MESSENGER ^® is the first commercialized product from a new class of chemistry called harpin proteins. Harpin Ea, the active ingredient in MESSENGER, elicits an induced plant response resulting in pest management and growth promotion effects. Over 100 field trials evaluated MESSENGER on cotton during the 2000 season. Effects of MESSENGER application timing on cotton growth, yield, and nematodes are the focus of this report. Seven MESSENGER application regimes were tested from combinations of five foliar application timings: two-leaf (2-L), pinhead square (PHS), two weeks after pinhead square (PHS+2), first flower or first bloom (FB), and three weeks after first bloom (FB+3). In nematode trials, treatments of MESSENGER alone and aldicarb (Temik ^® ) followed by MESSENGER were assessed for influence on yield and nematodes. All trials included an untreated control. Measurements included stand counts, plant mapping at three weeks after first bloom and at harvest, leaf tissue analysis for extractable nutrients at first bloom and six weeks after first bloom, nematode density and species, and lint yield and fiber quality.

Based on field trials conducted during the 2000 season and in previous years, MESSENGER appears to have significant beneficial effects on cotton yield and on cotton pests such as nematodes and potentially boll rot. MESSENGER timing field trials documented positive cotton yield effects. Across 20 timing trials, median cotton lint yield increases above the untreated control ranged from 11 to 96 lb lint/acre. Three MESSENGER timings (PHS, FB, FB+3; PHS, PH+2, FB, FB+3; and 2-L, PHS, PH+2, FB, FB+3) resulted in a median yield increase ranging from 83 to 96 lbs/acre of cotton lint above the untreated control. At some locations throughout the cotton belt, considerable yield increases were observed including a 230 lb/acre increase in cotton lint at one location. However, variation in yield response was observed. In many areas of the cotton belt, the 2000 production season was characterized as having severe environmental conditions. Influence of high temperature, low soil moisture, potassium availability, and time interval between MESSENGER applications on the timing trial results is discussed. In the nematode trials, treatments of MESSENGER alone and aldicarb followed by MESSENGER provided significant yield increases and positively influenced nematode densities (root-knot and reniform nematodes). MESSENGER applications provided benefits for cotton produced in soils infested with nematodes, and combinations of MESSENGER and aldicarb appeared to be complementary.