Cotton Pest Management Strategies and Related Pesticide Use and Yield

The use of pesticides is an integral part of pest management for cotton (Gossypium hirsutum L.) production. However, in response to environmental and public safety concerns, alternative pest management strategies focused to reducing pesticide usage is becoming more important. The objective of this study is to evaluate various pest control practices as substitutes or complements to pesticides in maintaining or enhancing cotton yields. A tobit model is estimated using data from the 1994 USDA Cropping Practices Survey of cotton producers in the six major cotton-producing states to assess the effects of pest control strategies on yield and pesticide use in cotton production. Statistical tests were performed to assess the significance of differences between (i) high and low integrated pest management (IPM) fields, (ii) high and low pesticide use fields, and (iii) high and low yield fields, in terms of yield, pesticide use, use of individual IPM practices, and use of tillage and irrigation. High IPM fields had significantly higher yield, lower yield risk, and higher use of pesticide treatments than low IPM fields. High pesticide use fields generally used more IPM practices and had higher yield and lower yield risk than low pesticide use fields. High yield fields had lower yield risk, used significantly more IPM practices, but also used more pesticide treatments per acre than low yield fields. Research QuestionCotton producers generally rely on pesticides as the most effective and efficient method of pest management. In response to consumer and environmental concerns, use of alternative pest management strategies to reduce reliance on pesticides are becoming increasingly important as available registered pesticide uses become more limited. Some pesticide reduction policies are based on the widely held hypothesis that integrated pest management (IPM) strategies or practices reduce pesticide use. The primary objective of this study is to evaluate various pest management practices as substitutes or complements to pesticides in maintaining or enhancing yields. Literature SummaryIn some cases, IPM adoption by farmers has led to an increase in pesticide use. In Mississippi and Georgia, net returns per acre are higher and less variable for IPM users, than for nonusers, with increased pesticide cost per acre with each increase in level of IPM use. High users of IPM had higher yields and net returns than the low users, but high user expenditures for pesticides were higher in Mississippi and Texas by $18 and $10 per acre, respectively. Summarizing the economic effects of IPM programs is difficult, however, because of differences in locations, time periods, measures of pesticide use, and practices considered in the studies. Study DescriptionThe data used in the analysis are from the 1994 USDA Agricultural Cropping Practices Survey of cotton producers. The data include six major cotton production states: Arizona, Arkansas, California, Louisiana, Mississippi, and Texas, which represented 75% of the upland cotton acreage planted in 1994 in all cotton-producing states. Use of IPM practices is examined by comparing “high-IPM” fields, those fields on which an above average number of IPM practices are used, with “low IPM” fields, those receiving a below average number of IPM practices. Mean values of the six states, i.e., the number of IPM practices used, are used to allocate data observations to high and low IPM fields. Statistical tests were performed to assess the significance of differences between high and low IPM fields in terms of yield, pesticide use, use of individual IPM practices, and use of tillage and irrigation. T-tests were used to test the significance of differences in means and chi-square tests were used to test the significance of differences in proportions. A similar analysis was performed for fields with high and low pesticide use in terms of the number of pesticide treatments and fields with high and low yields, using the six-state average (treatments or yield) to allocate the high and low fields. Applied QuestionsHow did high-IPM fields compare with low IPM fields in terms of yield, yield risk, and pesticide use? High-IPM fields averaged five IPM practices compared with two practices on low-IPM fields. High-IPM fields had significantly higher yields, 885 lb/acre versus 494 lb/acre for the low IPM fields. Yield risk faced by cotton producers, as measured by the ratio of the standard deviation to the mean yield, was lower for high-IPM fields. However, high-IPM fields also had greater use of pesticide treatments, 11 versus 4.5 treatments respectively. Significantly higher proportions of high-lPM fields had herbicides, insecticides, and fungicides applied. High-IPM fields were more likely to be tilled more frequently, receive irrigation, and less likely to be classed as highly erodible land. How did high-pesticide-use fields compare with low-pesticide-use fields in terms of yield, yield risk, and pesticide use? For the six states, fields with higher-than-average pesticide use averaged about five IPM practices, compared with nearly three practices for low fields. Nearly 100% of the high-pesticide-use fields reported using insecticides as compared with about only half of the low-pesticide-use fields. The same proportion of fields, 96%, reported using herbicides. With the exception of crop rotation, significantly more high-pesticide-use fields used the IPM strategies to reduce pest resistance, protect beneficials, pheromones for controlling or monitoring pests, and applied herbicides based on weed infestation in previous year, type of weeds in current year, and computer mapping (see Fig. 1). Yield was significantly higher and yield risk significantly lower for high pesticide use fields. Also, significantly more high pesticide use fields were irrigated and significantly fewer were classed as highly erodible land. Fig. 1Proportion of fields using IPM, high versus low pesticide use fields. How did high yield fields compare with low yield fields in terms of yield, yield risk, and pesticide use? Fields with higher-than-average yields, based on the average yield for the six-state, averaged 1,037 lb/acre as compared with only 354 lb/acre on low-yield fields. High-yield fields used significantly more IPM practices and had lower yield risk, but also used more pesticide treatments per acre. Ninety percent of the high-yield fields received insecticide treatments versus only 49% of the low yield fields. There was no significant difference in use of herbicide. With the exception of crop rotation, high yield fields used a significantly higher percentage of each IPM practice (Fig. 2). Fig. 2Proportion of fields using IPM, nigh versus low yield fields. How did specific practices or strategies affect yield and pesticide use? Results indicated that use of IPM strategies generally increased yields but tended to be used as complements to pesticide use, rather than substitutes. Alternating pesticides to reduce resistance increased yield by 44 lb/acre of lint cotton and increased pesticide use by 0.7 treatment/acre. Crop rotation increased yields by 73 lb/acre with a negative but insignificant effect on pesticide use. Use of independent consultant services increased yield by 98 lb/acre and use of pesticides by about one treatment. Use of strategies to protect beneficial insects reduced yield by 42 lb/acre and had a negative-but-insignificant effect on pesticide use. Use of pheromones increased yield by 51 lb/acre but also increased pesticide use by two treatments. Use of computer mapping to determine pre-emergence herbicide treatments increased yields by 41 lb/acre with no significant effect on pesticide use. RecommendationsFor cotton farmers, we recommend generally increased adoption of IPM practices to enhance yields and lower yield risk or yield variability. This recommendation is based on our results which reflect the weather conditions and other factors affecting yield and yield risk in 1994. We recommend increased research on IPM practices that can substitute for pesticide use while maintaining or enhancing yield.