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Extension Entomology

Month: October 2015

Euonymus Scale: What Can You Do?

by–Dr. Raymond Cloyd

      This is the time of year when euonymus scale (Unaspis euonymi) becomes noticeable in landscapes on evergreen euonymus (Euonymus japonica) and Japanese pachysandra (Pachysandra terminalis). Euonymus scale typically overwinters as a mated female, primarily on plant stems. Eggs develop and mature underneath the scale, and then hatch over a two to three week period. The newly hatched crawlers migrate along the stem and start feeding near the base of host plants. Crawlers can also infect adjacent plants by being blown around on air currents, resulting in infestations often not being detected until populations are extensive and damage is noticeable—like right now. Leaves eventually become spotted with yellow or white areas. Plants located near structures such as foundations (Figure 1), walls or in parking areas are more susceptible to euonymus scale than plants growing in open areas that receive sunlight and air movement. In addition, the variegated forms of euonymus are more susceptible to euonymus scale than the green forms.

newFigure1EuonymusPlantsNearFoundationInfestedWithEuonymusScale

 

Figure 1:  Euonymus Plants Near Foundation infested with Euonymus Scale.

Heavy infestations of euonymus scale can ruin the aesthetic appearance of plants, causing complete defoliation or even plant death. Females are dark brown, flattened, and resemble an oyster shell. Males, however, are elongated, ridged, and white in color (Figure 2). Males tend to be located on leaves along leaf veins whereas females reside on the stems. There may be up to three generations per year.

newFigure2CloseupofEuonymusScaleFemalesandMales

 

Figure 2: Close up of Euonymus Scale Females and Males.

Cultural practices such as pruning out heavily infested branches—without ruining the aesthetic quality of the plant—is extremely effective in quickly reducing euonymus scale populations; especially this time of year. Be sure to immediately discard pruned branches away from the area. If feasible, avoid planting Euonymus japonica in landscapes since this species is highly susceptible to euonymus scale. Winged euonymus (Euonymus alata) is less susceptible to euonymus scale, even when adjacent plants are infested. Applications of insecticides in May through June, which is when the crawlers are most active, will help to alleviate problems with euonymus scale later in the season. Insecticides recommended for suppression of euonymus scale populations, primarily targeting the crawlers, include acephate (Orthene); pyrethroid-based insecticides such as bifenthrin (Talstar), cyfluthrin (Tempo), and lambda-cyhalothrin (Scimitar); potassium salts of fatty acids (insecticidal soap); and horticultural (petroleum or mineral-based) and neem (clarified hydrophobic extract of neem oil) oils. Always regularly check plants for the presence of crawlers, which will help time insecticide applications. In general, three to four applications performed at seven to 10-day intervals may be required; however, this is dependent on the level of the infestation. Euonymus scale is a hard or armored scale, so, in most cases, soil or drench applications of systemic insecticides such as imidacloprid (Merit) are not effective in suppressing euonymus scale populations; however, the systemic insecticide dinotefuran (Safari), due to its high-water solubility (39,000 ppm), may provide suppression of euonymus scale populations when applied as a drench to the soil. Dormant oil applications can be conducted in winter to kill the overwintering mated females on stems. However, thorough coverage of all plant parts is important in order to obtain sufficient mortality.

Euonymus scale is susceptible to a variety of natural enemies (e.g. parasitoids and predators). These include braconid and ichneumonid wasps, ladybird beetles, green lacewings, and minute pirate bugs. However, natural enemies may fail to provide enough mortality (‘killing power’) to significantly impact “high” populations of euonymus scale. Furthermore, insecticides such as acephate (Orthene), and many of the pyrethroid-based insecticides, including bifenthrin (Talstar), cyfluthrin (Tempo), and lambda-cyhalothrin (Scimitar) are very harmful to most natural enemies, so applications of these materials may disrupt any natural regulation or suppression.

Emerald Ash Borer In Kansas: Another Quarantined County

by–Dr. Raymond Cloyd

If you have not heard, on September 30, 2015 an Emerald ash borer (Agrilius planipennis) larva was found in a girdled trap tree in Eudora, KS (Douglas County) by the Kansas Department of Agriculture. This means that Kansas has four counties in which Emerald ash borer has been detected, and subsequently quarantined, including Wyandotte, Johnson, Leavenworth, and Douglas. First detected in 2002 in Michigan, the Emerald ash borer has been found in 23 states throughout the USA (Figure 1), and is responsible for causing the death of over 30 million ash trees. For more information regarding Emerald ash borer, contact the Kansas Department of Agriculture or the Department of Entomology at Kanas State University (Manhattan, KS).

Figure1DistributionMayofEmeraldAshBorerAugust32015

 

Figure 1: Distribution May of Emerald Ash Borer August 3, 2015

Sugarcane Aphids

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Sugarcane aphids (SCA) colonies have rapidly declined in some fields in north central Kansas, slowly declined in others, but actually increased somewhat in other fields.  In one field, approximately 90% of all previous SCA’s are gone and enormous numbers of lacewing adults remain (see pics).  However, prior to the latest cold front, most top leaves had winged aphids with nymphs.  This means, evidently, that they are still migrating in and trying to establish colonies.  However, with huge numbers of beneficials now present, it seems unlikely that they will be successful, especially with the recent cooler weather.  Everywhere that SCA colonies became established, they produced honeydew, which coated the sorghum leaves, and was then covered with a dark sooty mold.  However, when the colonies are eliminated the honeydew is no longer sticky and the black mold becomes dry and washes off (see pic).

brown lacewing

green lacewing

 

old honeydew

Armyworms and Army cutworms in Wheat

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Several planted fields have already been sprayed to control worms.  What we have been seeing in south central and north central Kansas are a combination of armyworms (see pic) and fall armyworms (see pic).  Both of these species will do a similar type of damage.  When they are small they will feed on one side of the wheat leaf causing what is commonly called ‘window paning’.  As the larvae grow they devour more and more tissue until it may become quite noticeable and, under unfavorable growing conditions, may even severely reduce the stand (see pic).  Armyworm larvae will feed, probably for a couple more weeks, depending upon temperatures, and then pupate. If we haven’t yet had a hard freeze, they may emerge as moths and lay eggs in other wheat fields.  The first hard freeze will terminate armyworms.  Army cutworms, on the other hand, will not be terminated by the first hard freeze but will continue to develop all winter, feeding anytime temperatures are over about 45°F and will complete their development in the spring (see pic).  So, it is important to make proper identification of armyworms feeding in wheat as armyworms and fall armyworms will not be feeding throughout the winter and early spring but army cutworms will.

armyworm

 

fall armyworm

 

armyworm damage wheat

 

 

army cutworm