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How to Manage Pests
UC Pest Management Guidelines
Floriculture and Ornamental Nurseries
Whiteflies
Scientific names: Greenhouse whitefly: Trialeurodes vaporariorum
Silverleaf whitefly: Bemisia argentifolii
(Reviewed 1/04,
updated 1/04)
In this Guideline:
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DESCRIPTION OF THE PESTS
Greenhouse whitefly. The greenhouse whitefly adult is 0.9 (male) to 1.1 mm
(female) long, with four wings, sucking mouthparts, a powdery waxy coating over
the body, and wings that give the otherwise yellow body a white color. The
wings are held nearly parallel to the leaf and cover the abdomen when the adult
is at rest. There are seven life stages: egg, four nymphal instars, pupal
stage, and the adult. Females occasionally lay eggs in circles on the
undersides of leaves of plants with smooth leaves. Egglaying on plants with
pubescent leaves results in random placement of the eggs. Eggs are partially
inserted into the leaf, initially they are yellowish, but close to hatching
they turn a purplish brown. The first nympal instar is called a crawler and has
functional legs, while the remaining instars are attached to the underside of
the leaf and do not move. The end of the fourth instar is called a pupa. The
pupal stage is the most important for
determining whitefly species identification. Greenhouse whitefly pupae are oval
and have vertical sides, giving the pupa a cakelike appearance from the side.
Along the perimeter of the upper surface is a fringe of filaments and
relatively large wax filaments project above the upper surface of the body. The
greenhouse whitefly can complete one generation in 21 to 26 days at 81°F.
Silverleaf whitefly. The
silverleaf whitefly adult is 0.8 (male)
to 1.0 mm (female) long, with four wings, and sucking mouthparts. The white,
waxy coating covering its body and wings is not as thick as it is on the
greenhouse whitefly and its yellow body has a whitish hue from the wax rather
than a white color. The wings are held at the sides of the body, partially
exposing the back of the abdomen when the adult is at rest. There are seven
life stages: egg, four nymphal instars,
pupa, and the adult. Eggs are not laid
in a circular pattern, are partially inserted into the leaf, and remain
yellowish until they hatch. The first nymphal instar is called a crawler and
has functional legs, while the remaining instars are attached to the leaf and
do not move. The end of the fourth instar is called a pupa. Silverleaf whitefly
pupae are ovoid, but with a slightly pointed hind end and red eye spots easily
visible from above. The pupa is fairly flat and does not have a marginal fringe
of filaments. The length of wax filaments projecting above the upper surface of
the body varies on different hosts. Silverleaf whiteflies can complete
development in 16 (86°F) to 31 (68°F) days.
DAMAGE
Whitefly adults and immatures feed on sap. As they feed, they excrete honeydew,
a sticky substance that causes unsightly glistening and supports the growth of
black sooty mold. Very large populations of whiteflies cause stunting of plant
growth, and leaves may senesce and die. Physiological abnormalities, such as
white stem on poinsettia, may also occur. Usually populations are not high
enough to stunt ornamentals, and damage is mostly caused by honeydew, sooty
mold, and nuisance populations of flying adults.
BIOLOGICAL CONTROL
Encarsia formosa, a tiny, stingless
parasitic wasp, is as an effective
biological control for greenhouse whiteflies.
Wasps are released once a week at a
rate of two to five parasites per plant for 8 to 10 weeks of the growing
season. This sort of release program can be effective if long residual
insecticides have not been applied in advance of the parasite release, and
where the initial population of whiteflies is quite low (only a few whiteflies
per plant). Greenhouse whitefly pupae turn black when parasitized by
Encarsia, which emerge as adults through circular exit holes.
Delphastus pusillus, a whitefly
predator, has been used against silverleaf whiteflies. Eretmocerus
eremicus is a commercially available whitefly parasite for silverleaf
whitefly. It will also attack greenhouse whitefly, whereas
Encarsia is ineffective against silverleaf whitefly.
CULTURAL CONTROL
Because whiteflies feed on a large variety of plant species, keep production
areas free of weeds, which can serve as hosts for whitefly populations.
Exclusion of winged adults can be accomplished by covering openings to the
greenhouse with screens that have a pore width of 405 microns or smaller.
Before starting a new crop, carefully inspect plants to ensure that they are
free of whiteflies and other pests. Treat or discard any infested plants.
MONITORING and WHEN TO TREAT
Yellow sticky cards placed in greenhouses will capture adult whiteflies.
However, traps need to be used at a greater density, one per 1,000 sq. ft.,
than for other pests. Trap monitoring should be supplemented with inspection of
leaves for nymphs and pupae. When monitoring plant samples, it is imperative to
look on the undersides of leaves for adults and nymphs.
Treatment thresholds vary with the crop. For example, cut flowers such as
Gerberas can tolerate more whiteflies than poinsettias because only the flowers
are harvested in the cut flower crop whereas the entire poinsettia plant is
marketed.
TREATMENT
Selected Materials Registered for Use on Greenhouse or Nursery Ornamentals
Read and follow the instructions on the label before using any pesticide.
Before using a pesticide for the first time or on a new crop or cultivar, treat
a few plants and check for phytotoxicity.
| Class |
|
Pesticide (commercial name) |
Manufacturer |
R.E.I.1 |
Comments |
| biological |
A. |
Beauveria bassiana (BotaniGard 22WP) |
Emerald BioAg. |
4 |
Treat every 7 days while insects are active. Do not tank mix
with most fungicides and wait 48 hours after application to apply a
fungicide. |
| B. |
(BotaniGard ES) |
|
12 |
|
| botanical |
A. |
pyrethrin/PBO2 (PT 1100 Pyrethrum TR) |
Whitmire MicroGen |
12 |
An aerosol. |
| B. |
pyrethrin/rotenone (Pyrellin EC) |
Webb Wright |
12 |
|
| insect growth regulator |
A. |
azadirachtin (Azatin XL Plus) |
Olympic
|
4
|
Must contact insect. Repeated applications as necessary. Label
permits low-volume application. |
| B. |
azadirachtin
(Ornazin 3%EC) |
SePRO |
12 |
Do not exceed 22.5 oz/acre/application. |
| C. |
diflubenzuron (Adept 25WP) |
Uniroyal |
12 |
Whitefly suppression. May damage poinsettias if used over
labeled rate. Also effective on fungus gnat larvae and lepidopteran
larvae. |
| D. |
novaluron (Pedestal) |
Uniroyal |
12 |
Use no more than twice per year and don't exceed 52
oz/acre/year. Don't use on poinsettia. |
| E. |
pyriproxyfen (Distance) |
Valent |
12 |
Do not apply more than 2 times per cropping cycle or per 6
months. Do not use through any type of irrigation system. |
| F. |
s-kinoprene (Enstar II) |
Wellmark |
4 |
Apply prebloom. Also labeled for low volume use. Do not apply
through any type of irrigation system. |
| macrocyclic lactone |
A. |
abamectin (Avid 0.15EC) |
Syngenta |
12 |
Label permits low-volume application. Do not apply through any
type of irrigation system. |
| neonicotinoid |
A. |
imidacloprid (Marathon 1G)
(Marathon II) |
Olympic |
12 |
Not to be used more than once every 16 weeks. Alternate with
insecticides that have a different mode of action to prevent development of
resistance to neonicotinoids. Do not apply to soils that are water logged or
saturated. Do not apply to bedding plants intended to be used as food
crops. |
| B. |
imidacloprid (Marathon 60WP) |
Olympic |
12 |
As above. Apply only as a drench. |
| oil3 |
A. |
clarified hydrophobic extract of neem oil (Triact 70) |
Certis |
4 |
Do not spray plants under stress. Target pest must be
completely covered with spray. Repeated application necessary. Check label for
list of plants that can be treated. May cause injury to flowers. Do not use
through any type of irrigation system. |
| B. |
horticultural oil Ultra-Fine Oil
SafTSide JMS Stylet Oil |
Whitmire MicroGen Brandt JMS Farms |
4
4 4
|
Use as above for neem oil. Also, do not use with sulfur fungicides; check label for tank mix restrictions.
|
| organochlorine |
A. |
endosulfan* (Endosulfan 3EC) |
Gowan |
24 |
Check local water/runoff restrictions. Some varieties of
chrysanthemum exhibit phytotoxicity. Do not use through any type of irrigation
system or apply more than 3 lb a.i./ acre/season. |
| organophosphate |
A. |
acephate (Address) |
Dow |
24 |
Do not use through any type of irrigation system. |
| B. |
acephate (Orthene T, T&O Spray) 75WP |
Valent |
24 |
A number of chrysanthemum varieties have exhibited phytotoxic
reactions. In the greenhouse, only labeled for use on anthurium, cacti,
carnation, rose, orchids, some foliage plants, young poinsettia and some
varieties of chrysanthemum. Can stunt new growth in roses. Do not use through
any type of irrigation system. |
| C. |
acephate (PT 1300 Orthene TR) |
Whitmire MicroGen |
24 |
An aerosol for greenhouse use only. |
| D. |
malathion (various) |
various |
12 |
Not for greenhouse use. |
organophosphate/ pyrethroid |
A. |
chloropyrifos/ cyfluthrin* (PT Duraplex TR) |
Whitmire MicroGen |
24 |
An aerosol. |
| pyrethroid |
A. |
bifenthrin* (Attain TR) |
Whitmire MicroGen |
12 |
Check label. A fogger for greenhouse use only. |
| B. |
bifenthrin* (Talstar Flowable) |
FMC |
12 |
Label permits low-volume application. Do not use through any
type of irrigation system. |
| C. |
cyfluthrin (Decathlon 20WP) |
Olympic |
12 |
Label permits low-volume application. Do not use through any
type of irrigation system. |
| D. |
fenpropathrin* (Tame 2.4EC) |
Valent |
24 |
Label permits low-volume application. Do not use through any
type of irrigation system. |
| E. |
fluvalinate (Mavrik Aquaflow) |
Wellmark |
12 |
Label permits low-volume application. Also labeled as a cutting
dip at 5 fl oz/100 gal. Do not use through any type of irrigation system. |
| F. |
permethrin* (Astro) |
FMC |
12 |
Direct application to blooms may cause browning of petals.
Marginal leaf burn may occur on salvia, diffenbachia and pteris fern. Label
permits low-volume application. Do not apply more than 2 lb
a.i./acre/year. |
| pyridazinone |
A. |
pyridaben (Sanmite 75WP) |
BASF |
12 |
|
| pyridine |
A. |
pymetrozine
(Endeavor) |
Syngenta |
12 |
Do not use through any type of irrigation system. Apply as
foliar spray at 7-14 day intervals. For outdoor use, do not apply more than 48
oz/acre/year; for indoor use, do not use more than 100 oz. |
| soap3 |
A. |
potash soap (Insecticidal soap)
(M-Pede) |
Olympic DowAgro |
12 12
|
Must contact insect, so thorough coverage is important. Repeat weekly as needed up to 3 times. Test for phytotoxicity. Do not spray new transplants or newly rooted cuttings. Do not add adjuvants.
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UC IPM Pest Management Guidelines: Floriculture and Ornamental Nurseries
UC ANR Publication 3392
Insects and Mites
K. L. Robb, UC Cooperative Extension, San Diego Co.
H. S. Costa, Entomology, UC Riverside
J. A. Bethke, Entomology, UC Riverside
M. P. Parrella, Entomology, UC Davis
Acknowledgment for contributions to the insects and mites section:
R. S. Cowles, Connecticut Agricultural Experiment Station, Windsor, CT
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