Ataenius spretulus (Haldeman) (Coleoptera: Scarabaeidae) is the most common grub in golf course fairways in Michigan. Ataenius spretulus grubs are 3- to 10-fold more abundant in golf course fairways (mowed at a height of 1.5 cm) than in the roughs (mowed at a height of 5.0 cm or higher). Predation and infection by Paenibacillus sp. were previously reported to be greater in the rough, and may partially explain outbreaks of A. spretulus grubs in golf course fairways. In addition to natural enemies, cultural practices of irrigation and mowing could also be important factors, especially if A. spretulus prefers to oviposit in the fairway over the rough. In this paper we examine the impact of soil moisture and mowing height on oviposition and habitat selection. In a greenhouse experiment where A. spretulus adults were given a choice of turf maintained at fairway or rough height, no ovipositional preference for one or the other was observed. In three different growth chamber experiments where adults were allowed to choose among fairway or rough turf plugs held in soil at different moisture levels, adults preferred turf plugs in soil at a volumetric moisture content of 13% to 26% over turf plugs in soil at 8% to 9% moisture for their habitat selection. We conclude from these greenhouse and growth chamber experiments that A. spretulus adults do not choose turf habitat based on mowing height, but may be influenced by soil moisture levels.
A change in orchard culture caused a significant reduction in activity of pine voles (Microtus pinetorum Le Conte). Cultivations in May, July, and November were not as effective as 2 cultivations plus 2 residual herbicide treatments (July and November). A single cultivation in November caused a small but significant reduction in vole activity but the effect was short lived. A heavy annual residual herbicide treatment in July caused a small but significant reduction in vole activity. No cultural treatment resulted in adequate control by December of 3 consecutive years and toxic hand placed baits were required each year to reduce populations.
Chilling sensitivity of ‘Fuerte’ and ‘Hass’ avocados (Persea americana Mill.) is a function of the stage of the climacteric. The least sensitive stage is postclimacteric where fruit can be kept at 2°C for 6 to 7 weeks. ‘Hass’ avocados on the climacteric rise and at the climacteric peak were most sensitive to chilling and showed injury after 19 days of treatment at 2°. Postclimacteric fruit could be transferred to 2° at 36 to 48 hours after the climacteric peak. The time preclimacteric fruit could be held at 2° varied during the picking season but could be as long as 30 days.
Investigation of optimum conditions for extraction, titrimetric assay and activity of avocado (Persea americana Mill cvs. Fuerte, Hass) pectinmethylesterase (PME) showed maximum extraction was obtained from lyophilized mesocarp using 0.4 m NaCl. Best assay conditions required a substrate of 0.5% pectin in 0.1 m NaCl. The enzyme was released from the tissue by salt but not by nonionic detergents. The Arrhenius plot between 3 and 32°C was a straight line which indicates no involvement with membrane lipid. Incubation with air or ethylene did not affect the enzyme. PME activity declined rapidly as ripening was initiated and reached a minimum shortly before the peak in respiration and ethylene production.
The ability of various leaf removal treatments or shoot tipping to induce lateral shoot development on current-season stoolbed shoots of MM.106 EMLA and M.26 EMLA apple (Malus domestica Borkh.) rootstocks was investigated. Removal of the five uppermost immature leaves or shoot tipping after every 20 to 25 cm of terminal growth produced more lateral budbreak than occurred on nontreated shoots. Shoot tipping resulted in the highest number of branches (≥5 cm) and greatest total branch length. Only tipping consistently induced lateral budbreak higher than 30 cm up the shoot. Removal of the 10 uppermost leaves and tipping resulted in the shortest terminal shoots. MM.106 shoots had more lateral budbreak, branches, and total branch length than did M.26 shoots.
Triclopyr was applied once or twice in consecutive years to Virginia creeper [Parthenocissus quinquefolia (L.) Planch.] that was growing along the ground beneath the peach [Prunus persica (L.) Batsch.] tree canopy. All rate (0 to 1.1 kg·ha-1) and month combinations controlled Virginia creeper during the season of application. A single application of triclopyr at 1.1 kg·ha-1 was insufficient for control beyond 1 year. Satisfactory control of Virginia creeper was obtained with two applications of triclopyr at 1.1 kg·ha-1 made in either August or September. Chemical name used: [(3,5,6-trichloro-2-pyridinyl)oxy]acetic acid (triclopyr).
Pine vole, Microtus pinetorum LeConte, activity in an apple orchard was reduced by cultivation of a 4 m-wide strip down the tree row. Bare-ground-culture using a single annual application of Simazine plus Amitrol (1964-71) or Paraquat (1972-73) herbicide for 10 years reduced pine vole activity.
Treatment with calcium (0.1 M CaSO4, 0.1 M CaCl2) depressed respiration of avocado fruits during preclimacteric and climacteric phases. Na2SO4 was ineffective. Calcium not only inhibited respiration but delayed the onset of the climacteric and depressed the peak of ethylene production at the climacteric rise. Determinations of endogenous Ca confirmed that higher levels were positively correlated to delay in ripening and negatively correlated to peak of CO2 and ethylene production. It is inferred that this difference in Ca level is one of the factors causing lack of uniformity in ripening.
As mango leaves increased in age, lower P and K contents were found, while Ca content was higher. The basal leaf was lower in N and Ca but higher in P and K contents when compared with the terminal leaf of the same shoots. Only small differences were observed when leaves were compared from fruiting and nonfruiting shoots. The practical application of data in sampling mango leaves is discussed.
Avocado fruit (Persea americana Mill. ‘Fuerte’) were stored in air with or without C2H4 treatment (100 ppm) at 6°, 9°, 12°, 14°, 16°, 20°, 24°, 27°, 30°, and 34°C. During the storage period, respiration was measured by an automated continuous gas flow system. Fruit stored in air for more than 20 days at 6° developed chilling injury as indicated by gray discoloration of the mesocarp tissue. At high temperatures (30°, 34°), avocado fruit ripened abnormally, showed considerable surface pitting, and had poor flavor. When fruit were stored with 100 ppm C2H4, tissue discoloration was severe below 12°, which implied that chilling sensitivity of avocado fruit increased with C2H4 treatment. Fruit, whether stored with C2H4 or not, showed breaking points around the same temperature region on an Arrhenius plot, suggesting possible involvement of other mechanisms in addition to phase changes of membrane lipid components.