The wheat coleoptile straight-growth test was used to determine the effects of (2-chloroethyl)phosphonic acid (ethephon) on endogenous auxins and inhibitors in seeds of ‘Late Santa Rosa’ plum. Seeds of both developing and abscissing ethephon-treated fruits attained higher levels of auxin activity than did their respective controls suggesting an ethylene-induced inhibition of auxin transport. The level of growth inhibitors remained similar throughout.
A greenhouse solution culture experiment was conducted to study the interactions of Ca, K and Mn supply on the concentration of 7 elements in bark tissues of ‘Delicious’ apple (Malus domestica Borkh) trees as related to internal bark necrosis (IBN). Under a regime of low Ca and high Mn, IBN symptoms developed late in the second growing season on the scion barks but not on the rootstock bark. Both the degree of severity and the incidence of the disorder increased with increasing K levels. Low Ca and high Mn concentrations in the barks are apparently necessary for the development of IBN, and under these conditions K affects the degree of severity. It is suggested that the higher K concentrations enhanced Mn toxicity by lowering the threshold for Mn-induced IBN, while Ca responded as a detoxifying agent. Low concentrations of B and P may contribute to IBN development, while Mg and Fe were not related to symptom development.
Integrated peat management (IPM) strategies for control of apple scab and codling moth (Cydia pomonolla) were compared with a traditional protestant spray program in an Iowa apple orchard over a 3-year period. IPM tactics for scab included a postinfection spray program and an integrated, reduced-spray program based on the use of demethylation inhibitor fungicides. Codling moth spray timing was determined by pheromone-trap captures and degree-day models. The IPM tactics resulted in an average of three fewer fungicide sprays and two fewer insecticide sprays than the protestant program. Neither yield, incidence of fruit scab, nor incidence of codling moth injury on fruit was significantly different among the two IPM treatments and the protestant treatment. A no-fungicide treatment had significantly lower yield and greater scab incidence than the other treatments. A partial budget analysis indicated that the treatment using the postinfection strategy was more costly per acre than the protectant program for orchards <20 acres, about equivalent in cost for 20 acres, but leas costly for 40 acres. A treatment incorporating the integrated, reduced-spray strategy was less costly than either postinfection or protestant strategies at orchard sizes from 5 to 40 acres. Return (total revenue - cost for control of primary scab and codling moth) per acre for the IPM strategies was somewhat lower than for the protestant program.