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Nematode Management

Nematode management is an issue of increasing concern for growers in many states. One study 30 found that nematodes overall caused $400 million in losses in 2004. The author pointed out that Root Knot nematode has been the predominant species, causing an estimated $214 million in losses in 2004, but that Reniform nematodes were becoming increasingly important, especially in some southern states, and it alone is estimated to have caused $116 million in losses. Other reports 5 suggest that Reniform nematodes have cost the cotton industry over $1 billion over the past 5 years. SSP has funded a significant number of studies addressing various aspects of nematode management.

In addition to asking whether or not growers typically manage nematodes, we also presented growers with a list of practices for managing nematodes and asked to what extent they rely on each one. For each item, growers circled a number from 0 (not at all) to 4 (very much).

Results

Our results show that a majority (52.3 %) of growers manage nematodes. There is significant variation by state however. Table 4 shows the proportion of growers in each state who said they typically manage nematodes. The proportion is highest in South Carolina (69.7%) and Georgia (59.3%).

Table 4 - Nematode Management by State

Grower responses to nematode management practices are presented in Figure H. The figure shows the practices we surveyed and the proportion of growers who say they rely on each one either moderately or very much.

Figure H - Nematode Management Practices Relied On by Southeastern Cotton Growers

Rotating with nematode-resistant crops (e.g. soybean, corn and peanut) was the most heavily relied on management technique. More than three-quarters of growers (77.4%) said they relied on this method moderately or very much. Nearly two-thirds (64.2%) relied on nematode resistant varieties and more than half (54.9%) used production practices that promote earliness. Sampling each field for nematodes, planting winter cover crops that do not encourage nematodes and applying soil fumigants in the furrow were all relied upon by slightly less than 40% of respondents. Slightly more than one-quarter (26.8%) reported planting in last year’s row middles, while even fewer (23.7%) incorporate poultry litter to deter nematodes.

It is encouraging that such a high percentage of southeast cotton growers appear to be avoiding continuous cotton. The overall benefit of rotations to non-host crops such as peanut and corn is well understood19. although, as noted elsewhere in this report, a cotton/soy rotation, at least prior to current high soybean prices, has been non-profitable.86

Grower preference for currently available nematode resistant/tolerant varieties 47,48,76 is also positive. Although adoption was low in our study, soil fumigants at planting have also been shown to improve cotton yield and net returns. 89,52

Conclusions

Southeastern growers appear to have benefited from SSP-supported studies of nematode management by rotation to non-host crops, using nematode resistant/tolerant varieties, and adopting planting practices to promote earliness. Relatively low use of soil fumigants and poultry litter amendments may again be due to state-by-state differences in pest pressure, or satisfaction with extent of control provided by cultural practices such as crop rotation and selection of resistant varieties. Differences in Extension program emphasis may also explain why more growers region-wide have not adopted the technique of planting into last year’s row middles. The surprisingly large percentage of growers that said that they select cotton varieties with nematode resistance appears to be a ready audience for such cotton. Future research to document the current extent of resistance and to identify or develop additional resistant germplasm would be valuable, especially if resulting varieties are high yielding, and tolerate reniform nematodes.

 

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