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Welcome to the first issue of North Carolina Pest News for 2007. North Carolina Pest News is a newsletter published in electronic form by the Departments of Entomology and Plant Pathology at North Carolina State University, and contains up to date information on the status of disease and insect pests in North Carolina from Extension specialists in the two departments. Steve Toth, Extension Entomologist and Associate Director of the Southern Region Integrated Pest Management Center, is the editor of the newsletter.
From now until the middle of September, new issues of North Carolina Pest News will be available every Monday morning at 8:00 a.m. via electronic mail to county Extension agents, University specialists, and others. By Monday afternoon, the newsletter will be available on the World Wide Web at the following location: http://ipm.ncsu.edu/current_ipm/pest_news.html.
We hope that North Carolina Pest News will meet your individual needs for information on the occurrence of diseases and insect pests in North Carolina. Please direct any suggestions or comments to Steve Toth (Steve_Toth@ncsu.edu).
From: Jack S. Bacheler, Extension Entomologist
We entomologists are skilled at explaining insect pest outbreaks -- during and at the end of the growing season. In hindsight, the causes of last year’s insect problems make sense. Although many interrelated factors impact the severity of upcoming “pest years” -- such as pest survival during the winter, the abundance and quality of nearby crops and weed hosts during the spring and early summer months, and the development of the cotton crop -- weather appears to tie these factors together. And with weather predictions on a farm or countywide basis often unreliable just a few days in advance, forecasting weather patterns that might impact insect levels weeks or months in advance are virtually worthless, especially in the Southeast. Additionally, all of our major insect pests -- thrips, bollworms, stink bugs, cotton aphids, spider mites, and others -- undergo several generations on other hosts before moving into cotton, making early predictions even less reliable. However, a few observations may be in order.
Thrips levels are almost always higher and more damaging in the Carolinas and Virginia than elsewhere in the Cotton Belt. This is, in part, due to our slower seedling “grow off” conditions and high ratio of surrounding weed and small grains thrips host vegetation to our small (14-acre average) field size. Unfortunately, both 2005 and 2006 were rough thrips years, primarily due to moderate to high thrips levels and poor seedling “grow off” conditions. Unfortunately, this situation is more the rule than the exception in this area. Behind the seed treatments Gaucho Grande, Cruiser, Avicta, and Aeris, plan on a foliar spray targeted at the first true leaf stage or at 3 weeks after planting (whichever comes first, unless cotton is planted after about May 20). With Temik at the 5 pound rate per acre, a foliar spray can often be avoided with adequate soil moisture.
Behind seed treatments, we often see higher levels of cotton aphids and spider mites than following Temik use.
Plant bugs are often kind to producers during the pre-bloom period (we have averaged approximately 3 to 8 percent treated acreage for plant bugs over the past 6 years), but they can be a scattered headache in post-bloom Bt cotton lines, particularly in our far-eastern counties. Both 2003 and 2004 witnessed moderate to high plant bug levels during the early boll set period in many areas. These tiny bugs were not as bad in 2005 and 2006. Weekly square retention counts should define most potential problem fields up to about a week or two beyond bloom initiation. Plus, they’re easy to do. The crushing or cutting of quarter-sized bolls is probably best correlated with treatment need in the post bloom period for both plant bugs and stink bugs, though monitoring “dirty blooms”, visual observations for adult/nymph plant bug ratios, sweepings and drop cloth sampling are also helpful.
Stink bug damage in 2004, in both conventional and on Bollgard cotton, was far and away our earliest and highest on record (I have been at North Carolina State University for 30 years). Stink bugs were also no picnic in 2005 in many areas of the state. Thankfully stink bug damage in general across the state was low in 2006. With our ever-higher adoption of Bt cotton -- more than 95 percent in 2006 -- we can probably count on the bug complex to continue to account for most of our late season boll damage. Being hard to effectively control with pyrethroid insecticides, brown stink bugs can complicate insecticide choices. No matter what 2007 has in store, we need to be paying much more attention to the bug complex in our Bt cotton. Additionally, as Bollgard II varieties become more widely planted in 2007 and beyond, our expected lack of treatment for caterpillars in all but a few circumstances will likely result in an even greater potential buildups of bug pests. Adequate sample sizes, a lot of interior boll examinations, and green versus brown adult stink bug ratios are a must in Bt cotton fields, especially during weeks 3 to 6 of the bloom period. Fortunately, the three or so applications typically sprayed on conventional cotton usually keep stink bug and plant damage to bolls low, although this was not always the case in 2004 through 2006. On the positive side, it appears that, on the average, a single stink bug damaged boll only accounts for about 1/3 as much yield loss as a bollworm damaged boll in North Carolina. Unfortunately, cotton fields with final year end boll damage of 20 to 30 percent were fairly common in 2004 and in 2005. That’s a pretty big hit. Pyrethroid insecticides are the best choice if green stink bugs predominate. If brown stink bugs make up a significant part of the stink bug mix, consider Bidrin with or without a pyrethroid insecticide in the tank.
Bollworm moth levels have seesawed up and down for the past 7 years here until 2003, when both 2002 and 2003 were rough bollworm years. The 2004 season showed only moderate bollworm levels. In 2005 the flight was both very late and exceptionally light, while 2006 was about average. Although bollworm damage to Bollgard cotton fields has averaged approximately 1 percent from 1996 to 2006, replicated tests show that a foliar application for stink bugs with either Orthene or Bidrin just prior to or during the initial 10 days or so of the moth flight can increase boll damage by bollworms by approximately three-fold, with proportional losses in yields. This will not likely be the case with Bollgard II cotton. Widestrike lines typically provide intermediate bollworm control between Bollgard and Bollgard II varieties.
Other caterpillars, such as fall and beet armyworms, European corn borers, and loopers continue to cause only minimal damage, even in conventional varieties, although fall armyworm damage to bolls was moderate in some eastern North Carolina counties in 2004 and was also found in scattered cotton fields in 2005 and in 2006. Unlike their Bollgard predecessor, Bollgard II and Widestrike varieties show high resistance to both armyworm species and loopers.
Upcoming weather patterns during upcoming crop year will essentially determine the timing and intensity of our potential 2007 insect outbreaks. As a general rule, North Carolina’s cotton crops fare worse with both insects and yields during “droughty” years. As of this late mid April date, we have a moisture deficit of over 4 inches throughout much of our cotton production region. Although meteorologists have difficulty in predicting weather patterns more than about a week in advance, sound insect and plant monitoring and well-timed sprays where needed play a major role in making the best of what nature has in store for us in 2007.
From: Stephen R. Koenning, Extension Plant Pathologist, and E. James Dunphy, Extension Crop Scientist
Did 2006 set the stage for a rust epidemic in 2007? No! As far as we can tell, there is little active soybean rust in the U.S. at this time. The field with rust in Texas has been plowed up and planted to grain sorghum. Kudzu was frozen back as far south as Tampa, and there is relatively little kudzu south of Tampa. The only site that is now positive for soybean rust is near Jacksonville Florida.
Soybean rust was able to reach further North in 2006 with positive finds on soybean in Virginia, Kentucky, Illinois, and Indiana. Spores were also detected in seed bins in Iowa. More counties were positive for soybean rust in 2006 but yield loss was estimated only from Florida (1.0 percent), Louisiana (1.0 percent), Alabama (1.0 percent), Georgia (2.5 percent), South Carolina (1.5 percent), Texas (0.10 percent), and North Carolina (0.13 percent).
A sentinel plot system, similar to what we used in 2005 and 2006, will be used for early detection of Asiatic soybean rust during the 2007 growing system. Currently soybean sentinel plots have been planted in Mississippi, Texas, and Florida and more will be planted throughout the South in the next several weeks. Soybean rust is being monitored on kudzu at the current time. You can obtain information on the sentinel plot system on the web at http://www.sbrusa.net.
Sentinel plots have been funded by the U.S. Department of Agriculture (USDA), United Soybean Board (USB), North Central Soybean Research Program (NCSRP), and local soybean producers associations (including North Carolina) for 2007. A total of 35 states and five Canadian provinces will have sentinel plots for monitoring soybean rust in 2007. Data from all sentinel plots will be uploaded to the USDA Legume Pest Information Platform for Extension and Education (PIPE) web site.
There are three important functions of the sentinel program for monitoring soybean rust. The primary function is to serve as a warning network for tracking the spread of the disease in North American soybean production regions. For this reason and because the pathogen can only over-winter in subtropical regions, southern and Mississippi Valley states have higher numbers of sentinel plots relative to their soybean acreages than states in other regions. The second function is to quantify the timing and amount of spore production in over-wintering and growing season source areas, an important input for the soybean rust aerobiology prediction system. A third function of the sentinel plot system is to collect data for epidemiological research.
From: Randy Weisz, Small Grain Extension Specialist
Freezing temperatures can be harmful to young wheat. Damage to leaf tips and heads has been reported across the state. Damage should be clearly evident about the end of next week. For pictures of current wheat damage and a complete guide to freeze damage to wheat, see the April 12 update on freeze damage to small grains or the North Carolina Small Grains Production website at http://www.smallgrains.ncsu.edu/.
My best advice is:
From: Kathleen A. Kidd, Plant Protection Section, Plant Industry Division, North Carolina Department of Agriculture & Consumer Services
I am looking for small grain fields with populations of cereal leaf beetles that I can collect. I am primarily looking for eggs, but would also like to collect larvae and adults. Adults will be collected by sweep net, and eggs and larvae by hand. I am looking for parasitoids for our biological control program. If you have cereal leaf beetles or know of a grower with them, contact me by telephone at 919-233-8214 or by electronic mail at Kathleen.Kidd@ncmail.net.
From: Stephen B. Bambara and Christine A. Casey, Extension Entomologists
Tent caterpillars have been webbing the crotches of certain trees like crabapple and cherry for several weeks. When they are done feeding, the last instar caterpillars leave the nest and seek pupation sites some distance away from the original tree. If found in a garden or when crossing the road, they pose no threat to other plants or automobiles.
The recent weeks of cold weather have slowed down the pace of insects despite what appeared to be an early start. Carpenter bees, paper wasps, aphids, lady beetles and other “critters” commenced their springtime activities, dropping back to low gear for a while. Other insects are still lying in wait for the right time. The late freeze has also burned back the tender new foliage of many plants. It is uncertain how this may affect insects that depend on this plant growth stage being available at a specific time. Since my crystal ball slipped out of my hands and broke the last time I dusted it off 15 years ago, I can't make any predictions. I won’t be surprised; however, if there is a flurry of insect activity during the next two weeks. Only Time will tell, and he's not talking.
Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age or disability. North Carolina State University, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.
Last modified on April 16, 2007 by Stephen J. Toth, Jr.