| ASTER
LEAFHOPPER
There
are many insects under the umbrella term of “leafhoppers” of which
the two that are economically important to potato growers are the
aster leafhopper (Macrosteles quadrillineatus) and the potato leafhopper
(Empoasca fabae). These are pests throughout the US mid-west and
southern Canada. Among entomologists, the leafhopper ranks third
as the most important insect pest in North America, after the Colorado
potato beetle and green peach aphid. Of the two leafhoppers above,
the potato leafhopper has the most effect on yield reduction.
ASTER
LEAFHOPPER
Aster
leafhopper (Macrosteles quadrillineatus) damages crops not only
through direct feeding on the sap but also by being a carrier for
a disease “aster yellows.” Aster yellows is caused by a mycoplasma-like
organism (MLO) or phytoplasma. These are similar to bacteria but
lack a cell wall. They are not air or water-borne but must be transmitted
through a carrier or vector.
Description
Adult
aster leafhoppers are wedge shaped and thin. They are a tenth to
a fifth of an inch long. The bodies are a dull light green and there
are six white spots on the top of the head and none on the thorax.
The wings are silvery gray and fold back at rest. Like potato leafhoppers,
nymphs are similar to adults but are smaller and wingless. Several
nymphal stages occur in the generation.
Life
Cycle
Aster
leafhoppers overwinter as adults in northern Texas, Oklahoma and
Arkansas. They fly on winds north to Kansas, Nebraska, the Dakotas,
Minnesota, and Wisconsin. It overwinters in grassy weeds and small
grains. Overwintering as eggs has been reported.
The
life cycle is similar to that of the potato leafhopper except that
aster leafhoppers do not mate and lay eggs on potatoes. Adults live
30-40 days but may live as much as 90 days and as much as 200 eggs
may be laid in an adult’s lifetime. Eggs hatch in ten days forming
nymphs which convert to adults within a fortnight.
Damage
 Injury
by aster leafhopper feeding is minimal and not economically important.
The problem rests in that it is a vector (carrier) of the ‘aster
yellow mycoplasma-like organism’ (AY-MLO). This MLO causes ‘aster
yellows’ also called ‘purple top.’ The MLO is acquired by the aster
leafhopper from small grains not from potato. A large aster leafhopper
population (severe population pressure) is needed for economic losses.
However, yield reduction can occur. Most importantly is that potato
tubers from infected plants with produce discolored potato chips
and french fries during processing.
Aster
Yellow
AY-MLO
causes one disease that has many names including purple top and
haywire. When as adult aster leafhopper first ingests the MLO, it
takes 10 to 21 days for the MLO to replicate sufficiently to be
able to be injected into potato plants. How the MLO causes the disease
symptoms is not yet known. Flowers are most affected. Petals develop
a green pigmentation and there is an abundant production of petals
and sepals, both appearing like leaflets. Leaflets will be small,
bunched and slightly rolled. A typical character of leaflets is
a yellowing or reddening of the leaflet, hence, giving the descriptions
of aster yellow and purple top. Aerial tubers and stem swelling
around nodes are typically observed. Wilting may occur. Discoloration
in potato chips is common. Harvested tubers may or may not be affected
for seed. When affected, tubers produce spindly sprouts called hair
sprouts. Symptoms vary widely and a laboratory identification is
recommended.
Aster
leafhopper does not pick up the MLO from potatoes.
Management
 Sustainable
Agriculture — Monitoring fields for populations and correctly identifying
the leafhopper is essential to good management as there are many
leafhoppers that do not damage potato. There is no threshold established
for aster leafhopper treatment.
Chemical
Management — The same insecticides that affect potato leafhopper
are effective against aster leafhopper.
The
chief important host for aster leafhopper are small grains where
they pick up the disease-causing MLO. Potato is not the preferred
host of the aster leafhopper.
Quick
Review / Aster Leafhopper
Appearance:
- Adults
- dull green, six white spots, 1/10-1/5 inch long
- Nymph
- like adult but smaller and wingless
Life
Cycle:
- Overwinters
- Texas, Oklahoma and Arkansas
- One
to three generation/ season in north-central U.S.
- Adults
- June to early July
Damage:
- Adult
- injects phytoplasma causing aster yellows feeding on sap (sucking-piercing
insect)
- Nymph
- feeds off of the sap
Management:
- Monitor
and Identify
- Economic
Threshold = none established
- At-planting
Insecticides
- Foliar
Insecticide
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