Horticulture Tips for June

Home Grown  by Keith Reed
The Payne County Extension office has been swamped with calls concerning “orange spots” on plant leaves of many different species. The weather has been ideal for this group of fungal diseases commonly referred to as rust. While rust won’t kill a mature tree or shrub, it will defoliate it if the disease pressure is high enough. Treatment is usually not suggested in trees and shrubs as the plants should recover once the environmental conditions change and the disease runs its course. If you have a high-value plant and want to treat anyway, most common fungicides offer some level of control although none work well enough to allow badly damaged leaves to recover. Additionally, here are a few other tips to keep your June landscape healthy:
  • Keep a close eye on irrigation needs, especially with new plants. Even though the rains have been adequate recently, plants can easily suffer from lack of moisture if we get a few hot windy days in a row. Remember to judge irrigation needs based on actual rainfall, not the “threat of rain”.
  • Remain diligent for insect activity. For vegetable growers, squash bugs have been a huge problem the last few years. Scout often so you can maintain the upper hand. Remove the early insects by hand, along with inspecting for and destroying eggs before they hatch should be a high priority. Often times this will eliminate the need for chemical control. If populations do warrant treatment, pay special attention to treating around the base of the plant as this is where the insects tend to congregate.
  • Spider mites have also been a problem the last several years. While they typically aren’t as bad in wet weather, this is the time of year you can expect them to make an appearance, so keep an eye out. Scouting these are more difficult as spider mites are extremely small and difficult to see with the naked eye. A nice tip is to place a piece of white paper under a leaf and tap on the leaf several times to knock the mites on the paper. The mites will be easy to spot as they scurry around. Insecticidal soaps and neem oil offer some control of mites but diligence is necessary to keep the populations low as they reproduce rapidly as the temperatures go up. Note that most all purpose insecticides do NOT provide spider mite control so product selection is somewhat limited. Even products that are labeled for control do not work well once populations become high and the mites protect themselves with webbing. Once webbing is evident, it is best to remove the infested leaves.
  • June is also a good time to begin controlling the growth of select flowering plants. Educate yourself on the growth habits of the specific plants in your garden as it is important to prune at the proper time so flowering is not adversely affected. In general terms, most annuals benefit from light pruning (pinching back) to prevent them from developing leggy weak stems and to encourage continued blooming. Many of the spring blooming perennials are now past their peak bloom and can be cut back as well.
  • Lastly, remember to remove any wraps that have been placed on trees to prevent winter injury or deer damage. Leaving this material on throughout the growing season increases the opportunity for insects and disease to attack your tree. Just make a note on your calendar now to replace it again in the fall.

For more information of this or any other horticultural topic, you can contact Keith Reed, the Horticulturist in the Payne County Extension office. Keith can be reached via email at keith.reed@okstate.edu, phone at 405-747-8320, or in person at the Payne County Extension office, located at 315 W. 6th in Stillwater.

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