Comparing Prophylactic Versus Threshold-Based Insecticide Programs for Striped Cucumber Beetle (Coleoptera: Chrysomelidae) Management in Watermelon

Abstract

In cucurbit crops such as watermelon, implementation of integrated pest management (IPM) is important due to the high reliance on bees for fruit set, along with mounting evidence of the risks of insecticide use associated with pollinator health. Yet, IPM adoption, on-farm pesticide use behaviors, their costs, and impacts on the primary insect pest (striped cucumber beetle, Acalymma vittatum F.) are poorly known in one of the key watermelon-growing regions, the Midwestern United States. To better understand how to implement IPM into watermelon production, we assessed pest management practices on commercial watermelon farms using 30 field sites in Indiana and Illinois over 2 yr in 2017 and 2018. Across all sampling dates, beetles never crossed the economic threshold of five beetles/plant at any farm and most were maintained at densities far below this level (i.e., <1 beetle/plant). Moreover, we documented a wide range of insecticide inputs (mean ca. 5 applications per field per season; max. 10 applications) that were largely dominated by inexpensive foliar pyrethroid sprays; however, insecticide application frequency was poorly correlated with pest counts, suggesting that most of these applications were unnecessary. We calculated that the cost of the average insecticide program far exceeds the cost of scouting, and thus IPM is estimated to save growers ca. $1,000 per field under average conditions (i.e., field size, insecticide cost). These data strongly indicate that current management practices on commercial farms in the Midwest would benefit from implementing more threshold-based IPM programs with potential increases in both farm profitability and pollination services.

Synergism between local‐ and landscape‐level pesticides reduces wild bee floral visitation in pollinator‐dependent crops

“…By leveraging our results, growers could adopt an integrated pest and pollinator management (IPPM) program, reducing pesticide hazards without sacrificing yields (Egan et al, 2020;Ternest et al, 2020). Since the method of pesticide application and chemistries varied across our study systems, crop-specific IPPM programs will need to be designed.…”

“…Within farms, pollinators are exposed to combinations of pesticides when insecticides and fungicides are co-applied to manage pathogens and insect pests (Schmuck et al, 2003). Pesticide co-application is a common practice on farms because pesticides are inexpensive compared to potential yield losses (Ternest et al, 2020). Thus, adding an 'insurance' insecticide when spraying fungicides is a conservative strategy to mitigate pest threats.…”

Supplemental forage ameliorates the negative impact of insecticides on bumblebees in a pollinator-dependent crop

“…The challenge will be to find opportunities for reducing pesticide inputs while maintaining farm productivity. This seems possible both in watermelon [ 36 ] and farming systems more generally [ 55 ] using IPM and related approaches aimed at increasing sustainability. Achieving this balance is particularly critical in pollinator-dependent crops, like watermelon, where pest management and pollinator conservation are central, but sometimes conflicting, goals.…”

“…In addition, the pyrethroid lambda-cyhalothrin (Warrior II with Zeon Technology ® at 140.2 ml ha −1 ) was applied to the watermelon plants using an electrostatic sprayer four weeks post-transplant. This combination of neonicotinoid at planting, followed by a subsequent foliar pyrethroid spray, is a commonly used insecticide regime targeting striped cucumber beetles ( Acalymma vittatum ) and other insect pests by watermelon growers in the midwestern USA [ 36 ].…”

Socioecological Factors and Farmer Perceptions Impacting Pesticide Use and Pollinator Conservation on Cucurbit Farms

“…Farmers use pesticides to reduce insect damage to crops, however, they have nontarget impacts on insect pollinator health (Biddinger and Rajotte, 2015;Egan et al, 2020). Thus, farmers growing pollinatordependent crops are faced with a potential tradeoff among two key production inputs, pollination and pesticides, and comanagement of pests and pollinators is needed to promote yields (Ternest et al, 2020). In developed countries, farmers are generally aware of the ramifications of direct spraying of insecticides on pollinators (Dicks et al, 2013;Bhattacharyya et al, 2017) and often refrain from doing so (Hevia et al, 2020;Nalepa et al, 2020;Park et al, 2020).…”