Gardeners in our county are amazing because they are out making it happen even in our hot, dry weather. Even as skilled as many are, they like to ask questions and as I walk, visit stores and sometimes even when I am in my office, people stop me, call or stop by with their gardening questions. Our USU Extension Grand County office is the place to find research-based answers to your questions and we are happy to help.
This last month a question has been repeating itself that involved a white cottony mass seen on cactus around town. Those cottony masses are mealybugs and are often seen on prickly pear cactus but lately have been finding their way onto other varieties of cactus. These insects cluster in waxy, cottony masses with the young being more mobile while the adults are more stationary. Like aphids, these insects excrete a fluid called honeydew so you might see shiny areas on the cactus. Mealybugs suck the sap out of the plant, which can cause it to become distorted and could, over time, kill the plant. You can apply an insecticide labeled for mealybugs or do as some have done and spray them off with water if the numbers aren’t too high. A common control for mealybugs on houseplants is to use rubbing alcohol but try it first on a few groups of them to make sure there is no negative effect on the cactus.
This time of year, we see the number of spider mites increase. What is it that spider mites love? Yes, it’s our hot and dry weather, which makes them really love Grand County this year! Spider mites can be found on all types of plants but lately have been seen on apple tree leaves and tomato plants. They are very tiny insects and you usually don’t start to see them until their numbers are high and the leaves of plants start to get stippled and off color. The mites suck fluid, which can include the chlorophyll, out of the plant cells causing the stippling. Unfortunately, they are not easy pests to control. If you have experienced spider mites in the past, I always recommend you start spraying susceptible plants early in the season because this simple act can keep the populations from building up since it’s no longer hot and dry, just hot and wet.
Once populations are noticed you can start to control them by spraying the plants with a soapy water solution. You need to spray very thoroughly, meaning top and bottom of leaves and stems and do so every 3 to 4 days for a while. If this doesn’t stop their advance you can go to organic insecticides like pyrethrins or Azadirachtin. Now some might suggest using a horticultural oil but there are concerns with using those at high temperatures due to potential plant damage.
A question was recently raised about having mulch around your plants and house due to concerns about potential fire issues after the recent terrible fire in Moab. I hadn’t thought of that but did think it was wise to consider any potential negative issues. Generally in a landscape, mulch is a wonderful garden helper keeping the soil moister and keeping weeds down. However, excessive amounts of mulch, meaning more than a few inches, especially next to your house might be something to limit.
Previous articles can be found on The Times-Independent website. If you have a topic you would like to know more about call the Utah State University Extension Grand County office at 259-7558 or email Mike at firstname.lastname@example.org.
ByBy Michael Johnson
Utah State University Extension Agent, Grand County