⚡ CHEAT SHEET

Ch.7: Program Evaluation

What the exam tests on insecticide evaluation, Abbott's and Mulla's formulas, sentinel caged studies, IGR evaluation, non-target effects, and resistance testing.

🎯 Top 5 Traps

IGRs (methoprene) CANNOT be evaluated by pre/post dipper samples alone. The IGR doesn't kill larvae directly — it prevents emergence. Larvae will still be there after treatment. Pupae must be brought to the lab and held to determine if adults emerge. Same logic as Ch.5: IGRs prevent development, don't kill on contact.

Sampling ≠ Collecting. SAMPLING gives relative abundance measures (systematic, comparable across stations). COLLECTING gives only presence/absence. Same vocabulary trap as Ch.4 — and the wrong answer "collecting is easier" or "sampling gathers more" both miss the methodological distinction.

Resistance HAS been detected in Michigan — moderate level — and testing requires specific protocols. Common misconception: "resistance is theoretical or hasn't happened here." Actually, low-efficacy evaluations should trigger a resistance test. Kits available from WHO; bottle assays from Florida PHEREC; advice from MSU Extension.

Abbott's formula = CAGED studies. Mulla's formula = FIELD before/after. Both calculate percent reduction; both apply to adulticides." Don't pair Abbott's with "Griswold's factor" or "square root of control mortality" — those are exam distractors.

Sentinel caged study specs: 20 to 25 mosquitoes per cage, minimum 4 to 6 cages in BOTH treated and control areas, transfer to clean cages 15 to 30 minutes after application, count at 1 hour and 12 hours post-treatment. All four numbers are testable. The control cages quantify background mortality.

🔢 Numbers You Must Know

Number

What It Represents

6 reasons

Reasons to evaluate insecticides: (1) ongoing efficacy, (2) retreatment check, (3) new insecticides, (4) new application methods, (5) non-target effects, (6) resistance testing

20 to 25 mosquitoes

Mosquitoes placed in each sentinel cage (same or closely related species)

size 16 to 18 mesh

Cage screen size that works well for sentinel mosquito containment (or mosquito-screen)

4 to 6 cages

Minimum number of sentinel cages in EACH of treated and control areas (more = more accurate)

15 to 30 minutes

Time after application at which sentinel mosquitoes are transferred to clean cages

1 hour and 12 hours

Post-treatment intervals at which dead mosquitoes are counted in each cage

350 ml

Standard mosquito dipper capacity — used for pre/post larvicide sampling (same as Ch.4)

95.8 percent

Worked Mulla's-formula example: with C1=71, C2=65, T1=79, T2=3, the percent reduction

🔀 Easily Confused

Pair / Group

Distinguishing Feature

Sampling vs Collecting

Sampling: systematic; gives RELATIVE ABUNDANCE estimates over time and across stations. Collecting: ad-hoc; gives little more than presence or absence.

Abbott's formula vs Mulla's formula

Abbott's: caged studies — uses treated and control percent mortality. Mulla's: field studies (larvicide or adulticide) — uses mean counts before AND after in treated AND control areas.

Adulticide vs Larvicide evaluation

Adulticide: sentinel caged mosquitoes for new formulations; landing counts and trap catches in field. Use Abbott's (cage) or Mulla's (field). Larvicide: pre/post dipper sampling — drastic reduction (near zero) indicates effectiveness. Use Mulla's. EXCEPTION: IGRs require lab pupae hold.

IGR evaluation vs Direct-kill larvicide evaluation

Direct-kill (Bti, Bs, temephos, oils): post-treatment dipper count drops to near zero — easy. IGR (methoprene): larvae still present but won't emerge — bring pupae to lab, hold, calculate Emergence Inhibition.

Treated area vs Control area

Treated: receives insecticide application — measure mortality/abundance. Control: receives no application — quantifies background mortality (cage studies) or natural population fluctuation (field studies). Without control, you cannot determine treatment effect.

C1, T1, C2, T2 (Mulla's notation)

Subscript 1 = BEFORE application. Subscript 2 = AFTER application. C = mean count in control area. T = mean count in treated area. Easy to swap in formula recall.

Coquillettidia perturbans evaluation challenge

Cattail mosquito — larvae attached to underwater plant roots, NOT at surface. Standard 350 ml dipper misses them. Use bilge pump in cattail stands; or adult emergence cages when sampling is impractical.

🧪 Evaluation Formulas Quick Reference

Formula

When to Use

Notation

Abbott's formula

Caged sentinel adulticide studies — corrects observed mortality for control (background) mortality

%R = (%TM - %CM)(100 - %CM) x 100. TM = treated mortality, CM = control mortality. R = percent reduction (or percent mortality).

Mulla's formula

Field evaluation of larvicide OR adulticide treatments — uses pre/post counts in both treated and control areas

%R = 100 - [C1T1 x T2C2] x 100. C = control mean, T = treated mean. Subscript 1 = before, 2 = after. Worked example: C1=71, C2=65, T1=79, T2=3 yields 95.8 percent reduction.

Emergence Inhibition (EI)

IGR larvicide evaluation (e.g., methoprene) — pupae brought to lab and held until they die or adults emerge

% EI = (DP + DA + AA)(DP + DA) x 100. DP = dead pupae, DA = dead adults on water surface, AA = live adults in container.

🦟 Sentinel Cage Study Setup

Element

Specification

Mosquitoes per cage

20 to 25 of the same or closely related species; reared in laboratory or wild-caught

Cage material

Mosquito-screen or size 16 to 18 mesh; provide a sugar source for nutrition

Number of cages

Minimum 4 to 6 cages in TREATED area AND 4 to 6 cages in CONTROL area; more cages = more accurate assessment

Cage placement

Strategic placement in zones that receive (treated) or do not receive (control) the adulticide application

Transfer timing

15 to 30 minutes after application, transfer surviving mosquitoes to clean cages

Mortality counts

Count dead mosquitoes at 1 hour and 12 hours post-treatment in each cage; calculate percent mortality per cage = (dead / total) x 100

Calculation

Take mean percent mortality across treated cages and across control cages; apply Abbott's formula to compute percent reduction

💡 Memory Hooks

Abbott vs Mulla: "Abbott for cages, Mulla for fields." Both calculate percent reduction; the context (caged study vs field pre/post) tells you which.

Sentinel cage specs: "20 to 25 in 4 to 6 cages, count at 1 and 12." Mosquitoes per cage, cages per area, count timing.

Sampling: "Sampling shows trends; collecting just shows up." Sampling is comparable across time and place; collecting just confirms a species was there.

IGR evaluation: "Methoprene needs lab follow-up." Dipper alone won't show effect — IGRs prevent emergence, so larvae are still there.

Resistance: "Already in Michigan — test it." Moderate resistance has been detected. WHO test kits, PHEREC bottle assays, MSU Extension.

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