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These 10 free RMS questions are organized by exam domain, so you can see how each part of the Certified Crop Adviser - Resistance Management Specialty blueprint is tested. Reveal the answer and explanation under each question.
After a postemergence herbicide application, a CCA finds waterhemp, lambsquarters, and foxtail surviving together in narrow, regularly spaced bands running with the sprayer passes. All three species are well controlled between the bands. The rate controller recorded the intended average application rate. Which action should come first?
Correct answer: C - Check individual nozzle flow and spray patterns in the affected boom sections.
Two herbicides acting on different target enzymes fail against the same weed population. Controlled experiments show that one inherited detoxification mechanism breaks down both herbicides more rapidly than in a susceptible population; the target enzymes themselves retain normal sensitivity. The second herbicide had never been used in the affected field. The resistance pattern is best described as:
Correct answer: B - Metabolic cross-resistance, with one inherited detoxification mechanism reducing susceptibility to both herbicides.
A laboratory measures the fungicide concentration that inhibits fungal growth by 50% (EC50). In the same replicated assay, the suspect isolate has an EC50 of 1.6 mg/L and the susceptible reference has an EC50 of 0.08 mg/L. An older publication gives a susceptible value of 0.4 mg/L, but used a different medium and incubation period. Field efficacy has not been measured. How should the CCA interpret the comparison?
Correct answer: A - The matched assay shows a 20-fold EC50 increase, not a measured loss of field control.
A high-dose/refuge strategy for a diploid moth pest of Bt corn assumes that resistance to one Bt protein is controlled by a completely recessive allele, R. Susceptible refuge insects are SS. Controlled crosses between RR survivors and SS insects produce RS offspring, but those offspring survive the Bt exposure actually delivered by the crop. Which assumption of the strategy has been undermined?
Correct answer: C - The crop exposure kills heterozygous offspring produced by resistant-by-susceptible matings.
The proposed three-active herbicide premix contains HRAC Groups 2, 9, and 14. At the proposed rates and timing, tests on the field's weeds show that Groups 2 and 9 control foxtail but fail on waterhemp. Group 14 controls waterhemp but has no useful activity on the foxtail. No interaction changes those results when the ingredients are combined. How many effective sites of action does each target weed face?
Correct answer: A - One effective site against waterhemp and two against foxtail.
The first caterpillar generation in a vegetable field was treated with chlorantraniliprole, an IRAC Group 28 insecticide. The next generation now exceeds the treatment threshold, and its treatment window has opened. Local testing supports spinetoram and cyantraniliprole but documents poor control with bifenthrin. Each listed insecticide is registered for this crop and pest, and its label permits an application now. Select the treatment that provides an effective change of mode of action.
Correct answer: D - Apply spinetoram at an effective labeled rate during the new treatment window.
In a Minnesota soybean field at R4, representative samples show the average live aphid count rising from 170 to 360 per plant over four days. Ninety percent of sampled plants are infested. Lady beetles are present, but aphid numbers continue to rise across the field. A locally effective insecticide can be applied within all label restrictions. Under University of Minnesota recommendations, which advice best fits these findings?
Correct answer: D - Treat with the effective labeled insecticide, then scout to verify control and assess any surviving aphids.
An earlier fungicide spray contained tebuconazole and azoxystrobin. For the next justified application, an adviser wants neither single-site FRAC group from that spray to be repeated. Each proposed mixture is permitted by the relevant labels, and each component is independently effective against the diagnosed pathogen at the proposed dose and timing. Which mixture meets the rotation objective?
Correct answer: C - Boscalid plus mancozeb.
A few waterhemp plants in a soybean field are approaching seed production. Resistance to the herbicide group already used has been confirmed, and no effective labeled in-crop chemical rescue remains. The plants can still be removed before viable seed develops. The field is highly erodible, and its conservation plan requires the current protective residue cover. Which response best addresses the immediate resistance-management risk?
Correct answer: B - Remove the escapes before seed matures while retaining the protective residue cover.
During an insecticide application, the wind changes and spray begins drifting onto a flowering field margin where bees are actively foraging. The product label prohibits this exposure. The target pest is above its treatment threshold, and the beekeeper was notified before spraying. The adviser sees the drift while the sprayer is still operating. The immediate instruction should be to:
Correct answer: D - Shut off the spray; correct the exposure problem before resuming in compliance with the label.
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