PERFORMANCE OF ACROBAT MZ IN GROWER-LEVEL PLOTS, 1996
by William Nesmith

Below are some data taken from grower-level demonstration plots conducted with Acrobat MZ in 1996. These plots were designed to measure the efficacy and economic benefit of using Acrobat MZ under the Emergency Exemption. The growers made all fungicide applications as per their individual understandings of the label, but drop nozzles and moderate pressure were used in all three cases reported here. The entire field was sprayed with Acrobat MZ as indicated, except for four untreated areas ( the width of the spray boom, or at least 4 rows wide, and 25-50 feet long). The data were collected by the University of Kentucky, however.

Significant control of blue mold was obtained at all three sites, but economic benefit occurred only at the sites of higher disease pressure. These data will be used to support the 1997 application to EPA for use of Acrobat MZ in 1997.

Table 1: Effects of Four, Foliar Applications of Acrobat MZ on the Control of Blue Mold and Yield of Burley Tobacco (Variety, Tn 90), Clark Co, 1996.

		% Leaf Damaged from Blue Mold*		Yield/A Market
Treatment	Low	Middle	Top	(lbs)	Value ($)
Unsprayed	82a***	19a	0.4a	2384b	4577
Acrobat MZ	24b	3.4b	0.0a	2782a	5341

* Ratings are visual estimates of the % leaf surface damaged by blue mold in the lower third, middle third, and top third of the plant about 10 days after topping.

** Yields are cured weights, ready for market. Costs of fungicide treatments: Chemical costs: $205/A ($30 for spray application plus $85 for the fungicide, market value at $10/lb) gross benefit = $764/A, Net benefit from Acrobat MZ = $559/A.

*** Values within the same column sharing different letters are significantly different at the 95% confidence level, as determined by the Tukey's Honestly Significant Difference Procedure.

Table 2. Effects of Five, Foliar Applications of Acrobat MZ on the Control of Blue Mold and Yield of Burley Tobacco, Fayette Co, 1996, Variety R-711.

	% Leaf Damaged from B. Mold*		Yield/A Market
Treatment	7/12	7/24	(lbs)**	Value ($)
Unsprayed	56.7a	78.3a	2289b	4394
Acrobat	3.3b	13.3b	3107a	5965

* Ratings are visual estimates of the % leaf surface damaged by blue mold on various dates.

** Yields are cured weights, ready for market. Costs of fungicide treatments: Chemical costs: $235/A ($30 for each spray application (5 applications) plus $85 for the fungicide, market value at $10/lb). gross benefit = $1571; Net benefit from Acrobat MZ = $1336/A

*** Values within the same column sharing different letters are significantly different at the 95% confidence level, as determined by the Tukey's Honestly Significant Difference Procedure.

Table 3. Effects of Four, Foliar Applications of Acrobat MZ on the Control of Blue Mold and Yield of Burley Tobacco - Jessamine County, 1996, Variety Tn 90.

	% Leaf Damaged from B. Mold*			Yield/A Market
Treatment	Low	Middle	Top	(llbs)	Value ($)
Unsprayed	15 a***	0.5 a	0.07a	2868 a	5506
Acrobat MZ	1.6b	0.3 a	0.2 a	2810 a	5395

* Ratings are visual estimates of the % leaf surface damaged by blue mold in the low third, middle third, and top third of the plant about 15 days after topping.

** Yields are cured weights, ready for market. Costs of fungicide treatments: Chemical costs: $220/A ($30 for each spray application plus $100 for the fungicide, market value at $10/lb) gross Benefit = -$111/a, Net benefit from Acrobat MZ = -$331/A

*** Values within the same column sharing different letters are significantly different at the 95% confidence level, as determined by the Tukey's Honestly Significant Difference Procedure.

BLACK SHANK ADVISORY FOR 1997 CROP
by William Nesmith

Damage from black shank in the 1996 crop was well below the losses sustained in recent years, but do not allow that rest to mislead. Several of the risk factors associated with major epidemics of black shank in the past are beginning to come together, increasing the probability of a black shank epidemic in 1997. Consequently, tobacco growers are advised to increase their efforts to manage black shank in 1997.

The following are some factors that increase the potential for black shank:

• Continuously cropping tobacco favors black shank - with the large crop planned, increased number of sites will be planted following tobacco.
• Black shank fungus should have over-wintered well, due to a mild winter, so we expect a larger population earlier in the season.
• Extensive flooding increases the contamination of new land, and irrigation sources, and recontamination of rotated sites. Carefully, reconsider the black shank potential based on this issue!
• Many growers plan to reduce their use of Ridomil, because they have assumed it was only being used for blue mold control, not recognizing the benefit in black shank control they might have received.

Here are some guidelines to consider in planning for increased black shank potential.

• Use rotated sites as much as possible.
• Consider preplant-soil fumigation for non-rotated sites with a strong history of black shank and other root diseases. Basically, this is a new option for Kentucky's growers, but it is not a cure-all.
• Use a black shank resistant variety on the sites with a history of black shank, or those potentially contaminated. Carefully, reconsider the variety decisions made a month ago, because they could have changed after the flood.
• Apply Ridomil 2E or Ridomil Gold both preplant plus at cultivation/layby (consult the label) for sites at risks of black shank.
• Take steps in problem fields to insure good soil drainage through ditching, etc. Nothing increases black shank more than standing and moving water. Be especially careful at transplanting not to compact the soil.
• Maintain a strong sanitation program to reduce introduction and spread, be especially rigorous with sanitation in transplant production.

1996 BT-CORN EVALUATION FOR CORN EARWORM
by Aaron Anderson and Ric Bessin

While evaluating five Bt-corn hybrids for control of European corn borer and yield at the UK REC substation in Princeton, we also had the opportunity to evaluate the effect on corn earworm. The five hybrids (and the type of Bt technology) were as follows: NorthrupKing 6800BT (YieldGard), Mycogen 7959 (NatureGard), Mycogen 7559 (NatureGard), Ciba Maximizer 454 (Knockout), and Monsanto 810 (Yieldgard). They were compared with Mycogen 7660, NorthrupKing 6800, Ciba 4494, and Monsanto B73/Mo17. The Bt-corn technologies were developed primarily for control of European corn borer, however, the Bt protein that is produced is toxic to a large number of lepidopterous insects (e.g. caterpillars of moths and butterflies).

With corn earworm, the attack begins just as the plants begin to silk. The egg-laying females seek out fresh green silk on which to lay their eggs. In three to five days, the eggs hatch and the young larvae feed on the silks as they begin moving towards the developing tip of the ear. Each of the different Bt-corn technologies will "express" the Bt protein in slightly different ways in the plant. What that means is that different tissues, green tissue, pith, grain, silks, tassel, pollen, etc., in the plant may have the Bt protein depending on which Bt-technology has been incorporated. Corn earworm has never been an insect that we could control economically in field corn because of the expense of the repeated insecticide applications that would be needed for control. However, in some years grain loss by earworms, particularly in late planted corn, can be substantial.

Resistance to corn earworm was evaluated in the field and laboratory. With the lab study, newly emerged earworm larvae were fed fresh silks removed from the plants. Their weights were recorded after 6 days of feeding. In the field, earworm evaluation was done at harvest by determining the extent of tip damage. The length of the damage to the tip was measured. It needs to be noted that tip damage can also be caused by European corn borer and fall armyworm. In this study, the majority of the tip damage was attributed to earworms.

Hybrid averages by types of technology	Silk feeding study (6-day weigh)	Tip Damage (cm)
Standard hybrids	128.2 a	0.79 b
Maximizer	51.9 b	0.89 a
NatureGard	51.6 b	0.63 c
YieldGard	14.8 c	0.46 d

This data suggests that there are different levels of resistance to corn earworm by the Bt-corn technologies. All of the Bt technologies reduced weight gain in the laboratory silk feeding experiment. In the field, the NatureGard and YieldGard had significantly less tip feeding damage than the standard hybrids without the Bt gene.

This study suggests that using some Bt hybrids for European corn borer control may also have the benefit of limiting the damage caused by corn earworm. Because yield loss to corn earworm is the greatest with later plantings, the benefits of these hybrids would be greatest with these plantings.. However, keep in mind that later plantings also have a much higher chance of fall armyworm infestation, an insect not controlled with Bt-corn technology.

Corn hybrids that have the gene to produce the Bt endotoxin do not necessarily yield more. If you are interested in using this technology, you should select a hybrid that has the complete package of characteristics you need, including yield potential, disease resistance, and local adaptability for your cropping situation. In the absence of insect pests, your Bt-hybrid should yield as least much as your standard hybrids that you are currently using.

ALFALFA WEEVIL WINTER EGG-LAYING ACTIVITY
by Lee Townsend and John Parr

According to UK AG Weather Center data, recent mild weather has resulted in a significant buildup of alfalfa weevil degree days (AWDD). Just a few more days with temperatures above the 48o F threshold will push accumulations above 190 in south-central and western Kentucky. For example, the March 1 AWDDs for some selected sites were - Bardstown- 143, Bowling Green- 185, Lexington- 127, Princeton- 201, and Somerset-174.

The accumulation of 190 or more AWDD at a location means that some of the fall-laid eggs have will hatch and tip-feeding will begin soon. This is the earliest that weevil activity can be expected but well before the peak of the population. It would be premature to apply an insecticide at this time unless larval numbers were unusually high. However, it is time to begin checking established fields for the characteristic "pin-hole" symptoms.

Mr. John Parr, forage entomology research specialist, made stem collections during late February. From these he calculated egg numbers /square foot in some fields that have been sampled for several years. Here are the results, along with some previous years for comparison.

Eggs/ square foot
County	1996	1997
		Site 1	Site 2
Barren	149	341	--
Fayette	10	41	19
Hart	142	572	223
Nelson	12	86	--
Owen	--	86	26*
Warren	104	394	134

Many of the eggs are in the "black head" stage, which means that they will be hatching soon. About 80% of these eggs will hatch and the small weevils will climb to the tips and begin to feed. An average of 100 or more eggs per square foot (based on 35 - 50 stems per square foot) can lead to treatable populations. These females are continuing to lay eggs in alfalfa stems for the one generation that will develop this year.

SPRING APHID OUTLOOK
by Lee Townsend and Don Hershman

Aphids found in wheat in the spring are primarily from two sources 1) overwintering survival from fall flight and 2) spring flight. The bird cherry-oat aphid (BCOA) is the predominant fall species. Prolonged feeding then could reduce winter-hardiness of wheat plants, in addition to infection with Barley Yellow Dwarf Virus (BYDV). The English grain aphid moves into wheat fields in the spring and can carry BYDV, too. In both cases, winged migrants land in the fields, feed some and deposit live young on the plants. Typically, these develop into wingless adults that produce offspring over several generations. Wingless aphids spread gradually in the field by crawling from plant to plant and leaving behind their young.

Fall infestation
The numbers of aphids arriving in the fall depends largely upon two factors 1) general growing conditions during the summer and 2) when the first hard frost occurs in relation to crop emergence. Normal or greater rainfall during the summer should mean an adequate amount and quality of host crops for aphids during the summer. It also increases the potential for plants infected with BYDV to survive and be a source of the virus that aphids can pick up. During a drier than normal summer, fewer aphids should be produced, due to reduced plant quality, and a greater proportion of BYDV- infected host plants should die due to the extra stress. In the fall, significant rain can wash small aphids off plants, many of them will die.

Crops that emerge long before a hard freeze have a greater potential for infestation than those emerging after a freeze. The "fly free" date, which is used to control Hessian fly infestation is based upon that principle, and works well if the freeze actually occurs when it should.

Winter survival
Aphids arriving in the fall will continue to move and reproduce as long as temperatures remain above about 48 F. Mild temperatures or some insulating snow cover during cold spells should increase survival of the aphids during the winter. Harsher weather should produce greater mortality.

Spring infestation
The English grain aphid has a spring flight. This aphid arrives around spring green-up time. The numbers of these winged aphids should depend on the same factors that determine survival of the BCOA. Good conditions for survival should produce larger spring flights. The English grain aphid can carry BYDV into the field. It also colonizes wheat and can occur on the developing grain heads in numbers sufficient to reduce yields.

A look at of some weather data from BYDV plot work by Don Hershman and Doug Johnson at Princeton allows some comparison for 1996-97. The table below compares some weather observations for 1992-93 winter, when high BYD incidence was seen, with that of 1993-94 - a low virus year.

Winter (10/16-2/28)	BYDV Severity	1st hard freeze	Days low temp < 30 F	Days high temp > 32 F	Preciptation (in)
1992-93	High	11/14	39	2	14.4
1993-94	Low	10/28	55	9	21.2

Compared to the winter of 1992-93 when disease incidence was high, the winter of 1993-94 had an earlier frost, more days with a low temperature below 30 F and more days when the daily high never got above freezing. This probably resulted in greater overwintering mortality of aphids. In addition, the high rainfall during that winter probably contributed to some aphid death.

1996 - 1997 Outlook (10/16 - 2/20)

Location	1st Hard Freeze	Days low temp < 30 F	Days high temp > 32 F	Precipitation (in)
Bardstown	10/20	51	15	18.0
Bowling Green	11/3	45	11	19.1
Henderson	11/2	54	15	17.1
Princeton	11/3	42	9	23.1

Weather observations from four selected locations for 1996-97(table above) are more similar to the low BYDV fall and winter of 1992-93 than 1993-94. The first hard frost was relatively early and the general severity of the winter, based upon numbers of sub-freezing days, points to low aphid survival over the winter. This is true for aphids in wheat fields, as well as those such as the English grain aphid that will be flying in this spring.

This is supported by aphid counts taken in Fayette county wheat (planted 9/25/97). The numbers of bird cherry oat aphids /100 plants by sampling date show an early infestation, fall increase, and collapse:

Oct 22	19
Oct 30	51
Nov 12	152
Dec 16	231
Feb 27/97	3

Insecticide applications should be made at green-up only if field scouting shows significant numbers of live aphids (more than 10 per foot of row). At this point, preventive insecticide sprays applied just because other inputs are going on, are not justified. In addition, conditions appear to favor a relatively light spring flight. Sound management strategy dictates a "what and wait" approach.

CURRENT USDA/APHIS CONUNDRUM COULD BE GOOD NEWS FOR KENTUCKY AND TENNESSEE WHEAT PRODUCERS
by Donald Hershman

In a February 12, 1997 update, APHIS confirmed that spores of a fungus, identical in appearance to those which cause Karnal bunt in wheat, were found to be associated with ryegrass seed from Oregon. Results of laboratory tests (PCR/DNA technique)used to confirm wheat Karnal bunt spores were also positive for the spores from ryegrass.

On the surface it appears as though Karnal bunt affects both wheat and ryegrass. However, to know this for sure requires cross-inoculation studies between wheat and the ryegrass fungus, as well as between ryegrass and the Karnal bunt fungus. In addition, the PCR/DNA test being used to confirm Karnal bunt needs to be scrutinized for accuracy. It is possible that the PCR/DNA test being used is also giving a postive reaction for a closely related fungus which affects ryegrass but not wheat. USDA/APHIS is currently studying both of these areas intensively.

If wheat Karnal bunt is found to affect ryegrass, then Karnal bunt is likely to have world-wide distribution. The reality is that Oregon has shipped ryegrass seed around the world for many years. Tests have shown that one-half to two-thirds of all the ryegrass seed tested from Oregon from 1996 contain Karnal bunt-like spores. Also, Karnal bunt-like spores have been found in ryegrass seed samples dating back as early as 1989. It's clear from this evidence that this disease, whatever it is, is firmly established in ryegrass.

Alternatively, if the fungus from ryegrass does not cause wheat Karnal bunt, but the PCR/DNA tests being used for Karnal bunt does not distinguish between the two fungi, than all positive results of tests come into question. Unlike the western U.S. situation where Karnal bunt has been observed in harvested wheat kernals, all positives in the southeast have been based only on observation of spores and results of PCR/DNA tests. In other words, Karnal bunt has not actually been observed. Thus, there is a strong possibility that the Karnal bunt fungus may not be present in the southeast and that what APHIS is picking up is the ryegrass fungus. This would explain why "Karnal bunt" has been found in counties of Alabama, Georgia and Tennessee better known for cover crops and grazing than for wheat production.

Either scenario may be good news for Kentucky and Tennessee wheat producers. If Karnal bunt is widely distributed throughout the world, than import restrictions will have to be changed to reflect this fact. In the long term, this will make all quarantine measures unnecessary. If, on the other hand, Alabama, Georgia and Tennessee do not have Karnal bunt after all, then all attention will return to keeping Karnal bunt out of our region. Forthcoming data from USDA/APHIS will, hopefully, shed new light on this situation.

DISEASE HAZARDS OF SPRING AND SUMMER FERTILIZER TO LAWNS
by Paul Vincelli

With the mild weather of late, many lawns have begun to green up. The emerald-green color of a lawn breaking winter dormancy is very appealing. It is only natural for homeowners to want to encourage this process and get out there with a fertilizer spreader. However, this is not the time of year when lawns should be fertilized.

There should be no need for nitrogen fertilizer this time of year in lawns of Kentucky bluegrass or tall fescue, especially if they were fertilized at least once last autumn (the preferred time to fertilize). In fact, heavy fertilizer applications during spring and into the summer can actually increase the risk of several destructive diseases. In tall fescue, the greater the spring and summer N fertility, the worse is brown patch. In Kentucky bluegrass, melting out and patch diseases are worse where most of the fertilizer is applied in spring and summer (as compared to autumn); also, brown patch can be very damaging in new seedings of Kentucky bluegrass under high fertility.

In fact, even under a high maintenance lawn management program, now is agronomically a poor time to fertilize. If any fertilizer is to be applied, apply no more than 1/2 lb N per thousand sq. ft. in May or June. Yes, this will favor the diseases mentioned above, but March or April are not recommended times for lawn fertilizer applications. As always, apply most--or even all--of your nitrogen fertilizer during the autumn months. This reduces disease activity and allows recovery of the turf from summertime diseases and stresses. County Extension agents can provide more information on proper lawn fertilization.

Bottom line: Resist the temptation to fertilize the lawn as it greens up. Apply most or all of the fertilizer next autumn to minimize diseases.

by Monte P. Johnson

KENTUCKY'S ENDANGERED AND THREATENED SPECIES LIST
The following is a list of those species found in Kentucky that are considered federally endangered or threatened by the U.S. Fish & Wildlife Service. The source for this list is an article published in the Transactions of the Kentucky Academy of Science in 1996 by the Kentucky State Nature Preserves Commission, a state agency mandated to identify and protect natural areas. Definitions for endangered and threatened are as follows:

• ENDANGERED - E = endangered - any species in danger of extinction throughout all or a significant portion of its range
• THREATENED - T = threatened - any species likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range (USFWS 1992).

• PLANTS:
  • Price's potato-bean, Apios priceana, T
  • Braun's rock cress, Arabis perstellata, E
  • Cumberland-rosemary, Conradina verticillata, T
  • Cumberland sandwort, Minuartia cumberlandensisChaffseed, Schwalbea americana, E
  • White-haired goldenrod, Solidago albopilosa, T
  • Short's goldenrod, Solidago shortii, E
  • Running buffalo clover,Trifolium stoloniferum, E
• ANIMALS
  • (Unionid Bivalves - Mussels):
    • Fanshell, Cyprogenia stegaria, E
    • Catspaw, Epioblasma obliquata obliquata, E
    • Northern riffleshell, Epioblasma torulosa rangiana, E
    • Pink mucket, Lampsilis abrupta, E
    • Ring pink, Obovaria retusa, E
    • Little-wing pearlymussel, Pegias fabula, E
    • Orange-foot pimpleback, Plethobasus cooperianus, E
    • Clubshell, Pleurobema clava, E
    • Rough pigtoe, Pleurobema plenum, E
    • Fat pocketbook, Potamilus capax, E
    • Cumberland bean, Villosa trabalis, E
  • (Crustaceans):
    • Mammoth Cave shrimp, Palaemonias ganteri, E
  • (Insects):
    • American burying beetle, Nicrophorus americanus, E
  • (Fishes):
    • Relict darter, Etheostoma chienense, E
    • Palezone shiner (undescribed), Notropis sp., E
    • Blackside dace, Phoxinus cumberlandensis, T
    • Pallid sturgeon, Scaphirhynchus albus, E
  • (Birds):
    • Bald eagle, Haliaeetus leucocephalus, E
    • Red-cockaded woodpecker, Picoides borealis, E
    • Interior least tern, Sterna antillarum athalassos, E
  • (Mammals):
    • Virginia big-eared bat, Corynorhinus townsendii virginianus, E
    • Gray myotis, Myotis grisescens, E
    • Indiana myotis, Myotis sodalis, E