COTTON THRIPS AND PLANT STAND DENSITIES

All cotton fields in our area have been planted and “capped off”. A majority of them have plants at the cotyledon stage. I have not seen much thrips damage yet. In the Texas high plains, thrips are considered a key pest in pre-squaring stage cotton (David Kerns et. al., Developing an action threshold for thrips in the Texas high plains, 2010). The currently accepted action threshold for thrips is 1 thrips per true leaf, but based on recent findings, these AgriLife Researchers suggest that it may be necessary to update thrips thresholds in cotton to the following levels: cotyledon stage = 0.5 thrips per plant, 1 true leaf = 1 thrips per plant, 2 true leaves = 1-1.5 thrips per plant, and 3-4 true leaves = 2 thrips per plant. Cotton plants are most susceptible to thrips damage at the cotyledon stage and this susceptibility decreases as the cotton plant grows. Another caveat is that whole-plant samples placed into jars containing alcohol have been shown to be a more accurate sampling technique than simple visual inspections. Usually, warm weather allows cotton seedlings growth to compensate for thrips damage. The weather forecast calls for the next couple of days below average temperature and then return to warm conditions. I do not expect thrips to be a problem in El Paso and Hudspeth Counties this year, but it is wise to monitor the crop for thrips levels. There are some plants showing sandblast damage; especially in sections of fields with soils high in sand content.

            In recent years, I have observed that cotton fields in our region have an average plant stand density around 55,000 plants/acre, with fields planted as low as 30,000 plants/acre and as high as 63,000 plants/acre. Yesterday, I obtained four samples per farm from 4 cotton farms. For each sample I counted the number of plants in 11 feet of row. The first 3 farms had plant stand densities falling within expectations: 41,818; 59,459; and 63,828 plants/acre. However, the last farm sampled now holds the highest plant stand density that I have observed so far: 105,981 plants/acre. It is generally accepted that 2-4 plants/foot of row maximizes yields. This is equivalent to 26,136 - 52,272 plants/acre in fields with 40 inches between rows. Most cotton fields that I have visited this season have been planted at 40 inches between rows and a few at 38 inches. It seems to me that some growers could gain substantial savings in seed costs by planting at recommended densities.