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PLANT HEALTH CARE All photos provided by Rainbow Treecare Scientific Advancements I By Brandon M. Gallagher Watson nsects are one of the most successful groups of organisms on the planet. For hundreds of millions of years, insects and plants have coevolved,sometimes antagonistically,sometimes to the benefit of both parties. Insects are also of considerable concern to arborists, but we are long past the days in which we just spray indiscriminately and hope we kill the bad ones.Insect management today requires knowledge of biology, ecology, tree physiology, phenology, and chemistry so we can protect trees with minimal impact on beneficial insects and the rest of the ecosystem. So what are the basics we need to know to safely but effectively manage shade tree insect pests? First, we need to wrap our heads around the sheer number of insects and their diversity.The current count is more than one million named species, representing about half of all animal species alive on the planet today.The estimates of not-yet-named species is anywhere between six and 10 million species; so if you have an interest in discovering and naming new species, entomology may be the field for you. Insects are grouped with other invertebrates such as spiders, millipedes and lobsters, but have some distinguishing characteristics. Like these other arthropods (from the 20 Arbor Age / March 2013 Greek word for "jointed leg"), insects have, of course, jointed appendages, exoskeletons made from chitin, and segmented body parts. Every organism classified into the Class Insecta will have six legs, two antennae, a three-part body consisting of a head, abdomen, and thorax, and two pairs of wings. All insects go through some form of metamorphosis, but not all of them do it the same way. Some insects go through a complete metamorphosis (known as "holometabolis"), where the immature insect looks nothing like the adult. Look no further than the differences between a caterpillar and a butterfly to understand this process. Other examples would be grubs, maggots, and whatever you call those cool looking ladybug larvae — all of them start life with one body type, then go through a pupa stage where they emerge looking like something else altogether.The adults and their offspring not only look different, they often have completely different diets, and, often, completely different relationships to plants. As larvae, an insect may be a plant parasite eating the leaves and disfiguring the appearance, but, as an adult, they may be an important pollinator of their flowers. INSECTS ARE MIND-BOGGLING IN THEIR NUMBERS AND DIVERSITY, BUT, FORTUNATELY FOR ARBORISTS, NOT ALL OF THEM ARE REQUIRED READING. www.arborage.com