Many scouts and consultants are reporting declining square retention even when no or below threshold numbers of plant bugs are detected. Reports of malformed squares (extra bracts and extruding reproductive structures, see picture below) are being reported from many fields. Many malformed squares are caused by physical damage from insects (possibly due to heavy thrips infestations this year), but can occur due to adverse weather conditions affecting meristems. Typically, the lower fruiting branches are where most four-bract squares occur. Four-bract squares are more susceptible to shedding from insect damage from the fourth bract providing an opening for insects to enter a young square. Additionally, any square malformity (including four-bract squares) can cause shed. Why are there more four-bract squares this year? Most affected cotton was planted from May 10-25 and experienced high temperatures in the upper 90’s, low temperatures in the upper 70’s for two and a half weeks the first of June. Microscopic squares begin to form as early as the two leave stage (as many as 40 days prior to seeing a pinhead square). Any stressed experienced during this period (temperatures, thrips, drought, etc) can cause malformed squares. Four-bract squares can be found every year. The last year where we had higher than average four-bract squares was 2007. During that year early heat and drought peristed through the growing season and where four-bract squares were monitored, ~60% eventually aborted. This year the heat and dry weater has subsided, but I still would not have much hope of keeping malformed squares on the plant.

Chimera, what is that? Chimeras are plant abnormalities that can be confused with nutritional or chemical disorders. “Chimera” is used to describe a single plant with two genetically different tissue types. Leaf variegation (see picture below) is the most common example of chimeras in plant species. The difference in foliage color and the banding of those colors are due to cell mutations in the meristematic tissue. Variegation on an individual stem and not over the entire plant is possibly a chimera and not an abiotic disorder related to plant nutrition or chemical injury. Typically, in cotton you will see this disorder in very low frequency (single plant per several acres). This year with our highly variable weather pattern chimeras are appearing in higher frequency than normal. This abnormality has been observed across multiple varieties in my variety trials. It is not limited to a single germplasm background, but can be seen more in certain vaieties.