EENY-119
Diamondback Moth, Plutella xylostella (Linnaeus)
(Insecta: Lepidoptera: Plutellidae) 1
J. L. Capinera 2
1. This document is EENY-119, one of a series of the Department of Entomology and Nematology, UF/IFAS Extension. Original publication date January
2000. Revised September 2011 and December 2018. Visit the EDIS website at http://edis.ifas.ufl.edu . This document is also available on the Featured
Creatures website at http://entnemdept.ifas.ufl.edu/creatures/ .
2. J. L. Capinera, professor emeritus and chairman, Entomology and Nematology Department; UF/IFAS Extension, Gainesville, FL 32611.
The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county’s UF/IFAS Extension office.
U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.
Distribution
The diamondback moth is probably of European origin
but is now found throughout the Americas and in Europe,
Southeast Asia, Australia, and New Zealand. It was first
observed in North America in 1854, in Illinois, but had
spread to Florida and the Rocky Mountains by 1883, and
was reported from British Columbia by 1905. In North
America, diamondback moth is now recorded everywhere
that cabbage is grown. However, it is highly dispersive,
and is often found in areas where it cannot successfully
overwinter, including most of Canada.
Life Cycle
Total development time from the egg to pupal stage aver -
ages 25 to 30 days, depending on weather, with a range of
about 17 to 51 days. The number of generations varies from
four in cold climates such as southern Canada to perhaps
eight to 12 in the south. Overwintering survival is positively
correlated with the abundance of snowfall in northern
climates.
Description
Egg
Diamondback moth eggs are oval and flattened, and
measure 0.44 mm long and 0.26 mm wide. Eggs are yellow
or pale green in color, and are deposited singly or in small
groups of two to eight eggs in depressions on the surface of
foliage, or occasionally on other plant parts. Females may
deposit 250 to 300, eggs but average total egg production is
probably 150 eggs. Development time averages 5.6 days.
Larva
The diamondback moth has four instars. Average and range
of development time is about 4.5 (3–7), 4 (2–7), 4 (2–8),
and 5 (2–10) days, respectively. Throughout their develop -
ment, larvae remain quite small and active. If disturbed,
they often wriggle violently, move backward, and spin down
from the plant on a strand of silk. Overall length of each
instar rarely exceeds 1.7, 3.5, 7.0, and 11.2 mm, respectively,
for instars 1 through 4. Mean head capsule widths for
these instars are about 0.16, 0.25, 0.37, and 0.61 mm. The
larval body form tapers at both ends, and a pair of prolegs
protrudes from the posterior end, forming a distinctive “V.”
The larvae are colorless in the first instar, but thereafter are
green. The body bears relatively few hairs, which are short
in length, and most are marked by the presence of small
white patches. There are five pairs of prolegs. Initially, the
feeding habit of first instar larvae is leaf mining, although
they are so small that the mines are difficult to notice. The
larvae emerge from their mines at the conclusion of the
first instar, molt beneath the leaf, and thereafter feed on the
lower surface of the leaf. Their chewing results in irregular
patches of damage, and the upper leaf epidermis is often left
intact.
2 Diamondback Moth, Plutella xylostella (Linnaeus) (Insecta: Lepidoptera: Plutellidae)
Pupa
Pupation occurs in a loose silk cocoon, usually formed
on the lower or outer leaves. In cauliflower and broccoli,
pupation may occur in the florets. The yellowish pupa is
7 to 9 mm in length. The duration of the cocoon averages
about 8.5 days (range five to 15 days).
Adult
The adult is a small, slender, grayish-brown moth with
pronounced antennae. It is about 6 mm long, and marked
with a broad cream or light brown band along the back.
The band is sometimes constricted to form one or more
light-colored diamonds on the back, which is the basis
for the common name of this insect. When viewed from
the side, the tips of the wings can be seen to turn upward
slightly. Adult males and females live about 12 and 16 days,
respectively, and females deposit eggs for about 10 days.
The moths are weak fliers, usually flying within 2 m of the
ground, and not flying long distances. However, they are
readily carried by the wind. The adult is the overwintering
stage in temperate areas, but moths do not survive cold
winters such as is found in most of Canada. They routinely
re-invade these areas each spring, evidently aided by
southerly winds.
Detailed biology of diamondback moth can be found in
Marsh (1917) and Harcourt (1955, 1957, 1963). A survey of
the world literature was published by Talekar et al. (1985).
A recent review of biology and management is provided by
Philips et al. (2014).
Host Plants
Diamondback moth attacks only plants in the family
Cruciferae. Virtually all cruciferous vegetable crops are
eaten, including broccoli, Brussels sprouts, cabbage, Chi -
nese cabbage, cauliflower, collard, kale, kohlrabi, mustard,
radish, turnip, and watercress. Not all are equally preferred,
however, and collard will usually be chosen by ovipositing
moths relative to cabbage. Several cruciferous weeds are
important hosts, especially early in the season before
cultivated crops are available.
Damage
Plant damage is caused by larval feeding. Although the
larvae are very small, they can be quite numerous, resulting
in complete removal of foliar tissue except for the leaf veins.
This is particularly damaging to seedlings, and may disrupt
head formation in cabbage, broccoli, and cauliflower. The
presence of larvae in florets can result in complete rejection
of produce, even if the level of plant tissue removal is
insignificant.
Diamondback moth was long considered a relatively
insignificant pest. Its impact was overshadowed by such
serious defoliators as imported cabbageworm, Pieris rapae
(Linnaeus), and cabbage looper , Trichoplusia ni (Hubner).
However, in the 1950s the general level of abundance began
to increase, and by the 1970s it became troublesome to
crucifers in some areas. Insecticide resistance was long
Figure 1. Larva of the diamondback moth, Plutella xylostella (Linnaeus).
Credits: Lyle Buss, UF/IFAS
Figure 2. Pupa of the diamondback moth, Plutella xylostella (Linnaeus).
Credits: Lyle Buss, UF/IFAS
Figure 3. Adult diamondback moth, Plutella xylostella (Linnaeus).
Credits: Lyle Buss, UF/IFAS
3 Diamondback Moth, Plutella xylostella (Linnaeus) (Insecta: Lepidoptera: Plutellidae)
suspected to be a component of the problem. This was
confirmed in the 1980s as pyrethroid insecticides began
to fail, and soon thereafter virtually all insecticides were
ineffective. Relaxation of insecticide use, and particularly
elimination of pyrethroid use, can return diamondback
moth to minor pest status by favoring survival of
parasitoids.
Natural Enemies
Large larvae, prepupae, and pupae are often killed by the
parasitoids Microplitis plutellae (Muesbeck) (Hymenoptera:
Braconidae), Diadegma insulare (Cresson) (Hymenoptera:
Ichneumonidae), and Diadromus subtilicornis (Graven -
horst) (Hymenoptera: Ichneumonidae). All are specific
on P. xylostella . The larval parasitoids Diadegma insulare
(Cresson) (Hymenoptera: Ichneumonidae) and Microplites
plutellae (Muesebeck) (Hymenoptera: Braconidae) are
quite important in North America (Philips et al. 2014). In
warmer climates such as the southeastern United States,
Oomyzus sokolowski (Kurdjumov) (Hymenoptera: Eulo -
phidae) assumes importance as a larval parasitoid. Nectar
produced by wildflowers is important in determining
parasitism rates by D. insulare . Egg parasites are unknown.
Fungi, granulosis virus, and nuclear polyhedrosis virus
sometimes occur in high density diamondback moth larval
populations.
Weather
A large proportion of young larvae are often killed by
rainfall. However, the most important factor determining
population trends is thought to be adult mortality. Adult
survival was thought to be principally a function of
weather, although this hypothesis has not been examined
r i g o r o u s l y.
Management
Sampling
Populations are usually monitored by making counts of
larvae, or by the level of damage. In Texas, average popula -
tion densities of up to 0.3 larvae per plant are considered
to be below the treatment level. In Florida and Georgia,
treatment is recommended only when damage equals or
exceeds one hole per plant. When growers monitor fields
and subscribe to these treatment thresholds rather than
trying to prevent any insects or damage from occurring in
their fields, considerably fewer insecticide applications are
needed to produce a satisfactory crop. A minimum plant
sample size of 40 to 50 is recommended, except for the egg
stage, where 150 plants should be examined for accurate
population estimates.
Pheromone traps can be used to monitor adult populations
and may predict larval populations 11 to 21 days later.
However, because of variation among locations, each crop
field requires independent monitoring.
Insecticides
Protection of crucifer crops from damage often requires
application of insecticide to plant foliage, sometimes
as frequently as twice per week. However, resistance to
insecticides is widespread, and includes most classes
of insecticides including some Bacillus thuringiensis
products. Rotation of insecticide classes is recommended,
and the use of B. thuringiensis is considered especially
important because it favors survival of parasitoids. Even
B. thuringiensis products should be rotated, and current
recommendations generally suggest alternating the kurstaki
and aizawa strains because resistance to these microbial
insecticides occurs in some locations. Mixtures of chemical
insecticides, or chemicals and microbials, are often recom -
mended for diamondback moth control. This is due partly
to the widespread occurrence of resistance, but also because
pest complexes often plague crucifer crops, and the insects
vary in susceptibility to individual insecticides.
For specific insecticide recommendations see: Insect
Management Guide for Cole Crops (http://edis.ifas.ufl.edu/
IG150 ).
Cultural Practices
Rainfall has been identified as a major mortality factor for
young larvae, so it is not surprising that crucifer crops with
overhead sprinkle irrigation tend to have fewer diamond -
back moth larvae than drip or furrow-irrigated crops. Best
results were obtained with daily evening applications.
Crop diversity can influence abundance of diamondback
moth. Larvae generally are fewer in number and more
heavily parasitized when crucifer crops are interplanted
with another crop or when weeds are present. This does
not necessarily lead to reduction in damage, however.
Surrounding cabbage crops with two or more rows of more
preferred hosts such as collard and mustard can delay or
prevent the dispersal of diamondback moth into cabbage
crops.
Crucifer transplants are often shipped long distances prior
to planting, and diamondback moth may be included with
the transplants. In the United States, many transplants are
4 Diamondback Moth, Plutella xylostella (Linnaeus) (Insecta: Lepidoptera: Plutellidae)
produced in the southern states and then moved north as
weather allows. Cryptic insects such as young diamondback
moth larvae are sometimes transported and inoculated in
this manner. The transport of insecticide-resistant popula -
tions also may occur. Every effort should be made to assure
that transplants are free of insects prior to planting.
Host Plant Resistance
Crucifer crops differ somewhat in their susceptibility to
attack by diamondback moth. Mustard, turnip, and kohl -
rabi are among the more resistant crucifers, but resistance
is not as pronounced as it is for imported cabbageworm
and cabbage looper. Varieties also differ in susceptibility to
damage by diamondback moth, and a major component of
this resistance is the presence of leaf wax. Glossy varieties,
lacking the normal waxy bloom and, therefore, green rather
than grayish green, are somewhat resistant to larvae. Larvae
apparently spend more time searching and less time feeding
on glossy varieties. Glossy varieties also tend to have fewer
imported cabbageworm larvae and cabbage aphids, but
more cabbage flea beetles.
Selected References
Cartwright B, Edelson JV, Chambers C. 1987. “Composite
action thresholds for the control of lepidopterous pests on
fresh-market cabbage in the lower Rio Grande Valley of
Texas.” Journal of Economic Entomology 80:175–181.
Harcourt DG. 1955. “Biology of the diamondback moth,
Plutella maculipennis (Curt.) (Lepidoptera: Plutellidae),
in eastern Ontario.” Report of the Quebec Society for the
Protection of Plants 37:155–160.
Harcourt DG. 1957. “Biology of the diamondback moth,
Plutella maculipennis (Curt.) (Lepidoptera: Plutellidae),
in Eastern Ontario. II. Life-history, behaviour, and host
relationships.” Canadian Entomologist 89:554–564.
Harcourt DG. 1963. “Major mortality factors in the
population dynamics of the diamondback moth, Plutella
maculipennis (Curt.) (Lepidoptera: Plutellidae).” Memoirs of
the Entomological Society of Canada 32:55–66.
Marsh HO. 1917. “Life history of Plutella maculipennis ,
the diamond-back moth.” Journal of Apicultural Research
10:1–10.
McHugh Jr. JJ, Foster RE. 1995. “Reduction of diamondback
moth (Lepidoptera: Plutellidae) infestation in head cabbage
by overhead irrigation.” Journal of Economic Entomology
88:162–168.
Philips CR, Fu Z, Kuhar TP, Shelton AM, Cordero RJ. 2014.
“Natural history, ecology, and management of diamond -
back moth (Lepidoptera: Plutellidae), with emphasis on the
United States.” Journal of Integrated Pest Management 5 (3).
Stoner KA. 1990. “Glossy leaf wax and plant resistance
to insects in Brassica oleracea under natural infestation.”
Environmental Entomology 19:730–739.
Talekar, N.S., H.C. Yang, S.T. Lee, B.S. Chen, and L.Y. Sun
(eds.). 1985. Annotated Bibliography of Diamondback
Moth. Asian Vegetable Research and Development Center,
Taipei, Taiwan. 469 pp.
Workman RB, Chalfant RB, and Schuster DJ. 1980.
“Management of the cabbage looper and diamondback
moth on cabbage by using two damage thresholds and five
insecticide treatments.” Journal of Economic Entomology
73:757–758.
