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Extension Entomology

Tag: infestations

Sorghum Pest Update

— by Dr. Jeff Whitworth, Dr. Holly Schwarting and J.R. Ewing

Much sorghum throughout north central Kansas is at least in the soft dough stage and thus has passed through the most susceptible stages for sorghum headworm infestations.  However, any sorghum yet to head out will still be susceptible to these headworms as there will still be at least one more generation.

All four aphids species, corn leaf, greenbugs, sugarcane, and yellow sugarcane, are still in every sorghum field we sampled throughout north central Kansas.  All populations seem to be increasing but there are relatively healthy populations of beneficials present as well.

SCAwLB

Rose Sawflies: Out With a Vengeance!

–by Dr. Raymond Cloyd

We are receiving numerous questions regarding insects feeding and completely devouring rose plants. These insects are sawflies, and there are at least two species that attack roses during this time of year: the rose slug (Endelomyia aethiops) and bristly rose slug (Cladius difformis). Rose slugs are the immature or larval stage of sawflies, which are black to yellow colored wasps.

Rose sawfly females create pockets or slits along the edges of rose leaves with their saw-like ovipositor (egg-laying devise) and insert individual eggs. Larvae hatch from eggs and resemble a slug. The larvae are 1.2 cm long when full-grown and yellow-green with an orange head (Figure 1). Larvae eventually fall on the soil surface to pupate. Rose slugs overwinter as pupae in earthen cells created by the larvae. There is typically one generation per year in Kansas. Bristly rose slug larvae are pale-green and 1.5 to 2.0 cm in length. The body is covered with numerous bristle-like hairs (Figure 2). There is generally one generation per year in Kansas.

Figure 1. RoseSawflyLarvaeFeedingonRoseLeaf
Figure 1: Rose Sawfly Larvae Feeding on Rose Leaf

Figure 2. BristlyRoseSlugLarvaeFeedingOnLeafUndersideofRose
Figure 2: Bristly Rose Slug Larvae Feeding on Spirea Plant

Rose slug larvae feed on the underside of rose leaves; resulting in leaves with a skeletonized appearance (Figures 3 and 4) and eventually they create notches or holes on the leaf margins. Bristly rose slug larvae feed on the underside of rose leaves and also cause leaves to appear skeletonized. However, the larvae may chew larger holes than the rose slug.

Figure 3. DamageonRosePlantCausedByRoseSlug
Figure 3: Damage on Rose Plant Caused by Rose Slug

Figure 4. DamageonRoseLeafCausedByRoseSlug
Figure 4: Damage on Rose Leaf Caused by Rose Slug

Small infestations of either the rose sawfly or bristly rose slug can be removed by hand and placed into a container of soapy water. A forceful water spray will quickly dislodge sawfly larvae from rose plants and they will not be able to crawl back onto rose plants. There are a number of contact insecticides with various active ingredients that are effective in suppressing populations of both sawflies. However, the bacterium, Bacillus thuringiensis subsp. kurstaki (sold as Dipel or Thuricide) will have no activity on sawflies as this compound only works on caterpillars.

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