Stink bugs can be difficult for growers to manage because they are highly mobile, feed on more than 200 cultivated and noncultivated hosts, and tend to be highly aggregated.
To meet the unusual challenges posed by this pest complex, growers need to be aware of alternate stink bug host plants.
These resource patches may act as stink bug sources and sinks over the course of the year.
Agricultural entomologists generally make crop-specific recommendations for managing insect pests, but the stink bug complex requires an integrated approach that includes consideration for the whole farm or farm scape as it relates to habitat suitability at a given time.
Research entomologists at Clemson University and the University of Georgia investigated the distribution of stink bugs across commercial cotton fields from 2007 to 2008.
To describe these distributions, researchers sampled weekly – starting at first bloom – using 20 bolls and 50 sweeps per acre with a sweep net.
Results showed that both stink bugs and internal feeding symptoms to quarter-sized cotton bolls occurred near field edges (within 100 feet of the border) at least one week before appearing in the interior portions of the field. Unfortunately, it was difficult to predict where stink bug infestations or damage would appear in subsequent weeks.
One notable exception was a field that was only 300 feet wide but more than one-half mile long. In that case, the damage was extremely unpredictable because the apparent “edge effect” extended throughout the field.
That one exception notwithstanding, the prior occurrence of damage in the field edges gives savvy pest managers an opportunity to suppress these populations before they spread and damage other parts of the field.
Researchers in Georgia recently examined how adjacent crops – including corn, peanuts, and soybeans – affected stink bug damage and fiber quality in cotton fields. From the third through the sixth weeks of bloom, 20 quartersized cotton bolls were examined weekly from rows 1, 10, 20, and 40.
At the end of the year, representative cotton plots from these same locations were mechanically picked, and the cotton was ginned and classed to better understand changes in fiber quality. Results clearly showed that boll damage, seed cotton yield, gin turnout, fiber color, and overall lint value were negatively affected in the first 10 to 19 rows from adjacent peanut and soybean borders.
Generally speaking, lint in the infested areas classed one color grade worse than the field average; the overall lint value of the cotton harvested from the edges adjacent to peanuts and soybeans was one-third less valuable than cotton harvested 20 rows or more from the same crops.
Interestingly, cotton planted adjacent to early-planted corn did not suffer yield or fiber quality penalties. Regardless of adjacent crop, there were no differences in damage, yield, or fiber quality when comparing row 20 with row 40.
These data are compelling because corn is a good stink bug host early in the year. It appears that bugs leaving the early-planted corn bypassed the pre-bloom cotton in search of more suitable hosts, such as the blooming soybeans and peanuts.
There are several schools of thought on how to best utilize knowledge of stink bug farmscape ecology when sampling and integrating management tactics for stink bugs in cotton.
From a sampling perspective, pest-management professionals should target their initial scouting efforts to field edges and borders adjacent to hosts with a similar or slightly earlier maturity.
From a management perspective, growers should attempt to spatially separate cotton fields from other plant-crop hosts with similar maturities.
Experts generally agree that stink bugs are strong fliers and some individuals will eventually find these isolated fields, but populations forced to disperse longer distances will be diluted over a larger geographical area while experiencing increased mortality from predation and desiccation.
In cases where spatial isolation is not practical, the data suggest that infield border sprays and border vegetation manipulations (i.e., regular mowing and removal of weeds to prevent seed production) may be appropriate.
Well-timed border sprays should be considered anytime that aphid, white fly, and spider mite outbreaks are a concern, because natural enemies that inhabit the interior of the field will be conserved. Growers who choose to treat field borders other than cotton should be aware that insecticides labeled for use on cotton may not be labeled for use on other crops.
Finally, some producers report that they are able to suppress serious damage to cotton with trap crops, planting a few rows of a highly attractive and earlier maturing host (e.g., soybeans) with the intent to spray the trap crop only before the stink bugs move into the cotton. Research on the efficacy of these management techniques is ongoing.
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