Seasonal Maximum, PHI, and a Neighbor at 120 Feet
A sweet corn grower has 40 acres at whorl-to-tassel stage with corn earworm trap counts climbing. The insecticide label states: 'Apply 6 to 10 fl oz/A. Do not apply more than 20 fl oz/A per season. Do not make more than 2 applications per season. PHI 7 days. REI 24 hours. Do not apply by air within 150 feet of a dwelling.' He applied 10 fl oz/A eighteen days ago. He wants to spray 10 fl oz tomorrow and harvest in 9 days. He also plans to tank-mix a Group 3A pyrethroid 'to be sure' - the same IRAC group as the first product. A neighbor's house sits 120 feet from the field edge, and he intends to use his ground rig.
1. Is a second 10 fl oz/A application legal, and does the harvest date work?
Read the worked answer
Legal, but tight on both counts.
- Seasonal cap: 10 oz used + 10 oz planned = 20 oz, exactly the seasonal maximum. Legal, but it uses the entire budget - there is no room for a respray if rain falls or the population rebounds.
- Application cap: this is application #2 of a maximum of 2. Legal, but it exhausts the label allowance.
- PHI: 7 days from tomorrow's application means earliest harvest is day 7; harvest is planned for day 9, a 2-day cushion. Do not count from the earlier application - the PHI applies to the last application, and any delay that pushes the second spray later eats that cushion.
Before treating, read the whole label for any rate-by-growth-stage restriction, resistance-management statement, or mandatory rotation language. If the label contains a rotation requirement (e.g., 'do not apply the same mode of action in consecutive applications'), the plan as written is noncompliant and the second product must be a different IRAC group.
2. Evaluate his tank-mix decision from a resistance-management and label standpoint.
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The tank-mix is the weakest part of the plan.
- Adding a Group 3A pyrethroid to a product that is already Group 3A is not a tank-mix tactic - it is two consecutive exposures to one mode of action, which selects for resistance and is specifically what resistance-management sections warn against. Many labels state that consecutive Group 3A applications must be avoided or rotated.
- Corn earworm populations in much of the Corn Belt carry pyrethroid resistance; doubling the dose of the same chemistry buys nothing but cost and nontarget impact.
- If a tank-mix partner is truly needed, the defensible move is a product from a different IRAC group with a different target site, after confirming both labels permit the mix, that neither label prohibits mixing with the other's class, and that the adjuvant/surfactant limits line up.
- Check the mixer's own label first: many labels say 'follow the most restrictive label directions' and prohibit mixes not listed.
If rotation to another mode of action is not possible this season, apply the remaining 10 oz alone and accept that the program is a rescue action.
3. He plans to spray with the ground rig at 120 feet from the neighbor's house. Is the 150-foot restriction a problem, and what else governs the decision?
Read the worked answer
The 150-foot restriction does not apply here - read it precisely: it is limited to aerial application. A ground rig at 120 feet satisfies the label as written.
That does not end the analysis:
- State/local law: several states impose buffer, notification, or setback requirements for ground applications near dwellings or public areas. The label is a floor, not a ceiling.
- Drift: 120 feet is within reach of a fine-droplet ground spray in a 10-mph crosswind. He should select a coarse/very coarse air-induction tip, keep pressure low, spray when wind is under about 10 mph and blowing away from the house, and avoid the field edge during the hottest, gustiest part of the day.
- REI: 24 hours. The neighbor must be warned, and field workers - including the harvest crew scouting ahead of harvest - must be kept out unless wearing label-specified PPE.
- Recordkeeping: document the rate, date, time, wind, buffer distance, and the fact that the application met the label's ground-restriction language.