they are helpful not harmful to plants
Protists can be both helpful and harmful. Some protists are beneficial as they play key roles in ecosystems, such as being primary producers in marine environments. However, some protists can also be harmful pathogens that cause diseases in humans, animals, and plants.
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Ladybird's favorite food is Aphid (greenfly/blackfly) which attack plants. Ladybirds are a beneficial insect and gardners and Horticulturalists encourage them.
Marsupials are helpful to humans in that they keep grasses and plants at manageable levels. They are only harmful to humans when they get too close and scare the animals.
Bacteria can be both harmful and helpful. Harmful bacteria can cause diseases in humans, animals, and plants. However, some bacteria are beneficial and play important roles in processes like digestion, nutrient cycling, and decomposition.
it can be helpful or harmful
sometimes they are helpful and harmful.
Sandpaper is both helpful and harmful.
parasite
helpful
helpful