Citrus Research Report 1998
ABOUT THE COLLECTION
The Citrus Report, first published in 1978, is one of several commodity-based agricultural research reports published by the University of Arizona. The purpose of the report is to provide an annual research update to farmers, researchers, and those in the agricultural industry. The research is conducted by University of Arizona and USDA-ARS scientists.
Both historical and current Citrus Reports have been made available via the UA Campus Repository, as part of a collaboration between the College of Agriculture and Life Sciences and the University Libraries.
Contents for Citrus Research Report 1998Citrus
- Efficacy of Insecticides to Citrus Thrips on Lemons in Yuma Arizona 1997
- Commercial Evaluation of M-96-015 for Control of Citrus Mealybug, Woolly Whitefly and Citrus Thrips in Lemons
- Susceptibility of Lemons to Citrus Thrips Scarring Based on Fruit Size
- Seasonal Abundance and Field Testing of a Citrus Thrips Temperature Development Model in Arizona Citrus
- Citrus Peel Miner Marmara salictella Monitoring Techniques and Control Measures 1996-1997
- Improving Management and Control of Fungal Diseases Affecting Arizona Citrus Trees, 1997
- Applying Roundup to the Base of Lemon Tree Canopies: Preliminary Effects on Leaves, Flowers, Fruitlets, and Yield
- Evaluation of Milestone Herbicide for Early Post-emergence Weed Control in Citrus on the Yuma Mesa
- Results of Scion and Rootstock Trials for Citrus in Arizona - 1997
- International Society of Citrus Nurserymen Conference Report
- Growing Blackberries in the Low Desert
- Effective Management Tools for Septoria Leaf Spot of Pistachio in Arizona
- Effect of Foliar Application of Benomyl on Severity of Septoria Leaf Spot on Pistachio in Southeastern Arizona
- Foliar Applications of Boron to Pecan Trees Does Not Affect Fruit Set
- Influence of Nut Cluster Position on the Incidence of Viviparity for the Pecan Cultivars "Western Schley" and "Wichita"
- Revitalizing "Wichita" Pecan Productivity Through Corrective Pruning - First Year Results
- Nutritional Status of Wine Grap Cultivars Grown in Southern Arizona
- Pruning Methods Affect Yield and Fruit Quality of 'Merlot' and 'Sauvignon Blanc' Grapevines
- The Response of Table Grape Growth, Production, and Ripening to Water Stress
The Response of Table Grape Growth, Production, and Ripening to Water StressFour year old 'Flame Seedless' grapevines, located in a commercial vineyard, were subjected to increased water stress levels based on infrared canopy temperatures and the Crop Water Stress Index (CWSI) for two years. CWSI levels were approximately .18, .30 and .33 for the wet, medium and dry treatments. In the first year there were no significant differences in yield however, there was a significant reduction in the amount of water applied in both the medium and dry treatments when compared to the wet treatment. In addition, the wet treatment had significantly greater growth during the first growing season when comparing pruning weights.
Pruning Methods Affect Yield and Fruit Quality of 'Merlot' and 'Sauvignon Blanc' GrapevinesOne red and one white cultivar of winegrapes grown in Southern Arizona was pruned to four different methods. The red cultivar was 'Merlot' and the white was 'Sauvignon Blanc'. The pruning methods were 2 bud spur, 4 bud spur, cane and basal buds only. The basal bud treatment was eliminated for 'Sauvignon Blanc'. The 4 bud spur method resulted in significantly greater yield when compared to the other methods. Fruit produced from the basal bud only treatment resulted in fruit that was significantly greater in pH and acid content. The 'Sauvignon Blanc' cultivar had significantly higher yield with cane pruning with no difference in fruit quality.
Nutritional Status of Wine Grap Cultivars Grown in Southern ArizonaTen winegrape vineyards consisting of different cultivars were leaf petiole sampled at bloomtime. Petioles were analyzed and results composited for the survey. There were indications that boron, iron, nitrogen and phosphorus were nutrients where potential problems (deficiencies) were likely to occur. This survey supplied information for the basis of developing a monitoring program on an annual basis.
Revitalizing "Wichita" Pecan Productivity Through Corrective Pruning - First Year ResultsA pruning study was established in stressed pecan trees to identify effective means of returning unproductive trees to full productivity. The study was comprised of two pruning systems and one untreated check. The number of nuts harvested from pruned trees was lower than that harvested from the unpruned trees, but the quality of the nuts from the pruned trees was improved when compared with the unpruned trees.
Influence of Nut Cluster Position on the Incidence of Viviparity for the Pecan Cultivars "Western Schley" and "Wichita"Vivaparity, a significant quality- reducing condition found in pecans grown in warm, temperate climates, was evaluated by location of the pecan nut within the cluster in two varieties, "Wichita " and "Western Schley". Percentage vivaparity was not affected by position.
Foliar Applications of Boron to Pecan Trees Does Not Affect Fruit SetBoron was applied as a foliar spray to pecan trees in a pecan orchard located in Cochise County. Single or repeated application prior to pollination did not affect nutlet set. Leaf analysis indicated that the boron levels in all trees were in the sufficient range for optimum growth and production.
Effect of Foliar Application of Benomyl on Severity of Septoria Leaf Spot on Pistachio in Southeastern ArizonaThe fungicide, benomyl (Benlate) was foliar applied by a commercial air blast sprayer at the rate of 1.0 lb. a.i. per acre in early to late August. Treatments varied with a number of applications i.e. one or two and were compared to an untreated control. Benomyl significantly reduced leaf necrosis surrounding nut clusters and the number of leaf spot lesions when compared to control. One or two applications were equally effective in controlling Septoria leaf spot.
Effective Management Tools for Septoria Leaf Spot of Pistachio in ArizonaSeptoria leaf spot was detected in the United States for the first time in 1964 within an experimental pistachio planting at Brownwood, Texas. The first observation of the same disease in Arizona pistachio trees did not occur until 1986. In 1988, a survey of the 2,000 acres of pistachio orchards in southeastern Arizona revealed a widespread incidence of the disease. Since the initial discovery of the disease, Septoria leaf spot has appeared annually in some of the Arizona pistachio acreage. The onset and severity of the disease is influenced by summer rainfall that occurs in this region. Disease management trials conducted since 1992 have shown that as few as two applications of chlorothalonil in July and August can virtually prevent disease development. Applications of copper hydroxide or benomyl alone or in combination also effectively arrest disease development. Leaves around nut clusters on infected trees not receiving fungicide treatments were usually senescent at crop maturity, whereas leaves on treated trees showed no sign of senescence. Pistachio trees infected with Septoria leaf spot and not treated with an effective fungicide can defoliate in the autumn up to 2 months prematurely.
Growing Blackberries in the Low DesertTwenty-five plants of each of ten blackberry cultivars from Arkansas and Texas were established at the Yuma Mesa Agriculture Center in spring 1994. All the Arkansas cultivars died. Of the Texas cultivars, 'Rosborough' and 'Womack' performed the best, followed by 'Grison' and 'Brazos'. Important cultural practices, harvesting practices and potential marketing strategies are discussed
International Society of Citrus Nurserymen Conference ReportThis report summarizes some of the information that I gained during a trip to the Mediterranean region during Spring 1997. The first two days of the trip were spent in Murcia, Spain, as a guest of Dr. Angel Garda Lidón. We discussed the Spanish lemon industry. After Murcia, I traveled to Valencia, Spain to take part in an International Society of Citrus Nurserymen pre-conference tour. The conference itself took place in Montpellier, France. Following the conference, I participated in a post-conference tour to Sicily.
Results of Scion and Rootstock Trials for Citrus in Arizona - 1997Five rootstocks, 'Carrizo' citrange, Citrus macrophylla, Rough lemon, Swingle citrumelo and Citrus volkameriana were selected for evaluation using 'Limoneira 8A Lisbon' as the scion. Early results indicate that trees on C. volkameriana and C. macrophylla are superior to those on other rootstocks in both growth and yield. 'Swingle' and Carrizo' are performing poorly. In a similar trial, Four 'Lisbon' lemon selections, 'Frost Nucellar', 'Corona Foothills', 'Limoneira 8A' and 'Prior' from the University of Arizona Citrus Budwood Certification plot were selected for evaluation on Citrus volkameriana rootstock. Early results indicate that the 'Limoneira 8A Lisbon' selection is outperforming the other selections in both growth and yield. Preliminary results from another lemon cultivar trial and a navel orange cultivar trial are presented as well.
Evaluation of Milestone Herbicide for Early Post-emergence Weed Control in Citrus on the Yuma MesaWhen applied early-postemergence, Milestone at 0.75 and 1.0 lbs-ai/A provided excellent control of summer annual grasses and broadleaf weed for as long as 4 months, equivalent to Karmex. Princep and Krovar also provided good weed control but appeared to offer slightly shorter residual against some broadleaf species. Solicam, although it provided good weed control, particularly of the grasses, was the weakest material evaluated in this trial. Although Karmex is notorious for causing crop injury on the sandy soils of the Yuma Mesa, we did not detect any injury from this herbicide or any others in this trial.
Applying Roundup to the Base of Lemon Tree Canopies: Preliminary Effects on Leaves, Flowers, Fruitlets, and YieldThe effect of Roundup on lemon trees was evaluated by repeatedly spraying 0.5, 0.75, 1, 1.25, and 1.5 lb. a.i./acre on the bottom 20 to 24 inches of the tree canopies over a three year period. The Roundup applications caused significant leaf injury in the sprayed area of the canopies and there was also significant defoliation of branches at the higher Roundup rates in all three years of the study. In 1996, flower and fruitlet counts were not affected by the Roundup applications and the 1998 data were inconclusive. However, flower and fruitlet counts in 1997 in the sprayed zone of the canopy were significantly reduced by Roundup and the effect increased with increasing Roundup rate. The 1996 and 1997 yield data indicated that Roundup applied to the bottom 20 to 24 inches of the tree canopies did not significantly affect lemon yield. The preliminary data suggest that accidental drift or misapplication of Roundup on to lemon trees when spraying weeds on the orchard floor has no short-term effect on grove productivity.
Improving Management and Control of Fungal Diseases Affecting Arizona Citrus Trees, 1997Studies were conducted to evaluate potential chemical disease management tools for Alternaria fruit rot on navel oranges and Coniophora brown wood rot on lemon trees, to investigate the possible effect of branch diameter on development of Coniophora wood rot on lemon trees and to summarize our evaluations of citrus rootstocks with respect to relative resistance to root rot and stem canker development when challenged with Phytophthora citrophthora and P. parasitica. We were unable to reduce the level of Alternaria fruit rot on navel oranges with single applications of Abound or copper hydroxide following significant rainfall events. Wood decay in lemon branches inoculated with Coniophora eremophila was significantly suppressed by Abound and a thick formulation of sodium tetrathiocarbonate. The degree of Coniophora brown wood rot in lemon branches of different diameters was variable, although the level of disease in 10 mm diameter branches was significantly smaller than the amount of wood decay in 30 mm diameter branches. Root loss due to Phytophthora citrophthora and P. parasitica in Citrus macrophylla, rough lemon, C. volkameriana and Troyer citrange was lower than most of the 36 different rootstocks tested. On the other hand, root loss on Carrizo citrange, C-35 citrange and sour orange was among the higher values of disease recorded. Stem canker development due to both species of Phytophthora on Troyer citrange, Carrizo citrange, sour orange and Citrus macrophylla was lower than most of the 36 rootstocks tested. Stem cankers on rough lemon and Citrus volkameriana were among the higher values of disease recorded.
Citrus Peel Miner Marmara salictella Monitoring Techniques and Control Measures 1996-1997Citrus peel miner populations were monitored to evaluate various methods of trapping citrus peel miners. Observing 25 fruit per tree and 10 trees per block on the lower three feet of the tree canopy provided the best technique for determining the level of citrus peel miner infestations. The use of oleander plants, clear plates and green 3 inch diameter balls sprayed with Tangle-Trap were not effective in trapping citrus peel miner. In 1996, the first of September citrus leaf miner populations rose above the 10% infestation level. Success, Lorsban, Alert and Agri-Mek provided the highest mortality levels of citrus peel miner larvae. In citrus fruit, Success, Lorsban and Alert had the greatest efficacy of citrus peel miner larvae.
Seasonal Abundance and Field Testing of a Citrus Thrips Temperature Development Model in Arizona CitrusCitrus thrips populations (adults and nymphs) were monitored through the spring of 1991-1992 in several locations throughout most of the commercial citrus production areas in Yuma County to determine if citrus thrips seasonality was similar to that previously reported in California. Study findings indicate that seasonality is similar throughout the winter and very early spring. Adult thrips numbers increase rapidly in groves due to attractive foliage, whether it is weeds or citrus. High nymph numbers did not always follow adult peaks, and were not statistically correlated. Predatory mites and rains may have affected 1992 results.
Susceptibility of Lemons to Citrus Thrips Scarring Based on Fruit SizeLemons appear to be most susceptible to damage by citrus thrips from petal fall until they reach 1.0 inch in diameter. Correlation analysis suggests that fruit greater than 1.0 inch in diameter may not be highly susceptible to thrips scarring and thus may not require protection. 1f this relationship can be verged with additional data, late- season thrips sprays may be avoided.
Commercial Evaluation of M-96-015 for Control of Citrus Mealybug, Woolly Whitefly and Citrus Thrips in LemonsM-96-015 did not appear to effectively control woolly whitefly but does appear to kill citrus mealybug. However, as with other insecticides coverage is a problem. The real benefit of M-96-015 towards citrus mealybug would occur if it prevented their spread. However, we were not able to measure this in this study. As with previous trials, M-96-015 is an effective citrus thrips material.
Efficacy of Insecticides to Citrus Thrips on Lemons in Yuma Arizona 1997Three small plot efficacy trials were conducted evaluating different insecticide rotation regimes using commercially available insecticides and the effectiveness of new insecticide chemistries to control citrus thrips. Because of its long residual activity, and ability to control post- application egg hatches, Carzol appears to be the product that best fits the petal fall application window. Agri-Mek, Baythroid, Dimethoate or Vydate are probably good follow -up insecticides. However, Agri-Mek and Baythroid will probably provide greater control, especially under hotter conditions. If temperatures are cool, Agri-Mek looks good at reduced rates. The best insecticide for subsequent applications depends on temperatures and what was previously applied. Avoid making back -to -back applications of the same materials, and Dimethoate or Vydate applications should probably be followed by Carzol to catch post- application egg hatches. Overall, Vydate appears to be very similar to Dimethoate in efficacy and residual activity, while Baythroid appears to be slightly better. Although the addition of Lannate to Dimethoate does slightly enhance thrips control, the additional cost probably does not justify the tank mix. Of the new chemistries (Alert, Success, Ni-25, and M-96-015) evaluated, Success and M-96-015 appeared to offer the best fruit protection. However, M-96-015 does not appear to be very effective in killing the thrips, but is very effective in repelling them. Also, M-96-015 will need to be applied at a high gallonage, i.e. 500 gal/A. None of the new products tested appear to fit the petal fall application window very well. Ni-25, Alert and Success appear to lack the residual activity of Carzol, and M-96-015 should not be used as a clean-up material but preventively following Carzol at petal fall.