Kansas Phytopathological Notes: 1950

Abstract

As usual the weather was a very important factor in the development, distribution, and severity of crop diseases. Rainfall during June and July 1949 was above normal in most parts of the state, especially in some western counties. This produced early germination and lush fall growth of volunteer and early-sown winter wheat. Such wheat became very heavily infected with leaf rust during October and November. The combination of too much fall growth and heavy leaf rust infection rapidly depleted the top-soil moisture and weakened the plants. This favored injury from low temperatures, and large acreages of wheat in the western third of the state died during the ensuing winter. Rainfall was deficient in nearly all parts of the state during the winter and early spring of 1950. The droughty conditions continued during April, May, and June, the period of rapid growth and fruiting of the small grain crops. As a consequence of these conditions there were extremely light infections of all of the ordinary spring diseases of cereal crops such as the rusts, powdery mildew, Septoria leaf blotch, Septoria glume blotch, black chaff, basal glume rot, and scab. This was in sharp contrast with 1949 when a wet spring season favored about the heaviest infections of most of the foregoing diseases ever observed. For example the estimated loss from leaf rust of wheat (Puccinia rubigo-vera tritici) was 10 percent in 1949, the second highest on record, but was only a trace in 1950. In many localities only scattered uredia of leaf rust could be found in 1950 where extremely heavy infections had occurred in 1949. Infections of all of the other rusts of small grains also were very light in 1950. Stem rust of wheat (P. graminis tritici) occurred only as traces and could not be found in many fields. It is worthy of note, however