For 5/9/03:
Alfalfa
Alfalfa at the SUNY Cobleskill farm was 8 to 12 inches tall (May 7).
Alfalfa Weevil Eggs Present!
Jeff Miller (Oneida County) and Kevin Ganoe (Chenango, Otsego, Herkimer,
Fulton & Montgomery Counties) are finding many adult alfalfa weevils
present in fields (May 7-8). I found tons of adult weevils and eggs
laid in alfalfa stems at the SUNY Cobleskill farm (May 7).
The predominate question after eggs have been laid in stems is, „When
will larvae hatch?‰ The 1st instar larvae hatch from eggs at 280
degree-days (base temp. 48F). This is just a few days at our typical
spring temperatures. Newly hatched larvae are about 1/16 inches long
and yellow to light green in color. As larvae feed, grow and molt they
become green with white stripes down their back, have a dark brown head.
Larvae ultimately grow to reach 3/8 inches long before pupation about
early June in New York. Recall that these larger larvae have big appetites
and are responsible for 80% of the alfalfa lost to weevil feeding.
Do you know the number of growing degree-days in your region today?
Check this website: NEW
YORK GROWING DEGREE-DAY TRACKER
(Base Temp. 50F)
Alfalfa
Weevil Eggs
Alfalfa
Weevil Larvae
Check out our on-line publication, IPM
for Alfalfa Weevil. 1.2 Mb pdf file
Clover-root curculio, What is that?
While scouting a 2nd year alfalfa field I encountered droves of adult
clover-root curculio. Some of you might ask, "What are clover-root
curculio weevils?" Well, I am glad you asked; adult clover-root
curculio weevils are 1/8 inch long and 1/16 inch wide with short, broad
snouts. The adult weevil is brownish-black and covered with grayish
hair and scales. Adult curculios chew the margins of leaves leaving
C shaped notches. Clover-root curculio larvae feed on nodules, small
rootlets, and chew out portions of the main root. As a result of larval
feeding on roots alfalfa diseases can enter the plant.
Picture
of an adult Clover-root curculio
Picture
of the larvae of the Clover-root curculio
Clover:
Ischnopterapion
virens: I discovered many tiny blue weevils called Ischnopterapion
virens in a clover field at SUNY Cobleskill (May 7). This weevil
is native to Europe and is relatively new to the United States. Adults
are metallic blue, about 3/16 inches long, with a distinctive snout
and straight antennae. Adults make small circular holes in leaves of
white clover. Larvae tunnel in the runners of clover and stems of red
clover. The economic damage status of this weevil is not known.
Field Corn
Corn fields at the SUNY Cobleskill farm are in the process of being
prepared for planting (May 7).
True Armyworm
Lisa Fields (Schoharie County) reports finding only one armyworm moth
in two traps (May 7). At the SUNY Cobleskill farm no moths were captured
in the pheromone traps (May 7).
Black Cutworm
Are grass weeds a problem in your corn? Could be just what a mother
black cutworm moth is looking for. Grasses, winter annual broadleaves,
and chickweed are favorite targets. If cutworm moths lay eggs in the
field and the field is treated with an herbicide, hatching cutworm larvae
bail off the dying weeds and look for greener food sources such as emerging
corn seedlings. Cutworms can be an annual problem in some fields; particularly
those with histories of poor weed control or have low wet areas in the
field. Field margins, especially those next to ditch banks, grassy lanes,
and hay fields are potential sites for infestation. Doing an early season
plant population count is a good way to check corn fields for cutworm
damage and other corn emergence problems.
Black Cutworm larvae vary in color from light gray to black with a
pale brown to black head. Larvae have a greasy, shiny appearance with
coarse granules present over their body. During the day larvae burrow
into the soil next to the corn plant. These larvae curl into a „C‰
shape when disturbed. Symptoms of damage are leaf feeding, irregular
holes in stem, notched and cut or missing plants. No-till fields and
those with a lot of grass weeds are at particular risk to black cutworm.
Monitor fields to find cutworm larvae when they are less than 1/2 inch
long. If there are sufficient numbers and damage present, an insecticide
could be justified. Treat only the affected area and a 20 to 40-foot
border around the infestation. Rarely does a whole field need to be
treated for cutworm. Larger cutworm larvae, greater than 1/2 inch long,
are much more difficult to control. If the majority of cutworm larvae
are 1/2 inch long or larger their damage is already done. These large
larvae are also more tolerant of insecticides, reducing the effectiveness
and economic viability of this option.
Check out our on-line publication, Black
Cutworm in Field Corn Management Guide 912K pdf file
Have a good week!
Ken Wise
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