Extension Notes. Pest Management at Monarch Waystations. Beth Wilson Pulaski County Extension Office

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1 Extension Notes Beth Wilson Pulaski County Extension Office Pest Management at Monarch Waystations Even though you may not have an official Monarch Waystation, if you are concerned about monarchs and pollinators and plant flowering plants for them, there are some concerns about how to manage pests to keep those pollinator and monarchs happy. According to the monarch butterfly migration page, the first reported sightings of monarch butterflies (see photo) in Kentucky were April 10 in Holland KY, April 15 in Louisville, and April 19 in Lexington. Previous monarch research by UK entomologists documented the presence of many adults in May but little evidence of eggs. Few individuals were seen during June but the butterflies, their eggs, and larvae were abundant in July. Defensive chemicals in milkweed plants protect them from most insect herbivores. However, a handful of aphids, beetles and caterpillars can deal with the plant s cardiac glycosides and milky, sticky sap. In sufficient numbers, these pests can eat a significant amount of foliage, or they can affect plant vigor and perhaps plant attractiveness to monarchs. Fortunately, most of these are minor concerns, so management can be limited to a watchful eye and hand-picking to remove them. Here is a look at common aphid species that feed on milkweed. Several species of aphids can infest milkweed. Colonies develop when winged females land on plants and deposit small numbers of live young on tender terminal foliage. Clusters of these small, soft-bodied insects build up on lower surfaces of developing leaves or tender new stems where their numbers steadily increase. Sap removal while feeding can lead to deformed leaves and stems or even death of plant terminals. In some cases ants can be seen on infested plants (see photo). They tend the aphids to collect their nutrient-rich waste for their colonies and in turn protect aphids from predators. Lady beetles and other natural enemies eat aphids, but the reproductive capacity of these small, softbodied insects generally outpaces consumption.

2 At least 5 aphid species of various color (black, green, and red) can be found on milkweed, usually early and again late in the growing season. Aphids can cover the upper growth damaging growing tips, leaves, and pods (see photo). Mechanical control (crushing, etc) or sprays of insecticidal soap can provide satisfactory control. Winged aphids are active over most of the growing season so new infestations can start at any time. Weekly checking of terminal foliage during the growing season is the main way of keeping these insects from reaching damaging levels. For more information about this topic, contact the Pulaski County Extension Service office at and request FOR-98 Attracting Butterflies with Native Plants. Become a fan of Pulaski County Horticulture on Facebook and on Twitter and kyplants on Instagram. Many other classes are happening at the Pulaski Co Extension office. To see what s going on, go to the Pulaski County Extension webpage ( and click on Upcoming Events. Educational programs of Kentucky Cooperative Extension serve all people regardless of economic or social status and will not discriminate on the basis of race, color, ethnic origin, national origin, creed, religion, political belief, sex, sexual orientation, gender identity, gender expression, pregnancy, marital status, genetic information, age, veteran status, or physical or mental disability.

3 Monarch butterfly on zinnia (Photo by Lee Townsend, University of Kentucky)

4 The distinctive oleander aphid is easily noticed; other species are more cryptic (Photo by Lee Townsend, University of Kentucky)

5 Aphids being tended by ants (Photo by Lee Townsend, University of Kentucky)