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Serving Princeton, Rosewood, Brogden, E. Johnston Co., W. Wayne Co., North Carolina |
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johnston co agriculture report8 August 2007 — Tobacco Disease Identification As the growing season progresses, tobacco diseases are becoming more prevalent in Johnston County tobacco fields. It is important for tobacco growers to accurately identify diseases that affect tobacco. Late in the season, it can become complicated to differentiate between diseases in the field. Therefore, it is critical to know the signs and symptoms of the various diseases that affect tobacco. It is especially important to know the difference between Granville wilt and Black Shank. Varieties differ in their resistance to these two diseases and management practices like crop rotations and chemical controls also differ for these two pathogens. It is even possible to have both diseases in the same field, as has been observed in some fields this year. Black Shank This disease seems to be the most prevalent disease problem in Johnston County tobacco at the present time. Black Shank is caused by the fungus Phytophthora parasitica var. nicotiana which lives in the soil. This pathogen thrives when soil moisture levels are high. You may think that we have not had high soil moisture this year and you would be correct. However, we have evidently had enough soil moisture to cause some black shank problems. The primary symptoms of Black Shank include rapid yellowing and wilting of the entire plant followed by death. A dark brown to black lesion usually appears on the stalk near the ground. When stalks are split, the pith (tissue in the center of the stalk) is often separated into discs resembling a stack of dinner plates. This last symptom is easier to find on a plant that is showing mild to moderate symptoms. Dead plants will often have complete decay in the pith and no discs will be found. Granville Wilt This disease is also present in many Johnston County fields. Granville wilt is caused by a bacteria (Ralstonia solanacearum). The bacterium is spread by anything that moves infested soil or water. Major means of spread include water and farm vehicles moving from field to field. Machines like automatic toppers that cut the stalk can easily spread the bacteria from infected plants to healthy plants. The first symptom of Granville wilt is wilting on one side of the plant. As the disease progresses, the entire plant usually wilts and death generally follows. It is common to find some roots that appear rotten, mushy and slimy. Like black shank, the stalk usually turns black at the ground level. However, splitting stalks does not normally reveal discing in the pith as with Black Shank. Fusarium Wilt Some local fields are showing symptoms of Fusarium wilt. This disease is much less common than either Granville wilt or Black Shank. This fungal disease causes slow yellowing and drying of the leaves. Symptoms are usually more pronounced on one side of the plant. Leaves may not wilt at first, but those on affected sides of the plants are usually stunted. The top of the plant may be drawn toward the diseased side. Wilting eventually occurs and upper leaves have a bronze or even purplish cast. On the affected side of the plant, wood beneath the outer bark has a uniform chocolate brown discoloration. Such discoloration can also be seen in the midribs of affected leaves. The one-sided wilting and the vascular discoloration can cause confusion between Fusarium wilt and Granville wilt. However, roots on plants affected with Fusarium wilt are normally much healthier than plants with Granville wilt. The coloration of the leaves and the lack of slimy mushy roots are an indication of Fusarium wilt. Fusarium wilt is frequently accompanied by root-knot nematode infection. In some fields, this disease is appearing along truck middles which were not treated with fumigants. It is important to note the presence of these diseases late in the season. Proper identification will be helpful for planning future rotations and variety selections. Especially for Black Shank, it is important to note the variety that is planted in the field. Some tobacco varieties (CC 27, Speight 168, NC 71, NC 297) are immune to race 0 Black Shank while having varied levels of partial resistance to other races. Other varieties (K 346) have only partial resistance to all races of Black Shank. For assistance with tobacco disease identification, please contact Bryant Spivey at the Johnston County Extension Center at (919) 989-5380. Fish Gotta Breathe All animals need to acquire oxygen by some means from their environment, even fish. Fish have gills, which take in water and remove oxygen to allow the fish to breath. Without the oxygen in the water fish can drown. When the oxygen levels get low in a fishpond, many problems can arise. The damages will depend on how low the levels get and for how long they stay low. Low levels will cause fish to eat less, have poor growth rates, increases susceptibility to infectious diseases, or even death by suffocation. In nature the oxygen levels are high enough to prevent fish kills. There is an equal balance of plants, wildlife, and water movement to create the adequate amount. In pond type situations there is usually more fish then the pond can support, no water movement, or too many aquatic weeds. In the summer time, low levels of oxygen will normally happen at night or early morning. When the water temperature goes above 80° F fish kills can become more prevalent. Drastic climate changes, such as cold rainfall or hale on a hot day, can lower the oxygen to dangerous levels. During these conditions, it is important to keep the oxygen levels in line. To balance out the oxygen levels, water movement is a must. Fountains, pumps, aerators, bubblers, or different users can provide water movement and the addition of oxygen. Another benefit is aquatic weed control. Many pond plants would prefer still waters to those, which bump and shift them around. More information can be found on the Southern Regional Aquaculture Center’s website at www.sepond.com, in an article by Craig Tucker, entitled “Pond Aeration." The Johnston County Cooperative Extension has agents who can provide advice and management tips specific to our area. They can be reached at 919-989-5380. Bollworms on Cotton Although the bollworm moth flight is now present throughout North Carolina, you wouldn’t know it in some areas due to the low moth numbers. Trap numbers are “all over the board” this week, generally far lower at this time compared with any of the past three years. Given the increased corn acreage and hot dry conditions that we normally associate with high levels of bollworm moths, we expected much higher moth numbers and associated bollworm problems than has been the case. The underground bollworm pupal stage seems to have the capacity to remain in that state during dry conditions, and then emerge as moths after a penetrating rainfall. Also, both bollworm moths and stink bugs often gravitate toward areas that have received higher moisture levels, so watch for higher levels of both of these pests in ranker cotton and lower levels in cotton which has begun to “cut out. Threshold levels of bollworms that have been found this past week have been mostly developing on small bolls in both conventional and on Bollgard cotton, and less in the terminals. Stink Bugs on Cotton Stink bugs also seem to be giving us a significant break so far this year. Most consultants and producers are reporting internal boll damage levels of less than 10 percent, though some fields have higher damage levels, such as our stink bug threshold test in Wayne County where a 20 percent threshold treatment was met yesterday. Unfortunately, another situation has presented itself that cotton producers hate to see in early August called premature “cut out.” In cases where “cut out” and dry weather have conspired to throw off small bolls, most of the remaining bolls may be too old and big for stink bugs to damage. That is 3.5 weeks old or about 1 and one fourth inches in diameter. If this situation is observed, be sure to raise the internal boll damage threshold accordingly. For example, if half of the bolls are in this “bug safe” category, the 10 percent threshold may be raised to 20 percent. Beet Armyworms on Cotton An odd occurrence of high levels of beet armyworms feeding on Bollgard II cotton was pointed out by a consultant this past week in Nash County. They were apparently feeding on a lot of adjacent pigweed. Past experience with beet armyworms on Bollgard II cotton suggests low armyworm survival when beet armyworm egg masses are deposited directly on the cotton by adult females. Bollgard cotton, however, provides only limited protection from beet armyworms, and conventional cotton none. This might be a good year to look out for beet armyworms, especially in the “all too many” cotton fields with high Palmer pigweed populations. Fortunately, we now have larvicides that are very effective against beet armyworms. Soybean Rust Update Asiatic soybean rust has been confirmed on soybeans in Louisiana, Texas, Oklahoma and Arkansas during the past two weeks, but there have been no new finds east of the Mississippi River. The closest rust to North Carolina confirmed to date remains in Florida, which was reported on July 16. The Marion County site is approximately 490 miles from Johnston County and puts us in the low risk category currently. To date, Asiatic soybean rust has been found on soybeans or kudzu in five counties in Alabama (one on soybeans), two counties in Arkansas (both on soybeans), 10 counties in Florida (two on soybeans), five counties in Georgia (all on kudzu), six parishes in Louisiana (five on soybeans), one county in Mississippi (kudzu), two counties in Oklahoma, and 21 counties in Texas (20 on soybeans). Storms moving rust from one state to another remains our biggest concern, so growers should continue to monitor for confirmed cases. 2007 HAY GROWING SEASON ASSESSMENT As most of you are aware, much of North Carolina has experienced severe drought over the past summer. These conditions follow an Easter freeze that had devastating effects on the hay crop. While there have been some spots that have received adequate rain, the statistical data available statewide shows substantial deficits in precipitation. As a result of the Easter freeze and the rainfall shortages, many of the state’s livestock producers face shortages in hay supplies. Many have enough hay for their immediate needs, but that is only because they are already beginning to feed what they would otherwise save for the late fall and winter. North Carolina Cooperative Extension and North Carolina Department of Agriculture and Consumer Services have developed a questionnaire for assessing the county level hay needs of livestock producers and the supply of hay across our state. Many hay producers have been affected by the spring freeze and the drought conditions that are currently affecting our state. Your participation in the survey is invaluable in providing officials with realistic data to use in assessing the hay availability and needs across NC. 1.Do you grow your own hay or forage for livestock? Y_____ N____(skip to 4) Your participation in this survey is greatly appreciated. Please send a reply to Johnston County Cooperative Extension Service, Ron Hughes, 2736 NC 210 Highway, Smithfield, NC 27577, by August 10. You may also email ronald_hughes@ncsu.edu or call (919) 989-5380
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