Author
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Snodgrass, Gordon |
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Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 10/9/2002 Publication Date: 4/30/2003 Citation: Snodgrass, G.L. 2003. Role of reproductive diapause in the adaptation of the tarnished plant bug (Heteroptera; Miridae) to its winter habitat in the Mississippi River Delta. Environmental Entomology. 32: 945-952. Interpretive Summary: The tarnished plant bug is a serious pest of many crops grown in North America. In the mid-south it is primarily a pest of cotton in which it is controlled exclusively with insecticides. It has developed resistance to pyrethroid insecticides and has tolerance to many of the organophosphate, carbamate, and cyclodiene insecticides. It can still be controlled in cotton with insecticides, but control is expensive and more than one application is frequently needed. In areas where the boll weevil has been or is being eradicated, many of the benefits from eradication will be lost if insecticides have to be used to control plant bugs. Non-insecticidial control measures for plant bugs are needed in order to develop an integrated control program for plant bugs in cotton. The biology of the plant bug must be known in order to develop these alternative control measures. One important part of this biology is reproductive diapause, since it allows plant bugs to survive as adults during the winter months. In the present study, reproductive diapause was studied in the field and laboratory over a three-year period at Stoneville, MS. Diapause was found to be caused by decreasing day length, and nymphs were found to be the sensitive stage. Diapausing adults began to be produced in the third week of August and the critical photoperiod ( the day length at which 50% went into diapause) was found to be 12.5 hours which occurred on 12 September. Intensity of diapause varied. Part of the population remained active on winter hosts in December and January, and broke diapause in mid- to late-December. Other adults were found in plant debris not associated with winter host plants. These adults broke diapause about a month later than those found on winter hosts. In mild winters nymphs can be found on winter hosts beginning in January, and plant bugs take advantage of the weather and hosts to produce a new generation by mid-March. In colder winters there is no advantage to having part of the population reproductive by the end of December. This study showed how well plant bugs were adapted to survive winters in the mid-south and provided basic information very useful to the development of control measures designed for use in the fall, winter, and spring. Technical Abstract: Reproductive diapause in the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), was studied by dissection of field collected adults or adults rearing from field collected nymphs in 1999-2001 near Stoneville in Washington County, MS. The critical photoperiod for diapause induction was approximately 12.5:11.5 L:D h, or 12 September. Overwintering adults collected from winter host plants in December 1999 and 2001 began breaking diapause in the second and third weeks of December at a day length near 10:14 L:D h. Most of the overwintering females collected on winter host plants had mature eggs by the end of December in both winters. Overwintering adults were collected in January 2002 from plant debris not associated with any winter host plant. Most of the females overwintering in the plant debris had mature eggs at the end of January, about one month later than overwintering females collected from winter hosts. This indicated that the adults from plant debris were in a more intense state of diapause, since they did not overwinter on a food source and matured reproductively at a later date. Having part of their population reproductive by the end of December allowed tarnished plant bugs to produce an early new generation in the winters of 1998-1999 and 1999-2000. In these mild winters, host plants were not killed or stunted by cold weather. In the cold winter of 2000-2001, reproduction by tarnished plant bugs overwintering in a more intense state of diapause in plant debris was probably favored, since these adults would be more likely to survive until suitable host plants were available. |
