-Foraging Around, Lancaster Farming, Saturday, April 21,2001
220
Paul H. Craig
Capital Region Extension
Agronomy Team, Forages
Dauphin County
Pennsylvania hay producers have
developed a very profitable hay
market for timothy grass hay. Timo
thy hay is the favored species of
grass hay for most horse producers
throughout the state and neighbor
ing states.
It has been estimated that there
are about 175,000 acres of timothy
in Pennsylvania and 75,000 acres in
Maryland. Recent hay prices range
from $75 to $165 per ton for timothy
hay.
At top production levels and
price, timothy can gross $5OO per
acre or more. In recent years, how
ever, many timothy producers have
noted decreased yields and thinning
stands across south central Pennsyl
vania.
In the spring of 2000, the cause
for this reduction of stands was
identified as a new pest in Pennsyl
vania, the cereal rust mite. Travels
across south central Pennsylvania
revealed that the problem is wide
spread and that most stands of tim
othy more than two 2-years-old
have some level of infestation of the
cereal rust mite, commonly, but in
correctly, referred to as the timothy
mite.
The cereal rust mite is an ex
tremely small pest. It cannot be seen
without the use of a 20-power hand
lens or a microscope. They are
shaped like a grain of rice, soft
bodied, with four legs located near
the head of this critter. They can
move fairly easily up and down the
leaves of the timothy plant, but they
prefer to feed on the youngest tissue
of the plant.
Don’t let the size of this pest lull
you into indifference. High popula
tion levels can be very destructive to
timothy stands.
The cereal rust mite feeds on
single cells at the base of the grooves
between veins on the timothy leaves.
The mite inserts a “needle-like”
mouthpart into the cell and draws
out the cell contents, leaving a
shrunken cell. The mite then moves
to another cell and resumes feeding.
Very rapidly, the plant displays a
“rolled leaf’ characteristic that is
very similar to drought stress. The
tip off to an infestation is the
droughty symptom seen in late
April or early May when adequate
soil moisture is available.
Severe mite infestations have two
negative impacts for timothy pro
ducers. Severe feeding causes sub
stantial yield losses. Yield loss
estimates range from 30 to 70 per
cent. Severe feeding has resulted in
stressed stands that are not able to
withstand extreme summer growing
conditions, especially droughts and
high temperatures. As a result, older
stands can be severely thinned out.
A second impact of the mite is re
lated to forage quality. Under high
mite pressures, the hay cures with a
brownish discoloration. This “off
color” makes horse producers reluc
tant to pay top dollar.
In the mid 19905, this pest was
first brought to the attention of
forage researchers at the University
of Maryland. Entomologists Galen
Dively and Terry Patton quickly
noted the widespread occurrence in
The Mite That Roared!
small research trials to evaluate con
trol materials and to gain additional
knowledge on the mite.
In the spring of 2000, ag service
representatives in southern Pennsyl
vania informed members of the
Penn State University Capital
Region Extension Agronomy Team
of the possible spread of this pest
into Pennsylvania. In travels across
the region the pest has been noted
from western Franklin County to
eastern Lancaster County and north
to upper Dauphin County.
Unlike most crop pests, the cereal
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The cereal rust mite is almost microscopic in size.
rust mite prefers colder conditions
to summer weather. The mites
overwinter in the crown area of tim
othy plants as adults and eggs.
Maryland has recorded breeding ac
tivity as early as January. Each
female can lay 20 to 40 eggs that
rapidly reach maturity in 16-18
days. As a result, populations rap
idly increase. As the leaves on the
plant elongate the mature mites will
move out on the leaves and then
“stand up” on their tails. They are
then dispersed by winds. The mites
have such a great preference for
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timothy that if they land on a differ
ent species of plant, they will stand
up and move again.
By mid April, mite populations
are rapidly building up and this is
the time when injury can first be
noted. By May, signs of heavy feed
ing can be noted by looking for the
draughted characteristic. When
summer temperatures arrive, the
mite enters a dormancy period and
is rarely observed on regrowth.
Growers of timothy forage crops
should begin to monitor their stands
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