A single case of blue mold was reported in Wayne County on August 24. Diseased plants were scattered
throughout a 2-acre field, and actively sporulating lesions were limited to the upper plant canopy.
A single case of blue mold was reported in Wayne County on August 24. Diseased plants were scattered
throughout a 2-acre field, and actively sporulating lesions were limited to the upper plant canopy.
We will likely face severe risk of blue mold infection in susceptible crops around the state during the week of August 29. Wet weather stemming from Hurricane Katrina could create conditions that will be favorable for the development and spread of blue mold in some areas during the early part of the week. However, heavy rains that are predicted for the middle of the week could also result in washout of spores. We may also see some lodging on saturated soils if high winds occur. In the past, we've also seen some problems with hollow stalk and soft rot of leaves and stems following rainy periods. The bacteria that cause these rots, generally Erwinia spp., are common in our soils and on weeds that grow in an around fields of tobacco. These bacteria enter plants through wounds caused by topping and by damage associated with storms (wind, hail). There are no chemical treatments for these types of rots. To minimize damage, avoid cutting wet tobacco and also consider removing rotten plants from sticks before hanging to limit spread of disease. High relative humidity could cause some problems with barn rots, so ensuring good ventilation once the wet weather passes will be important.
For the latest blue mold status and other tobacco disease information, check the KY Blue Mold Warning System online.
http://www.uky.edu/Agriculture/kpn/kyblue/kyblue.htm
For more information about tobacco pests, visit "Insect Management Recommendations".
The drought stress during and following silking that many areas experienced this season may lead to reduced stalk strength and to stalks rots in corn. Grain fill is a period of heavy demand for photosynthate (the products of photosynthesis), and drought stress at that time can reduce stalk strength. Here is how this happens. Within the plant, biosynthetic metabolic pathways including photosynthesis are sensitive to even mild water stress, so less photosynthate is produced by plants when water becomes limited. Yet plants under water stress will still attempt to fill the grain. However, when photosynthesis cannot meet the demand, the plants draw carbohydrates from the stalk. This weakens the stalk, and it sets it up for invasion by stalk-rot fungi. In addition to the drought stress earlier this summer, the sustained cloudy, wet weather expected this week may favor stalk rots by reducing late-season photosynthesis and favoring fun gal infection.
Several stalk rots are possible under the conditions prevailing this summer: Fusarium stalk rot, charcoal stalk rot, and possibly late-season Gibberella rot. Fusarium stalk rot causes a whitish to light pinkish color in the pith, and no distinctive fruiting bodies are present on the plant. Thus, field symptoms and signs are nondescript, and a field diagnosis is not really possible. With charcoal rot, the pith contains many tiny black fungal structures, giving it a charred appearance. The roots may be rotted and black. Charcoal rot also attacks soybean, and has been diagnosed in several fields in Western Kentucky this season. Corn fields badly affected by charcoal rot may be best rotated to a crop other than soybean. Gibberella stalk rot produces a dark pinkish to reddish discoloration in or on infected stalks. Very tiny, dark purple to black fruiting bodies that can be scraped off with a thumbnail are often produced on stalks affected by Gibberella.
The weather experienced this summer may lead to enhanced stalk rot pressure in some fields. In addition, other factors can increase the risk of stalk rots and lodging. High plant populations are probably top on the list. High nitrogen level can also increase the stalk rot risk. Ear set in a high position on the plant can also increase the risk, by making the plant top-heavy.
While widespread and serious problems with stalk rots seem unlikely at this time, it is always advisable to scout corn for lodging potential as it approaches maturity. This practice helps identify fields that should be harvested early and dried down. A simple way to scout for lodging potential is to walk the field and push plants 12-18 inches from vertical at about chest height. Stalks that don't spring back have the potential to lodge. If 10-15% of the field shows such lodging potential, plan on harvesting the field soon after the grain is physiologically mature (development of black layer, about 30-35% grain moisture).
For information about corn pests, visit
"Insect Management Recommendations".
Glen Roberts, Wayne Co Agent for Ag and Natural Resources reported an infestation of Mexican bean beetles on soybeans late last week. The spiny yellow larvae and coppery brown adults with small black spots, were causing noticeable lacy defoliation of the upper canopy. They may feed on pods but rarely damage developing beans. The larvae should finish feeding soon and will pupate on plant leaves. Adults, the overwintering stage, will continue to feed on soybean foliage prior to leaving the field to find a protected site.
Shake cloth sampling or estimation of percent defoliation can be used to assess the need for control. An average of 16 or more larvae or adults per 4 feet of row from bloom through pod set is the treatment guide line for shake cloth samples. Check ENT 13 2005 Insecticide Recommendations for Soybeans for defoliation charts for the appropriate growth stage and anticipated yield.
Normally a pest of garden beans, this species usually shows no interest in soybeans. For a few seasons in the early 1980's, the MBB fed heavily on soybean along Ohio River counties. The beetles disappeared following the very hot, dry summer of 1983. They had not been reported on Kentucky soybeans since then.
Stinkbugs, especially the green stinkbug, can be serious late season pests of soybean in Kentucky. While this insect is commonly seen on leaves, there are no obvious symptoms to "tip-off" the fact that damage is being done.
Stinkbugs have piercing-sucking mouth parts which they insert into the bloom or developing pods. They then suck the juices and nutrients right out of developing ovaries and seeds, leaving little sign of their presence until the beans are harvested and many shriveled, and or discolored seeds are seen.
Adults are about ½ "long, green (there is also a brown stinkbug but it is not a numerous) insects with piercing-sucking mouthparts. The body is shield-shaped. Nymphs are wingless and variable in color but generally have the same shape as the adults.
In wide row beans use a shake cloth to sample for stink bugs. Shake four row feet (two feet from each row) over the cloth and count the stink bugs that fall on the cloth. An average of 2 or more stinkbugs, (either species, both adults and or nymphs) per 4 row feet indicates a need for control.
For narrow row soybeans, take 25 sweeps per sample site using a 15" sweep net. If you collect an average of 3 or more stinkbugs per site from bloom to mid-pod, or 9 stinkbugs per site during mid-pod to late-pod stages of development, a control measure may be justified.
For more information about soybean pests, visit
"Insect Management Recommendations".
Season-long dry weather, and now several days of hurricane Katrina-influenced wet weather, are favoring two late-season diseases of grapes. After the grape harvest, growers often put away their spray equipment, assuming that disease management tasks are finished for the season. Growers need to be aware that two diseases, downy mildew and powdery mildew, that can take their toll on next year's crop if not controlled for the rest of this season. Both downy mildew and powdery mildew cause defoliation. Leaves covered with mildew are not functioning normally, so diseased plants are effectively defoliated, much the same as if the leaves have died or dropped off. Defoliated vines, (whether from downy mildew, powdery mildew, other diseases, or insect feeding), will have reduced fruit production next year and will not survive winter cold temperatures as well as vines retaining their leaves through late summer and early fall.
Downy mildew. This important disease is present now in many Kentucky vineyards. The fungus causes yield losses resulting from premature defoliation of vines due to leaf and shoot infections, including those that occur after harvest. Premature defoliation is a serious problem because it predisposes the vine to winter injury. In general, vinifera (Vitis vinifera) varieties are much more susceptible than American types and the French hybrids are somewhat intermediate in susceptibility. Highly susceptible cultivars include Catawba, Chancellor, Chardonnay, Delaware, Fredonia, Ives, Niagara, White Riesling, and Rougeon.
Early in the season, infected leaves develop yellowish-green lesions on their upper surfaces and on the underside of the leaves, the fungus sporulates by forming sporangia on numerous branched structures, called sporangiophores, that protrude through stomata. This gives the lesion surface on the leaf underside its characteristic white, downy appearance. Severely infected leaves may curl and drop from the vine. The disease attacks older leaves in late summer and autumn, producing a mosaic of small, angular, yellow to red-brown spots on the upper leaf surface. Lesions commonly form along leaf veins and the fungus sporulates in these areas on the lower leaf surface.
Powdery mildew. If not controlled on susceptible cultivars, powdery mildew disease can reduce vine growth, yield, quality, and winter hardiness. Cultivars of Vitis vinifera and its hybrids (French hybrids) are generally much more susceptible to powdery mildew than are native American varieties such as Concord.
The fungal conidia and mycelia give a powdery or dusty appearance to infected plant parts. Leaves remain susceptible throughout the season. Therefore, a full season fungicide program is generally required for powdery mildew control on susceptible varieties. Leaf wetness is not required for powdery mildew infection; atmospheric moisture consisting of 40 to 100% relative humidity is sufficient for germination of conidia and infection. This is in contrast to downy mildew, that requires free water on the plant surface before the spores can germinate and infect. Thus, powdery mildew can be a serious problem during growing seasons when it is too dry for other diseases such as black rot or downy mildew to develop. Dry, but humid weather for most of the past two months, has been favorable for powdery mildew. Thick canopies that retain high levels of relative humidity are highly conducive to infections.
Disease management. In some years downy and powdery mildews cause post-harvest defoliation well before the onset of cool weather in the fall. Post-harvest early defoliation predisposes the vines to winter injury and reduces fruit set the following season. Thus it is important to maintain protection against foliar infections by these fungi. Since downy mildew and powdery mildew diseases are very different from each other, completely different fungicides are needed for their management. Rates and suggestions combinations of fungicides to use are found in U.K. Cooperative Extension publication ID-94, Midwest Commercial Small Fruit and Grape Spray Guide 2005, available at Kentucky County Extension offices.
Several new insecticides have been recently received federal registration for vegetable crops. These are not in the 2004-2005 Vegetable production Guide. Many of the inseciticides listed below have also received registration on other field and fruit crops.
Acramite 50 WS (bifenazate) has been labeled for mite control on cucurbit (cucumbers, melons, squash, pumpkins and watermelon) and fruit vegetables (eggplant, pepper, and tomato) crop groupings. On approved vegetable crops, only one application per season is permitted. This is a general use insecticide with a 'Caution' signal word and a 12 hour REI for vegetables. This is an IRAC group 25 insecticide.
Concur (imidacloprid-metalaxyl) and Latitude (imidacloprid-carboxin-metalaxyl) have been labeled as hopperbox treatments for sweet corn. These contain imidacloprid as the insecticide to control seedcorn maggot, seed corn beetle, white grub, wireworm, and flea beetle. This is the same active ingredient as Gaucho and at a comparable rate when used at 1.5oz/bu. Gaucho Extra and Prescribe have higher raters of imidacloprid. Imidacloprid is an IRAC group 4A insecticide.
(spiromesifen) has been labeled for mite and whitefly control on cucurbits, fruiting vegetables, leafy greens (lettuce, spinach, etc), brassica leafy vegetables (cabbage, broccoli, cauliflower, collards, mustard greens, etc), and tuberous and corm vegetable (potato, sweet potato, etc.) crop groupings. This is a general use insecticide with a 'Caution' signal word and a 12 hour REI. This is an IRAC group 23 insecticide.
Venom 20 SG (dinotefuran) has been labeled for aphid, whitefly, leafhopper, leafminer, thrips, flea beetle, and Colorado potato beetle control on potato, cucurbit, fruiting vegetables, leafy vegetables and head and stem brassica vegetables (cabbage, broccoli, cauliflower, etc) crop groupings. This is a general use insecticide with a 'Caution' signal word and a 12 hour REI. This is labeled for either soil application or foliar application, but not both, because of the potential resistance development. Growers should not use foliar applications of Actara, Assail, Provado, or Venom following soil applications of Admire, Platinum, or Venom. This is an IRAC group 4A insecticide.
Kentucky cattle should be treated for grubs between July 31 and October 15. During this period the grubs are very small and vulnerable. Complications can occur if treatments are applied later, when the grubs are in esophagus or spinal cord tissue. Use care when treating for cattle grubs. Accurate animal weight estimates allow economical and effective treatment. Over-dosing wastes money and may cause animal stress while under-dosing may result in unsatisfactory control.
Grubs damage muscle tissue along the back line of cattle and cut holes in the hide to breathe. The result of their handiwork isn't visible until February or March but now is the time to apply the preventive treatment that will keep them under control.
For more information livestock pests, visit "Insect Management Recommendations".
Recent samples in the Diagnostic Laboratory have included downy mildew, frogeye leaf spot, sudden death syndrome and potassium deficiency on soybean; black shank, hollow stalk and soreshin on tobacco.
On fruit and vegetable samples, we have diagnosed brown rot and scab on peach; common bean rust and Fusarium root rot on bean; powdery mildew and the virus complex on pumpkin; and root knot nematode, early blight and stinkbug injury on tomato.
On ornamentals and turf, we have seen black root rot on pansy; Pythium and Rhizoctonia root rots and manganese deficiency on chrysanthemum; Cercospora leaf spot on hydrangea; Ascochyta dieback and Alternaria leaf spot on clematis; Botryosphaeria canker on ash and dogwood, as well as Phyllosticta leaf spot on dogwood; bacterial scorch on oak; Cytospora canker on willow; summer patch on bluegrass; and brown patch on fescue.
UKREC-Princeton, KY, August 19-August 26, 2005| Corn Earworm
| 55
| European Corn Borer
| 1
| Southwestern Corn Borer
| 33
| Fall Armyworm
| 35
| | |
View Princeton trap counts for the entire 2005 season at - http://www.uky.edu/Ag/IPMPrinceton/Counts/2005trapsfp.htm
Fulton County trap counts are available at -http://ces.ca.uky.edu/fulton/anr/Insect%20Counts.htm
For information on trap counts in southern Illinois visit the Hines Report at - http://www.ipm.uiuc.edu/pubs/hines_report/comments.html The Hines Report is posted weekly by Ron Hines, Senior Research Specialist, at the University of Illinois Dixon Springs Agricultural Center.
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