NEWARK, Del. - Alfalfa is an
important crop for dairy farmers.
Other producers have also been
growing more of it recently as a
cash crop. Though expensive to
establish, with proper
management it can be profitable to
grow. Now that the first cutting of
the season has been made, the
challenge is to protect regrowth
from potato leafhopper attack and
weed competition.
Scouts for Delaware Extension’s
alfalfa integrated pest
management program have been
finding leafhoppers since late May
in Delaware fields. According to
University of Delaware extension
agricultural agent Bob Hochmuth,
over 1,000 acres are now enrolled
in this program, most of them in
Kent County. Participating far
mers have already been alerted to
the leafhqpper threat, but other
alfalfa producers should also be on
the lookout for the pest.
“I’ve always felt that growers
underestimate leafhopper
damage,” Hochmuth says. “In
many instances, producers aren’t
familiar with this insect. They
don’t know how to detect or control
it. We started our alfalfa IPM
program two years ago to help
farmers monitor this and other
pests.”
The county agent considers the
potato leafhopper the most
damaging insect on alfalfa in
Delaware. Though it doesn’t
overwinter this far north, it can be
found in Delaware in early sum
mer. The first alfalfa cutting
generally escapes damage if
harvest is not delayed, but later
growth is vulnerable to attack.
Potato leafhopper feeding
causes the greatest loss on new
spring seedings and on the
regrowth of second and third
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cuttings, Hochmuth says. The
insect lays its eggs in alfalfa stems
and large leaf veins. During the
summer, development from egg to
adult occurs in three weeks, so
several generations can develop
during the course of one growing
season.
Both adults and nymphs feed on
alfalfa, but nymphs cause the most
severe damage. Initial feeding
appears as yellow wedge-shaped
areas on leaves. This is often
referred to as hopper burn. A
heavy infestation may cause
leaves to turn entirely yellow.
Leafhopper feeding stunts plants,
destroys new stands and regrowth,
lowers protein content and
generally reduces alfalfa quality.
“Start sampling for the potato
COLLEGE PARK, Md. - Spider
mites just love hot, dry weather. So
this spring has been a good one for
those pesky, microscopic critters
which can literally suck plant
leaves to death.
With 12 major species common
in Maryland, there’s virtually no
kind of ornamental and vegetable
plant safe from attack, notes John
A. Davidson, an Extension en
tomologist at the University of
Maryland in College Park.
Usually less than l/50th of an
inch in length, mites are difficult to
see with the human eye. But the
damage they cause to growing
plants can be severe, Dr. Davidson
says.
As they feed, spider mites suck
the green chlorophyll out of plant
leaves. This causes small white
dots to appear. Mites also appear
to inject toxins into plant leaves,
causing varying degrees of leaf
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Tetchier
▼WATMSIM RIOHT*
for Leafhoppers in Alfalfa
leafhopper shortly after har
vesting the first cutting-when
plants are two inches high,”
Hochmuth advises. Continue
scouting on a weekly basis until the
final cutting. Take 20 sweeps in
five areas of the field to determine
the average number of leafhoppers
per sweep. Also take stem samples
from the same five areas. Collect
six stems per area and measure
the length from stem base to
growing tip.
Use the following guidelines to
make a control decision:
Leafhoppers/
Plant Height 100 Sweeps
3" or less 20
4" to 6" 50
7" to 12" 100
12” or more 150
Oil Spray Aids
discoloration and distortion,
If you have access to a sprayer,
the temptation is to load it up with
a suitable pesticide and spray
every ornamental and vegetable
plant in sight.
But wait! You may end up doing
more harm than good in the long
run, Dr. Davidson warns. Why?
Because indiscriminate
spraying with chemicals also kills
the predator insects and other tiny
creatures which feed on mites and
help to keep them under control.
Upsetting the balance of nature by
killing off their natural enemies
could then allow mites to multiply
far faster than jackrabbits in
Australia.
Consider examining the un
dersides of plant leaves weekly
with a magnifying glass to check
for mites and mite damage. If you
don’t have a magnifying glass,
simply tap two ro three leaves - or
cSP'Sav
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VALVE provides
ry of 15 gal. per
Many insecticides are effective
for leafhopper control. For
recommendations, Hochmuth
advises growers to call their
county extension agent.
“The leafhopper is the pest of
greatest problem on alfalfa as we
go through the summer,” he says,
“but with the dry weather, there
are other areas of concern this
year. Regrowth from the first
cutting is progressing slowly and
on droughty soils may not shade
the ground enough to out-compete
weeds.
“If we get rain during this
regrowth,” he warns, “it may
stimulate weeds to germinate in
alfalfa fields before the second
cutting is taken off. So scout fields
carefully for weeds immediately
in Mite Control
a small branch tip - against a
sheet of white paper. Look for
dislodged mites crawling on the
paper. If you see five or more,
consider spraying.
Instead of a chemical spray, try
an oil spray. This can be very
effective against mites and other
soft-bodied, sucking pests. But it
has a minimal effect on predators
and parasites of these pests. Just
make sure that plants are not
drought-stressed at the time that
you apply the oil spray.
Dr. Davidson admits that many
persons - including even some
horticulture professionals - are
reluctant to use an oil spray in the
summertime. This is mainly
because horticultural oils have
been considered primarily as
dormant sprays ever since their
introduction in the early 1900 s
Monroe
HARRISBURG - Two con
servation education awards have
been awarded to Monroe County
under the 1986 Deutz-AUis Con
servation Education Awards
Contest in cooperation with the
National Association of Con
servation Districts.
The Monroe County Con
servation District has won both the
state and regional competition for
the outstanding conservation
district education program and
will move forward into the national
level contest this fall. As the
Northeast Regional winner, the
Monroe County Conservation
District will receive a check for
$2OO from NACD and will receive
an award at the Northeast NACD
Regional Meeting in August in
Hagerstown, Maryland.
after that cutting. Grasses will be
the most likely problems.”
Herbicides that can be applied
after a cutting include Sinbar,
Paraquat and Gramozone.
Paraquat and Gramozone kill only
weeds that have emerged, and
either one of these materials must
be applied within five days after
cutting, Hochmuth says. Sinbar
will kill young emerged annual
grasses and provides ezcellent
residual control. It must be applied
before two inches of regrowth
occur on the alfalfa.
Paraquat, Gramozone and
Sinbar, cannot be used on alfalfa
that has been established less than
a year, the agent cautions. Read
the label directions carefully
before using any of these
materials.
It’s true that oil sprays for many
years were heavy and contained
impurities. This meant they dried
slowly and turned plant leaves
brown.
But today’s horticultural oils are
much different, Davidson says.
They are so light that they dry in
an hour or so. And they contain
few, if any, impurities. So they are
no more harmful to the foliage of
most plants than the insecticides
formulated in petroleum carriers
that are called emulsifiable con
centrates.
While the recommended ap
plication rate for dormant sprays
is three gallons of oil per 100
gallons of dilute spray, the
University of Maryland specialist
suggests using only two gallons of
oil per 100 gallons of dilute spray
during the growing season.
Co, Receives Conservation
Education Atvards
The state teacher award has
been won by Donna Foulk, a high
school teacher at Pleasant Valley
High School, Brodheadsville,
Monroe County. Both Ms. Foulk
and the Monroe County Con
servation District will be honored
at the 39th Joint Annual Con
ference of the Pennsylvania
Association of Conservation
District Directors, Inc. and the
State Conservation Commission.
The purpose of the Deutz-
Allis/NACD awards program is to
encourage the development of
creative learning experiences in
conservation for young people. The
awards program also makes the
community at large aware of the
efforts being put forth by teachers
and conservation districts in the
area of conservation.