Contributions of short- and long-shoots to yield of ‘Kerman’ pistachio (Pistacia vera L.)

The canopy of a mature ‘Kerman’ pistachio (Pistacia vera L.) tree is composed of two types of shoots: short-shoots composed entirely of preformed nodes, and long-shoots composed of both preformed and neoformed nodes. Since the production of these two types of shoots is known to be related to rootstock and rootstock influences yield of pistachio the relationship of these two types of shoots to yield was investigated during two cropping years. Individual short-shoots produced significantly less yield and had fewer fruit clusters per shoot compared with long-shoots, but collectively produced 55–60% of the total yield. Long-shoots positively affected yield components in one year, but had no effect in the other year. Whether the differences in the one year were due to canopy position and light interception or differences in the carbohydrate allocation within the two types of shoots could not be determined from the current data. Long-shoots initiated more inflorescence buds, although inflorescence bud formation was restricted to the preformed growth and only the 3–4 earliest neoformed nodes. However, when expressed as a percentage, long-shoots retained a lower percentage of initiated inflorescence buds, compared with short-shoots. Regardless of shoot type, less than half of the retained inflorescence buds produced mature fruit clusters. Thus, inflorescence bud retention, a previously hypothesized mechanism of pistachio alternate bearing, may not be the primary limiting factor to yield in pistachio.     

Epibionts of pond-reared adult Malaysian prawns,Macrobrachium rosenbergii (de Man), in South Carolina

During 1976, epibionts were noted on adult Malaysian prawns reared in a special ‘brood stock pond’. These epibionts have not previously been recorded on Macrobrachium rosenbergii. Dense algal growths, covering much of the carapace, were observed on 58.3% of the males (mean size, 147.1 g) and on none of the females at harvest. Species composition was primarily (about 90%) the Chlorophyte Oedogonium crassiusculum, with the Cyanophyte Lyngbya, the secondary dominant. The large infested males were sluggish and in some cases functionally blind due to the algal covering. However, once moved to indoor culture tanks the algae were lost and the prawns' behavior returned to normal.Eggs of the water boatman, Ramphocorixa acuminata, were observed on 52.5% of the females (mean size, 78.0 g) and 5.9% of the males at harvest. Egg deposition was limited to the cephalothorax and/or the first and/or second abdominal segments. This epibiont was not noted in the six adjacent rearing ponds containing approximately 84,000 smaller prawns. The insect eggs appeared to cause no injury and disappeared shortly after the infested prawns were returned to laboratory tanks.Although both epibionts exhibited apparent sex specificity in the brood stock pond, data from other rearing ponds did not support this specificity. The occurrence of these epibionts should pose no problem to the successful pond culture of M. rosenbergii in South Carolina.     

Daily shoot extension growth of peach trees growing on rootstocks that reduce scion growth is related to daily dynamics of stem water potential

We studied relationships between diurnal patterns of stem water potential (PsiSTEM) and stem extension growth of the same scion cultivar growing on three rootstocks with differing size-controlling potentials. The peach trees (Prunus persica (L.) Batsch) used in this field experiment consisted of an early-maturing freestone cultivar, 'Flavorcrest,' grafted onto three different rootstocks: Nemaguard (a vigorous seed-propagated control, P. persica x P. davidiana hybrid), Hiawatha (an intermediate vigor rootstock, derived from an open pollinated seedling of a P. besseyi x P. salicina hybrid) and K-146-43 (a semi-dwarfing rootstock, P. salicina x P. persica hybrid). Diurnal patterns of PsiSTEM and stem extension growth were measured on six dates (March 29, April 12, April 26, May 10, May 24 and June 18) during the primary period of peach shoot extension growth. Rootstocks clearly affected diurnal patterns of PsiSTEM and stem extension growth. Trees on K-146-43 had the lowest midday PsiSTEM and stem extension growth. Differences among rootstocks in the amount of diurnal oscillation in PsiSTEM explained stem extension rate differences induced by the three rootstocks. The sensitivity of shoot extension growth to tree water relations tended to decrease as the season progressed and was not apparent by mid-June. The results of the study indicate that water relations may play an important role in the dwarfing mechanism induced by size-controlling peach rootstocks.     

Preformation in vegetative buds of pistachio (Pistacia vera): relationship to shoot morphology, crown structure and rootstock vigor

Effects of rootstock, shoot carbohydrate status, crop load and crown position on the number of preformed leaf primordia in the dormant terminal and lateral buds of mature and immature 'Kerman' pistachio (Pistacia vera L.) trees were investigated to determine if rootstock vigor is associated with greater shoot preformation. There was no significant variation in preformation related to the factors studied, suggesting strong genetic control of preformation in 'Kerman' pistachio. The growth differences observed among trees on different rootstocks were associated with greater stimulation of neoformed growth in trees on the more vigorous rootstocks. However, most annual extension growth in mature tree crowns was preformed, contrasting with the relatively high rate of neoformation found in young tree crowns. Large amounts of neoformed growth in young trees may allow the trees to become established quickly and secure resources, whereas predominantly preformed growth in mature trees may allow for continued crown expansion without outgrowing available resources. We hypothesized that the stimulation of neoformed growth by the more vigorous rootstocks is associated with greater resource uptake or transport, or both. Understanding the source of variation in shoot extension growth on different rootstocks has important implications for orchard management practices.     

Spur behaviour in almond trees: relationships between previous year spur leaf area, fruit bearing and mortality

In mature almond (Prunus dulcis) orchards, the majority of crop is borne on spurs (short, proleptic shoots) that can live for several years and can produce from one to five fruits. Previous research has led to the hypothesis that spur longevity is related to spur light exposure, cropping and age. However, limited quantitative data are available to substantiate these hypotheses. The objective of this study was to determine spur characteristics that were most highly correlated with spur productivity and longevity in mature, bearing almond trees. Previous year spur leaf area was strongly related to spur viability and flowering; the greater the leaf area in the previous year, the higher the probability of spur survival into the next year and the higher the probability for the spur to bear one or more flowers. Previous year bearing also appeared to influence viability and return bloom, especially in spurs with low leaf area. These results suggest that spur source-sink balance is basic to the life cycle of almond spurs. Furthermore, the results are consistent with the hypothesis that spurs are semi-autonomous organs with respect to carbohydrate balance for much of the growing season. Finally, this information provides general thresholds for maintaining spur viability and productivity that will be useful for developing and evaluating tree training systems and orchard management practices.     

Bermudagrass (Cynodon spp) dose-response relationships with clethodim, glufosinate and glyphosate

Greenhouse studies were conducted to evaluate the sensitivity of three commercial cultivars, eight experimental cultivars and common bermudagrass to clethodim, glufosinate and glyphosate. Each herbicide was applied at eight doses. Data were regressed on herbicide dose using a log-logistic curve (R2 = 0.56-0.95 for clethodim, R2 = 0.60-0.94 for glufosinate, and R2 = 0.70-0.96 for glyphosate). The herbicide rate that elicited a 50% plant response (I50) in the bermudagrass cultivars ranged from 0.04 to 0.19 kg ha(-1) clethodim, 0.19 to 1.33 kg ha(-1) glufosinate and 0.34 to 1.14 kg ha(-1) glyphosate. Relative to other cultivars, common bermudagrass was intermediate in its response to clethodim and among the most tolerant cultivars to glufosinate and glyphosate. TifSport was relatively tolerant to clethodim and glufosinate compared with other cultivars, but relatively sensitive to glyphosate. One cultivar, 94-437, was consistently among the most sensitive cultivars to each of the herbicides. While there were differential herbicide tolerances among the tested bermudagrass cultivars, there did not appear to be any naturally occurring herbicide resistance that could be commercially utilized. However, research indicated that breeding efforts should target herbicide resistance that is at least four times the registered use rate. Also, TifSport and Tifway have been identified as suitable representatives of triploid hybrid bermudagrass cultivars to be used to evaluate the success of turfgrass renovation programs.     

Dose determination and confirmation for ceftiofur crystalline-free acid administered in the posterior aspect of the ear for control and treatment of bovine respiratory disease

Three studies were conducted to determine and confirm the effective dosage rate of ceftiofur crystalline-free acid sterile suspension (CCFA-SS, 200 mg ceftiofur equivalents [CE]/ml), a long-acting ceftiofur formulation, for control and treatment of bovine respiratory disease (BRD). In each study, CCFA-SS was administered once by subcutaneous (SC) injection in the middle third of the posterior aspect of the ear. Study 1 was conducted using an intratracheal challenge with Mannheimia (formerly Pasteurella) haemolytica and dosages ranging from 0 to 8.8 mg CE/kg to select a dosage for further field testing. In Study 2, a single dose of CCFA-SS at 0.0, 4.4, or 6.6 mg CE/kg was administered when uniform clinical signs of BRD were present in feedlot cattle. Study 3 was conducted in several feedlots to evaluate the efficacy, practicality, and safety of CCFA-SS at 4.4 or 6.6 mg CE/kg compared with a placebo control or tilmicosin for preemptive control of BRD. In Study 1, the effective dose was determined to be 5.35 mg CE/kg; therefore, 4.4 and 6.6 mg CE/kg were selected as the dosages for further field testing. Administration of CCFA-SS at 4.4 or 6.6 mg CE/kg improved treatment success compared with negative controls (P < or =.05 for both doses) in Study 2. In Study 3, a single administration of 4.4 or 6.6 mg CE/kg was comparable to tilmicosin (P <.001) and was significantly better than placebo (P <.001) for the control of BRD. Using the ear as an administration site was acceptable under field conditions and was well tolerated by all animals. These studies demonstrated that a single administration of CCFA-SS by SC injection in the middle third of the posterior aspect of the ear at 4.4 or 6.6 mg CE/kg is effective, safe, and practical for preemptive control and treatment of the bacterial component of BRD in feedlot cattle. Administration in an inedible tissue results in a short withdrawal time and no injection-site trimming at slaughter.