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  • Author or Editor: G.R. McEachern x
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Abstract

Chilling requirements for 3 pecan cultivars are reported for the first time. Stem cuttings with 4 buds of ‘Desirable’, ‘Mahan’, and ‘Stuart’ pecan (Carya illinoensis (Wang.) K. Koch) were forced in a greenhouse after each 100 hours of field chilling below 7.2°C during the 1969-70, 1970-71 and 1971-72 dormant seasons and bud break measured 21 days later. A chilling requirement of 500 hours was determined for ‘Desirable’ and ‘Mahan’, and 600 hours for Stuart.

Open Access

Since 1977, it was believed the grape strain of Xylella fastidiosa, Pierce's Disease (PD), was limited to sites receiving less than 800 hours of winter chilling below 45 °F. Warm winters since 1992–93 resulted in numerous PD-positive vineyards in central Texas which were previously nonaffected. Vine mortality ranges from minimal to over 80% dead vines. A Davis Mountains site receiving over 1,000 hours was also severely infected in 1996. The last severe winter in Texas was 1989–90; therefore, warm winters could be contributing. This climatic change could have affected vines, vectors, bacteria, and/or hosts. Recent work based on a study of 20 PD samples, 11 from Texas and 9 from other states, including California and Florida, indicates that the samples of PD grape strain of Xylella fastidiosa are clonally related. ELISA tests failed to identify PD from 1994–96; therefore, a sensitive REP-PCR test is needed before vine, bacteria, vector, and host management strategies can be developed.

Free access

Five Texas orchards were selected in Spring 1993 in commercial pecan counties for testing three types of soil aeration equipment. Mechanical aeration spikes were either 20 or 46 cm long, and a pneumatic spike was 20 cm long. The mechanical spikes are on a rolling cylinder that can be manufactured in sufficient lengths to fit the tree spacing in different orchards. The pneumatic probe is manually inserted into the soil so that a quick burst of 130-psi air can be delivered to effect soil profile fracturing. The fourth replicated treatment was an nontreated control. There were no differences in trunk diameter increases and yield in 1993 between May-applied replicated treatments. The May treatments and November measurements will continue for two more years to allow for differences in soil aeration to influence growth and yield. Shoot growth measurements will be taken in Spring 1995. Irrigation water has penetrated the soil under aerated trees more readily than in nonaerated controls.

Free access