Pecan Diseases and Pests and Their Control — John Shaqi
Pecan Diseases and Pests and Their ControlRosburg, David W.
Science
Pecan Diseases and Pests and Their Control
Rosburg, David W.
Pecan -- Diseases and pests; Pecan -- Diseases and pests -- Control
Mites usually are light green and are just large enough to be seen
without the aid of a hand lens. They are wingless and feed principally
on the underside of the leaves along the midrib. Colonies of them
produce webs in which molted skins and eggs may be found. The life cycle
of mites is very short and several generations occur each year. Large
populations may develop during the late summer and fall.
The use of certain insecticides for the control of the pecan nut
casebearer or bordeaux mixture for scab control frequently contributes
to increases in mite populations later in the season.
_Control._—Mites may be controlled in three ways when damaging
infestations develop. An application of 2 pounds of wettable sulfur per
100 gallons of water may be made; 6 pounds of wettable sulfur per 100
gallons of water may be added to the spray applied for the control of
the nut casebearer; and repeated applications of zineb included in a
regular spray schedule for pecan scab control will effectively control
mites. However, a single application of zineb is not effective[7].
PECAN LEAF CASEBEARER
On occasion, this insect, _Acrobasis juglandis_ (LeB.), develops to
damaging numbers and causes economic injury. Early in the spring the
larva feeds on unfolding leaves and buds. It may prevent leaf
development for weeks, resulting in a greatly decreased yield of nuts.
The adult is a dark gray moth marked with brown. Its forewings, which
have a spread of about two-thirds inch, are gray with black blotches.
There is a reddish mark near the base of the forewings.
The immature larva is brown, but changes to dark green as it develops to
a length of one-half inch. It has a shiny, brownish black head and is
enclosed in a gray case which completely covers the body and is borne in
a position nearly perpendicular to the leaf on which the larva is
feeding.
The pecan leaf casebearer overwinters as an immature larva in a
hibernaculum around a bud. It emerges in late March or early April as
the buds open. The larvae mature in April, May and June and transform
into pupae within their gray cases, Figure 15. The moths are present
from May until early August. Eggs are deposited during this period on
the underside of the leaves. The larvae which hatch from these eggs
develop slowly, and do not attain a length of more than one-sixteenth
inch during that season. They construct little winding cases in which
they live. Their feeding produces irregular blotches on the leaf
surface, Figure 16. Before the leaves drop in the fall, the larvae
migrate to the buds, and construct their overwintering hibernacula. Only
one generation is completed each year.
_Control._—Control of this insect is accomplished by spraying for the
pecan nut casebearer. See spray schedule, page 4. The insecticides
recommended for nut casebearer control also reduce infestations of the
leaf casebearer.
[Illustration: Figure 15. Overwintered larvae of pecan leaf
casebearer in their cases.]
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