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Insect Management

SSP has funded numerous studies aimed at assessing insecticide toxicity to non-target organisms, and addressing the issue of managing resistance. SSP has also funded studies dealing with insect thresholds, including: development of specific thresholds for key pests, use of multi-pest or cumulative thresholds, and adjusting thresholds in Bt cotton. Others have assessed different management strategies for key non-Lepidopteran insect pests as well.

Although not the subject of SSP research per se, we asked growers who is it that typically monitors for pests on their farm and what factors they consider when choosing insecticides. We presented growers with a list of factors and asked them how important each was in their insecticide choices. For each item, growers circled a number from 1 (not at all important) to 4 (very important). Growers were also presented with a list of thresholds for making decisions about pesticide treatments and were asked to what extent they rely on each one. Growers responded by circling a number from 1 (not at all) to 4 (very much).

Given their importance in the southeastern United States, we included questions on whether growers managed two specific pests, stinkbugs and thrips. We provided a list of monitoring techniques and asked growers how often they rely on each one. Growers responded by circling a number from 1 (never) to 4 (always). We also presented a list of factors that could affect when they control for stinkbugs and asked to what extent each one influenced their decisions. Growers responded by circling a number from 1 (not at all) to 4 (very much). We took a similar approach to managing thrips and growers again responded by circling a number from 1 (never) to 4 (always).

Results

Monitoring

Grower responses for who monitors for pests are presented in Table 5. Most pest monitoring is performed by the farm owner (50.2%), followed by Private Consultants (43%), University/County Agents (14.5%), farm staff (10.9), and Other (3.4%). Note that the sum of all responses exceeds 100%, indicating that pest monitoring is often done by several parties.

Choosing pesticides

Reponses to items about the importance of various factors in grower insecticide choices are shown in Table 6. Specifically, the figure shows the combined proportion of growers who said each factor was very important and moderately important.

Table 6 - Importance of Factors in Grower Pesticide Choices

Growers said that effectiveness was the most important factor they consider in choosing pesticides. Nearly nine in ten growers (89.4%) said it was very important, while another 10.2% said it was moderately important. “Cost” and “toxicity to applicators/workers” were identical when looking at the proportion of growers who say this was very important. The proportion was substantially higher for “cost” when both moderately and very important responses are considered together. Less than half the growers said toxicity to beneficial insects was very important, but when responses are combined with those who deem this moderately important the portion encompasses a substantial majority (88.5%).

Threshold Use

Grower responses to questions about the pest thresholds they rely on appear in Table 7.

Table 7 - Importance of Thresholds for Decisions About Pesticide Treatments

Multi-pest thresholds are relied on (moderately to very much) by 61.7% of growers. Cumulative thresholds were used by 60.9% and published tobacco bud worm/cotton boll worm thresholds for conventional cotton by 71.7%. In Bt cotton, 78% of growers reported relying on increased thresholds for fall army worm either moderately or very much and 80.6% said they increased thresholds, when beneficial natural enemies are present.

Stink Bugs

According to our survey 83.7% of growers say they typically manage stinkbugs. Figure J shows the proportion of growers who said they use various mechanisms when monitoring for stink bugs. Specifically, the figure shows the proportion who rely on each either often or always.

Figure J - Monitoring Stink Bugs

The most frequently used method for determining stink bugs levels is evaluating feeding damage on bolls. This approach is used either always or often by 90.2% of respondents. Shaking plants over a beating cloth was also relatively common (70.0%) Net sweeps were much less widely used (28.4%) followed by evaluating the number of bugs in a sorghum (or other) trap crop (18%), and the Florida stink bug trap (8.2%).

Table 8 presents grower responses on their decisions about when to control for stink bugs.

Table 8 - Decisions About When to Control for Stinkbugs

The most frequently used threshold for stink bugs was 10-20% damaged bolls. This approach influenced 83.6% of growers’ decisions either moderately or very much. More than half (55.6%) said that finding 1 bug per 6 row feet was an important factor affecting their decisions about stinkbug control.

Thrips

The great majority of growers (92.7%) typically manage thrips. Figure K shows the proportion of growers who said they use various strategies to manage thrips. Specifically, the figure shows the proportion who use each strategy either often or always.

Figure K - Managing Thrips

The most frequently used technique was systemic insecticide in-furrow (often or always used by 80.5% of respondents), followed by treated seed (65.8%), and foliar insecticides (55.7%).

Analysis - Thrips

With over 91% of United States grown cotton infested in 2005104 thrips are an important pest. Hence, research into their management is clearly justified. Thrips are reported to cause over $15 million in losses 32,103 while planting and rescue treatments cost about $8/A and the cost to manage were $9.75/A. Banks5 describes early season insect control via an in-furrow systemic as a BMP, but Herbert et al.37 found that all commonly used treatments were equally effective against thrips.

Analysis - Stink Bugs

As discussed previously, 47% of U.S. cotton acreage that is infested is infested with stink bugs with an estimated control cost of $5.43 per acre.104 The 6 most eastern cotton-producing states in particular have a significant problem with stink bugs, given the dramatic adoption of Bt cotton and resulting changes in pesticide use. As a consequence, over 87% of survey respondents said that they manage stink bugs. Grower awareness and use of stink bug action thresholds, including those that have been studied with SSP funding, appears to be both extensive and sophisticated.

High levels of stink bug monitoring indicates that growers appreciate the economic benefit of the practice. This is consistent with observations 66 that scouting and spot spraying was economically valuable in that it reduced fuel expenditure, repairs and maintenance by 27% or more.

Conclusions

In addition to considering insecticide toxicity when choosing pesticides, Southeastern growers have substantially adopted published thresholds and monitoring techniques for key insect pests. Similarly, since 43% of respondents report that consultants monitor pests on their farms, it appears that research leading to these pest management tactics has diffused throughout the cotton industry. Many studies have shown that selection of pesticides that reduce natural enemy populations is ultimately a costly practice for farmers in many crop systems. In addition, numerous workers have documented the economic benefits of using scouting and thresholds. Therefore, we conclude that SSP research in this area has achieved its goal of improving grower profitability.

SSP research on thrips management has focused primarily on use of systemic insecticides using either in-furrow, seed treatment, or foliar applications, on precision placement of insecticides near seed rather than in-furrow in hill drop plantings, and to a lesser extent, assessing cotton varieties with an eye towards thrips resistance. All of the approaches have been widely adopted with the exception of near seed placement of insecticides. This probably reflects lack of equipment for this purpose. 69 Low use of thrips resistant varieties likely reflects lack of availability of varieties that are truly resistant.

Thrips management approaches studied with SSP funding also appear to be in widespread use. Without SSP-funded studies, crop loss from thrips would likely be greater as would be the effect on grower profitability. No specific questions were asked about chemical controls of stink bugs. However, many materials trials have been supported by SSP. This fact, combined with the high value placed on research based information on crop protection chemicals (See Cotton Education section below), leads to a logical conclusion that SSP funding has helped growers do a better job with stink bug management.

 

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