Significance Of Planting Date For Tarnished Plant Bug Management In Cotton

TYLER TOWLES, DON COOK AND WHITNEY CROW

MISSISSIPPI STATE, MISSISSIPPI

With planting season right around the corner, it is important to discuss the role that planting dates play in cotton from an arthropod pest management standpoint. I am specifically referring to tarnished plant bugs, as they can be extremely destructive from the time we set the first square until after cutout. To make matters worse, tarnished plant bugs are not cheap insects to manage. Just like many other important decisions that cotton producers make, one of the most important decisions we can make for plant bug management happens before we even open the seed bag. Planting dates have long been altered to minimize the time that high insect pest pressure coexists with susceptible crop stages. If the weather during planting season cooperates and planting is not significantly delayed, this is an easy way to lessen the load on cotton budgets later in the growing season.

Hunter Lipsey, a Ph.D. student located at the Delta Research and Extension Center, has been studying the effects that planting dates play in relation to tarnished plant bugs in cotton. To address this topic, we conducted experiments in Stoneville on both non-ThryvOn (Deltapine 2333) and ThryvOn (Deltapine 2328) cotton varieties. Cotton of each variety was planted in mid-April, early May, mid-May, and early June during the 2024 growing season. Half of the plots were managed season-long for tarnished plant bugs (treated), while the other half was left untreated so that comparisons could be made (untreated). Cotton was scouted for tarnished plant bugs from squaring until insecticide termination. Scouting was conducted using sweep nets until bloom and drop cloths for the remainder of the season. If plots met or exceeded the economic threshold for plant bugs, insecticide applications were applied. Each insecticide application consisted of Transform tank mixed with acephate so that insecticide applications could be standardized.

We observed that when cotton was planted in either mid-April or early May, the tarnished plant bug economic threshold was not reached until the second week of bloom in either the non-ThryvOn or Thryvon variety. Inversely, when planting occurred in mid-May or early June, the tarnished plant bug threshold was exceeded between the first and second week of squaring. This meant that when we planted earlier, we saved several insecticide applications and set many of our high-value positions during low plant bug pressure.

Non-ThryvOn Treatments

Figure 1 shows that in the untreated plots, yield was maximized when planting occurred in mid-April, with the early May planting date close behind. However, we saw significant reductions in yield when planting occurred in mid-May and later. Where plant bugs were managed in the treated plots, there were no significant differences in yield regardless of planting date. However, for every 15 days that cotton planting was delayed, an extra insecticide application was needed to maintain similar yields. For example, cotton planted in mid-April required 2 insecticide applications for tarnished plant bugs compared to 6 insecticide applications for early-June cotton. This data indicates that the difference in April-planted cotton and June-planted cotton is 4 insecticide applications and ~$85 in insecticide costs.   ∆

TYLER TOWLES, DON COOK AND WHITNEY CROW: Mississippi State University