Blue mold is now active in Florida, involving old plant beds and commercial tobacco fields. We have received no reports of active blue mold in commercial burley or dark tobacco transplants growing in the southeast. Dr. Tom Kuchareck, Florida's Blue Mold Coordinator, reported on April 24 that blue mold had been found in Alachua, Columbia and Union counties of northern Florida. All indications are that the level of disease is low, but conditions have been favorable for increased development locally in Florida and spread outside the immediate area.
Blue mold also remains active on the wild tobacco in Texas and conditions have been favorable to support development locally with very low level risks of long range transport outside the region.
As of April 28, blue mold has not been found in Kentucky. Yes, my laboratory has received several samples of Florida plants from local growers to be evaluated due to symptoms suggestive of blue mold, but none have proved to be positive for blue mold.
Kentucky tobacco producers should remain alert to the possibility that low levels of blue mold may have arrived via airborne or transplant-borne routes. Although recent weather patterns have developed such that the risk of viable spores reaching Kentucky have been very low, the risk has not been zero. My advice is to continue to keep regular fungicide sprays of either Dithane or Ferbam (Carbamate) in place (5-day spray interval). Assume all transplants from the southeast may have been exposed to blue mold. If southern transplants must be used, keep the plants treated with fungicides at labeled rates and intervals. Also, should blue mold be discovered in southern transplants, immediately collect a sample and submit it through the local county extension office to our laboratory; plus, promptly destroy the entire lot of plants by covering them with clear plastic and solarizing or fumigated them with methyl bromide (as per labeled directions). If blue mold is found in southern transplants already set to the field, promptly destroy the plants by disking after collecting a sample for the labs. PLEASE DO NOT ALLOW BLUE MOLD ASSOCIATED WITH TRANSPLANTS TO GO UNREPORTED.
Historically, burley tobacco has experienced very low residues of fungicides in the marketed leaf, because few fungicides have been used. However, fungicide use in burley tobacco has increased in recent years, so expect concerns about fungicide residues in cured leaf to increase as well.
The Pesticide Residue Research Laboratory at North Carolina State University, led by Drs. R. B. Leidy and T. J. Sheets, has long monitored pesticide residues in tobacco auction markets about the US. This laboratory also coordinates the smoke-flavor evaluation program with experimental chemicals under consideration for labeling on tobacco. Pesticides labeled on tobacco must not significantly alter the flavor of the smoke, a requirement established by the tobacco industry and not of concern to EPA. This laboratory's service is of great value to the tobacco industry and agriculture in general.
The levels of two fungicides were evaluated in burley leaf marketed from the 1996 season and reported at a recent meeting. Dimethomorph (one of the compounds in Acrobat MZ) and metalaxyl (the active ingredient in Ridomil) were evaluated from random samples submitted and composited from four burley marketing regions of the US. Residues assays for mancozeb (the active ingredient in Dithane and the major component of Acrobat MZ) have not been completed but the data are expected to be available later in the season.
The samples taken from the markets are at random with the treatment status of the crop sampled being unknown, so both treated and non-treated tobaccos are being sampled. The market-regions are identified as:
Residue levels of dimethomorph in burley auction market samples are shown in Table 1. Levels varied from 1.6 to 8.2 ppm (parts per million), with a weighted average for all burley areas of 3.8 ppm. Since 1996 was the season of initial use of a dimethomorph-containing fungicide, other market averages were not available. As a comparison, assays from experimental tobaccos treated in the field with dimethomorph and assayed following normal harvesting and simulated marketing conditions, have generally averaged between 20 and 30 ppm.
The residue levels of metalaxyl in burley auction market samples are shown in Table 2. Detected levels ranged from less than 0.01 to 1.4 ppm. This is much higher than the levels present in flue-cured tobaccos which ranged from less than 0.1 to 0.16 ppm. The residue levels for metalaxyl are considerably lower compared to those found over the last five years. This decline probably reflects both the decline in Ridomil use and the extremely wet season of 1996.
Table 1: Residues of Dimethomorph in 1996 Burley Auction Market Tobacco*
| Stalk position | Weighted avg. (ppm) | ||||
| Market | No. | Bottom (ppm**) | Middle (ppm) | Top (ppm) | |
| A | I | 3.76 | 4.27 | 6.86 | 4.52 |
| II | 2.39 | 3.13 | 3.03 | ||
| B | I | 1.66 | 2.05 | 2.20 | 1.84 |
| II | 1.69 | 1.38 | 1.59 | ||
| C | I | 2.82 | 6.81 | 8.17 | 6.54 |
| II | 4.88 | 5.47 | 5.80 | ||
| D | I | 4.31 | 4.48 | 2.30 | 2.38 |
| II | 1.58 | 1.75 | 1.85 | ||
| Weighted Average | 2.82 | 3.40 | 4.01 | 3.79 |
*13% Moisture
**ppm - parts per million
Table 2: Results of Metalaxyl in 1996 Burley Auction Market*
| Stalk position | Weighted avg. (ppm) | ||||
| Market | No. | Bottom (ppm**) | Middle (ppm) | Top (ppm) | |
| A | I | 0.07 | 0.90 | <0.01 | 0.27 |
| II | <0.01 | 1.43 | <0.01 | ||
| B | I | .46 | 0.70 | 0.13 | 0.31 |
| II | <0.01 | 1.02 | 0.16 | ||
| C | I | 0.02 | 0.14 | 0.06 | 0.16 |
| II | <0.01 | 0.76 | 0.10 | ||
| D | I | 0.02 | 0.10 | 0.31 | 0.15 |
| II | 0.05 | 0.19 | 0.01 | ||
| Weighted Average | 0.08 | 0.88 | 0.07 | 0.25 |
*13% Moisture
**ppm = parts per million
In 1994, claims were published that alfalfa could successfully be interseeded into established alfalfa by applying Ridomil fungicide to either the seed or to the soil at seeding. At the time, the claim had not been tested in a carefully conducted field trial. We in the UK Forage Program did not recommend this treatment for several reasons, including the fact that this seemed to be a violation of the Ridomil label.
A study on this was conducted by C. M. Hurd, K. J. Moore. E. C. Brummer, S. K. Barnhart, D. R. Buxton, and J. R. George at Iowa State University. They planted two alfalfa varieties--one susceptible to diseases and another with multiple pest resistance--into field with established alfalfa and another field with established orchardgrass. Fungicide treatments consisted of a control, Ridomil applied to the soil at 1x and 2x label recommendations, Apron fungicide applied to seed at 1x and 2x label recommendations, and Apron and Ridomil applied together each at recommended rate.
Fungicide had no effect on alfalfa seedling survival in either existing alfalfa stands nor in orchardgrass. [UK research has also failed to show any notable benefit from a Ridomil soil application when seeding alfalfa into a conventional seedbed; in fact, in some cases we have seen a small but significant yield depression from a Ridomil application.] The Iowa State researchers found that seedling emergence was greatly inhibited where alfalfa was seeded into existing alfalfa as compared to seeding into orchardgrass, most likely from autotoxicity.
Bottom line: Based on the results from Iowa State and our own work at UK, there is no benefit to using Ridomil soil applications when seeding alfalfa. Furthermore, the Iowa State research shows that Ridomil does not alleviate the risks associated with seeding alfalfa into an established stand of alfalfa.
Several cases of Sclerotinia crown and stem rot have come into the Lexington Diagnostic Lab. Just as a reminder, this disease attacks fall-seeded stands just during that first winter. For field diagnosis, examine dead plants for sclerotia attached somewhere (sometimes even about 1/4" to 1/2" below ground). These are fungal survival bodies that are somewhat irregular in shape; they are white as they develop but black when mature. Cut these open with a pocket knife: they should appear dark gray to white inside; they will clearly have a lighter color inside than outside.
Not all stand loss in fall-seeded alfalfa over the winter is caused by Sclerotinia. Be on the lookout for heaved plants. Small plants that never got a chance to develop a good root system can heave easily, particularly in a conventional seedbed. The dead remains of these can be hard to find at this point. Of course, other causes of stand loss are possible, as well.
A fungicide with a new mode of action has recently been labelled for turf disease control. The product is called Heritage 50WG (active ingredient is azoxystrobin), and is marketed by Zeneca Inc. The active ingredient is active on leaf surfaces but also has systemic activity.
Interestingly, azoxystrobin was derived from, and is chemically very similar to, a class of naturally occurring fungicides called strobilurins. These are chemicals produced by various wood decay fungi. These fungi produce these to eliminate other fungi from competing with them for nutrients.
As with all systemics, there is some concern about the possibility of resistance to Heritage. Users should use the product wisely, and avoid overuse of the product. Read the label carefully for some of the guidelines relating to resistance management.
I have conducted research with Heritage for two years, and have seen quite a bit of data from other field trials with the product, as well. Below is a summary of approximate efficacy of the product for several diseases of interest to turf managers in Kentucky.
Brown patch and anthracnose. At labelled rates, this is an outstanding product, the best available for both diseases. I suspect the temptation to overuse the product on putting greens in summer will be strong. Golf course superintendents should practice sound fungicide resistance management practices, including use of cultural controls to reduce disease pressure. This product will definitely make easier the job of controlling these summertime diseases.
Dollar spot. Heritage is not labelled for dollar spot, nor does it have any activity at normal use rates. In some tests, including one of my own, the product actually enhances dollar spot activity. This happened very strikingly during hot weather in July, 1995, at a time when the disease activity was declining in all other treatments. At its worst, we observed almost seven times as many dollar spot infection centers in the Heritage plots as in the plots treated with water alone. Note that this was the extreme case, and that often there is no difference between Heritage and check plots relative to dollar spot intensity. The fact that dollar spot can sometimes continue to increase in Heritage-treated plots while declining in others suggests:
Resistance in the dollar spot fungus to benzimidazoles occurs regularly in Kentucky, and resistance to the ergosterol inhibitor fungicides (also called DMI fungicides) also has occurred several times.
Pythium blight. Heritage is labelled for Pythium blight, but this is not its greatest strength. It is labelled for use at a high rate of 0.4 oz ($8.75/1000 sq ft), and then provides protection for no more than 10-14 days under high disease pressure. Heritage shouldn't be the only Pythium fungicide used, and the labelled restricts the uses from more than two back-to- back applications against Pythium blight. However, since the product is effective for at least 10 days, superintendents who apply it on their greens at the labelled rate can hold off on applying other Pythium fungicides for 10-14 days.
Summer Patch. I've seen only a few studies on the efficacy of Heritage against summer patch, but what I've seen looks excellent. If this holds up, this gives superintendents with Poa annua greens an option against summer patch that does not run the risk of growth regulating effects, which is often a concern with the high rates of DMI fungicides necessary for summer patch control.
Pythium Root Rot. Data on the efficacy of Heritage against this poorly understood disease complex are extremely limited. It is labelled and may perform well, but there is insufficient experimentation for recommendations to be made.
Pink Snow Mold. While labelled, the product is somewhat weak against pink snow mold (also called Fusarium patch and Microdochium patch). It must be tank-mixed for best results, but there are other products that are quite effective by themselves against this disease.
Take All Patch. I've seen results of few studies against this disease, but it appears to be very good, especially if both spring and fall applications are made. It is nice to have other options against this disease, which appears to be increasing in importance nationwide.
Powdery mildew has been quite noticeable this season on many Kentucky bluegrass lawns. This disease is favored by high nitrogen fertility and shady conditions. It is often a minor problem, but it can seriously thin the turf if the site is too shady for Kentucky bluegrass. In those cases, consider planting a more shade-tolerant turf (tall fescue or one of the fine fescues) or a shade-tolerant ground cover.
Fungicide sprays are an option, but a temporary one that will need to be used each year. Furthermore, if a growing shade tree is creating the favorable condition for powdery mildew, then fungicide sprays are almost a lost cause: the site will eventually be too shady for Kentucky bluegrass anyway. If fungicides are of interest, products containing the following will be effective: cyproconazole, fenarimol, myclobutanil, propiconazole, or triadimefon. Most of the products containing these fungicides are used only by commercial turf managers and applicators, not homeowners.
The cereal leaf beetle should be emerging from overwintering sites and moving to small grains to feed some and lay small clusters of yellow eggs on the leaves. This insect is about 1/4" long with a black head and metallic bluish-black wing covers. The legs and a small segment behind the head are red.
Adults chew elongated strips parallel with the leaf veins. The small, grub-like larvae also feed on the foliage but do not chew completely through the leaf. The result is long, narrow "scratching" on the leaf similar to that caused by flea beetles on corn. Cereal leaf beetle larvae are covered with a thin, protective coating that gives them the appearance of small drops of muddy water on the leaves. You may soon be seeing adults, eggs, and larvae in fields.
The treatment guideline for this insect is an average of 1 or more adults (or larvae) per head-bearing stem. Fields with exceptional yield potentials may benefit from treatment at population averages of 0.5 to 0.75 insects per stem. Assess infested fields carefully before making a decision. Unnecessary application of an insecticide now can decimate beneficial insects in the field and allow damaging populations of armyworms to develop.
As a matter of fact, armyworm moths are being captured at Princeton. Females will be laying masses of eggs in lush, lodged grasses. The larvae prefer to feed on succulent leaves at the top of the plant at night and hide in surface cracks or under litter during the day. Treatment is recommended when 16 or more armyworms are found per 4 square feet of ground. It should be at least mid-May before feeding is apparent.
The entomology department often receives calls from people wanting to know what can be done to protect their home from termites -- or if a certain practice or condition is likely to cause termite problems. Homeowners can reduce the risk of termite attack by following these suggestions.
Preventively treating a home for termites is a reasonable investment, especially if the structure has no prior history of treatment. If the building was previously treated by a pest control firm, it's a good idea to maintain the service agreement by paying the annual renewal fee. Should termites reinfest the building (which can happen even if the initial treatment was performed correctly), the company will return and retreat the affected area at no additional charge.
Whether or not a person chooses to have their home treated, they should know the signs of termite infestation:
Detecting hidden termite infestation requires a trained eye. Most pest control firms perform inspections free of charge and will alert the homeowner to any conditions they uncover that are conducive to termite attack.
We are seeing quite a bit of cold injury as a result of the wide fluctuations in temperature, both recently and earlier this year. Cold (and freeze) injury on tobacco and wheat has been common; woody ornamentals, fruit trees and raspberries are showing winter injury. Nutritional problems on greenhouse ornamentals and vegetable transplants have also been common, including nitrogen and phosphorus deficiency on geranium, impatiens, cabbage and tomato, and boron deficiency on purple wave petunia.
Brown spot needle blight was diagnosed on Scots and Austrian pine.
| Princeton | |
| Black Cutworm | 13 |
| True Armyworm | 35 |
| European Cornworm | 0 |