Most of us are familiar with the results of drought stress, but did you know that high temperatures alone can cause significant damage to the health of your plants? Given that many areas are recording rising temperatures, we should become aware of how warmer temperatures affect the physiology of plants.
High temperatures reduce photosynthetic rates faster than they reduce respiration rates. The result is an imbalance because the carbohydrates produced by photosynthesis are used faster than they can be replaced. Higher temperatures increase the loss of water through stomates in the leaves, and thereby increase demands on the root system to take up water to cool the tree via transpiration. (High temperatures are usually accompanied by low rainfall—adding insult to injury.) Cellular membranes also become unstable and result in ion leakage within the leaf cellular structure.
Wood boring insects feed on the inner wood (xylem) of roots, trunks, branches or shoots of a plant. While there are hundreds of wood boring species that are not considered pests, some species can cause branch dieback or even mortality. Recently transplanted young plants and stressed plants are most susceptible to attack from wood boring insects. Damage occurs when the larvae of wood boring insects chew through the nutrient and water transporting tubes of the plant.
Mites are minute, plant-feeding arachnids that feed on chlorophyll, the pigment that gives plants their lovely green color. By removing chlorophyll, mites can cause plant foliage to appear bleached or bronzed. Because mites reproduce rapidly, damage to healthy foliage can occur within a relatively short period.
Aphids are small, sap-sucking insects. Some of them feed on more than one type of plant— for example, apple grass aphids feed on young new leaves and blossoms of apples until the beginning of summer when they migrate to oats, grasses and reeds for the rest of the season. Others feed on just one food source, like the lime leaf aphid, which feeds only on limes. Many different species exist, impacting a huge range of broad-leaf trees and shrubs.