and will persist in the crop as long as the spider mites are there.
Aphid infestations are controlled by releasing Aphidoletes directly at the infestation point. An approximate ratio of 1 Aphidoletes to 100 aphids will bring control back within 3 weeks. The Aphidoletes will cycle in the field and over winter so subsequent seasons should see fewer aphid hot spots. Aphidoletes should be released at dusk, after the wind has died down.

Spider Mite Strategy Overview:

Spider Mites, in ornamentals, are the most dangerous pest. The damage caused is permanent causing economic loss almost immediately. The only realistic approach to managing Spider Mites is to approach the problem on a preventative basis. The use of bush Beans, especially early in the season is a good start. Spider Mites love Beans, so they will tend to go to the Beans first. The Beans show Spider Mite damage within 24 hours, so early detection is possible. If persimilis is applied to the Beans fast enough, a balanced culture can result, stopping the Spider Mites at the beans.

For plants that are susceptible to Spider Mites, fallacis has proven to be a star. Apply fallacis to all of these plants at a rate of 1 to 2 per square meter, just after the true leaves have opened. Fallacis are capable of staying with clean plants for over 1 month, staying even longer if any prey or pollen is present. Once established, they are very effective in preventing a Spider Mite attack. In long term plants, we find it very easy to re-collect fallacis years after the original introduction, both indoors and outdoors. Unlike persimilis, fallacis is effective against all of the commercially significant mite pests.

P. persimilis is still the main beneficial, but only in the case of the 2 spotted spider mite. The leaf product will work about twice as fast and with half the inoculums compared to the product in a granular carrier. During hot weather, the persimilis will avoid the exposed tops of the plants in order to prevent themselves from drying out. Stethorus will quickly move into the exposed tops of the plants and feed on a tremendous number of spider mites.

Whitefly Strategy Overview:

Whitefly is an insidious pest. Low numbers can give the grower a false sense of security. The longevity and fecundity of the whitefly can lead to overwhelming situations very quickly. The only sure way to control whitefly is to start clean and prevent any significant buildup.

Weekly releases of preventative Encarsia must be considered similar to an insurance policy.
Using Eggplant as a trap/banker can be very effective, although, in our experience, Encarsia Max, starting clean, will be all you need. Whitefly has a very advance sense of smell and will move onto the Eggplant in a very profound way.

If Bemisia have established, parasitoids are at a disadvantage because they are all reared on Greenhouse whitefly and parasitoids always work best on their established host. All parasitoids will adapt to Bemisia and will all host feed aggressively. The use of Delphastus will have a major impact on Bemisia, and, if started early, will eliminate the Bemisia before they move on to the Greenhouse whitefly. Bemisia are much harder to monitor because they don’t evenly distribute themselves the way Greenhouse whitefly does.

Thrip Strategy Overview:

Prevention of Thrips is impossible. They can penetrate any screen and will always get in. Monitoring is essential to determine when they first arrive. Yellow or blue sticky traps are preferable over waiting to see damage on the crop. Once Thrips arrive, your response must be immediate and overwhelming. A. cucumeris should be applied at a rate of at least 200 mites per square meter. They can be shaken out onto the crop from the bulk tube, scattered over the crop by using a hand spreader, puffed out over the crop by pouring the bulk product into a rose duster (the bran will stay behind) or blasted over the crop using a modified and governed Echo backpack leaf blower. The cucumeris, however, can only feed on the early instar Thrips. The eggs of the Thrip are injected into the plant tissue, making them unavailable to predators. For many Thrips, pupation is away from the plant, further impairing the predators’ ability to gain the upper hand. Adult Thrips are rapid movers and capable of flight. Therefore cucumeris needs help. Hypoaspis at the pupating site will help prevent the Thrip from successfully cycling in the house.

Major inflows of Thrips occur when they are disturbed from their outside habitat. Develop a communication with local farmers so that you are aware when they are about to harvest or mow their crop of alfalpha or hay. Unfortunately they usually only mow on a sunny day, which means the wind will be up and the vents will be open, but reducing the opening gap and duration can have a significant reduction in the number of Thrips that will move into the house.

The use of blue sticky cards helps track the arrival of Thrips because only Thrips like blue, to a significant level. The incorporation of Vanilla to the traps will increase the trapping of the adults and can have a control effect. Use a cotton ball on the card to hold the Vanilla.
Flowering Marigolds are very attractive to Thrips, and will pull Thrips out of your crop. Always keep a flat of yellow “Hero” Marigolds in propagation so that you have a continuing supply of them throughout the season. The trapping Marigolds should have lots of Hm in the soil and Ac on the foliage. If the marigold becomes overwhelmed by Thrips, carefully place the plant in a plastic bag and remove it from the house.

Aphid Strategy Overview:

In recent years, the range and species of pest aphids has dramatically increased.
Regular, low releases of Aphidoletes will prevent the establishment of all species of aphids. A rate of 5000 per hectare per week will protect the crop from aphids. Aphid hot spots must also be treated by direct release of Aphidoletes.

During the cooler growing season, Aphidoletes slows down to a point where the Green Peach Aphid can effectively stay ahead of them. Once the average temperature in the house goes below 15 C, Aphidoletes should be supplemented with Aphidius matricariae or Micromus variegatus (Brown Lacewing) which perform much better during this period. If Foxglove are present during this period, Micromus is essential or, if not available, double the Aphidoletes rate.

For outdoor use, release directly into the infestation. Aphidoletes will cycle and over-winter.