People love peppers, and Midwest growers grow a lot of them. The crop is valued at more than $20 million annually in the region.
However, flower thrips threaten pepper yield through feeding on fruit and transmitting pathogens. Thrips populations can be controlled with natural enemies, like minute pirate bugs, but these are often undervalued and compromised by insecticide use.
Arnold Gomez and Ashley Leach of the Ohio State Entomology Department recently did some work evaluating the impact of an IPM program on thrips and natural enemies in peppers. The objective of their study was to evaluate the impact of a multifactorial IPM program in pepper on flower thrips density, natural enemy density and marketable yield.
They noted thrips management in the Midwest relies on insecticides – but reflective mulches and reduced fertility have shown potential as complementary cultural controls.
In their study, different combinations of insecticide use (weekly or untreated), mulch (black mulch or diamond reflective mulch) and fertility rates (unfertilized, sufficient rates of NPK or 1.5 times rates of NPK) were evaluated.
Two flowers per plant were randomly selected and examined for thrips and minute pirate bug densities over eight weeks. At the end of the season, yield was assessed on three harvest events following USDA standards.
What did the research team find? When looking at the effect of insecticide, mulch and fertility on thrips, fewer thrips were observed on plots with weekly insecticide treatments, diamond reflective or no mulch and were unfertilized. More thrips were observed on plots with the untreated control, black mulch and high or sufficient fertility rates.
When looking at the interaction of mulch and fertility on minute pirate bugs, the biocontrol, these natural enemies were most abundant on plots with black/diamond reflective mulch paired with high/sufficient fertility. Fewer were found on unfertilized plots with no mulch. (Insecticide had no impact on the minute pirate bugs.)
As for the interactions of mulch, fertility and insecticides on yield, harvested yield was the highest with diamond reflective mulch combined with either high or sufficient fertility rates, regardless of the insecticide program. Unfertilized or untreated plots without mulch had the lowest yield.
Gomez and Leach noted previous studies showed that mulch and fertility independently influence thrips populations in peppers, but their integration with chemical controls in an IPM framework is understudied.
“While no interaction between these factors was observed, significant independent effects were found – insecticide use, reflective mulch and no fertilizer reduced thrips densities,” they reported.
Ultimately, the best outcomes were observed in pepper plots with diamond reflective mulch and reduced fertility rates which supported thrips’ natural enemies and achieved highest yields. Using these methods may help complement chemical control for thrips management in Midwest pepper production.
