Michael L. Parker

Tree Growth, Fruit Size, and Yield Response of Mature Peach to Weed-Free Intervals

An experiment was conducted at one location in 1999 and two locations in 2000 to determine the critical weed-free period for peach in North Carolina. The cultivars for the three locations were ‘Contender’, ‘Norman’, and ‘Summerprince’. Weed-free intervals of 0, 3, 6, 9, 12, and 15 wk after peach tree bloom were established. Paraquat at 1.1 kg ai/ha plus nonionic surfactant at 0.25% v/v was applied every 10 d, after treatments were initiated at peach bloom, to maintain weed-free plots. Large crabgrass, hairy vetch, and smooth crabgrass were the primary weeds in Contender. Horseweed, smooth crabgrass, and large crabgrass were the primary weeds in Norman. Bermudagrass, smooth pigweed, and common lambsquarters were the primary weeds in Summerprince. No differences in trunk cross-sectional area were observed between the weed-free periods. Maintaining the orchard floor weed-free for 12 wk after peach tree bloom resulted in the greatest fruit size (individual fruit weight and diameter), total yield, and fruit number. Nomenclature:Paraquat, bermudagrass, Cynodon dactylon (L.) Pers. CYNDA, common lambsquarters, Chenopodium album L. CHEAL, hairy vetch, Vicia villosa Roth. VICVI, horseweed, Conyza canadensis (L.) Cronq. ERICA, large crabgrass, Digitaria sanguinalis (L.) Scop. DIGSA, smooth crabgrass, Digitaria ischaemum (Schreb.) Muhl. DIGIS, smooth pigweed, Amaranthus hybridus L. AMACH, peach, Prunus persica (L.) Batsch., ‘Contender’, ‘Norman’, and ‘Summerprince’

White Clover (Trifolium repens) Control and Flower Head Suppression in Apple Orchards

White clover is a weed in apple orchards that competes with the crop; also, flowers of this weed are unwanted attractants of honey bees at times when insecticides, which are harmful to these pollinators, are being applied. In 1997 and 1998, white clover flower head and plant control by clopyralid alone and with 2,4-D and apple tolerance to these herbicides were determined. Treatments consisted of clopyralid at 0.10 and 0.21 kg ae/ha, 2,4-D at 1.1 kg ae/ha, and 2,4-D at 1.1 kg ae/ha plus 0.03 or 0.05 kg ae/ha clopyralid, which were applied 2 wk before full apple bloom and 2 wk after full apple bloom, and a nontreated check. No crop injury occurred with any treatment. All herbicide treatments provided some white clover control and flower head suppression. No differences in white clover bloom reduction were observed through May among treatments containing clopyralid. As summer progressed, the effect of clopyralid rate became more apparent. Clopyralid at 0.21, regardless of application time, provided 99% vegetative control and 100% flower head reduction through July. Clopyralid plus 2,4-D controlled white clover better than 2,4-D alone. However, vegetative control and flower head reduction with clopyralid at reduced rates (0.03 or 0.05 kg ae/ha) plus 2,4-D were not acceptable (76% or less and 78% or less, respectively). Thus, clopyralid at 0.10 and 0.21 kg ae/ha will be necessary for acceptable white clover vegetation control and flower head reduction. Nomenclature: 2,4-D; clopyralid; white clover, Trifolium repens L. #3 TRFRE; apple, Malus domestica Borkh.; honey bees, Apis mellifera L. Additional index words: Orchard floor management, TRFRE, weed control. Abbreviations: 2WAFB, 2 wk after full apple bloom; 2WBFB, 2 wk before full apple bloom.

Interplanting wheat is not an effective postplant management tactic for Criconemella xenoplax in peach production

In two orchard experiments, interplanting wheat (Triticum aestivum cv. Stacy) around either newly planted or 4-year-old well-established peach trees did not suppress (P ≤ 0.05) the population density of the ring nematode, Criconemella xenoplax, after 3 years. Furthermore, inter-planting wheat around newly planted trees reduced tree growth, perhaps the result of competition for water and (or) nutrients. Wheat root exudate was not as attractive to C. xenoplax as peach root exudate, but wheat root exudate did not repel the nematode either. Stacy wheat appeared to be more beneficial as a preplant rather than as a postplant ground cover management tool for suppressing the population density of C. xenoplax.