A significant portion of harvested produce never reaches the consumer due to, postharvest diseases. Various chemicals have been used to reduce the incidence of postharvest diseases. Many of these materials have been removed from the market in recent years due to economic, environmental, or health concerns. Although somewhat limited in the range of diseases controlled, chlorination is effective when combined with proper postharvest handling practices. Additionally, it is a relatively inexpensive postharvest disease control method that poses little threat to health or the environment. The proper use of chlorination in the management of postharvest diseases in fresh fruits and vegetables is discussed.
M.D. Boyette, D.F. Ritchie, S.J. Carballo, S.M. Blankenship, and D.C. Sanders
Steve Kovach, Larry Curtis, and Jim Allen
Irrigating with a micro-irrigation (drip) system offers improved crop quality and yield with significant savings of energy and water. To deliver these benefits reliably, a grower's system must include chlorinations or some other effective water treatment program to prevent clogging, the most common problem of micro-irrigation. Step-by-step procedures of chlorination of micro-irrigation systems are discussed. Injected into micro-irrigation systems, chlorine kills the micro-organisms—bacteria, fungi and algae—that may be in a water source and are the most common system cloggers.
Because drip irrigation systems are very susceptible to clogging, maintenance revolves around flushing the system. Both primary and secondary filters and main and lateral lines and drip tubes require flushing on a regular basis. Chlorination and use of acid often are necessary for keeping lines clear of contaminants. Rubber gaskets and diaphragms should be replaced every 2 years. A water meter will assist in assuring that desired application rates are being obtained. The use of air vents assures that air locks do not reduce system efficiency. The calibration of injector pumps should be verified at least two times per season.
Sergio J. Carballo, Sylvia M. Blankenship, Douglas C. Sanders, David F. Ritchie, and Michael D. Boyette
Commercial packing lines in Sampson County, N.C., were surveyed during two growing seasons to study handling methods on susceptibility of bell pepper fruits (Capsicum annuum L.) to bacterial soft rot (Erwinia carotovora subsp. carotovora). Samples were taken from two field packers and one packing house in 1991 and from two field packers and four packing houses in 1992. One field packer and one packing house were common to both years. Fruits were either inoculated with bacteria or untreated and stored at 10 or 21C. Damaged fruits were counted and classified as crushed, cut, bruised, abraded, and other injuries. Fruit injury was less dependent on whether the operation was a packing house or a field packing line than on the overall handling practices of the individual grower. In general, packing peppers in packing houses resulted in an increased number of bruises, whereas fruit from field packing lines had more abrasions. More open skin injuries resulted in greater fruit decay. In both years, fruits stored at 10C had less top rot than fruits stored at 21C. In 1992, they also had less pod rot. Dry and chlorinated lines often had equivalent rot problems.
Muhammad Imran Al-Haq, Y. Seo, S. Oshita, and Y. Kawagoe
The fungicidal effectiveness of electrolyzed oxidizing (EO) water on peach [Prunus persica (L.) Batsch.] fruit was studied. Fruit were inoculated with a spore suspension of 5 × 105 conidia/mL of Monilinia fructicola [(G. Wint.) Honey] applied as a drop on wounded and nonwounded fruits, or by a uniform spray-mist on nonwounded fruits. Fruit were immersed in tap water at 26 °C for 5 or 10 minutes (control), or treated with EO water varying in oxidation-reduction potential (ORP), pH, and free available chlorine (FAC). Following treatment, fruit were held at 20 °C and 95% relative humidity for 10 days to simulate retail conditions. Disease incidence was determined as the percentage of fruits showing symptoms of the disease, while severity was expressed as lesion diameter. EO water did not control brown rot in wound-inoculated fruits, but reduced disease incidence and severity in nonwound-inoculated peach. Symptoms of brown rot were further delayed in fruit inoculated by a uniform-spray mist compared with the nonwounded-drop-inoculated peaches. Fruit treated with EO water held for 8 days at 2 °C, 50% RH, did not develop brown rot, until they were transferred to 20 °C, 95% RH. The lowest disease incidence and severity occurred in fruit immersed in EO water for up to 5 minutes. EO water having pH 4.0, ORP 1,100 mV, FAC 290 mg·L-1 delayed the onset of brown rot to 7 days, i.e., about the period peach stays in the market from a packing house to consumer. No chlorine-induced phytotoxicity was observed on the treated fruit. This study revealed that EO water is an effective surface sanitizer, but only delayed disease development.
Gary A. Clark and Allen G. Smajstrla
The injection of chemicals into irrigation systems is discussed in terms of injection systems, concentration injections, bulk injections, quantity of chemicals to be injected, injection system calibration, and injection periods. Sufficient clean-water flush time should be scheduled to purge irrigation lines of injected chemicals unless it is desired to leave that particular chemical in the irrigation system for maintenance purposes. Chemical injection rates vary with desired chemical concentration in the irrigation water, concentration of the stock solution, volume of chemical to be injected, and duration of each injection. All injection systems should be calibrated and maintained in proper working order. This information is presented to assist irrigation system designers and operators with chemigation system design, scheduling, and management.
Diane Feliciano Cayanan, Mike Dixon, Youbin Zheng, and Jennifer Llewellyn
greenhouse crops and their free chlorine thresholds, which ranged from 2 mg·L −1 to 77 mg·L −1 . However, there is no known published information regarding the use of chlorinated irrigation water under typical nursery practices. The objective of the present
Diane Feliciano Cayanan, Ping Zhang, Weizhong Liu, Mike Dixon, and Youbin Zheng
surfactants, and chlorination ( Ehret et al., 2001 ; Hong et al., 2003 ). Chlorination is an economical method of disinfecting water and remains the primary method of treating municipal water ( Havard, 2003 ; Hong et al., 2003 ). Chlorination technology has
Diane Feliciano Cayanan, Youbin Zheng, Ping Zhang, Tom Graham, Mike Dixon, Calvin Chong, and Jennifer Llewellyn
copper, and chlorination ( Ehret et al., 2001 ; Havard, 2003 ; Hong et al., 2003 ; Igura et al., 2004 ; Newman, 2004 ; White, 1992 ). Chlorination is one of the most economical water decontamination methods. It was developed to treat municipal water
Dewayne L. Ingram, Charles R. Hall, and Joshua Knight
containers and 260 for transplanting from no. 1 to 2 containers or no. 2 or field transplants into no. 3 containers. All irrigation water was assumed to be chlorinated using calcium hypochlorite tablets injected at 8 ppm Cl. There would be an annual