Shell Hardening Research Articles

Large bugs damage pistachio nuts most severely during midseason

“Large bug” damage to pistachio nuts varies by season, as well as among insect species and development stages, with larger bugs typically causing more damage than smaller bugs. We investigated pistachio damage by three large bug species (leaffooted bug, redshouldered stink bug and flat green stink bug) at different development stages and throughout the season, using field surveys and cage studies. Before fruit set occurs in June, most damaged nuts are dropped from the cluster without reducing fruit load. The midseason period (June to July) is the most critical because the damaged nuts remain in the cluster. After shell hardening, the kernel is largely protected from bug feeding.

Insect Damage Estimates for ‘Stuart’ Pecan Nutlets from Nut Set to Shell Hardening in Insecticide-Treated and Untreated Trees

Pecan nut loss due to pecan nut casebearer, Acrobasis nuxvorella Neunzig, damage was significantly lower in the chlorpyrifos-treated, ‘Stuart’, pecan trees (0%) than in untreated trees (16%). Percentage loss due to nut drop from all causes between nut set and shell-hardening was significantly lower in the treated (27%) than in the untreated trees (42%). Treated trees had significantly higher average yield (38 kg/tree) than the untreated (29 kg/tree). Nut size was significantly smaller in untreated (156 nuts/kg) than in treated trees (145 nuts/kg). Monitoring the fate of ‘Stuart’ pecan nutlets from nut set to harvest indicated that the number of nuts/cluster at nut set was often positively correlated with kernel weight at harvest, whereas, nut cluster size later in the season was positively correlated with kernel weight at two orchards and negatively correlated with kernel weight in the control treatment at a third orchard. A commercial orchard where pecan nut casebearer, hickory shuckworm, Cydia caryana (Fitch) and nut curculio, Conatrachelus hicoriae Schoof, were controlled with insecticide sprays in the spring had similar total nut drop over the entire season as an orchard where these insects were not controlled. The majority of the pecans that dropped from the trees did not have discernible signs of plant disease, insect feeding damage or insect oviposition.

Plant Protection for Pistachio

Pistachio (Pistacia vera) was successfully introduced into California and initially touted as a tree nut crop with no disease or insect pests. Unfortunately, these expectations were dashed as a number of diseases and pests followed commercial plantings, making plant protection practices integral to production. Verticillium wilt (Verticillium dahliae) devastated early plantings but is now controlled with the use of resistant rootstocks. Botryosphaeria blight (Botryosphaeria dothidea) and alternaria late blight (Alternaria alternata) are recently arrived foliar fungal diseases that blight fruit clusters and defoliate trees, respectively, and multiple fungicide applications are needed for control. The conversion to low volume irrigation systems, specifically to drip or buried drip, has reduced disease. Pruning out botryosphaeria blight infections has reduced overwintering inoculum and disease, while current research aims at accurately predicting infection events to increase fungicide efficacy. A number of hemipteran insect pests have been associated with epicarp lesion: spring treatments have been replaced with dormant carbaryl and oil applications which are less toxic to beneficial insects while controlling phytocoris (Phytocoris californicus and P. relativus) and soft scale pests. Early season insect damage can be tolerated because trees compensate by maturing a higher percentage of remaining fruit kernels. Some mirid (Calocoris spp.) pests can be effectively reduced by eliminating alternate hosts in an effective weed control program. If lygus (Lygus hesperus) populations are present, weeds should not be disturbed from bloom until shell hardening to prevent movement by insects into the trees where feeding can result in epicarp lesion. Stink bugs (Pentatomidae) and leaffooted bugs (Leptoglossus clypealis and L. occidentalis) can penetrate the hardened shell and cause internal nut necrosis along with epicarp lesion. Trap crops are used to monitor pest populations in order to develop treatment thresholds. Degree-day based timing of treatments increase insecticide efficacy for the control of navel orangeworm (Amyelois transitella) and obliquebanded leafroller (Choristonuera rosaceana), but navel orangeworm populations are more effectively managed by destroying unharvested over wintering fruit. Bacillus thuriengiensis sprays, liquid-lime-sulfur, and biological control show promise in controlling obliquebanded leafroller.

Insufficient spring irrigation increases abnormal splitting of pistachio nuts

Abnormal pistachio nuts, known as “early-split nuts,” have both the hull and shell split while still on the tree, exposing the kernel to invasion by insects and molds. Deficit irrigation of pistachio trees in April and May resulted in substantial increases in the formation of early-split nuts in late summer, while extreme deficit irrigation in July and August resulted in decreased formation. However, deficit irrigation during the period of shell hardening, mainly in June, did not affect early-split formation.

Factors Influencing Water Split of Pecan Fruit

Water stage fruit split (WS) is an erratic and complex problem often causing major crop losses to susceptible pecan [Carya illinoinensis (Wangenh.) K. Koch] cultivars. This study identified two episodes of WS for `Wichita' pecan—a highly susceptible cultivar. The previously recognized precipitation-induced fruit splitting is the major episode; however, a previously unrecognized precipitation-independent, minor episode can also occured before the major episode. This minor episode was associated with the low solar irradiance and high relative humidity—conditions commonly associated with August rains. The crop characteristics of affected trees also influenced WS in that WS increased as crop load per tree increased. Fruits were also more likely to exhibit WS if located within the lower tree canopy. Treatment of foliage with an antitranspirant immediately before split-inducing conditions increased WS. Maintenance of moist soils for ≈2 weeks before WS-inducing conditions substantially reduced WS-related crop losses. These findings help to explain the erratic nature of WS and indicate that maintenance of trees in a well-watered state for ≈2 weeks before the initiation of shell hardening may substantially reduce WS-related crop losses in certain years.

The Effect of Diet on Weight Gain, Shell Hardness, and Flavor of New-Shell American Lobster, Homarus americanus

Harvested newly-shed American lobsters, Homants americanus, placed in pounds for long-term storage are prone to damage resulting from high-density confinement. It is beneficial for the new shell to harden as soon as possible after shedding. Artificial diets offer the potential for adding supplements to increase weight, muscle gain, and shell hardening. In this study, lobsters were fed 5 different diets: herring, fish racks, and prepared diets with three levels of vitamin D for a period of 38 days. After the feeding trial, lobsters were reweighed, and samples of the carapace and claw shell were removed and subjected to a compressive force/deformation test to measure shell strength. Results indicate a significant (P< 0.05) difference in weight gain, with the highest level of vitamin D actually inhibiting gain. Subsamples tested for compressive force yielded a positive correlation between the carapace measurement and feed type. Flavor tests on subsamples showed significant differences between all treatments; herring was the best, followed by pelleted feed and then fish racks. No off-flavors were detected in lobsters fed any of the three diet types.

The Effect of Disulfiram in Egg Shell Formation in Adult Trichuris muris

The effect of disulfiram on egg shell morphology in the parasitic nematode Trichuris muris was studied in vitro and in vivo. Daily disulfiram treatment of mice infected with T. muris beginning 25 days after infection and continuing for 26 days resulted in the production of malformed eggs by adult female worms in all treated groups. In addition, significantly fewer adult worms were found at necropsy in mice treated with 5.0 or 7.5 mg/kg/day of disulfiram as compared with mice treated with 2.5 mg/kg/day or control mice. Adult worms collected from infected, untreated mice and placed in aerobic culture for 5 days in media containing 4 or 8 micrograms/ml of disulfiram released malformed eggs into the culture medium after 30 hr in culture. Oral inoculation of naive mice with malformed eggs did not result in T. muris infections in the mice. The results of these studies suggest that inhibition of phenol oxidase results in disruption of normal egg production by T. muris females and that the enzyme might be a useful target in the development of control strategies aimed at nematode parasites that rely on phenol oxidase for egg shell hardening.

Swelling of wolffish, Anarhichas lupus L., eggs and prevention of their adhesiveness

Wolffish, Anarhichas lupus L. has internal fertilization. The eggs are released into water before the beginning of cleavage and stick together in clutches. To develop methods for separating eggs for subsequent incubation, changes during egg swelling and egg shell hardening were observed. Uninseminated eggs did not swell in ovarian fluid, but a perivitelline space formed in sea water because of a partial cortical reaction. In inseminated eggs kept in ovarian fluid, a cortical reaction took place and swelling was caused by elevation of the yolk membrane. Shrinkage of the yolk and absorption of water were observed after inseminated eggs were placed in sea water. Eggs swelled in ovarian fluid diluted by less than 30% sea water showed abnormal cleavage during subsequent development. An effective method for preventing egg stickiness after fertilization was to distribute them in trays with stagnant sea water for at least 5-6 h. Milk was effective for loss of egg adhesiveness at 50% concentration, but some eggs cleaved abnormally and subsequent mortality was high. The influences of ovarian fluid and milk on initial egg development with respect to peculiarities of egg swelling are discussed.

Effect of Calocoris norvegicus (Hemiptera: Miridae) on Pistachio Yields

Exposure of pistachio ( Pistacia vera L.) nut clusters to adult Calocoris norvegicus (Gmelin) during different periods of pistachio nut development showed that the period of susceptibility occurred between nut set and shell hardening, or between early April and early June. Correlation of pistachio nut development with degree-days accumulated after 75% bloom in 1987 predicted shell hardening to occur within 2 d of observed shell hardening in 1988. Abortion rates of pistachio nuts exposed to C. norvegicus for 1 wk were not significantly higher than unexposed nut clusters. However, rates of epicarp lesion in the exposed clusters were significantly higher, which would lead to nut abortion and potential yield looses within a few weeks after exposure to C. norvegicus . The effect of C. norvegicus on yields of pistachios in the Sacramento valley was determined by creating four levels of epicarp lesion damage. Among the different levels of damage, epicarp lesion ranged from 4 to 48%. The number of nuts remaining on the clusters was significantly reduced in the highest damage level. Regression of percentage epicarp lesion with pistachio yields at harvest indicated that 31% of the variation in yield was explained by epicarp lesion due to C. norvegicus . The timing of insecticide treatments before the adult phase of C. norvegicus was shown to be an important means of protecting pistachios from extensive early season damage.

Ultrastructure of Mehlis' gland in the lung fluke,Paragonimus ohirai (Trematoda: Troglotrematidae)

Mehlis' gland of a digenetic trematode, Paragonimus ohirai, is composed of two types of secretory cells, DB and CB. The less abundant type (DB) produces dense bodies, with the cytoplasm characterized by greatly distended cisternae of rough endoplasmic reticulum. The other type (CB) synthesizes clear, vesicular bodies. Its cytoplasm contains numerous mitochondria, rough endoplasmic reticulum with narrow cisternae, and abundant Golgi complexes. Processes of the two cell types converge on the ootype-proximal uterine wall, pass through the epithelium, and finally open into the lumen. These proximal processes contain longitudinally arranged microtubules whose luminal ends are anchored to the epithelium by ring-form septate desmosomes. According to the distribution of the two types of processes, three different zones (DB, mixed, and CB) can be recognized within the epithelia. As the CB processes enter the lumen predominantly beyond the uterine valve region, this cell may produce secretions required for egg shell maturation or hardening. The role of DB cells (which enter the lumen more commonly in the ootype near the oviduct) remains unknown.

Epoxidation of 3-chlorobutene-1 by tert-butyl hydroperoxide: Ye. Mil'khert, Neftekhimiya 29, No. 5, 693–696, 1989

Bisphenol A (BPA), 4-cumylphenol (4-CP) and 2,4-bis-(dimethylbenzyl)phenol (2,4-DCP) are all high production volume chemicals and widely used in plastic and other consumer products. During the past two decades, BPA has attracted a great deal of scientific and public attention due to its presence in the environment and estrogenic property. Although 4-CP and 2,4-DCP are much more estrogenic and toxic than BPA, little information is available about their occurrence and fate in the environment. In this study, a rapid, selective, accurate and reliable analytical method was developed for the simultaneous determination of 4-CP, 2,4-DCP and BPA in prawn Macrobrachium rosenbergii. The method comprises an ultrasound-accelerated extraction followed by capillary gas chromatographic (GC) separation. The detection limits range from 1.50 to 36.4 ng kg−1 for the three alkylphenols. The calibration curves are linear over the concentration range tested with the coefficients of determination, R2, greater than 0.994. The developed method was successfully applied to the simultaneous determination of 4-CP, 2,4-DCP and BPA in prawn samples. The peak identification was confirmed using GC–MS. Bisphenol A, 2,4-bis-(dimethylbenzyl)phenol and 4-cumylphenol were found in prawn samples in the concentration ranges of 0.67–5.51, 0.36–1.61, and 0.00–1.96 ng g−1 (wet weight), respectively. All relative standard deviations are less than 4.8%. At these environmentally relevant concentration levels, 4-CP, 2,4-DCP and BPA may affect the reproduction and development of aquatic organisms, including negative influence on crustaceans’ larval survival, molting, metamorphosis and shell hardening. This is the first study reported on the occurrence of 4-CP, 2,4-DCP and BPA in prawn M. rosenbergii.