Role of Reproductive Diapause in the Adaption of the Tarnished Plant Bug (Heteroptera: Miridae) to Its Winter Habitat in the Mississippi River Delta

Abstract

Reproductive diapause in the tarnished plant bug, Lygus lineolaris (Palisot de Beau- vois), was studied by dissection of Þeld collected adults or adults reared from Þeld collected nymphs in 1999 Ð2001 in Washington County near Stoneville, MS. The critical photoperiod for diapause induction was 12.5:11.5 (L:D) h, or 12 September. This photoperiod was also near the day-length at which new generation adults produced in late winter and early spring became reproductive. 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, and new generation adults were produced on winter hosts by the second or third week in March. Overwintering adults also were collected in January 2002 from plant debris not associated with any winter host plant. Most of the females overwintering in plant debris had mature eggs at the end of January, approximately 1 month later than overwintering females collected from winter hosts. This indicated than the adults from plant debris were in a different state of diapause, because they did not overwinter on a food source and matured reproductively at a later date. The winters of 1998 Ð1999 and 1999 Ð2000 were mild, whereas in the winter of 2000 Ð2001, winter host plants were killed or stunted by cold weather. Diapause in plant debris in the winter of 2000 Ð2001 was probably favored, because these adults would be more likely to survive until suitable host plants were available.