Walk an alfalfa field anywhere in south-central Nebraska this week and you'll see what 200 growing degree days looks like. Pinpoint feeding holes on the upper leaves. Frayed growing tips. Beat a stem hard against the inside of a five-gallon bucket and a handful of pale-green, black-headed larvae curl up at the bottom.
That's the alfalfa weevil, and the May decision growers are sitting on right now is the same one we get every year: spray, cut early, or both — and if you're going to spray, does a drone fit?
Here's the framework, and where the drone honestly fits versus where it doesn't.
Don't Skip the Scouting Step
UNL Extension is specific on the trigger: start scouting once you've accumulated about 200 growing degree days on a base 48°F, which for most of southern and south-central Nebraska puts the front edge of the window in late April and the heart of it through mid-May. Adams, Clay, Webster, Nuckolls, Thayer, and Fillmore County stands are well past 200 GDD by now.
The scouting protocol is straightforward: pick five random sites across the field, cut six stems at each at ground level, and shake the larvae off into a deep bucket. Average the count.
The treatment threshold is not a single number. It slides with hay value, treatment cost, and stand height — about 1 larva per stem on tall, valuable hay up to 7 larvae per stem on short, low-value cuts. At the hay prices and product costs most Nebraska growers see this spring, most operators are pulling the trigger somewhere in the 1.5–2.5 larvae per stem range. Below that, scout again in 4 or 5 days. Larva counts climb fast in 70°F-and-above weather — last week's clean number does not mean a clean field this week.
Spray, Cut, or Both?
The May calendar drives the second half of the decision. Most south-central Nebraska first cuttings land somewhere between late May and the first week of June.
If you're inside two weeks of normal first cutting, extension entomologists at Iowa State, UNL, and the University of Wisconsin all push hard for early cutting over an insecticide pass when:
- Alfalfa has reached 50% bud or later
- Hay is expected to dry within a few days of cutting
- Windrows can be off the field quickly
Cutting strips the larvae of food and shelter, exposes them to direct sun and wind, and if your normal cutting timing was already close, you save the spray dollars entirely.
The catch — and this is the part growers under-scout — is that adult weevils survive the cut, and the survivors and any late-hatching larvae feed on the regrowth. Stunted second-cutting regrowth in mid-June is almost always alfalfa weevil that nobody scouted after first cut. UNL's recommendation is straightforward: if you see significant feeding on stubble within 4 to 7 days of cutting, that's a treatable situation.
So the actual three-option decision tree is:
- Pre-cut spray — more than two weeks from cutting and over threshold
- Cut early — within two weeks of normal harvest, hay is mature enough, dry conditions ahead
- Post-cut stubble spray — regrowth getting chewed flat, 4–10 days after first cut
The drone fits some of those better than others.
Where the Drone Wins on Alfalfa
A spray drone applies at 2–3 gallons per acre with prop downwash forcing droplets into the canopy. For weevil larvae specifically — they're feeding on upper leaves and growing tips at this stage, not buried at the crown — that carrier volume is enough.
Smaller fields and odd-shaped pivots. A 40-acre alfalfa stand isn't worth setting up the airplane minimum, and at our $400 trip floor and $18–22/ac, the math gets the field treated without overshooting the budget. The classic case is a small alfalfa pivot tucked between a homestead and a tree row where the airplane minimum doesn't pencil and a wet spring keeps the ground rig out — that's the field a drone treats in a couple of hours.
Border and tree-row precision. Alfalfa fields next to homes, organic neighbors, sensitive specialty crops, or commercial beehives need controlled drift. The drone's slow ground speed, tight 26-foot swath, and ability to turn off individual nozzles at boundaries beat both the airplane and a high-clearance ground rig on neighbor-sensitive applications.
Speed of response. When you scout Tuesday and you're at threshold, every additional day costs upper-canopy leaf area. A local drone gets on most fields within 24–48 hours of the call without waiting for an airplane window or a ground rig schedule.
Post-cut stubble passes. This is the underrated drone application on alfalfa. Stubble is 3–4 inches tall, the canopy isn't fighting you, droplet placement is excellent, and we can put the right rate on the new growth without compaction or wheel tracks where you'd be cutting again in 25 days.
Where the Drone Loses
Big, contiguous, square 320-acre alfalfa blocks headed straight to first cutting. The airplane is faster, probably $4–6/ac cheaper at sticker, and if you're going to cut anyway the pre-cut application is best done quick or skipped. We'll send you to the airplane if that's what you have.
Heavy infestations on a thick, late-stage canopy. Once you're at 5+ larvae per stem on dense, knee-high alfalfa, you want carrier volume — 10–15 gallons per acre from a ground rig — to get adequate exposure into the canopy. We can fly it, but at our rate card the math probably says cut now and treat the regrowth instead.
The Resistance Conversation Nobody Wants to Have
If you've been spraying alfalfa weevil with a pyrethroid every year for the last decade, this is the year to pay attention. USDA and university trials across the western US — Arizona, Wyoming, Montana, Oregon, Washington, and California — have documented widespread alfalfa weevil resistance to lambda-cyhalothrin and other Type II pyrethroids, with field control failures that look exactly like a missed application or a poor rate.
Nebraska populations haven't been formally surveyed at the same scale, but University of Minnesota and Wisconsin researchers have flagged the same resistance pattern moving east. The practical move: if you treated last year and saw a poor knockdown — surviving larvae two days later, regrowth still being chewed — switch chemistry.
The tank options that still work consistently:
- Indoxacarb (Steward EC) — Group 22A, no documented field resistance, and a 7-day pre-harvest interval on alfalfa. The premium product, but it earns its keep where pyrethroids are slipping.
- Spinosad (Blackhawk; Entrust on organic ground) — Group 5, expensive but clean.
- Chlorantraniliprole (Coragen, Vantacor) — Group 28, longer residual, better for the post-cut stubble pass.
If you want to stay with a pyrethroid (Mustang Maxx, Warrior II, Baythroid XL — all Group 3A) on a budget pass, the single best practice is to rotate to a different mode of action on the next pass. Mustang Maxx has the shortest pre-harvest interval at the label rate — 3 days to cutting or grazing — which is why it shows up so often on pre-cut applications. Spraying the same active twice a year, year over year, is exactly how the western states ended up with control failures and a much smaller toolbox.
A drone doesn't change the chemistry decision, but it does make a small-acre indoxacarb pass economically reasonable on a 60-acre stand where the airplane minimum would have priced it out — and that's how you keep a working mode of action working.
What We Charge
Same rate card as our herbicide and fungicide work: $18–22/ac, $400 trip minimum, no upper acreage cap. We can supply the chemistry or fly your supplied product. Either way the application rate is locked to the label, and the carrier volume is tuned to the canopy in front of us.
If you've scouted and you're at threshold, or you want a second set of eyes on the count before you decide on spray-versus-cut, call us at (402) 326-5811 or visit our insect abatement service page. The best decisions on alfalfa weevil are the ones made within a week of scouting — not three weeks later when the regrowth is already showing it.