November 5, 1997
1997 Wood Preservative Workshop
Hardin Co. Cooperative Extension Office
Elizabethtown, KY
Remaining 1997 Commercial Pesticide Applicator Training and Testing Dates (Categories 1, 2a, 3, 4, 10, 12)
Categories 2a: 8:30 AM - 12:20 PM, Testing at 1:00 PM;
Cat. 3, 10. 12: 8:30 AM - Noon, Testing at 1:00 PM;
Cat. 1, 4, 10, 12: 9:45 AM - 2:00 PM,Testing at 2:00 PM
November 11, 1997
McCracken Co. Extension Office
Paducah, KY
November 18, 1997
Fayette Co. Extension Office
Lexington, KY
December 22, 1997
419 Reed Hall
Morehead State University
by Paul Vincelli
Several kinds of ear and kernel rots can reduce yield, quality, and feed value of corn. These rots occur to some extent each year. Factors that enhance the development of ear and kernel rots include insect and bird damage; lodging of stalks, bringing ears in contact with soil; incomplete coverage of ears by husks; maturation of ears in an upright rather than downward position; and stress during grain fill.
Although many of the ear rots originate in the field, these rots can proliferate in storage when conditions of high moisture and high temperature exist. Ear and kernel rots reduce nutritive value, and some can also create additional problems through production of mycotoxins (poisons produced by fungi) in the decayed area.
Ear and kernel rots often found in Kentucky are as follows:
* Fusarium kernel rot is characterized by whitish or pinkish mold growing on individual kernels or clusters of kernels. These rotted kernels or clusters of kernels occur randomly throughout the ear. Fusarium ear rot can lead to contamination of the corn with fumonisins, mycotoxins that are very toxic to swine and horses. This ear rot can be a significant problem in Kentucky and the region. Concern over this rot is highest when stressful conditions occur during grain fill. Much remains to be learned about the specific conditions that enhance this disease and the associated fumonisin contamination.
* Stenocarpella (=Diplodia) ear rot results in extensive white mold growth around and between kernels that usually progresses from the base of the cob upwards and from the cob outward. No mycotoxins are associated with this rot in the U.S. This ear rot has generally been the most common in recent years in Kentucky, in my experience. So far, 1997 seems to have had lighter disease pressure than last year in many areas.
* Gibberella ear rot is identified by the pinkish to reddish mold growth that occurs, usually beginning at ear tips and moving toward the base of the ear. This does not appear to be particularly widespread at harvest most years in Kentucky, but it can develop during storage if moisture is above recommended levels.
* Penicillium rot is characterized by a powdery green or blue-green mold on and between kernels, often at the ear tip.
* Aspergillus rot produces a greenish-yellow mold on and between kernels. This one can be of concern because of possible contamination by aflatoxins. Aflatoxins are mycotoxins which are toxic to various livestock and of concern to human health. Aflatoxin content of corn is subject to Food and Drug Administration regulations. Note that preharvest contamination of corn with aflatoxins is very uncommon in Kentucky. I don't expect a problem with this one given the cool conditions that prevailed in most areas during the grain fill period.
Another related point: Producers should always be aware of the risks of feeding screenings from corn or other grains. Screenings from several grains can contain dangerous levels of mycotoxins. In particular, screenings from production of shelled corn and tall fescue seed have been associated with mycotoxin poisonings of livestock in Kentucky. Corn screenings can potentially be contaminated with fumonisins, and the this might also happen with aflatoxins. Raise a red flag if you learn of a producer using screenings from grain production as a feed. Screenings can be hazardous.
More information on selected ear rots is available in the following Extension publications:
by Ric Bessin and Lincoln Martin
Examples of three types of transgenic corn hybrids (Maximizer®, YieldGard®, and NatureGard®) were evaluated for control of first generation and second generation European and southwestern corn borers. The Maximizer technology was represented by MAX 454, the YieldGard by NK 7590BT, NK 7639BT, PI 31B13, PI 33A14, PI 33V08, and PI 33Y09, and the NatureGard by NG 2787, NG 2801, NG 7559, and NG 7959. Three non transgenic hybrids, NK 7590, PI 3394, and SS812 were also included. Two pairs of isolines, PI 3394/PI 33V08 and NK7590/NK7590 BT, included in this study allow for an evaluation of Bt technology on yield. The hybrids in these isoline pairs are essentially identical except for the presence or absence of the Bt insert.
The test plot was planted in a second-year corn field on the farm of Jeff Burnette in Fulton County on May 14 as a randomized block design with 3 replicates. This test plot was surrounded by soybeans. Individual plots consisted of five rows, 50 feet long, with 20 inch row spacing. Bicep 6L at 2.4 quarts per acre was used for weed control at planting. Liquid nitrogen was applied at 60 gallons per acre of 30%N. On July 2, twenty consecutive plants from the center row of each plot were evaluated for first generation corn borer damage using the 1-9 Guthrie scale that is based on leaf feeding. On September 2 and 3, ten consecutive stalks from one of the rows adjacent to the middle row were split and the number of European and southwestern corn borers recorded as well as the number of galleries and the length of stalk tunneling. On October 1, two-25 foot row samples were hand harvested for yield and moisture measurements. All yield information has been adjusted to 15.5% moisture.
Cool soil and air temperatures delayed corn emergence, early season growth, and the onset of the first generation of the corn borers. Intermittent rainfall during mid summer had a negative impact on yield in this study. While first generation pressure appeared to be light as measured by the leaf feeding, late season pressure by both of the target pests was intense. It is important to note that all of the transgenic hybrids in the study provided superior control of both first and second generation corn borers for all variables measured (Table 1, see page 4). It is unlikely that any of the transgenic hybrids suffered any yield loss due to corn borer injury. When comparing the level of protection on average provided by the different technologies (Table 2, see page 4), there are some differences among the technologies but these differences are minor compared to the damage to the standard hybrids.
Presence of the Bt gene in a hybrid does not increase yield, it only aids in preventing yield loss due to these corn borers. Yield potential is determined by the entire genetics of a hybrid. The impact of this technology on grain yield can be estimated by comparing the sets of isolines. The first pair had a positive yield increase of 18.9 bushels per acre (PI 3394 vs. PI 33V08) while the second pair had a slight yield drop of 0.9 bushels per acre (NK 7590 vs. NK 7590BT). PI 33V08 and NK 7590BT use the same BT insert, so on average this provided a 9 bushel per acre yield advantage. Keep in mind that this yield information is derived from a single location in a single year. Producers need to watch for the 1997 Kentucky Hybrid Corn Performance trials for more in depth and longer term yield information. This year four Bt hybrids were evaluated in those tests.
In summary, this technology looks promising and holds many advantages for producers. However, producers considering planting Bt hybrids should ask themselves what has been the yield loss they have experienced with corn borers in the past ten years. It does not make sense to use these hybrids in fields that have not had problems with corn borers. European corn borer populations tend to run in cycles of 5 to 7 years. The past two seasons have been high points in that cycle. However, some fields and some areas have a history of above average corn borer activity. Southwestern corn borer does not follow the same pattern as the European corn borer and we have seen a gradual increase in activity with this pest since 1992.
How should these hybrids be positioned on the farm? Early planted corn can be predisposed to increased problems with first generation European corn borer, using these on the earliest planted fields would be one strategy. Late planted corn is more predisposed to damage from second generation European corn borer, southwestern corn borer, and fall armyworm. Bt hybrids will protect against the first two pests but producers may still need to treat for fall armyworm.
Protecting against the development of insect resistance IS the responsibility of ALL producers using these hybrids. This is not a responsibility to be taken lightly, development of resistance by corn borers to these hybrids is a real threat. The strategy that producers must adopt is called refugia. This means that a portion of their corn crop must be planted with non-Bt hybrids. This will need to be 25 to 30% if they plan on using any foliar insecticides to control corn borers, fall armyworm, armyworms, Japanese beetles, or other silk clipping insects. If no foliar insecticides will be used at all, then only 5 to 10% of their acreage needs to planted in non-Bt hybrids. How the Bt and non-Bt hybrids are arranged on the farm is also important. These hybrids need to arranged such that any moths that happen to emerge from Bt hybrids mate with moths from the non-Bt hybrids. Look to coming KPN articles to discuss insect resistance and Bt hybrids this fall.
by Lee Townsend
Eprinex Pour-On for Beef and Dairy Cattle controls a broad range of internal and external parasites of cattle. The active ingredient, eprinomectin, is a member of the avermectin group. Among the arthropod pests included on the product label are horn flies (7 days), cattle grubs, four species of mange mites, four species of lice (including biting lice) and two species of mange mites. There is no meat or slaughter withdrawal, nor is there any milk-withholding period.
This pour-on is applied topically along the back line in a narrow strip from the withers to the tail head. The dose rate is 1 milliliter per 10 kilograms (22 lbs). Eprinomectin binds tightly to the soil and becomes inactivated so it should not be applied to areas of the animal covered with mud or manure. (Merck AgVet Division, Merck, Inc.)
by Lee Townsend
Hollowed or rotting iris rhizomes are probably the result of iris borer damage earlier in the year. The pinkish caterpillars with brown heads have completed their development and have transformed into the adult or moth. The moths are finishing up their egg-laying activity and will soon die. Earlier feeding by the caterpillars damaged plant foliage and the underground rhizomes. In addition to tissue destruction, the caterpillar's feeding sites allow the introduction of bacteria that cause the repulsive soft rot that ruins so many tubers.
The only alternative at this point is to clean up and destroy all of the old foliage and debris on the ground, especially around the base of the plant. This is where the overwinter stage (eggs) of the borer are laid. They will remain there and hatch next spring. An aggressive sanitation program now will help to reduce problems next season. An application of Sevin or malathion in April or when the fans start to grow may help to reduce larval numbers, too.
by Lee Townsend
The third week in October is generally when the Asian lady beetles begin to fly toward overwintering sites. Expect them to be active in the mid-afternoon on warm sunny days. The latest information on them is contained in ENT 64 "Asian lady beetle infestation of structure".
Cluster flies will be moving indoors also. Entfact 624 deals with this common fall invader.
by Michael F. Potter, Extension Entomologist
According to a statewide poll of Kentucky householders, 93% expressed concern over finding insects within their home. More than half indicated that a single cockroach, cricket, or spider would prompt them to use a can of bug spray or call an exterminator. Despite their "high-profile" presence within the home, most pests encountered indoors have either flown or crawled in from outdoors.
One of the best ways to limit unwanted intrusions by insects, rodents, birds, squirrels and other pests is to deny them entry -- a procedure known as pest proofing. Many pests seek refuge in homes and other buildings in response to changes in weather, such as extended periods of rain or drought, or the onset of cooler temperatures in autumn. Taking steps to block their entry before they end up inside can greatly reduce the chances of future sitings.
Outlined below are six useful tips for pest proofing one's home or place of business. Steps 1-3 will also conserve energy and increase the comfort level during summer and winter. Equipment and materials mentioned can be purchased at most home improvement or hardware stores.
Apply caulk (see #3 below) along bottom outside edge and sides of door thresholds to exclude ants and other small insects. Garage doors should be fitted with a bottom seal constructed of rubber (vinyl seals poorly in cold weather). Gaps under sliding glass doors can be sealed by lining the bottom track with ½ to 3/4"-wide foam weatherstripping.
Buy a good caulking gun. Features to look for include a back-off trigger to halt the flow of caulk when desired, a built-in "slicer" for cutting the tip off of new caulking tubes, and a nail for puncturing the seal within. (Hardware stores sell guns with these features for less than $10.00.) Prior to sealing, cracks should be cleaned and any peeling caulk removed to aid adhesion. For a professional look, smooth the bead of caulk after application with a damp rag or a moistened finger.
Clients who choose not to tackle these activities may wish to hire a professional pest control firm. Many firms are beginning to offer pest proofing as an adjunct to other services. When all else fails, a vacuum cleaner or broom is often the best response to the occasional bug that wanders in from outdoors.
by John Hartman
Poinsettias in Kentucky greenhouses are now in full production for the upcoming holiday season. Powdery mildew, a disease capable of quickly destroying a crop, has become an important problem of poinsettia in the U.S. The causal fungus is Oidium, the typical imperfect stage of most powdery mildews; despite the similarity of appearance, powdery mildews for the most part are different for each crop. Disease symptoms are very distinct and powdery fungal signs are readily seen on red bracts and green leaves. Fungal growth on white bracts are less obvious, but can readily be seen with close examination. Fungal mycelium and conidia may be found on both tops and undersides of the leaves.
Once the disease gets started, it is capable of "exploding" so rapidly that plants appear to be "flocked" within just a few weeks. Cool, (daytime temperatures remaining less than 85 F) and moist greenhouse environments with crowded plants favor rapid disease development this time of year. All poinsettia cultivars are apparently susceptible. Kentucky growers who suspect powdery mildew in their poinsettias are urged to have the problem diagnosed.
Powdery mildew infection and spread can be reduced by doing the following:
a) Inspect plants frequently, carefully examining at least one in thirty, or one in ten if conditions favor the disease.
b) Remove infected leaves while disease levels are still low.
c) Space plants well to provide good air circulation.
d) Ventilate the greenhouse and keep the air well circulated within the house.
e) Apply fungicides labeled for poinsettia if needed (See list below.).
Fungicides such as Terraguard and Strike have been shown to be especially effective. Growers need to be aware that although fungicides can be costly and may leave residues on the bracts, powdery mildew mars the bracts more. So, frequent inspection now, and being prepared to react if the disease is detected, are essential to protecting poinsettias from this devastating disease.
Other important poinsettia diseases. Rhizoctonia root and stem rot causes a brown, dry canker at the stem base, and root browning. Bacterial soft rot infected cuttings become soft and mushy at the base of the stem. Pythium root rot causes discoloration and decay of feeder roots and this loss of root function produces yellowing, wilting, and possibly death of infected plants, especially under stressful growing conditions. Black root rot infected roots show black dead tips or distinct black bands or lesions, and eventually blackened root systems. Botrytis blight symptoms include tan to gray-brown blotches on bracts or target spot lesions on leaves. Damaged areas may be covered by the fuzzy gray growth (spores) of the fungus. Botrytis may also cause a stem blight on cuttings and plants.
Sanitation for disease control.
a) Remove pathogen-infested plant debris and soil from the greenhouse.
b) Clean and disinfect the benches and equipment with a germicide.
c) Root cuttings in well aerated, sterilized rooting medium.
d) Transplant rooted cuttings into sterilized soil mix.
e) Regularly collect and remove organic debris such as shed leaves or bracts or declining plants from the greenhouse.
Crop management for disease control.
a) Reduce nitrogen fertilization to harden plants before taking cuttings.
b) Inspect purchased cuttings and reject those that are diseased.
c) Handle cuttings carefully and plant at the correct depth.
d) Maintain optimum growing conditions.
e) Monitor mineral nutrient levels regularly through soil testing.
f) Watch for and correct soluble salts and over-or under-watering problems.
g) Provide plant spacing that allows good air movement.
h) Avoid splashing water on foliage.
i) Use greenhouse ventilation systems to maintain low humidity.
Fungicides for poinsettia disease control.
a) Botrytis gray mold - Chipco 26019, Cleary's 3336, Daconil 2787, Domain, Exotherm Termil, Ornalin.
b) Pythium root rot - Banol, Banrot, Subdue, Terrazole, Truban.
c) Rhizoctonia stem and root rot; Black root rot - Banrot, Chipco 26019, Cleary's 3336, Domain, Terrachlor.
d) Powdery mildew - Benefit, Cleary's 3336, ConSyst, Domain, Duosan, Fungo-Flo, Phyton 27, Pipron, Sunspray Ultrafine Spray Oil, Strike, Systhane, Terraguard, Triact, and Zyban.
Read and follow fungicide label directions before use. If a grower has not previously used a particular fungicide, it needs to be tried out on a few plants at first. Some fungicides may be phytotoxic under some conditions.
by Julie Beale and Paul Bachi
Diagnostic lab samples over the past two weeks have included:
Field crops - Fusarium and Diplodia ear rots on corn, and Aspergillus mold on corn; false broomrape (related to a hostile root environment) and frogeye leaf spot on tobacco.
Ornamentals - Phomopsis twig blight (enhanced by low light conditions) on Ficus trees; Banrot injury and distortion of unknown origin on poinsettia; rose rust; white pine decline and normal fall needle drop on white pine; bacterial scorch, leaf blister, fungal branch cankers, and powdery mildew on oak; and Mycosphaerella leaf spot on black gum.
Vegetables - downy mildew on squash; fruit decay (unknown bacterial agent present) on gourd; scurf, improper curing and growth cracks on sweet potato; white spot (Cercosporella) on turnip; and blackleg on cabbage.
Lee Townsend
Extension Entomologist