sentences:  Diseases often have subtle symptoms which are easily misdiagnosed and can affect leaves, roots, and stems.Some pests, such as the alfalfa weevil, aphids, armyworms, and the potato leafhopper, can reduce alfalfa yields dramatically, particularly with the second cutting when weather is warmest.Spotted alfalfa aphid, broadly spread in Australia, not only sucks sap but also injects salivary toxins into the leaves.