Wet Weather Means Aphids and Fungal Diseases on the Rise
The weather plays a large role in determining what pest problems we see each year. This year’s wet spring and early summer weather has created a perfect environment for aphids and fungal diseases to thrive.
Lady bugs, the most common beneficial predator that feed on aphids, don’t like cool wet weather. They don’t reproduce or feed as much as they normally would, which allows aphid populations to explode. While there are hundreds of species of aphids in Colorado and almost all plants can be hosts, we are currently seeing large numbers of aphids on aspens, cottonwoods, cherries, plums, dogwood shrubs and spireas. Shiny leaves and sticky honeydew dripping from trees are indicative of a large aphid population. If control is required, there are many options including sprays, soil injections or trunk injections.
Cottonwood foliage is prone to infection by septoria leaf spot. This disease causes tan colored spots to form on the leaves and premature leaf drop. Like aspens, some cottonwoods are already dropping leaves. Once again, preventive fungicide sprays and/or raking and disposing of infected leaves are the best treatment options.
Turf grass is vulnerable to several common fungal pathogens during extended wet periods. Symptoms include purple or black spots on the leaf blades, sometimes accompanied by a narrowing, or pinching, of the blade and a general yellowing of the grass. Reducing irrigation during rainy weather is critical in controlling these diseases. Allowing the turf to dry is the simplest way to minimize fungal infections. If treatment is necessary, fungicide sprays offer control.