Cotton Insect Situation

Pre-season
March 11, 2002

Blake Layton
Extension Cotton Entomology Specialist

Area Specialists:
Dr. Gordon Andrews
Dr. Scott Stewart
 Dr. Mike Williams

Cotton Insect Hotline: 1-800-445-4931

Advanced Cotton Pest Management Short Course: The Advanced Cotton Pest Management Short Course is scheduled for March 20 of 2002. Note that the program has been shortened to one day this year. The purpose of this training is to provide detailed information on the biology, management, and control of the insects, diseases, and weeds that affect cotton. The training is approved for consultant license renewal, Research and Demonstration license renewal, and CCA Training Credits.

Advanced Cotton Pest Management Short Course
Begins: 8:30 AM, March 20, 2002 (registration begins at 8:00 AM, $10.00)
Ends: 4:00 PM, March 20, 2002
Location: Bost Building, Theater, Mississippi State University

Program Outline:    8:30 - 9:30 AM        Weed Science Session 
                                  9:45 - 11:45 AM      Plant Pathology Session
                                  1:15 - 4:00 PM         Entomology Session

Subscription Renewal Cards: Please complete and return the enclosed card if you would like to continue receiving the Mississippi Cotton Insect Situation Newsletter in 2002. Also, if you know someone who would like to have their name added to the newsletter mailing list, they can do so by calling 662-325-2085, or by sending their name and address to: Cotton Insect Situation Newsletter, Box 9775, Mississippi State, MS 39762-9775.

Review of 2001 Cotton Entomology Season: Each year each cotton-producing state prepares a summary of the cotton insect season for inclusion in the Proceedings of the Beltwide Cotton Conference. These summaries provide a historical record of cotton insect pressure. A copy of the summary for last year in Mississippi is enclosed. One can also access summaries for past years by going to the MSUCARES Cotton Insect Web Site (www.msucares.com/insects/cotton) and selecting "Annual Summaries of Mississippi’s Cotton Insect Season" from the menu at the bottom of the page.

 

Review of the 2001 Cotton Insect Season In Mississippi

Blake Layton
Extension Cotton Entomology Specialist

Mississippi: Mississippi cotton producers planted approximately 1.7 million acres of cotton in 2001, which was a substantial increase over the 1.3 million acres planted in 2000. Approximately 80% of the crop was planted to transgenic Bt varieties, with Paymaster 1218

BG/RR, Deltapine 451 BR, and Stoneville 4892 BR being the dominant varieties.

Active Boll Weevil Eradication Programs (BWEP) were underway in all areas of the state. The Hill Region, which contained approximately 554,000 acres, was in its fifth year of BWEP. The South Delta Region, consisting of approximately 276,000 acres, was in its fourth year, while the approximately 839,000 acres in the North Delta was in the third year of BWEP. This was the final year for the BWEP in the Hill Region, but growers in this region voted to enter a ten-year Boll Weevil Eradication Maintenance Program. The annual assessment fee for this maintenance program, which is not to exceed $12.00 per acre, will be used to complete the eradication effort, service residual debt from the original program, and to run an effective eradication maintenance program. Growers in the South Delta are scheduled to vote on a maintenance program in 2002.

The winter of 2000-2001 was relatively severe and low winter temperatures greatly enhanced Mississippi’s boll weevil eradication efforts. As a result, boll weevil populations were extremely low throughout the state in 2001. As of July 4, only 7,252 boll weevils had been captured in the state, 99.3% less than were caught by this date in 2000. Eighty-seven percent of the fields in the state remained boll weevil free by July 4, and only 3.4 % of the acreage in the state had been treated for boll weevils. By October 24, a total of 344,000 boll weevils had been captured in the state, which, despite the increased acreage, was 87% less than were caught by this date in 2000. Fifty-one percent of the fields in the state remained boll weevil free for the entire growing season, and only 32% of the state’s cotton acreage received treatments of ULV malathion for control of boll weevils. Treated fields received an average of 3.8 malathion sprays per acre, which is an average of approximately 1.2 malathion sprays per acre statewide. No yield losses were attributed to boll weevils in 2001.

Thrips and cutworm pressure on seedling cotton was relatively light in 2001, but there were a number of unusual early season pest problems. Grasshoppers were observed causing stand reduction, and even stand destruction, in a few reduced tillage fields, especially fields that had been planted to soybeans in 2000. False chinch bugs (Nysius spp.) were also a problem in some reduced tillage fields but were less common than they had been the previous year. Increased adoption of herbicide tolerant cotton varieties and reduced tillage systems is the primary reason for the increased number of "unusual" early season pest problems.

Saltmarsh caterpillars were the most unusual pest problem of seedling cotton, especially in the Delta Region. Many fields of seedling cotton experienced infestations of late-instar saltmarsh caterpillars, which migrated from field borders. Plants younger than the three-leaf stage often suffered complete defoliation and even destruction of the terminal bud due to the feeding by these caterpillars, and a number of fields were treated for this pest to prevent stand loss. Plants that had developed to the five-leaf stage or beyond usually were able to tolerate the defoliation without sustaining serious damage. In some cases, re-infestation from field borders resulted in the need for multiple treatments. The growth regulator methoxyfenozide (Intrepid) proved to be one of the more cost-effective treatments for this pest.

Cotton aphid populations were unusually low in 2001, and very few fields received a treatment for aphids. These low aphid numbers are attributed, at least partially, to the relatively low number of malathion treatments that were made by the BWEP before July 4. In past years regions that received multiple applications of ULV malathion before July 4 often experienced high aphid populations and/or required more treatments for aphids. Furadan was again available for use against aphids under a Section 18 Emergency Exemption, but there was relatively little use of this product because of the low populations. Thiamethoxam (Centric), which was labeled for use against cotton aphids in 2001, provided good control of aphids in fields and trials where it was used.

Early season tarnished plant bug populations were somewhat lower than normal throughout the state. However, the Delta Region experienced heavy infestations of plant bugs during mid and late season, due to heavy immigration into cotton from senescing alternate hosts. Because of the low numbers of boll weevils and the high percentage of Bt cotton, plant bugs were the most common insect pest of Delta cotton in 2001. Some producers applied as many as seven to eight sprays, specifically to control plant bugs, but the average number of treatments applied to control plant bugs in the Delta was approximately 3.7 sprays per field. Plant bug populations were much lower in the Hill Region, where an average of approximately 1.0 sprays was applied to control this pest. Control was often difficult to achieve because of resistance and because many fields developed exceptionally heavy canopies that interfered with spray coverage. Acephate (Orthene) and dicrotophos (Bidrin) continued to be the most effective treatments for plant bugs, but the newly registered thiamethoxam (Centric) also provided good control. Successful control of established, late-season plant bug infestations required the application of repeated, close interval sprays. Despite this unusually heavy plant bug infestation, the yield potential of the 2001 crop was exceptionally high until it sustained heavy late-season weather damage.

Stink bugs continued to increase in importance as a pest of Mississippi cotton because of the reduced spray environment fostered by BWEP and Bt cotton, but they are still a relatively minor pest. Although it was not difficult to find low numbers of stink bugs in most fields, it was relatively uncommon to encounter fields with economically damaging infestations. However, damaging infestations of stink bugs did occur, especially during late season due to immigration from maturing corn and/or soybeans.

With approximately 80% of the crop planted to Bt varieties, tobacco budworm infestations were relatively uncommon, but some non-Bt fields did require treatment for tobacco budworms. Bollworms were much more common, especially in the Delta Region, where corn acreage is more concentrated. Based on results of a statewide survey, Bt fields received an average of 0.8 sprays for control of bollworm/budworm, while non-Bt fields received 2.3 sprays. However, overall heliothine pressure was much heavier in the Delta Region than in the Hills. Bt fields in the Delta received an average of 1.3 bollworm sprays, while non-Bt fields received an average of 3.9 bollworm/budworm treatments. Populations were much lower in the Hills, with Bt and non-Bt fields receiving an average of 0.2 and 0.6 bollworm/budworm sprays, respectively. It is noteworthy that there were many non-Bt fields, as well as Bt fields, in the Hill Region that received no foliar insecticide sprays yet sustained very little insect-induced boll damage. This is evidence of the success of the BWEP, which by eliminating boll weevils, allowed greater reliance on beneficial insects and reduced use of insecticides to control other insect pests.

Armyworms were not a problem in Mississippi cotton in 2001. Beet armyworms were uncommon, and although low numbers of fall armyworms could be found feeding on bolls in some fields, very few fields required treatment. Some late-maturing fields did require treatment for loopers, but this involved a very small percent of total acreage. Damaging infestations of whiteflies were also uncommon, and only a few fields required treatment for spider mites.

As of mid-August, the 2001 crop had developed an exceptional boll load and yield potential was much better than average. However, a prolonged period of unusually heavy rainfall during late August and early September resulted in heavy yield loss. This yield loss was the result of unusually high levels of boll rot and "hard lock". Conditions were so severe that seed sprouting in bolls was commonly observed, and losses to boll rot and "hard lock" exceeded 20 to 30% in many fields. This weather damage was greatest on fields that had begun to open before the rainfall began, and late maturing fields were less affected. Fortunately, after this rainy period subsided, growers enjoyed a favorable harvest season, and little additional weather damage occurred. Despite this severe weather damage, estimated statewide yield is approximately 708 lbs (January, 2002 NASS Estimate), which is higher than the previous two years, but below the five-year average of 761 lbs.

In summary, overall insect pressure was relatively low for the state as a whole, although the Delta Region did experience increased problems with plant bugs and bollworms. Excessive, prolonged rainfall during late season resulted in heavy weather related yield loss in what was otherwise an exceptional crop. Mississippi made excellent progress in its effort to eradicate the boll weevil, but low numbers of this pest are still present in the state. Statewide, insect induced yield losses were estimated at 7.9%, and the estimated average costs of insect control were $95/acre. Overall insect pressure was considerably higher in the Delta Region, with an average cost of $108/acre, than in the Hills where insect control costs averaged $69/acre.

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