Alfalfa Pest Management
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Alfalfa Pest Management
Alfalfa Insect Management Recommendations
Sampling Guidelines
Pest | Sampling Method |
| Growth Stage: Mid- March to First Cutting | |
| Alfalfa weevil | Minimum of 30 stems per field collected in a W-pattern, place stems top first in bucket, measure stem height and count the number of larvae per stem |
| Pea aphid | Collect a minimum of 30 stems per field and count the number of aphids and beneficial insects present per stem ( e.g. lady beetles and syrphid fly larvae ) |
| Growth Stage: After First Cutting (mid-May) to September | |
| Alfalfa weevil – only for 2 weeks after first cutting | Minimum of 30 stems/crowns per field in a W-pattern, place stems top first in bucket and count the number of larvae per stem/crown |
| Potato leafhopper | Ten sweeps in ten locations – plants should be dry |
| Blister Beetle | 10 sweeps in ten locations< |
| Garden webworm and other defoliators | Estimate defoliation in 10 location |
Alfalfa Insect Thresholds
| Pest | March – April | May – early June | mid June – mid Sept. |
| Alfalfa weevil | 0-11 in. – 0.7 per stem12 in. – 1.0 per stem 13-15 in. – 1.5 per stem 16 in. – 2.0 per stem 17-18 in. – 2.5 per stem | 0-11 in. – 0.7 per stem12 in. – 1.0 per stem 13-15 in. – 1.5 per stem 16 in. – 2.0 per stem 17-18 in. – 2.5 per stem after 1st cutting – 2 per crown | |
| Pea aphid | <10 in. – 50 per stem>10 in. – 100 per stem 1 or more beneficials per 50 aphids should provide control | <10 in. – 50 per stem>10 in. – 100 per stem 1 or more beneficials per 50 aphids should provide control | |
| Potato leafhopper | 3 in. or less – 20 per 100 sweeps4-6 in. – 50 per 100 sweeps 7-11 in. – 100 per 100 sweeps 12 in. or more – 150 per 100 sweeps | 3 in. or less – 20 per 100 sweeps4-6 in. – 50 per 100 sweeps 7-11 in. – 100 per 100 sweeps 12 in. or more – 150 per 100 sweeps | |
| Garden webworm / general defoliators | 25-30% of tips damaged | ||
| Blister beetles | 1 per sweep |
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