Lecture 5.2 - Alfalfa Weevil Control

Question 1

what is a major alfalfa pest in SK

Answer 1

alfalfa weevil

Question 2

what are some weevil feeding signs

Answer 2

-skeletonized leaf (in severe cases)
-round holes
-notches along leaf edge
-pinholes
-eaten flower buds
- sections of field look silver/grey

Question 3

weevil life cycle

Answer 3

adult mates in May
lay eggs in mid May which hatch mid June
larvae eat leaves til mid July
become pupa at end of July
live as adult till end of August

Question 4

how many instar larvae stages do alfalfa weevils have

Answer 4

4

Question 5

why is there not a specific time to check for weevils

Answer 5

because it depends on the temperature in spring, timing

Question 6

what is the threshold for alfalfa weevil

Answer 6

twenty 3rd and 4th instar larvae per 180 degree sweep

Question 7

University of Wisconsin Method calculating for alfalfa weevil threshold

Answer 7

-walk in M shape and look at 50 alfalfa stems
-count stems with any feeding sign (no counting larvae)
- more than 20 stems with feeding sign is threshold

Question 8

what is the most economical and effective control method of weevil

Answer 8

early harvest

Question 9

chemical control of alfalfa weevil

Answer 9

Matador
Cygon 480 EC/Lagon
Decis 5EC

Question 10

what are some other methods of alfalfa weevil control

Answer 10

-livestock grazing (tramples and reduces leaf material)
-early spring burning
-pulling weighted land rollers over fields (squash eggs)