Calendar Spray Research Articles

Evaluation of the Alter-Rater model for spray timing for control of Alternaria brown spot on Murcott tangor in Brazil

Alternaria brown spot, caused by Alternaria alternata, recently appeared in Brazil and is now causing serious damage to Murcott tangors in São Paulo State. The Alter-Rater model and other systems for timing fungicide applications as well as different fungicide programs were evaluated in two seasons in different citrus-growing areas of São Paulo State. Alternaria brown spot severely reduced yields of Murcotts in the unsprayed controls in both years. Fungicide applications reduced fruit drop and increased yields in many cases. Regression analyses showed that yield declined as disease severity increased. A copper fungicide applied according to the Alter-Rater model with a trigger value of 50 required one to two more applications than a calendar program in both locations in 2002–03. Use of the Alter-Rater 50 increased the number of fruit harvested in both locations, but did not improve fruit quality when compared to the calendar program. Use of the Alter-Rater with trigger values of 100 or 150, or the Copper model forecast fewer sprays and resulted in poor disease control and low yields. In a test in 2003–04, fungicide applications timed with the Alter-Rater 50 were no more effective than calendar sprays. Copper fungicides throughout the season or programs with copper applied early followed by dithiocarbamates or QoI fungicides later provided better disease control than a full-season mancozeb program. Murcott product in some citrus growing areas in Brazil will be possible only if the value of the crop is sufficient to justify 10 or more fungicide applications per year.

Response of peanuts ( Arachis hypogaea) to weather-based fungicide advisory sprays

Field studies were conducted in 2001 and 2002 near Yoakum, Texas, to determine the effect of advisory-based fungicide sprays on foliar and soil-borne disease development and peanut yield compared with fungicide sprays based on a calendar schedule. Chlorothalonil applied on a regular schedule seven times during the growing season was compared with a chlorothalonil/tebucanozole combination and advisory sprays of azoxystrobin, pyraclostrobin, and tebucanozole. Three advisory sprays were applied in both years with chlorothalonil applied at 40 and 110 days after application (DAP) and azoxystrobin, pyraclostrobin, or tebucanozole at 88 DAP in 2001, while in 2002, azoxystrobin, pyraclostrobin, or tebucanozole were applied 39 and 77 DAP followed by chlorothalonil applied 101 DAP. The chlorothalonil/tebuconazole combination consisted of chlorothalonil applied 59 and 74 DAP, followed by tebuconazole applied 74, 89, 104, and 118 DAP with a final chlorothalonil application 132 DAP. All fungicide sprays reduced foliar and soil-borne disease development when compared with the untreated check. No difference in foliar or soil-borne disease development or peanut yield was noted between chlorothalonil alone or tebucanozole applied on a calendar spray schedule and azoxystrobin, pyraclostrobin, or tebucanozole applied by advisory sprays. Peanut yield response reflected the improved disease control with fungicides. All fungicides improved peanut yield over the untreated check by at least 25% in 2001 and more than 70% in 2002.

Copper Fungicide Spray Timings for Melanose Control in Grapefruit: Comparison of Computer Modelling of Copper Residues vs. Calendar Sprays

Grapefruit are susceptible to melanose from initial set until fruit diam. is 6-7 cm, which can span 3 months. Common Indian River melanose-control practice has been application of Cu fungicides at petal fall, with reapplication every three wks. through the infection period. Research data were previously used to develop a computer model to estimate Cu levels on fruit and indicate when reapplication is needed to prevent potential infection. The purpose of this study was to compare melanose control using spray timings suggested by the computer model vs. standard 3 week intervals vs. non-sprayed checks and was conducted over 3 years in mature grapefruit groves near Ft. Pierce, Fla. All applications were made using airblast at 1180 L· ha-1. Melanose and melanose-like Cu injury could not be distinguished and were combined in a melanose/Cu marking (MCM) score for each fruit. Separate fruit samples from the interior and exterior of tree canopies were randomly selected from each tree. In no year was there a significant difference in interior fruit MCM from computer model vs. calendar spray timings when treated with standard rates of Cu fungicide. However, rainfall never occurred when calendar-sprayed fruit were projected to be at low Cu levels. In 2 of 3 yrs. exterior fruit in the non-sprayed checks had less MCM than those from trees treated with Cu, indicating that Cu injury predominated over melanose on exterior fruit. In these fruit, MCM increased linearly with maximum fruit Cu concentration, which was lower on trees managed using the computer model. The computer model appears to be a sound approach to managing melanose, but economic benefit over calendar-based spray timing may only become apparent when practiced over numerous groves and seasons.

Patterns of pesticide use in California and the implications for strategies for reduction of pesticides.

We used the California Pesticide Use Reports to study use of fungicides, bactericides, fumigants, and selected insecticides, primarily for vegetable, fruit, and nut production in California from 1993 to 2000. There were no obvious trends in decreased use of most compounds used to treat plant disease. However, growers have rapidly adopted recently introduced "conventional" compounds. There is very limited use of microbial biocontrol agents to control plant disease and no indication of an increase. We used case studies to explore the potential of different strategies to reduce pesticide use or risk. There have been reductions in use of organophosphate insecticides, largely by substitution with pyrethroids. Theoretically, replacement of "calendar spray" pesticide programs with "environmentally driven" programs could reduce pesticide use in years with lower disease pressure, but this assumes that the majority of growers currently use a "calendar spray" program and that growers who use less than recommended by an environmentally driven program would not increase their use.

Evaluation of the Alter-Rater Model for Timing of Fungicide Applications for Control of Alternaria Brown Spot of Citrus.

Alternaria brown spot, caused by Alternaria alternata, results in serious yield losses of tangerines and their hybrids in Florida. The Alter-Rater model predicts the need for fungicide applications based on daily cumulative points that are assigned on the basis of rainfall, leaf wetness, and temperature. Previously, Alter-Rater threshold or trigger values of 50, 75, 100, and 150 points for application of copper fungicides were suggested for groves with different cultivars and disease histories. In this study, we evaluated thresholds of 50, 100, and 150 points in four Minneola tangelo and Murcott tangor groves in 2000 and 2001. For comparison, copper fungicides were applied according to the DISC Copper Model in 2000 and according to calendar sprays in 2001. Use of the Alter-Rater model resulted in fewer sprays in three of the four groves in 2000 and better fruit quality in the other grove than the Copper Model. Compared to a calendar spray schedule in 2001, use of the Alter-Rater model resulted in fewer sprays in two of the four groves but more sprays in one grove. The results confirmed that the Alter-Rater is a valuable tool for timing fungicide applications and that its use results in better disease control or fewer sprays.

DEVELOPMENT AND IMPLEMENTATION OF A PEACH INTEGRATED PEST MANAGEMENT PROGRAM IN THE SOUTHERN USA

Peach producers in the Southern USA generally follow a calendar spray program. Peach growers and county extension agents in AR, AL, FL and OK learned how to implement an integrated pest management program (IPM). Degree-days (DD, base 10°C) for plum curculio (PC) were accumulated daily after the PC biofix (second day when air temperature exceeded 21.1°C) and first trap catch of oriental fruit moth (OFM) (base 10°C). After bloom, weekly estimates were made of the density of PC, stink bug (SB), OFM and percent new pest damaged fruit. Economic thresholds were 0.1 PC per day or 1 SB or 1 PC jarred from peach limbs or 1% new fruit damage between 56 to 222 DD and from 611 DD to harvest. Participating growers and county agents received scouting recommendations and localized recommendations were updated on the Internet. Overwintered adult PC and SB moved to orchards in late February to early March in AL and FL and late March to early April in AR and OK. All states recorded low population levels of PC and OFM and less than 1% fruit damage whereas SBs caused from 3 to 6% damage. In Alabama, no PC or OFM adults were caught in traps in the demonstration orchards. Initially, participating growers applied between 7 to 12 insecticide sprays per season. The IPM program was implemented in 2000 and 2001 resulting in <=8 sprays and <=4 sprays per season, respectively. The OK research IPM block required only 3 sprays per season in 1999, 1 in 2000 and 1 in 2001. Isomate-M dispensers depressed mating of OFM from May to harvest in 1997 and 1998 in 200 acres of processing peaches and in 2000 and 2001 in 30 acres of fresh market peaches resulting in <1% damage.

An Algorithm for Predicting Outbreaks of Sclerotinia Blight of Peanut and Improving the Timing of Fungicide Sprays.

Algorithms were evaluated for computing disease risk and improving the timing of fungicide applications for control of Sclerotinia blight of peanut. Disease risk was calculated by multiplying indices of moisture, soil temperature, vine growth, and canopy density each day, and summing values for the previous 5 days to obtain a 5-day risk index (FDI). After fungicide application, the FDI was reset to zero for 3 weeks. Fluazinam at 0.58 kg a.i./ha applied at FDI 24 or 32 in 1994 and 1995 suppressed disease and increased yield as much as or more than programs of weekly scouting and applying fungicide at the initial onset of disease with additional sprays at 3- to 4-week intervals. The FDI algorithm was also more efficient than calendar sprays at 60, 90, and 120 days after planting (DAP). Environmental and host parameters were expanded in 1996 and 1997 by adding new temperature and new vine growth indices. These parameters along with DAP-dependent thresholds consistently improved the timing of fungicide sprays and disease management when using the FDI algorithm in comparison to weekly scouting or calendar sprays at 60, 90, and 120 DAP.

Complementing TOMCAST by Developing a Comprehensive Tomato Integrated Pest Management (IPM) Program

ABSTRACT Long-term field studies were undertaken to compare TOMCAST to conventional (calendar) spray programs for processing tomatoes in Ohio. In a ten-year period fruit quality, yield and disease control did not differ between fields sprayed with the TOMCAST system compared to calendar spray schedules. In most years TOMCAST reduced the number of fungicide applications. A series of research and demonstration trials were conducted to adapt TOMCAST to changing needs within the processing tomato industry. The influence of cultivar resistance and different fungicides were tested, and fungicide spray intervals were modified to meet the needs of fresh market and whole pack growers. For TOMCAST to be part of a complete tomato IPM program, insect monitoring guidelines were developed to help growers coordinate insecticide and fungicide sprays.

Farmers' knowledge, perceptions and practices in mango pest management in the Mekong Delta, Vietnam

A survey of mango farmers' knowledge, perceptions and practices in pest management was conducted during the dry season of 1998 in the Mekong Delta, Vietnam. Identification and control of pests was often based on damage symptoms, rather than on recording of causal agents. Damage caused by the seed-borer Deanolis albizonalis (Hampson) was often wrongly attributed to the fruit flies Bactrocera dorsalis Hendel. Nearly all farmers applied calendar sprays of insecticides (97%) and fungicides (79%) from pre-flowering until harvest, with on average 13.4 and 11.6 applications per year, respectively. Pyrethroids were most popular (57%), followed by organophosphates (25%) and carbamates (15%). Around 20% of the insecticides used belonged to WHO Toxicity Class I, while the rest nearly all belonged to Class II. Half of all the target sprays were done with three pyrethroid products only. Farmers' estimated yield loss due to insect pests was strongly correlated to estimated pest severity. Due to pesticide sellers' recommendations, farmer's sprayload significantly increased from 26 to 37 sprays per year, whereas the number of insecticide products used per farmer increased from 2.6 to 3.9 with advice fromextension staff and media. Expenditure for pesticides was correlated with that of fertilizers. There was no relationship between the amount of pesticides sprayed and yield. On-farm research is needed to evaluate whether significant savings can be obtained given a more judicious use of pesticides. Only 10% of the 93 participating farmers knew about natural enemies, all of which were predators.

Comparison of armoured scale spray thresholds in kiwifruit

The potential of a pest monitoring system to reduce the number of spray applications while still maintaining control of armoured scale was assessed. Armoured scale were monitored on leaves within a block and sprays were only applied if a predetermined percentage of leaves were infested with live armoured scale. The thresholds compared were either 4 or 8% of leaves infested. The number of sprays applied and armoured scale infestation at harvest were recorded. All blocks managed using the monitoring system received a reduced number of sprays compared with a calendar spray programme, although an increase in armoured scale on fruit was recorded. Increases in armoured scale levels on fruit under reduced spray programmes were generally economically insignificant.

Influence of Bacterial Speck Control Materials and Application Timing on Yield of Processing Tomatoes

Bacterial speck caused by Pseudomonas syringae pv tomato is a major springtime disease of tomato during rainy weather conditions in California. Application timing as a calendar spray was compared to pre-anticipated rainfall treatments of either cupric hydroxide alone or in a combined tank-mix with mancozeb. Plots were established in grower fields with natural infestations. In some instances, moderately severe infestations of speck caused as much as a 25% reduction in yield and slight delays in fruit maturity. Timing of treatments prior to rainfall was superior to calendar sprays. Slight improvement in disease suppression was achieved with a tank mix of mancozeb with copper compared to copper alone.

Assessment of Peanut Leaf Spot Disease Control Guidelines Using Climatological Data

Early leaf spot, caused by Cercospora arachidicola, and late leaf spot, caused by Cercosporidium personatum, can be controlled by foliar fungicides. Extension recommendations in South Carolina suggest planting peanuts between 15 April and 15 May. The recommended starting date to initiate 10- to 14-day fungicide spray schedules to control leaf spot is 15 June. The 1980-1990 climatological data for Sumter, Florence, and Blackville, South Carolina, were used to simulate calendar spray schedules and a method for spray timing developed at Auburn University (AUPNUT) that used observed and forecast rainfall. This simulation showed that adoption of AUPNUT scheduling in South Carolina could result in less foliar fungicide usage than the 10- and 14-day calendar-based spray schedules. The study showed: (i) the number of AUPNUT sprays depended on location in the state; (ii) the AUPNUT schedule added one application prior to 15 June on early-planted fields but averaged less than one additional spray per year for later plantings when compared to a 14-day calendar-based schedule that started on 15 June; (iii) at least one spray per year can be saved regardless of planting time, and up to five sprays can be saved depending on the distribution of days with rain; and (iv) a simulation using historical weather data can demonstrate potential savings associated with adoption of new application schedules.

Studies on the training needs of extension workers on thresholds in cotton IPM in Zambia

A questionnaire survey was conducted to find out the information and knowledge of extension workers on thresholds of cotton boll worms, (Helicoverpa armigera and Diparopsis castanea). A sample of 30 extension officers was interviewed in Southern and Central provinces of Zambia. The results showed crucial deficiencies in extension worker’s knowledge on thresholds of key pests and their implementation in cotton IPM. More than 60% extension officers were not aware of the basic information and knowledge such as thresholds of cotton bollworms, the recommended time to start scouting (weeks after germination of cotton) and the number of cotton plants to be examined for pest observance in each field. All extension officers indicated a desperate need for more field oriented practical training on thresholds. The recent increase in the incidence of aphids, Aphis gossypii as reported by 50 % extension workers is obviously due to calendar sprays of synthetic pyrethroids and the lack of a suitable aphicide in current spray programme. Demonstrations on the practical aspects of thresholds deserve much more attention at college level and also during the in-service training. More co-operation in cotton IPM training for extension officers within Central and Southern Africa is suggested.

Management practice for cotton jassid,Amrasca devastans(Dist.) in Bangladesh

Abstract Experiments were conducted during 1988–89, 1989–90 and 1990–91 in three major cotton areas of Bangladesh to determine the most cost‐effective management practice for cotton jassid, Amrasca devastans (Dist.). The effectiveness of 14‐day interval calendar‐based fixed sprays currently recommended was compared with sprays at two population thresholds (0.67 jassid/leaf and one jassid/leaf) and two damage thresholds (0.5 jassid damage grade/plant, i.e. leaf edge curled but no discoloration) and one jassid damage grade/plant, (i.e. leaf edge curled with discoloration on 50% of leaves) sprays of monocrotophos (Azodrin 40 WSC). The fixed spray treatments required up to eight calendar sprays during the season. The mean benefit cost (b/c) ratio in this treatment was the lowest (3–1) and was not cost‐effective. The 0.5 jassid damage grade threshold treatment also required many sprays, with a low b/c ratio of 9.0 and was also not cost‐effective. The one jassid/leaf threshold treatment required only two to fou...

Calendar and monitored insecticide application for the control of cowpea pests

‘Monitored’ sprays are applied when the action threshold (AT) has been reached or exceeded, based on monitoring of crop damage or pest infestation, whereas ‘calendar’ sprays are applied at specific days after planting without taking into account continued presence or absence of the pest. In this study a comparison was made between monitored and calendar spray applications to determine whether monitored spraying would reduce the number of insecticide applications and still produce yields comparable to calendar spraying. The study focused on four insect pests — the cowpea aphid ( Aphis craccivora Koch), legume bud thrips ( Megalurothrips sjostedti Tryb.), legume pod borer ( Maruca testulalis Geyer) and pod-sucking bugs. These pests damage cowpea at various stages of growth. The trials were carried out at three locations in Nigeria — Ibadan (forest transition zone), Mokwa and Bida (in the southern Guinea savanna zone). At all locations the two calendar schedules used were 7- and 10-day spray intervals. Differences in their effect on insect pest numbers were not significant, neither were there differences in grain yield ( p ≥ 0.05). In general, the calendar schedules recorded lower infestation/damage by aphids, flower thrips and pod borers than monitored spraying but grain yields did not differ between them. Monitored spraying required only two sprays at Ibadan and Mokwa and three at Bida. This was half the number used for calendar spraying. Monitored spraying therefore looks quite attractive as a component in the overall management of cowpea pests.

Use Of a Simulation Model to Explore Fungicide Strategies for Control of Cercospora Leafspot of Peanut1

Abstract A sub-model describing persistence and efficacy of chlorothalonil fungicide was incorporated into a computer simulation model of Cercospora leafspot of peanut. The resultant model was validated using independent data sets from field trials over a two-year period. Predicted disease progress curves and area under the disease progress curve for different fungicide application schedules and rates were compared with field observations. The model was then used to compare predicted disease severity and area under the disease progress curve (AUDPC) for a calendar spray schedule vs a leafspot advisory program under different weather conditions. Predicted disease severity levels and area under disease progress curves were similar for advisory and calendar spray schedules. Results were insensitive to changes in parameters describing fungicide persistence or efficacy. The model described herein is a good estimator of the combined effects of weather and chlorothalonil treatments on disease progress, effectively ranks treatments or environmental conditions in terms of their effect on leafspot, and provides a basis for comparison of fungicide scheduling strategies. The simulation model predicted AUDPC more accurately than end-of-season disease, and AUDPC is a more reliable indicator of the effect of peanut leafspot disease on yield loss. Simulation experiments will be useful in optimizing fungicide or biocontrol strategies for long-term financial benefit to growers.

Problems of implementing improvements in pest control: a case study of apples in the UK

A major problem in improving pest control is to integrate new pest-control practices into complex, and changing, farming systems, while at the same time making them acceptable to farmers. Therefore, when designing and implementing improvements in pest control, the practical context in which the farmer operates, and particularly the economic attributes of alternatives, need to be understood. The case of pest control in English apples is used to illustrate the type of analysis required. The major pests, their changing status, and their impact on yield and quality are discussed in relation to overall cash flow. The pesticides used, and the strategies of calendar spraying, supervised control, and integrated pest control (IPC) are then considered. Compared with calendar spraying, supervised control seems likely to save up to £20 per hectare on the costs of control. However, because this strategy can result in additional damage to fruit, and a loss of £20 per hectare can easily occur with a slight (1–2%) drop in fruit grades, supervised control is likely to be too risky for many growers. The future prospects for supervised control and IPC are discussed within the context of five major constraints.