WHITEFLY PARASITES FACT SHEET & Release Instructions
Open package inside the greenhouse, as some may have hatched during
shipment. Parasite eggs come glued in a small circle on "cards", 100+on
each one. Hang them in shady areas throughout the greenhouse. Parasites
hatch within 2 weeks.
Hatched parasites, over their adult life-span of about 1 week, eat some
young whiteflies (nymphs), and lay their eggs into many more. This kills
the whiteflies, and produces a new generation of parasites about 4 weeks
Unless you look very closely, you may never actually see adult
parasites, because they're quite small. It's easy to see where they've
hatched, though. When a parasite hatches, it chews a tiny exit hole,
either on the front or back of the egg. Using a 16 power magnifier,
examine the eggs closely. When you see the exit hole, you'll know the
parasite has hatched.
Whiteflies nymphs resemble small white oval scales, and never move. They
just sit there, right on the leaves - mostly on the bottom half of the
plant, usually on the underside of leaves. After they've been
parasitized, within 2 weeks they turn from their normal, clearish color
to jet-black (greenhouse whitefly) or merely somewhat darker
(sweet-potato whitefly). The blackened nymph "shell" remains behind,
empty, after parasites hatch. By counting the percentage of nymphs that
have darkened, you can see how well the parasites are doing. By the end
of the first month, 15-20% of the nymphs should be turning black in
color, and good control is 75-80% parasitization (typically taking 2-3
Results are best when temperatures average 68-95¡F, and parasites are
released soon after whiteflies get started. (Use yellow-sticky traps for
monitoring.) Lower temperatures slow down parasite reproduction so
additional releases may be necessary in winter months. (This temperature
range is an average - for example, it could be 60¡ at night, and 80¡
daytimes, to average 70¡.) If you didn't spot whiteflies till you have
great flocks of them, reduce them first with a soapy spray (such as
Safers). Soapy sprays can be used right up to when the parasites arrive.
In fact, you can continue spraying soapy sprays on upper parts of the
plants even after the parasites are used, because parasites stay mostly
on the lower half of the plants, while whitefly adults prefer plant
tops. Some gardeners use a vacuum cleaner to suck whiteflies out of the
air - one person rustles the plants first to drive them out. Maybe you
can interest the kids! By reducing the whitefly population, parasites
have time and room to work.
Use at least one parasite for every square foot of greenhouse space, or
every 2 plants. For fastest control, make additional releases every 2
weeks for 4-10 weeks, or until 80% of whitefly nymphs are black. Check
pruned leaves for parasitized (blackened) whitefly nymphs before
throwing any away. Instead, leave these under plants for a week or two,
to make sure parasites hatch first.
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