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Vol. 17, No. 8
Article 8 of 10
May 1, 2007
Alfalfa Weevil Larvae Still Present in Many Fields
By Wayne Bailey
Alfalfa weevil larvae have survived
the cold weather and are still feeding in
many central and northern and some
southern Missouri alfalfa fields. Larvae
continue to feed on foliage in fields
which were not harvested following the
freezing conditions. In fields that were
harvested, larvae are present on the
soil surface where they are feeding on
developing plant tillers. Both types of
feeding by larvae can result in economic
damage to the alfalfa crop. In fields
where adult weevil numbers are high, an
insecticide application may be needed to
prevent the adult weevils from girdling
the new stems and limiting tiller growth.
Fields in which alfalfa weevil larvae and
adults are allowed to feed on developing
tillers often exhibit heavy weed growth
due to the lack of an alfalfa canopy.
Producers are encouraged to scout
alfalfa fields and determine numbers
of alfalfa weevil larvae and adults. The
threshold of an average one or more
larvae present per alfalfa stem is still
valid, but diffi cult to determine if plants
are no longer standing. Treatment
thresholds for larvae and adults feeding
on tillers have not been determined,
but treatment is recommended if either
feeding by larvae or adult alfalfa weevils
is preventing alfalfa tiller regrowth.
| Recommended Insecticides for Adult Alfalfa
Weevil Control - 2007 |
| Insect Pest |
| Alfalfa weevil Adults: |
Chemical name |
Common
name |
Rate of Formulated Material |
Rate of Active Ingredient (a.i.) |
| Carbofuran |
*Furadan 4F |
1 to 2 pts/acre |
0.5 to 1 lb/acre |
| Chlorpyrifos 4E |
*Lorsban 4E
*numerous products |
1 to 2 pts/acre
see specific labels |
0.5 to 1 lb/acre
see specific labels |
| Methyl Parathion |
*Chemnova Methyl 4EC |
1 pt/acre |
0.5 lb a.i./acre |
| Phosmet |
Imidan |
see specific label |
see specific label |
| Read and follow all label direction, precautions, and restrictions. |
| Be aware of preharvest restrictions following insecticide application to alfalfa crop | .
| * Designated a restricted use product. |
| Recommended Insecticides for Larval Alfalfa
Weevil Management - 2007 |
| Insect Pest |
| Alfalfa weevil Larvae: |
Chemical name |
Common name |
Rate of Formulated Material |
Rate of Active Ingredient (a.i.) |
| Beta-cyfluthrin |
*Baythroid XL |
1.6 to 2.8 fl oz/acre |
0.0125 to 0.022 lb a.i./acre |
| Carbofuran |
*Furadan 4F |
1/2 to 2 pts/acre |
0.25 to 1 lb/acre |
| Chlorpyrifos 4E |
*Lorsban 4E
*numerous products |
1 to 2 pts/acre
see specific labels |
0.5 to 1 lb/acre
see specific labels |
| Methyl Parathion |
*Chemnova Methyl 4EC |
1 pt/acre |
0.5 lb a.i./acre |
| Gamma-cyhalothrin |
*Proaxis |
2.56 to 3.84 fl oz/acre |
0.02 to 0.03 lb a.i./acre |
| Phosmet |
Imidan |
see specific label |
see specific label |
| Zeta-cypermethrin |
*Mustang Max |
2.24 to 4.0 fl oz/acre |
0.014 to 0.025 lb a.i./acre |
| Carbaryl |
Sevin 4F |
1.5 qts/acre |
1.5 lb a.i./acre |
| Carbaryl |
Sevin XLR Plus |
1.5 qts/acre |
1.5 lb a.i./acre |
| Lambda-cyhalothrin |
*Warrior
*Numerous products |
2.56 to 3.84 fl oz/acre
see specific labels |
0.02 to 0.03 lb a.i./acre
see specific labels |
| Read and follow all label direction, precautions, and restrictions. |
| * Designated a restricted use product. |
Wayne Bailey
573-864-9905 cell
BaileyW@missouri.edu
|
