Nov. 5-7 Kentucky Turfgrass Council Conference
Categories 3 (Turf and Ornamental), 10 (Demo and
Research), 18 (Golf Course ), 19 (Interiorscape), 20
(Sports Turf)
Holiday Inn University Plaza
Bowling Green, KY.
Credit hours are listed
Nov. 5 Cats 3, 10, 12, 18, 19, 20 4 Hrs
Initial training and testing
Nov. 6 Cats 3, 10, 12, 18, 19, 20 3 Hrs
Nov. 6 (Sports Turf Session) 10, 12, 20 1 Hr
Nov. 7 (Golf Turf Session) 10, 12, 18 1 Hr
Nov. 7 (Turf & Landscape Session) 3, 10, 12 1 Hr
A continuing education meeting is scheduled for November 15 at the Fayette Co Extension Office.
It has been approved for 6 hours of credit in Categories 3 (Turf and Ornamental), 10 (Demonstration and Research), 12 (Pesticide Sales Agent),
18 (Golf Course), 19 (Interior Plantscape) and 20 (Sports Turf). Topics will include greenhouse pest problems. The program begins at 9 AM and
ends at 3:30 PM (local time).
We have received several inquires about numerous, small green spots appearing in cured tobacco. Even though these green spots are being found
at stripping time, they result from infections that occurred in the field just prior to harvest. This is another phase of frogeye leaf spot caused by the
fungus Cercospora nicotianae. The greenspot phase develops when conditions are favorable for the fungus to sporulate and infect foliage a
few days prior to harvest.
Some crops had extensive frogeye development prior to harvest, and in those crops, there could have been opportunities for intensive infections near
harvest, especially where the disease was moving up the plant and high humidity (dew, fog, or rain) occurred a few days prior to harvest.
At harvest time, these green spot areas had incipient infection-the spores had infected and the fungus was colonizing the cells- but symptoms had not
yet appeared. The fungus continued to develop for several days after harvest. During curing, the chlorophyl normally breaks down, but in the infected
cells it fails to break down because the fungus has released a toxin that fixes the chlorophyl, leaving a greenish spot.
I am aware of no treatments or management steps that will remove this green spot after it has formed, but in some years it does decline in intensity with curing time. Rotated fields usually have less frogeye, other things being equal. There is increased potential for damage from green spot with delaying harvest/over-ripe tobacco, rains during harvest, and high humidity during early stages of curing. Also, high nitrogen rate has long been implicated in increased potential for developing frogeye and green spot in tobacco, especially in seasons with highly variable soil moisture yet periods of high humidity late in the season, which we experienced. Frogeye is favored by prolonged periods of wet foliage, so shady sites and bottom fields have greater potential of developing severe levels of disease. No commercial variety is resistant. No fungicide is labeled for frogeye leaf spot control in tobacco, but significantly lower levels of frogeye are often associated with plots treated until topping with either Dithane DF or Acrobat MZ for blue mold control. Hopefully, additional fungicides will become labeled for blue mold that have either improved efficacy on frogeye or allow later applications, or both.
Bt corn has become a common means of controlling damage by borers in late-planted corn in Kentucky. The use of Bt corn can also affect development
certain diseases. Most notably, in fields where high insect activity is expected (seeding after 10-15 May in Western Kentucky, for example), the use of corn
hybrids that express the Bt endotoxin in kernels may reduce Fusarium ear rot and fumonisin contamination in some cases. For more information on this
subject,
see the March 11, 2002, issue of Kentucky Pest News, available online or from county Extension agents.
Many corn producers in Kentucky experienced unusually high levels of stalk rot in 2000. At that time, there was some interest in whether Bt hybrids suffered substantially less stalk rot than non-Bt hybrids. Data collected at that time indicated that the widespread and severe problems relating to stalk rot and lodging were not directly linked to injuries caused by corn borers, although there may have been individual fields that suffered substantial lodging due to insect feeding. The limited data collected then also suggested that Bt hybrids were no less likely to suffer lodging in the absence of significant corn borer damage.
A recently published study by Dr. Gary Munkvold and colleagues from Iowa State University sheds more light on this issue. The results of that study are summarized here.
1. There is no advantage relative to stalk rot control when European stalk borer populations are low. This confirms previously published studies, and it is not a surprising result. Nevertheless, it is important to have evidence that refutes the notion that Bt hybrids are more prone-or less prone-to stalk rot in the absence of corn borers.
2. Under high pressure from European corn borers, the Bt trait events reduced stalk rot damage in certain events but not others. Significant reductions in disintegration of the pith of the stalk were observed from the Bt11 event (Northrup King's Yieldgard®) in all three years of the study. Of the events currently available commercially, two-Bt11 and 176--provided a significant reduction in lodging in at least one year during the study. However, the 176 event (Ciba Seeds Knockout®) resulted in enhanced lodging in one year of the study.
The authors concluded that, "...although specific Bt events in some years may cause reductions in stalk rot, the overall effect of Bt transformation on stalk rot occurrence is highly variable."
Thus, Kentucky producers should continue to use Bt hybrids where appropriate-that is to say, where the insect pressure justifies its use and markets exist for the harvest commodity. Certain Bt events--especially the Bt11 event--may reduce stalk rot and lodging in situations with high corn borer populations. However, these hybrids will not be a "magic bullet" for stalk rot problems.
For more information about corn pests, visit "Insect Management Recommendations".
Green June beetle grubs look like typical white grubs but have a unique behavior that makes them occasional but serious pests in fall and spring forage
seedings. Most white grubs remain below the soil surface where they feed on plant roots. In contrast, green June beetle grubs frequently travel to and
on the surface while feeding on decaying organic matter. The grubs can occur in virtually any field but are most abundant where there is some rotting
hay, silage, or animal manure. Fields under an intensive grazing regime or where poultry litter is spread are at higher risk.
Seedlings are uprooted as the grubs backstroke along, plowing the soil surface. They churn the top 4 inches of soil breaking root- soil contact which kills seedlings, creates dead spots or unacceptably thin stands, and produces bare areas that allow weed emergence. Numbers can be high in established grass or alfalfa fields but the damage potential is not as great.
The green June beetle grub is dirty white with a reddish brown head and legs. They may be found just below the surface in areas where the soil has been disturbed. The grubs typically move on the surface at night but may be forced up by heavy rain or flooding. The presence of 3 to 4 grubs per square foot can disrupt new stands, heavy infestations can have densities of 15 to 20 grubs per square foot. Grubs can move 60 feet or more along the surface in search of higher concentrations of organic matter.
Since green June beetle grubs move to and across the soil surface, they are susceptible to an insecticide application. They tend to die and rot on the surface, which produces a very unsatisfactory situation. In addition, birds feeding poisoned grubs may be poisoned. There is nothing to gain from a treatment at this time.
In Kentucky, green June beetle adults begin to emerge from the soil in late June. The population peaks in the last half of July and most are dead by mid-August. Females lay clusters of about 40 eggs a few inches below the soil surface of soil rich in organic matter. The eggs hatch in about two weeks and the larval stage is present until pupation in late May or early June. The pupal stage occurs in a earthen cell in the soil and lasts 2 to 3 weeks. There is one generation per year.
Unfortunately, it is only when apples cross the
grading line that certain insect problems become
apparent. By then it is too late to correct them. This
fall there have been three insect problems that have
been out of the ordinary - San Jose scale, oriental
fruit moth and codling moth.
San Jose scale: I have been getting a large number of San Jose scale infested apples from multiple orchards across the entire state. It is apparent that this difficult-to-control pest has reached damaging levels in most commercial orchards. The reason for this may be traced back to the loss of Lorsban after bloom and Penncap-M due to the implementation of the Food Quality Protection Act of 1996. These two products were the best materials we had for San Jose scale control.
San Jose scale is little more than a cosmetic defect to the fruit but when large numbers build, it can kill scaffold limbs or even an entire tree. The reason that it is so damaging is that the enzymes it injects while feeding are toxic to the plant. Feeding on young wood or green fruit will leave a characteristic red halo around the scale.
Control of San Jose scale begins with the application of a dormant oil spray. This must be a thorough application covering all parts of the tree. This requires proper pruning to insure the complete spray coverage. Growers have been doing this, and it has not provided enough control. The next step is targeting either the nymphs or crawler stage with an in-season insecticide. We are fortunate to have a new material for scale control on apples and pears. Esteem can be used at either half-inch green to control the nymphs or in late May to control the crawlers. Timing is important to crawler control, so growers must use double-sided tape on infested limbs to monitor for crawler emergence. Diazinon can also be used to control the crawlers, see ID-92 for a complete listing of chemicals.
Oriental fruit moth: We had a situation this season in which a grower was monitoring for codling moth and caught only a few moths the entire year. However, at the end of the year, the number of infested fruit was unacceptable. Although the damage appeared to be codling moth, it turned out to be caused by oriental fruit moth. The types of materials used to control codling moth and oriental fruit moth are the same but the timing for the applications can vary considerably.
Codling moth: In western Kentucky we had a situation this year in which a commercial orchard applied weekly Guthion or Imidan sprays for codling moth throughout the entire season and had high levels of codling moth damaged fruit at the end of the season. There were low trap catches in this orchard throughout the season, as well. This is very similar to what was reported from several commercial orchards in southern Illinois this year. In these orchards, aggressive spray programs with Imidan and Guthion were not effective against codling moth. Fortunately, we have recently gained some new materials for codling moth control, these include Intrepid, Danitol, and SpinTor, Assail, and Esteem.
Crane flies are small to very large flies that resemble
mosquitoes. Several species are active in the fall.
They have the delicate long legs of the mosquito
and one pair of wings. Mosquito wings have small
scales on the wing veins and a long slender set of
sucking mouthparts. Crane flies do not have scaly
wing veins and no long, slender mouthparts. Crane
fly larvae develop in moist soil with abundant
thatch or organic matter. Some species can damage
turf in low, wet areas, or where irrigation is used
frequently. Crane fly adults do not feed on humans
and live for only a few days.
Most people recognize fleas or flea bites but are not
familiar with the small worm-like larval stage.
Several samples of flea larvae have been sent in
during the past few days. They have been found on
bedding or areas where pets sleep. The larvae are
scavengers, feeding on dried blood particles and
debris in the bedding. Eggs and flea pupae also
occur in these places and this is the reason that
sanitation or vacuuming are essential components
of flea control programs.
There have been some frustrating flea problems in barns this year. Wild animals, racoons, etc. can be the source of these problems and a persistent effort is needed to clean them out.
Last week we received an insect sample for a
western KY broccoli field that we identified as
melonworm. This is unusual for two reasons. First,
this is a southern insect that in the past has not
occurred until late in the season in KY and then only
at low numbers. For this reason, melonworm until
now has not been a pest that we needed to control.
Secondly, melonworm is reported to only to attack
cucurbit crops, not cole crops. Melonworm is a light
green caterpillar, with a light green head capsule
and two white stripes on its back. It is primarily a
leaf feeder with cucurbits, but can damage fruit as
well.
Canker diseases caused by fungi may develop in most landscape trees and shrubs. Cankers are localized wounds or dead areas in bark which are often sunken beneath the surface of stems, twigs, and trunks of woody plants. The fungi that cause cankers grow between the tree's bark and the wood, killing the living portion of the bark. Canker diseases often girdle the infected branch and cause the entire branch to die. With important exceptions such as chestnut blight, dogwood anthracnose, pine tip blight, and a few other diseases, cankers rarely kill their host plants entirely. Nevertheless, cankers are difficult to manage and they may impact the aesthetic value of the landscape plant or provide openings for other diseases.
Canker diseases are often more severe when plants are growing under stressful conditions. Common environmental stresses include drought, flooding, unseasonable freezing temperatures, extreme temperature fluctuations, mineral element deficiencies, defoliation, chemical injury, transplant shock, and mechanical injuries. Fungal cankers usually start at a wound or a branch stub, but some fungi may penetrate healthy tissue or begin after a period of time as latent infections already existing inside the plant.
Over the past months and years, cankers of specific crops have been described in this newsletter. Common fungal cankers in Kentucky include:
For canker disease management, integration of several cultural practices may be needed.
Recent diagnostic samples have included anthracnose stalk rot on corn; Lepto leaf spot and anthracnose on alfalfa; charcoal rot on soybean; storage molds on curing tobacco; Phomopsis blight on grape; anthracnose on raspberry; sooty blotch/flyspeck on apple; Pythium root rot on pansy; Botryosphaeria canker on ash; black root rot on holly; bacterial leaf scorch on oak and planetree; Microdochium blight and anthracnose on pumpkin; root knot nematode on tomato; and Phytophthora fruit rot on cucumber.
NOTE: Trade names are used to simplify the information presented in this newsletter. No endorsement by the Cooperative Extension Service is intended, nor is criticism implied of similar products that are not named.
Lee Townsend
Extension Entomologist
