Agriculture Reference
In-Depth Information
Leafhoppers and relatives:
Cicadellidae, Delphacidae, Cixiidae
Beet leafhopper,
Circulifer tenellus
(Baker), is
the first well-studied example of a leafhopper
that affects potato in its role as vector of a phyto-
plasma. This leafhopper is thought to be native
to the Mediterranean region, but has become estab-
lished throughout the Americas, where it locally
damages crops and transmits pathogens such
as the phytoplasma called the beet leafhopper-
transmitted virescence agent (BLTVA), which
causes a potato purple top disease. Purple top in
potato consists of a suite of symptoms includ-
ing leaf yellowing, then purpling, curling, elong-
ation of axial buds, aerial tubers, and early plant
senescence.
Beet leafhopper is common in the natural-
ized vegetation in the arid and semi-arid potato
producing regions of the USA. It does not repro-
duce in the potato crop, but transmits BLTVA to
potato during its movements through the land-
scape. Aster leafhopper,
Macrosteles fascifrons
(Stål), transmits aster yellows phytoplasma to
potato in the eastern USA. It migrates from more
southern overwintering grounds to spend the
summer in potato producing regions. Much like
beet leafhopper, aster leafhopper does not repro-
duce on potato, but transmits phytoplasma dur-
ing casual visits to the crop.
Recognition
Leafhoppers are small (
2-
5 mm) sucking in-
sects that feed on cell contents or phloem.
They are usually broadest at the front, and
taper to a narrow caudal end, holding the
wings roof-like over the body. Eggs are depos-
ited in plant tissue by the female's specialized
ovipositor. Nymphs are active runners and
jumpers. Around the world there are many
local and regional species of leafhoppers
(Cicadellidae) and planthoppers (Delphacidae,
Cixiidae) that can be pests in potatoes. These
are divided into those that prefer potato as a
host and cause direct damage to the plant,
primarily species of
Empoasca
, and those
that transmit pathogens, especially phytoplas-
mas, to potato during temporary residency
in the crop. A few relatively well-studied ex-
amples are discussed briefly below. Brief men-
tions of many other regionally and locally
important species are made by Munyaneza
and Henne (2013).
Distribution and species
Sampling and monitoring
The name “potato leafhopper” is applied to the
cicadellid species,
Empoasca fabae
(Harris) in
mid-western and eastern North America, where
it is an important pest. It is thought to be na-
tive to North America, where it overwinters in
southern regions of the USA and migrates
northward each spring to infest potato crops,
and then returns south in the fall (as summar-
ized by Munyaneza and Henne, 2013).
The potato leafhopper has a wide host
range, but reproduces well in potato. As it
feeds, the leafhopper weakens plants and
causes a syndrome known as hopper burn
that results in stunting, yellowing, and even-
tually necrosis of affected leaves. Severity of
hopper burn is related directly to population
density in the crop. Biological and cultural
control options for this leafhopper are few, and
management typically consists of well-timed
insecticides. Other species of
Empoasca
can be
locally abundant, such as
Empoasca filamenta
(DeLong) in the Pacific Northwest of the USA,
and also cause hopper burn.
Sweep nets are commonly and effectively used
for leafhopper sampling, especially for species
resident in the crop. For
Empoasca
and related
leafhoppers causing direct damage, sampling for
field colonization by adults is useful. When large
influxes are detected, treatments are commonly
started when the first nymphs appear (Ragsdale
et al
., 2008). One reason for the delay until
nymphal emergence is because leafhopper eggs
are inserted into plant tissues, affording protec-
tion from many insecticides.
In the case of non-resident leafhoppers that
transmit pathogens, yellow sticky traps are often
used to detect the flights of each adult gener-
ation. Placement of traps is specific to the target
leafhopper. For example, yellow sticky traps
deployed to capture beet leafhopper must be
mounted close to the ground in sparse vegeta-
tion. There are not well-established treatment
thresholds for most leafhoppers in potatoes, with
general guidelines often in practice regionally
and locally.
