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Dean R. Evert and Paul F. Bertrand

More peach [Prunus persica (L.) Batsch.] trees survived when planted in killed bahiagrass (Paspalum notatum Flugge `Paraguayan-22') sod growing between previous orchard tree rows (98%) than when planted in previous tree sites (81%) or in previous tree rows, but halfway between previous tree sites (79%). The previous orchard was removed Nov. 1986, and new trees were planted Feb. 1987. Surviving trees in the killed sod grew better than trees at the other two sites. Tilling the sites before planting did not affect nematode populations or tree survival and growth. Soaking the tree roots in a fenamiphos solution (1 g·liter-1) for 20 minutes before planting resulted in 79% tree survival vs. 93% survival for the nonsoaked trees. Fenamiphos sprayed under the trees at a rate of 11.2 kg·ha-1 during the spring and fall of the planting year did not change nematode populations, tree survival, or tree growth. The fenamiphos sprays reduced the increase in trunk cross-sectional area by 3 cm2 for trees in the sod. Other than leaf Zn concentration, which was low, concentrations of the elements were within the sufficiency range for Georgia for all treatments. Trees planted in the killed sod had an increased leaf K concentration and decreased leaf Mg concentration when compared with trees planted in the rows. Chemical name used: ethyl 3-methyl-4-(methylthio)phenyl (1-methylethyl)phosphoramidate (fenamiphos).

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Dean R. Evert, Paul F. Bertrand, and `Benjamin G. Mullinix Jr.

Bahiagrass (Paspalum notatum Flugge cv. Paraguayan-22) growing under newly planted peach [Prunus persica (L.) Batsch.] trees severely stunted the trees. Neither supplemental fertilizer nor irrigating with two 3.8-liters·hour-1 emitters per tree eliminated tree stunting emitters were controlled by an automatic tensiometer set to maintain 3 kpa at a depth of 0.5 m under a tree in bahiagrass. Preplant fumigation with ethylene dibromide at 100 liters·ha-1 increased tree growth, but not tree survival. Fenamiphos, a nematicide, applied under the trees each spring and fall at a rate of 11 kg-ha -1 had no positive effect on tree survival, tree growth, or nematode populations. Bahiagrass tended to suppress populations of Meloidogyne spp. under the trees., Meloidogyne spp. were the only nematodes present that had mean populations > 65 per 150 cm3 of soil. Leaf concentrations of several elements differed between trees growing in bahiagrass sod and in. bare ground treated with herbicides. Leaf Ca was low for all treatments in spite of a soil pH near 6.5 and adequate soil Ca. The severe stunting of trees grown in bahiagrass, irrespective of the other treatments, demonstrated that bahiagrass should not be grown under newly planted trees. The low populations of parasitic nematodes in bahiagrass showed that bahiagrass has potential as a preplant biological control of nematodes harmful to peach trees. Chemical name used: ethyl 3-methy1-4-(methylthio) phenyl (1-methylethyl) phosphoramidate (fenamiphos).