“WHAT’S HAPPENING?”
The University of Tennessee/Agricultural Extension Service
Entomology & Plant Pathology - EPP #60
27April 2007
HOW MUCH WEED PRESSURE DOES IT TAKE TO REDUCE YIELD?
by Darrell Hensley
Syngenta Crop Protection has modified several journal articles to provide information concerning weed populations and their effects on yield.
To see this information you may visit the following URL:
http://www.farmassist.com/SoybeanRust/qow_detail.aspx?articleid=61601
The information was published on Syngenta's FarmAssist website.
FIELD CROP UPDATE
by Russ Patrick
Wheat:
It is a sad day for many wheat producers due to freeze damage to wheat in Tennessee. This is also the case for other states as well. I do not know if insects will be an added problem but we will continue to list our trap catches.
Corn:
Continue to scout for cutworms in corn. Cool temperatures and moist soil conditions will add to the potential threat from cutworms. If 3% of the plants are cut by these insects, treatment should be applied as soon as possible. There are a number of products that can be used. See the publication listed here for recommendations.
ATRAZINE UPDATES WEB PAGE AVAILABLE
by Darrell Hensley
A new web page is now available on the Environmental Protection Agency's pesticide reregistration Web site. The new page provides initial results from the programs, activities and studies required by the Atrazine Reregistration Eligibility Decision (RED). It presents followup activities in four areas, including the status of an atrazine monitoring program in Community Water Systems, an atrazine ecological watershed monitoring program, and research activities related to cancer and amphibians. As new information in these four areas becomes available, the Agency will present it on their web page, available at, http://www.epa.gov/oppsrrd1/reregistration/atrazine/atrazine_update.htm. For more information concerning atrazine visit its chemical page, http://www.epa.gov/pesticides/reregistration/atrazine/index.htm, located on the reregistration status table, http://www.epa.gov/pesticides/reregistration/status.htm.
LACE BUGS
by Frank A. Hale
Lace bugs are common pests on many types of ornamental plants. Whether it is the sycamore lace bug, basswood lace bug, birch lace bug, hawthorn lace bug, hackberry lace bug, oak lace bug, andromeda lace bug. rhododendron lace bug, or azalea lace bug, the type of damage that they cause is very similar. Wherever they feed with their piercing-sucking mouthparts, they remove the cell contents. These tiny chlorotic spots tend to coalesce over the growing season into bleached out looking leaves. They generally feed on the underside of leaves and their excrement is a shiny dark brown or black (varnish-like) and is often referred to as tar spots or resin spots.
Azalea lace bugs overwinter as eggs inserted into the underside of the leaf along the midvein in the fall. The spiny nymphs usually emerge by late March or early April and have now reached adulthood. They will continue to feed and lay eggs until later in the fall and can have four generations in Tennessee. The use of soil applied systemic insecticides such as imidacloprid in late winter has simplified control of lace bugs. Otherwise, foliar insecticide sprays should be made as soon as the nymphs emerge to limit spring feeding damage.
Hawthorn lace bugs overwinter as adults under the bark of pyracantha, cotoneaster or hawthorn or in the surrounding leaf litter. The adults have now moved to the underside of the leaves where they will cement their dark pointed eggs. Now is a good time to control the adults. A follow up spray may be needed in a few weeks or so to control any nymphs that hatched from eggs. There is probably only one generation per year of this pest. If not controlled, the bleached out leaves often take on an orange coloration.
ORNAMENTAL AND TURF PLANT PATHOGENS ARE ACTIVE
by Alan Windham
Botrytis blight (gray mold) was observed on geranium. Cool, wet conditions and senescing lower leaves are all that’s needed for this pathogen to become firmly established on geranium in garden centers. Spacing of plants to allow for some air movement, keeping foliage dry and removing older leaves will help manage this fungus. If our weather becomes cool and wet look for botrytis to infect senescing dogwood bracts. Once these infected bracts fall onto leaves, the fungus will move into the leaf tissue causing a leaf spot that looks very much like dogwood anthracnose.
Powdery mildew has been observed on rose, euonymus and columbine. White, powdery fungal growth is diagnostic for this disease.
Cedar Rusts - such as cedar-apple (CAR) rust and cedar-hawthorne rust (CHR) have been active for several weeks. CAR appears as orange galls, and CHR appears as cankers erupting with orange teliospores on twigs and branches on eastern red cedar and ornamental junipers. I have noticed golden leaf spots on hawthorne leaves and fruit from CHR infections.
Fire blight- has been observed on crabapple and ornamental pears. Wilted shoots soon turn brown to black depending on the host. The shoot blight phase will not be controlled by applying streptomycin sulfate at this time; pruning can be used as a stop gap measure.
Leaf spot diseases - Entomosporium leaf spot is flaring up on photinia; as is cercospora leaf spot and black spot on rose.
Turf diseases -zoysia patch is evident on Meyer zoysia as is spring dead spot on hybrid bermudagrass. Zoysia patch is close to running its course; whereas the fungus that causes spring dead spot of bermuda was active in the fall even though symptoms don’t appear till spring.
TO FERTILIZE OR NOT TO FERTILIZE FREEZE INJURED ORNAMENTAL SHRUBS AND TREES
by Alan Windham and Carol Reese
Most plant professionals agree that there is no need to rush out and fertilize ornamental shrubs and trees that were injured during the freeze Easter weekend. However, not everyone agrees with this advice. This is especially true among some arborists that feel that fertilization would benefit trees stressed from freeze injury. Where are the facts that support either camp? If you conduct a search on “freeze injury” on Google, you will find descriptions of freeze injury, the causes of freeze injury, but very little factual information on the treatment of woody plants after freeze injury. Most Extension advisors agree that the fertilization of damaged woody plants is not a good idea; few, if any offer an explanation other than saying it can cause additional stress.
One of the few sites that offers any advice is a fact sheet on “Rehabilitation of Freeze Damaged Citrus and Avocado Trees” by N. Sakovich and B. Faber, Farm Advisors with the Univ of CA. As to fertilization, they state: “There is no evidence to indicate that frozen trees respond to any special fertilizer that is supposed to stimulate growth. . . . Fertilizer applications should be greatly reduced, until the structure and balance (root and shoot growth) of the tree become re-established.”
Among texts on arboriculture, plant physiology and environmental stresses, most are silent on the treatment of trees damaged specifically by a spring freeze. Although not specifically addressing freeze injury, Alex Shigo in A New Tree Biology, does mention the treatment of trees stressed by damage from construction sites. Trees damaged by construction have low energy reserves, as do trees that have expended a tremendous amount of energy to produce shoots and leaves which were killed by the spring freeze. In both cases, trees are dangerously low in energy reserves. Dr. Shigo states, “Do not fertilize trees near construction sites until after the leaves mature. Then apply very light amounts of fertilizers. High amounts of nitrogen will stimulate the stressed tree to exhaust its energy reserves”. If this is true, it appears that the last thing one would want to do is fertilize a tree with low energy reserves, which is the current state of many of our deciduous trees.
Some additional thoughts from the Physiology of Woody Plants by Kramer and Kozlowski:
“ Carbohydrates are of special importance because they are direct products of photosynthesis and are, therefore primary energy storage compounds.” This is a reminder to us all that fertilizer is not “plant food” per se, it’s the products of photosynthesis which are true plant food. “The most important polysaccharides in trees are cellulose and starch”. “The most obvious use of reserve carbohydrates is in maintaining respiration and growth at times when food is not supplied directly from photosynthesis. . . . The importance of reserves in deciduous trees is further shown by the emergence of a second crop of young leaves from dormant buds of temperate zone trees in the spring when the first set of young leaves is killed by an early frost.”
To recap and summarize:
Where studies have been conducted (on citrus and avocado), fertilization was not of particular value to freeze injured woody plants.
Fertilization that causes rapid shoot growth may cause a stressed tree to exhaust its energy reserves.
The byproducts of photosynthesis are true plant food (not fertilizers). Stored starch and other polysaccharides are going to be the source of energy for a second crop of young leaves and shoots.
The roots of most damaged trees and shrubs are still healthy and are in native soils that have sufficient nutrients (minerals) for normal growth.
Trees and shrubs that were in a weakened condition prior to the freeze may not have the energy reserves to produce a second crop of shoots. Trees and shrubs weakened by drought, construction injury and now the freeze may be particularly susceptible to plant pathogens that cause canker diseases and wood decay.
Many areas of the state are several inches below normal rainfall levels, the addition of fertilizer may cause an additional stress by increasing the soluble salt level to a point where young roots could be damaged.
ENDANGERED SPECIES EFFECTS DETERMINATIONS FOR 66 PESTICIDES SET BY COURT ORDER FOR THE CALIFORNIA RED-LEGGED FROG.
by Darrell Hensley
The Environmental Protection Agency (EPA) has begun assessing the potential effects of 66 pesticides to the California red-legged frog (a species listed as threatened under the Endangered Species Act and native to California), and is issuing related materials. Under the terms of a Stipulated Injunction, EPA must follow a Court-ordered schedule for making effects determinations for each of the 66 pesticides named in a lawsuit brought against the Agency by the Center for Biological Diversity (CBD). The injunction also establishes interim injunctive measures stating that the named pesticides cannot be used for specific purposes in certain areas of California. Additionally, the injunction required EPA to develop a bilingual brochure regarding certain aspects of the injunction, the California red-legged frog and frogs in general, and pesticides. The first effects determinations for 10 pesticides are scheduled to be completed by July 20, 2007.
Once the Agency makes a determination that the pesticide's use has "no effect" on the California red-legged frog, or once EPA completes consultation with the U.S. Fish and Wildlife Service where EPA determined the pesticide's use may affect the species, the restrictions imposed by the interim injunctive measures would be eliminated for that use of the pesticide. .
The injunction required EPA to distribute the brochure to all commercial certified applicators within California; to all private certified applicators residing in counties where use authorizations have been set aside; to registrants of the 66 pesticides; to the California Departments of Pesticide Regulation, and Fish and Game; and to the Pacific Region of U.S. Fish and Wildlife Service. In addition, EPA is to distribute line250 copies of the brochure to the County Agricultural Commissioner and Cooperative Extension Agent offices in the affected counties. In addition to providing the bilingual brochure as required by the injunction, EPA has also made this brochure available on its Web site. Further, EPA has posted on its Web site maps of the areas in California where the injunctive relief applies and information to assist pesticide users in determining whether the provisions of the injunction apply to them. These materials, as well as a full text of the Stipulated Injunction and more information regarding
this case are available at www.epa.gov/espp. The injunction and availability of information was announced in a Federal Register notice on April 25, 2007.
TOBACCO FLOAT PLANT INSECT PESTS
by Gene Burgess
Fungus Gnats and Shore Flies may cause problems in greenhouses and float systems.
The fungus gnats are slender, mosquito-like insects with elongated coxae, long legs and one pair of clear wings. They are usually found in damp places where there is an abundance of decaying vegetation or fungi. Most fungus gnats are about the size of mosquitoes. The larvae of most species live in fungi, moist soil or decaying vegetation.
Occasionally, fungus gnat larvae can be serious pests in greenhouses. Most are scavengers, feeding on decaying organic matter in the growing media. However, some species will feed on root hairs, enter the roots, or even attack the crown or stem of the plant. Infested plants generally lack vigor and may begin to wilt. Adults (gnats) can be seen running on the foliage before injury caused by the larvae becomes apparent.
Female fungus gnats lay tiny ribbons of tiny yellowish white eggs in the growing media that hatch within 4 days. The clear larvae are legless and have black heads. Larvae feed for about 14 days and pupate near the surface of the medium. Adults live only about a week. Under greenhouse conditions, about 20-25 days are required to complete a generation.
Shore flies are small to very small. Most are dark-colored and a few have pictured wings. The adults are found in moist places: marshes, the shores of ponds and streams and the seashore. The larvae are aquatic and many species live in brackish or even strongly saline or alkaline water.
Very wet media, algal growth, and cool temperatures can contribute to problems with fungus gnats and shore flies in greenhouses and float systems. Adult shore flies are the noticeable stage but the larval stages can damage small plants in the cells, producing holes in the leaves that resemble the feeding of slugs and small cutworms.
Shore flies also are small gnats but have short antennae, red eyes, and heavier, darker bodies. A pair of smoky wings with several clear spots can be seen when looking closely at the insect. They are good fliers and can be seen resting on most any surface in the greenhouse. They resemble winged aphids but aphids have two pairs of wings and the distinctive, tube-like cornicles on the abdomen, and do not move as quickly.
The life cycle is similar to that of the fungus gnat. The yellow to brown larvae, which may be up to 1/4” long, differ in having no apparent head. Both larvae and adults feed mostly on algae growing on media, floors, benches, or pots. Some have been seen boring directly into the base of small plants. Damaged plants will easily break off at the soil surface. The adults may spread soil pathogens inside the greenhouse.
The presence of these insects is usually overlooked until there is a massive swarm of adults sitting on the plant leaves. Orthene will kill adults and eventually may reduce their numbers but probably won’t eliminate the problem. It is difficult to control the larval stages because they are down in the algae or under the protective cover of the leaves. Preventive control is based on keeping media from getting too wet and eliminating as many standing ground puddles as possible.
RECIPROCITY WITH KENTUCKY
by Gene Burgess
A reciprocity agreement on pesticide certification has been reached between Tennessee and Kentucky. In the new agreement, we reciprocate with Kentucky with all Tennessee categories except Category 7, Industrial, Institutional, Structural and Health Related.
We only reciprocate in Category 3 if all Kentucky categories related to Category 3 are held. In Kentucky these include Categories 3 (Ornamental and Lawn Care), 18 (Golf Course), 19 (Interior Plantscapes and 20 (Sports Turf).
Note, we do not reciprocate with regard to licenses with any state anymore.
WIREWORMS IN TOBACCO
by Gene Burgess
Wireworms are soil insects attacking tobacco. The yellow to brown, hard-bodied larvae are slender and cylindrical. The adult is a click beetle. Wireworms hatch in the summer, spend the winter in the soil and are usually most destructive to newly transplanted tobacco.
Wireworm larvae cut off small underground stems and roots and bore into larger stems and roots. They may be found tunneling in stems near the soil surface. Affected plants may become stunted or wilt and die within a few days. Tobacco following sod may be damaged by wireworms for one to five years because some species have long life cycles.
Wireworms are not as common in fescue sod as other types of grass. There may be a need for wireworm treatment if there is wireworm damage to the previous crop. Broadcast incorporated applications of products like Lorsban (chlorpyrifos), Mocap (ethoprop) or DiSyston(disulfoton). These should be made about two weeks before transplant in order to have time to work before the crop is set. Some transplant water or tray drench applications are labeled for wireworm suppression but may not be effective against high populations pressure. There are no rescue treatments for wireworms.
DISTANCE DIAGNOSTICS
by Frank A. Hale
If you have not used the distance diagnostics system (digital images for pest identification), now is a good time to give it a try. Send in a few samples, just to get the hang of it. Also, practice using your digital camera, especially the macro or close-up setting. You can upload five quality digital images when submitting a sample. Before sending any image, make sure that it is in focus. My favorite aspect of digital photography is that you can take lots of images, immediately view them on the camera, delete the out of focus ones, and keep shooting until you get the picture you want. Later, you can further sort and discard, label, and store them in convenient files on your computer.
If you have a winged insect, take a picture of the whole wing so that the wing veins are in focus. Take another image of the top side of the whole insect and another of the bottom side. That still leaves two more images that can be used to show any damage caused, a close-up of an interesting aspect of the pest, or perhaps a side shot. It is good to put a coin or a ruler in one of the shots so we know the size of the pest or plant damage.
Remember that each submission involves unique circumstances. Think of the submission as you would a crime scene and we are the detectives. The more good clues that we have to work with, the better that we can solve it. Try to describe the problem as thoroughly as possible so that we will have the information we need to make a proper identification and give control recommendations tailored to the needs of your client.
CUTWORMS IN TOBACCO
by Gene Burgess
Cutworms, including the black cutworm are generally dingy gray to dark brown or black. Faint longitudinal stripes may occur on the body.
Infestations are likely to occur in tobacco following sod or in fields with an abundance of winter annual weeds prior to tillage. Larvae feed for four to five weeks and can reduce stands by cutting off newly set transplants. Cutworms feed at night and can be found in the soil around freshly cut plants during the day. Cutworms may be very damaging in tobacco beds. Damage often appears first along weedy margins or portions or the bed lying along fence rows.
Black cutworm moths are flying now and laying their eggs on dense, low-growing plants. Tillage removes the food buy does not kill the cutworms. The preplant incorporated chlorpyrifos wireworm application should give good cutworm suppression. Orthene can be used as a foliar spray to control cutrworms after transplanting.
ORGANIC MATERIALS
by Darrell Hensley
The Organic Materials Review Institute (OMRI) is a national nonprofit organization that determines which input products are allowed for use in organic production and processing. OMRI Listed—or approved—products may be used on operations that are certified organic under the USDA National Organic Program.
OMRI's funding comes from a variety of sources, including sales of publications, grants, donations, and subscriptions. Mainly, however, the organization generates income through fees collected for the review of products intended for use in organic production or processing. Also, OMRI operates an organic seed information service to help growers find organic seeds. For more information concerning organic materials and organic crop production visit these listed URLS:
Organic Materials Review Institute (http://www.omri.org/OMRI_who.html)
National Organic Program National Organic Program
ORMI seeds database ORMI seeds database
OTHER UT NEWSLETTERS WITH PEST MANAGEMENT INFORMATION
http://web.utk.edu/~extepp/fpn/fpn.htm
Tennessee Crop and Pest Management Newsletter
http://www.utextension.utk.edu/fieldCrops/cotton/cotton_insects/ipmnewsletters.htm
This and other "What's Happening" issues can be found at attp://web.utk.edu/~extepp/whatshap.htm
Disclaimer Statement
Pesticides recommended in this publication were registered for the prescribed uses when printed. Pesticide regulations
are continuously reviewed. Should registration or a recommended pesticide be canceled, it would
no longer be recommended by the University of Tennessee.
Use of trade or brand names in this publication is for clarity and information; it does not imply approval of the
product to the exclusion of others that may be of similar, suitable composition, nor does it guarantee or
warrant the standard of the product.
Precautionary Statement
To protect people and the environment, pesticides should be used safely. This is everyone’s responsibility,
especially the user. Read and follow label directions carefully before you mix, apply store or dispose of a pesticide. According to laws regulating pesticides, they must be used only as directed by the label.
Persons who do not obey the law will be subject to penalties.
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