Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 12/1/2001
Publication Date: N/A
Interpretive Summary: The tarnished plant bug (TPB) is a key pest of Mid South cotton causing tremendous losses in yield. In pre-squaring cotton, these bugs prefer to feed in the terminal portions of plants. Their injury to this portion of the plant can delay squaring, flowering and, ultimately, crop maturity. Given adequate time and resources, the crop can recover from terminal injury with no reduction of yield; however, in northern portions of the Mid South growing season is shortened, and time for compensation is limited. Consequently, crop delays can result in costly yield penalties. Injury from TPB feeding in plant terminals can result in multiple terminals per plant, a condition sometimes referred to as "crazy cotton." The objective of our experiment was to investigate crop injury and recovery following pre-square injury from TPB nymphs of various ages. We found that differences in terminal damage between untreated plants and plants injured by TPB were not as great as in other studies where 98% terminal damage from one adult TPB/plant was reported. However we showed that injury from feeding by large immature TPB was sufficient to result in a significant crop delay as measured by average maturity date. Early season observations indicated that injury resulting from small immature TPB treatments was not as severe as that observed in medium or large bugs. Most of the injury occurred within the first two days after release when the small nymphs apparently were not able to injure the plants as severely as the medium and large nymphs. We showed that the size of plant bug nymphs infesting plants affects severity of injury, feeding by large immature TPB significantly delayed maturity by six days, which can result in significant monetary losses in those areas with shorter growing seasons.
Technical Abstract: Cotton at the 2-leaf stage was manually infested with small (1st-2nd instar), medium (3rd instar) and large (5th instar) tarnished plant bug nymphs in a field study in Northeastern Arkansas. One lab reared nymph was released per plant on 23 May (15 DAP). Plants were monitored weekly through cutout using COTMAN with end of season final mapping conducted using COTMAP. At 18 days after treatment the medium and large bug treated plants had significantly fewer leaves and fewer actively growing terminals compared to the untreated check and small bug treatments. A significant reduction in no. of squaring nodes per plant prior to first flowers in the medium and large nymph treatments indicates that injury was more severe than that associated with the small nymphs. There were significant differences in yield during the 1st and 2nd harvest; however, no differences were observed during the 3rd and 4th harvest. Results from mean maturity date calculations indicated a significant delay of 6 days associated with injury from large nymphs.