Applied Bio-nomics Ltd.
2010 Crop Recommendations
Hydroponic Lettuce
Overview:
Biological control of pests in hydroponic Lettuce requires a change in thinking for the
grower as well as the supplier of the products. The old concept of maintaining a balance of pests
and predators/parasitoids does not work in a crop where any insect or mite found on the plants is a
negative.
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 else ware.
The result is that “fresh” beneficials are capable of prevention of pests at low, regular
introductions.
The house must be clean and free of all extra plant materials. Office plants should be fake.
Strategy:
Preventative releases of healthy, fresh beneficials will prevent most pests from
establishment. For pests that can enter from outside, trapping plants and physical devices will
attract the pests away from the crop to where they can be eliminated.
Cold Season:
The influx of pests has been eliminated because of the cold weather outside. The only
pests remaining are now cycling in the production area.
Aphids are prevented by neutrally releasing 2,000 to 4,000 Aphidoletes aphidimyza per
hectare, on a weekly basis. It is important to release them away from the crop and especially any
known aphid hot spots. This will force the Aphidoletes to disperse and use their highly developed
sense of smell to locate any aphids. Known hot spots should be directly treated with Aphidoletes
by releasing the adults directly at the hot spot. A ratio of 1 to 100 (Aphidoletes to aphids) will
achieve control in 10 days. Circulation fans can physically damage the Aphidoletes adults, who
are most active in the early evening. If possible, turn off the fans overnight on the day of release,
or, at least, release the Aphidoletes downstream of the fans.
Whitefly should be removed by introducing Eggplants to the production area. Whitefly
prefer Eggplant over lettuce and will move to the Eggplant. Introduce 100 to 1000 Delphastus
catalinae per hectare, every two weeks until whitefly disappear. For higher infestations, introduce
Encarsia Max at 2 per square meter per week, in addition to the Delphastus. Delphastus feed on
the eggs, preventing the scale from forming on the Lettuce.
Any thrips over wintering should be pulled out of the crop by applying vanilla extract to
blue sticky cards and a “Bug Zapper” electrocution device, hung over the crop. The vanilla is a
very strong attractant. A major infestation of thrips should be treated with A.cucumeris also.
Empty a container of bulk cucumeris into the bowl of a rose duster and “puff” the mites onto the
lettuce. This will avoid the bran carrier from getting into the lettuce heads. If WFT is cycling in
the house it means that you still have some weeding to do, because WFT pupate off the plant.
Any outbreaks of spider mites must be dealt with as soon as possible, because the damage
is permanent. Apply P. persimilis directly to the infested plants at a ratio of 1 to 10 for immediate
control or 1 to 100 for control within 10 days. The rate will depend on how fast you notice the
pest and how much of a priority it is to prevent damage.
Applied Bio-nomics Ltd. www.appliedbio-nomics.com
Hot Season:
Unlike the cold season, control is only temporary, as new pests will continuously move
onto the crop. A continuous prevention program must be employed.
Aphids will be controlled at a weekly preventative rate of 2,000 to 5,000 Aphidoletes per
hectare. When low aphid numbers are seen, go to 2,000 per hectare. Never skip a week. When
aphids begin to be seen on the traps or in the crop move the rate up to 3,000 to 5,000 until the
numbers begin dropping off. Always treat known hot spots separately. If the aphid is the Green
Peach, you can take your time getting back in control, using less Aphidoletes. If the aphid is
Melon or a damaging aphid like Foxglove, you must control it faster, so direct releases of 1 to 50
or less will be needed.
Whitefly is a big problem because of the number of eggs they can lay and the disfiguring
scale that develops on the plant surface. If whitefly only appear infrequently, release 100
Delphastus per hectare every two weeks. The Delphastus will feed on the eggs, preventing the
scale from developing. If whitefly is a constant problem, place Eggplants around the production
area. 8 Eggplants per hectare will be needed. Place Encarsia on the Eggplant at 1 tag per 2 weeks.
The Eggplant will attract some Delphastus and act as a banker plant. Once Delphastus pupae are
seen on the Eggplant, you can stop releasing them in the house for the rest of the season.
Thrips cannot be prevented, so it is best to react rapidly to them. Strategically placed blue
sticky cards will help tell you when they arrive. Develop a good relationship with nearby farmers
who have fields of Hay and Alphalfa, especially the ones upwind. Have them notify you when
they plan to cut or disturb their fields so you can close the vents during the major disruption. The
Eggplants used for the whitefly control will help attract and hold volunteer Orius. Once thrips
invade, add vanilla extract to the blue sticky cards and turn on the “bug Zapper” every night
except the night that you release the Aphidoletes or Delphastus or Orius if you are adding them
also.
If spider mites show up, follow the same procedure as described for the cold season.
Employees who handle spider mite infested plants should do so only at the end of the day and
then directly leave the facility. Gloves and coveralls should be frozen overnight. Continuous
infestations should be handled by releasing 500 Stethorus puntillum per hectare, every 2 weeks
until eliminated. The Stethorus are small flying beetles that eat only spider mites and will find
very low numbers because of their advanced sense of smell.
Applied Bio-nomics Ltd. www.appliedbio-nomics.com
