Spongy moths lay eggs that hatch into caterpillars (larval stage) which are a major pest, defoliating and killing oak trees. The caterpillars are preyed upon by white-footed mice and can be parasitised by specific fungal species.
Spongy moth caterpillars have defensive hairs containing irritating toxins. However, almost all white-footed mice in the local forest population produce a specific liver enzyme that rapidly deactivates these toxins.
Explain how natural selection may have resulted in all white-footed mice having this toxin-deactivating liver enzyme.
Scientists are controlling spongy moth infestations to conserve oak forests. They spray the caterpillars with fungal spores. This biological method has been successful when spraying different concentrations of spores:
Name this type of pest control method.
By how many orders of magnitude is the concentration used on late-stage larvae higher than that used on early-stage larvae?
Scientists have also tested natural plant-based essential oils on the larvae. The table shows the effects of two plant oils on the caterpillars in laboratory conditions and on oak trees in the wild.
| Type of oil | Deaths per 1000 larvae in the laboratory | Deaths per 1000 larvae on oak trees |
|---|---|---|
| Neem | 620 | 806 |
| Thyme | 250 | 675 |
| Control treatment | 16 | 28 |
Calculate the percentage increase in the death of larvae on the oak trees compared to in the laboratory for the control treatment.
More larvae die on oak trees in the wild than in the laboratory across all treatments. Suggest one reason why.
Evaluate the effectiveness of the two plant oils in controlling the larvae. Use data from the table to support your answer.