YEAR-END COMMERCIAL PESTICIDE TRAINING OPPORTUNITIES
The meetings below are convenient opportunities to receive continuing education credit before December 31, 1998. Note: All meeting schedules are listed in local time.
Commercial applicators need to attend 2 approved training meetings in 5 years to remain certified. Any questions about the number of meetings needed by an individual should be directed to the Division of Pesticides (502) 564-7274.
December 3- 1998 Professional Horticulture Seminar (Category 3 and 10), IU Southeast Campus, New Albany, IN 9 am - 4 pm. (Approval pending). Contact- Roy Ballard, Floyd Co (IN) CES (812) 948- 5470. No certification testing available.
December 15 and 16- Kentuckiana Fertilizer and Ag Chemical Meeting, Radisson Hotel, Evansville, IN Categories 1, 10, and 12,
By Ric Bessin
After an absence of 15 years, southwestern corn borer has returned to Kentucky and once again become the most destructive insect pest of corn in the western half of the state. This insect was rediscovered in the state in 1992 during a European corn borer survey and since then has spread eastward in the state to Pulaski county in the south and Hardin county in central Kentucky. In addition to southwestern corn borer, European corn borer continues to pose a threat to corn producers across the state.
Western Kentucky represents the northeastern limit of the southwestern corn borer distribution. While European and southwestern corn borer infestations have been increasing over the last three years, during 1998 southwestern corn borer was particularly destructive in the river counties adjacent to the Ohio and Mississippi Rivers west of Owensboro. Despite numerous warnings, many producers were surprised by the amount of lodged corn at harvest.
Unlike European corn borer, southwestern corn borer tunneling does not "wander" through the stalk. Characteristically they make a straight line through the middle of the stalk. In the fall, borers that remain larvae migrate to the base of the plant and tunnel. Larvae often girdle the plant at the base before tunneling downward. This is the most serious damage caused by southwestern corn borer. Larvae girdle the stalk by chewing a complete or partial internal groove around the stalk near the base. This leaves only a thin outer layer of the stalk for support.
Typically, many corn producers in Kentucky do little to manage corn borer populations in the late summer because it requires very careful scouting or lack adequate equipment to spray tasseled corn. In years with high European corn borer populations, a portion of the corn acreage is treated with aerial insecticide applications. The high percentage of non- till and reduced tillage in Kentucky also contributes to southwestern corn borer losses by allowing increased winter survival of the larvae.
Some Bt transgenic corn technologies offer corn producers a practical control for southwestern corn borers. While Bt corn has been developed for European corn borer control, the full-season protection afforded by the YieldGard and StarLink hybrids also provide excellent southwestern corn borer protection. With the heightened awareness of southwestern corn borer and the performance of Bt corn, it is to be expected that a sizable proportion of corn acreage in 1999 will be planted with transgenic corn. Due to the nature of this type of corn borer management, the development of resistance by either of the corn borer species is a serious issue. The challenge facing the Kentucky Cooperative Extension Service is to educate corn producers about resistance management and to have those producers adopt and deploy effective resistance management strategies for European corn borer and southwestern corn borer.
The Kentucky Blue
Mold Warning System's URL address is:By William Nesmith
This is a two part article, which will be published in this and the next issue of Kentucky Pest News.
Infectious diseases of tobacco contributed significantly to losses in transplants and to low yields, as well as, to many headaches for growers and other facets of the tobacco industry during the past year. However, great variation in disease levels from farm to farm and from field to field strongly suggests that the levels of disease management in use is playing an important role in disease development. This is something that growers have control over.
Diseases during transplant production were particularly troublesome and are rapidly increasing in importance. This is mainly driven by the following facts: 1) float systems are ideal places for diseases once the pathogens arrive; 2) the pathogens are arriving in greater numbers mainly because of contaminated trays; and, 3) adequate chemical control options are not available. In the case of blue mold in these systems, introduction of the disease on plugs and pre-finished plants are important initially, but later these initial sites serve as airborne sources of the disease.
In the field, protracted periods of unfavorable weather for tobacco production favored infection and spread of both foliar and root diseases. Root diseases developed rapidly after transplanting and caused the greater losses in yield than did foliar diseases. This is primarily because the diseased roots reduced the plant's tolerance to drought. Foliar diseases, especially blue mold, were very important early in the season and did cause serious crop damage in some regions, but probably would have caused extensive damage if it were not for critical changes in the weather at key times.
In contrast to the above, losses resulting from virus diseases were low in 1998. This is a direct result of the high percentage of the crop planted to varieties which resist the aphid-borne, potyvirus complex. The incidence of Tobacco Mosaic (TMV) increased in 1998, but remains at a low level overall. This increase in TMV results from using TMV- susceptible varieties and clipping of plants. The incidence of Peanut Stunt (PSV) and Cucumber Mosaic (CMV) was greater than normal, but crop damage from these two virus diseases was minimal of low incidence within fields. Nonetheless, we need to remain watchful for these two viruses, because they are very damaging when plants are infected early. Furthermore, none of the currently available varieties have resistance to PSV or CMV.
ROOT AND STEM DISEASES IN 1998: Black shank disease of the stem and roots, black root rot, Pythium root and stem rot, Rhizoctonia root and stem rot (Soreshin), and Fusarium wilt, root, and stem rots were key diseases in 1998. Several of the minor diseases in this group, especially those caused by Fusarium, Rhizoctonia, and Pythium, are increasing in importance. These increases appear in- part to be connected to recent changes in transplant production.
Some cases of stem diseases resembling black shank in stem symptoms and lethal damage, and others resembling the stunting of black root rot are actually being caused by Pythium, Fusarium, or Rhizoctonia. When black shank is present with any of these other diseases, it is much more lethal and damaging.
Root knot nematodes remain a minor problem in Kentucky, but some changes may be occurring. Higher incidence and damage from root knot nematodes were noticed last year, involving both our native northern root knot and the southern root knot (introduced with southern transplants). This was probably tied to the better survival of nematodes associated with the mild winter. High root knot numbers greatly reduce crop yields and also cause damage by breaking resistance to Fusarium wilt and increasing susceptibility to black shank. Crop rotation and early root and stubble destruction are critical to resolving this problem before it gets a good start.
The greatest losses from root diseases were mainly in fields where crop rotation was not practiced. Here, even healthy transplants were immediately attack by high populations of pathogens waiting in the soil. This situation was aggravated where root development was slowed due to cold wet soils, compacted soil or herbicides in the root zone, or where diseased-transplants were used.
Another significant factor in the losses from soil borne diseases was related to the decline in the use of the soil fungicide Ridomil Gold. Many growers have stopped using this fungicide, because of its failure to control metalaxyl-resistant blue mold. Unfortunately, many of those individuals have black shank-infested farms or Pythium root rot present, and fail to appreciate the total range of benefits offered by this fungicide in tobacco production systems. The decision of whether to use Ridomil Gold, and timing of the applications in Kentucky, should be based on its potential to control the soilborne diseases black shank and Pythium root rot, rather than its failure to control certain strains of blue mold or the availability of alternative fungicides for blue mold control.
Dutch elm disease, caused by the fungus Ophiostoma ulmi, and its aggressive counterpart Ophiostoma novo-ulmi (sometimes referred to as American elm disease), has eliminated American elm trees from many Kentucky landscapes in past decades. The Lexington Herald-Leader newspaper recently profiled a northern Kentucky nurseryman, Dick Ammon, who is growing disease-resistant American elms. Thus, in Kentucky as well as nation-wide, there is interest in bringing back the American elm. The following material was adapted and summarized from an article from the proceedings of the recent Third International Elm Conference written by Keith Warren of the J. Frank Schmidt & Son Co.
The American elm, because of its tolerance to urban growing conditions and its favorable form was the dominant street tree in the U.S. in the early part of this century. Because Dutch elm disease all but eliminated this tree from the landscape, efforts have been underway for years to find elms to replace them. Nurseries like J. Frank Schmidt & Son (and Dick Ammon and others) have many disease- resistant elms in some stage of production now, with several already available for planting.
The elms of horticultural importance in the U.S. belong to four main groups: Chinese elm (Ulmus parvifolia); other Asian elms (U. pumila, U. japonica, U. wilsoniana); European (U. glabra, U. carpinifolia) and European-Asian hybrids; and American elm U. americana). Some of the cultivars used in the nursery trade that are resistant to Dutch elm disease are discussed below. Consult with horticultural and nursery professionals for more details of these disease-resistant cultivars.
Chinese elm (Ulmus parvifolia) group: Chinese elm, often called lacebark elm, is Dutch elm disease resistant and has desirable horticultural characteristics such as exfoliating bark. But with a size only about half that of American elm, it would be used differently in the landscape.
Although we may have to wait a few years for some of the new disease-resistant elms, several are available now. Now is a good time to plan to introduce some of them into our landscapes and along our streets, at least on a trial basis. American elm was the best of the urban street trees. Let's hope that they can make a comeback.
Hog lice and mange mites are two external parasites that can become serious swine pests during the winter. Cold temperatures favor the development of lice while bunching of animals increases contact and allows ectoparasites to spread quickly throughout the herd. Hog lice use piercing, sucking mouthparts to feed on blood. Heavy infestations can be especially serious for young pigs. In combination with other winter stresses, lice can harm large animals, too.
A hog louse lives about 5 weeks and spends its life cycle on the animal. Single eggs or nits are glued to hair shafts and hatch in 2 to 3 weeks. Lice feed on tender areas of skin- inside ears or in folds of skin on the neck. The slate blue lice can blend in with the skin and be overlooked, even though adults are about 1/4" long. The good spots get taken up, so lice may move and settle around upper inside areas of legs and around the tail of a heavily infested animal.
Lice feed frequently and produce a persistent and annoying itching sensation. Severe infestations cause the animal's skin to show measle-like bumps. "Lousy" animals repeatedly rub against feeders, posts, and other objects. This produces hair loss and cracked skin.
Lice can be seen with the naked eye but mange mites are much smaller. Positive diagnosis requires microscopic examination of skin scrapings. Mites burrow into skin- literally digesting their way through it. The life cycle takes about 2 weeks. As with lice, the feeding produces severe itching and causes the animals to rub. Mange lesions can start anywhere but usually occur first on the head, typically around the ears, eyes or nose. They are not exposed like lice so control with contact insecticides is tougher.
Do not make a hasty diagnosis. Skin lesions do not automatically mean lice or mites. Check animals carefully. Infestations do not have to be "either - or" - both lice and mites can occur on the same animal.
Options for lice and mange control include sprays, dusts, injection, or feed through. When using sprays, remember where these pests are on the animal and treat thoroughly. Spray pressure must be sufficient to be effective against mites and the animal must be wetted thoroughly. Treat on a warm, sunny day so animals will dry rapidly. Dusts are generally less effective than sprays but can be used for louse control if only a few animals need treatment or conditions do not allow spraying. Pour-ons and bedding/pen treatments are effective against lice and are recommended in cold weather when spraying is prevented. Lice and mites can only survive off of the animal for 2 to 3 days. They will not infest humans, pets, or other livestock. Follow up on treatments to check on results. A few mites or lice can survive to continue the infestation.
Recent samples sent to the diagnostic lab have included: Gibberella stalk rot of corn; bitter pit of apple resulting from calcium deficiency; cane canker of raspberry associated with a species of the fungus Colletotrichum; Rhizosphaera needle cast of spruce; and numerous stress-related symptoms in woody ornamentals.
Lee Townsend
Extension Entomologist