What type of agents cause damage to some plants through weather extremes, salts, air pollutants, and inadequate or excessive fertilization?

The correct choice identifies non-living agents as those that cause damage to plants through various factors such as weather extremes, salts, air pollutants, and inappropriate fertilization. Non-living agents are considered abiotic stressors, meaning they originate from sources that are not living organisms. For instance, extreme temperatures can lead to frost damage or heat stress, while excessive salts can result in plant dehydration and nutrient uptake issues. Similarly, air pollutants can adversely affect plant health, inhibiting growth or causing leaf damage. Adequate or excessive fertilization can directly impact plant growth, where imbalances can lead to nutrient toxicity or deficiency.

In contrast, the other choices refer to different concepts. Natural controls generally pertain to predators or parasitoids that regulate pest populations, rather than abiotic factors. Cultural control involves managing the growing environment and practices to reduce pests, which focuses more on living organisms and practices rather than the non-living factors in question. Biological control specifically refers to the use of living organisms to manage pests, which does not encompass the impact of non-living agents on plant health. Thus, non-living agents are the correct choice, as they encapsulate the effects of environmental and chemical factors impacting plant health.