Number 6 - May 29, 2012

Kermes Scale and some of the leaves die. Damage is noticed from the ground as scattered Kermes scales are occasionally found on branch tips appearing whitish and/or pin, white, bur, and other in Illinois. brownish due to dead leaves and the leaf They are most common on or near the distortion revealing more leaf branch tips and appear gall-like, so they undersides. The scales feed at the base are commonly misidentified as galls. of petioles, on leaf veins, and at twig They also tend to feed in leaf axils, so crotches. The scale is rounded and about they are sometimes misidentified as one-eighth inch in diameter. Although buds. The of kermes scale the scales are brownish, they frequently species is uncertain because early work appear blackish due to a coating of sooty relied heavily on color patterns, which mold. Sooty mold is a black fungus that we now know are variable. There are grows on the honeydew, the partially approximately 30 species of kermes that digested and concentrated plant sap occur in North America, but identification excreted by many scale species. is difficult. This goes beyond academic gymnastics, as different species produce Kermes scales have recently been seen crawlers at different times during the on bur in Illinois. These scales tend growing season. to be located on the twigs at or near leaf buds and at twig crotches near branch Control of scale relies on tips. They are rounded and up to one- application to the unprotected quarter inch in diameter. They vary in newly hatched nymphs or crawlers. At color from dark brown to tan with dark least one species produces crawlers in brown banding. Leaf and branch July, but crawlers of other species hatch in distortion is not evident, but they cause September. However, all species noticeable branch tip droppage. overwinter as first stage nymphs on the bark of trunks and branches, making them Overall, infested trees grow slower and susceptible to dormant oil application. are twiggy and bushier due to terminal Apply dormant oil when the tree is damage and subsequent lateral branch dormant and when the temperature does development. Kermes scales are native not drop below freezing for the next 24 insects, and their populations are kept in hours after application. check by several natural enemies including a parasitic , a lady , On white and bur oak, kermes scale and a predatory caterpillar. Although tends to cause twisting, crooking, and almost all caterpillars are herbivorous, other distortion of the branch tip. there are a few species of whose Leaves are also misshapen and twisted, larvae feed on other insects. (Phil Nixon) Aphids mature into adults, allowing them to to new, less infested hosts. Lengthening Aphids are more noticeable this spring, nights towards the end of the growing particularly on linden and tulip poplar, season cause females to give birth to than they have been for many years. nymphs that will mature as winged Since the late 1990’s when multicolored males and females that must mate to Asian lady became numerous in reproduce. The aphids fly to their winter the state, aphid numbers have tended to host, where the females lay eggs that be low. overwinter.

Aphids are soft-bodied, pear-shaped Typically, about 2 weeks after they insects. There are many species of become numerous, aphids that are aphids, with adults ranging from exposed on the leaves and stems are pinhead-sized to 1/4 inch long. On trees, usually controlled by natural enemies, most are closer to pinhead-sized, but a making insecticide application common aphid on willow is one of the unnecessary in most cases. Not only largest aphid species. Aphid species vary does the multicolored Asian lady beetle in color, with green being most common. feed on aphids, but so do other lady Even a population of one aphid species beetle species, lacewings, syrphid , on a plant may vary in color, apparently parasitic , and other insects. depending on factors such as temperature, crowding, and food It is more common to control aphids due quality. Aphids tend to have long, to their sticky honeydew coating spindly legs and long, slender antennae. sidewalks, cars, lawn furniture, and other objects under infested trees than Aphids overwinter as eggs, typically on a to control tree damage. Aphids tend to plant other than the one where they are feed near the tips of branches on the common during the summer. These eggs young leaves and stems. This feeding hatch into all wingless females that feed can cause the leaves to wrinkle, curl, on the winter host and give birth to twist, or become distorted in other more aphids. Usually after two to three ways. Similarly, young, green stems may generations on the winter host, the curl or twist due to aphid feeding. If aphids mature into winged adult needed, contact such as females that fly to the summer host. On insecticidal soap, summer spray oil, and the summer host, up to 30 generations pyrethroids are effective. The systemic of aphids are produced, all of them being insecticide, imidacloprid (Merit), is also females that give birth to living young effective against aphids. (Phil Nixon) without fertilization. Generations are commonly produced weekly, resulting in huge populations building up. Japanese Beetle

Aphid nymphs in crowded conditions Japanese beetle adults have emerged in are frequently bumped and jostled by Kentucky, so be watchful for emergence nearby aphids. These aphids will mature in southern Illinois. We continue to see into wingless females that give birth to insect emergence about two weeks nymphs that will develop wings as they ahead of schedule throughout Illinois. With emergence in southern Illinois symptoms along leaf veins, mottling on typically occurring around the middle of leaves, collapsed or sunken tissue, June, emergence is likely around the end general stunting of growth, necrosis, and of May. ring spots. Symptoms of HVX can be highly variable depending on infected Japanese beetle adults are present for cultivar. Symptoms of HVX are about six weeks and fly to new hosts consistent for specific cultivars, so every three days. They are strongly comparisons can be made for suspected attracted to previously attacked foliage, infections. particularly that damaged by Japanese beetles. Season-long control involves at HVX is normally transmitted from least three insecticide spray plant to plant through wound contact. applications. If only one application is Sap from infected plants can enter applied, it should be applied at early wounds on non-infected plants and emergence to reduce overall damage. quickly take up residence. The virus can also be spread when cuttings or Carbaryl (Sevin) and various labeled divisions are made of infected plants. pyrethroids including cyfluthrin HVX can even be spread through tissue (Tempo) and permethrin (Astro) are culture of infected hostas. Tissue effective, with each spray lasting about culture is a common way of two weeks. Systemic insecticides such as propagation for large hosta nurseries, imidacloprid (Merit, others) will provide so if an infected plant is chosen for control. Hand-picking in late afternoon culturing the spread of the virus can be and evening is also effective. Disturbed extensive. The vector of transmission beetles will drop into a jar held under outside of this is unknown as of now them. Add a couple of inches of rubbing (assuming there is one!), though it is alcohol or soapy water to the jar to kill known that the virus has no captured beetles. (Phil Nixon) survivability outside of the living host.

A fun fact on HVX is that occasionally Hosta Virus X (and becoming more common) hostas are intentionally infected with HVX to Hosta virus X (HVX) is a pathogen that produce cultivars with “cool” traits. has plagued gardeners worldwide. As While this might not sound like an awful with most viruses, HVX will not kill idea, these cosmetic hosta cultivars can hosta; however it can cause a number of lead to the increased spread of HVX to undesirable symptoms to appear on the hosta everywhere, which is definitely host. HVX is also a difficult virus to pin not “cool”. Some of these varieties down because symptoms can often take include (but are not limited to): years to appear in infected hosts, and in Leopard Frog, Blue Freckles, Lunacy, some cases no symptoms may ever Eternal Father, Kiwi, Watercolours, and appear. Breakdance.

Some major symptoms to look out for The only way to be sure of the presence include: rugose or wrinked leaves, light of HVX in a hosta is through a scientific green sections on leaves, ink bleed analysis (ELISA test). If you suspect that your hosta may be infected with HVX, on the leaves, stems, flowers, and fruits you can submit a sample of leaves to the of various plants. Anthracnose infections U of I Plant Clinic. The fee is $25 for an occur during rainy, spring weather, and ELISA test. Please be sure to include a usually subside by mid-summer. Oaks sample submission form with provided are specifically infected by a form of information with your sample. Discula anthracnose, Discula quercinia. Over 20 species of oak are prone to Sadly there is no easy fix for HVX. Once varying degrees of infection. White oak a hosta has been diagnosed as a host for (Quercus alba) is a highly susceptible HVX, it should be eradicated species. immediately. When removing infected hostas they should not be composted, Fungal spores of Discula quercina are as this can only increase spread. HVX present on the tree year round, hosts should be either burned or inhabiting the buds, twigs and leaves. bagged. If the infected hostas are The infection process is initiated during container grown and the container is to wet conditions in spring as spores are be reused, it should first be washed and splashed onto developing leaves. rinsed in a 1:10 solution of bleach to Ascospores, produced on fallen leaves, water. Infected landscape hostas also contribute to new infections. should be dug out and disposed of in the same manner. As much of the root There are three main types of symptoms material as possible should be related to oak anthracnose: twig and leaf removed, and that spot in the garden dieback, leaf distortion, and angular should remain vacant until all root necrotic spots on the mature leaf. material has decomposed in the soil. Symptoms are usually heaviest on the When working in the garden with lower branches. Fungal fruiting hostas, some techniques can be used to structures can be observed on leaves reduce the chance of spreading. Ideally, when viewed under a magnifying lens or knives or other tools used to split or cut microscope. The fungus also produces hosts should be disinfected after use ascervuli, which look like brown to with each plant. Of course one of the orange pustules on the twigs. The leaf best management practices for new infections continue along the leaf veins buyers: only buy your hostas from into the twigs. The fungus can be trusted nurseries or other sources. actively producing conidia within 2 (Stephanie Porter and Sean Mullahy) weeks after the initial infection. New conidia will contribute to further rounds of infection. If conditions are highly Oak Anthracnose favorable and the trees are stressed beforehand, the infection may cause After an abnormally warm, dry spring in defoliation and twig dieback. Do not be Illinois, anthracnose might still be alarmed by the defoliation. In most rearing its head. Anthracnose is a cases, the infection is not harmful to the disease caused by a variety of fungi, all long-term health of the tree. The oak can morphologically similar and with similar recover by producing new leaves to symptoms: tan to brown or black lesions replace dead ones.

There are several methods of control for oak anthracnose: Disease / Symptoms Pathogen 1. Large trees can be pruned to Oak Defoliation, twig dieback, improve air circulation. Improved Anthracnose necrotic spots of leaf air circulation will lessen the (Discula tissues. These symptoms amount of time the foliage remains quercinia) usually appear in the lower section of leaves because it wet, thereby reducing the likelihood is most damp there. of infection. Symptoms appear during 2. Sanitation can be helpful, especially spring when conditions are on smaller trees. Removal of wet. The host, however, can cankerous twigs to lower the spore recover from the disease. numbers can reduce the infection Bacterial Chlorosis and discoloration, rate. It is also recommended to Leaf Scorch stunted growth and remove infected plant debris during (Xylella scorching patterns of the winter so that primary inoculum fastidiosa) necrosis present on leaves. is reduced during the spring. The symptoms start on the 3. Proper watering and fertilization of upper layer of leaves, but leaves continue to remain the tree to reduce stress can make intact throughout the the tree less susceptible to infection season. As the years pass, in the upcoming spring. the infection can continue 4. Fungicides are not usually until finally the host is dead. recommended for anthracnose Oak Wilt Symptoms emerge around diseases. The damage caused by the (Ceratocytis spring and summer. They disease is mostly aesthetic. fagacearum) first appear at the top of the Additionally, spraying a large tree tree. Symptoms include with fungicides may be cost wilting, chlorosis along the prohibitive. Specific chemical veins of leaf tissue, leaf cast options are provided within and discolorations in the Management for the Home xylem. Because the fungus attacks the vascular system, Landscape. Apply a suggested it can kill the host. fungicide two or three times, at 14- day intervals, starting at leaf emergence. Thorough coverage is For more information, visit: required. The manufacturer's http://www.extension.umn.edu/distrib directions should be carefully ution/cropsystems/M1288.html followed. Spraying after the disease (Travis Cleveland and Zu Dienle Tan) is evident will only protect healthy new leaves. Catchweed Bedstraw – A Catchy Little It is common to mistake the symptoms Weed of oak anthracnose with other Quercus (oak) disease. Below is a more I’ve had a few queries about catchweed comprehensible chart listing some of the bedstraw lately. Galium aparine is an disease that it might be confused with: annual weed that has been quite prevalent this spring. It has a semi- in small hooks, again to aid in prostrate habit and is commonly found dissemination. Seeds are capable of in shaded or wooded areas climbing up germinating over an extended period of over the top of surrounding vegetation. time. One plant will typically produce It is primarily found in landscapes, 100 to 400 seeds, but occasionally 3,000 nurseries, small grains, and meadows. It or more can be produced according to earned the name bedstraw when it was IPM specialists at the University of used to minimize matting in mattress California. Seeds can remain viable in filling. This weed may also be known by the soil for up to three years. other names including cleavers, Velcro plant, stickywilly, goose-grass, grip- Catchweed bedstraw can be found grass, snatch-grass, and catch-grass. across North America. It appears to be The leaves are narrow, but it’s not a a more serious problem in the grass at all. Stickywilly? That’s just a Northwestern states. It can be pulled good name. fairly easily especially in moist soil as it has short roots. Blooming plants The leaves are sessile in whorls of 6-8 at should then be discarded so that seed the nodes. The leaf blades are development does not continue. The lanceolate in shape. Overall, the plant is preemergent herbicide oryzalin can fairly hairy or prickly allowing it to provide fair control of catchweed “catch” easily on skin, clothing, or fur so bedstraw. Postemergent herbicide that seeds are disseminated. The stems options include glyphosate, have recurved prickles on the ridges and oxyfluorfen, quinclorac, carfentrazone, leaves; they are square shaped and and diclobenil. This list is not all break easily. The upperside of the inclusive but is provided as a starting leaves are hairy. The underside has point. Always be sure to read and short prickly hairs which allow you to follow all label directions. Prevention perform magic tricks to impress young of seed dispersal is likely the best way children. I’d advise against it though. to prevent future infestations of this Recently, I stuck one to my arm in order plant. to demonstrate my profound ability to make it “hang magically” from my arm. A similar species is smooth bedstraw (G. Pulling it off hurt quite a bit and mollugo) which is a perennial and is surprisingly the pain lasted for a couple smooth overall except at the leaf of days. My 5 year old was only slightly margins. Carpetweed has a similar impressed with my super powers. But growth habit and leaf arrangement, but what else is new? the stem is round and it is more branched. The flowers of catchweed bedstraw are produced in May-June in clusters near Photos of catchweed bedstraw can be the axils of the whorls. They are white found here: with 4 petals and 4 stamens. Flowers http://www.inhs.illinois.edu/animals_pl can occur in only 8 weeks after /plants/ilgallery/ThePlants/GGener germination. The seeds are small (2-3 a/GalApa/GalApa.html mm in diameter) and typically covered (Michelle Wiesbrook)