Citrus Research Report 1986
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 1986
- Seasonal Variation in Susceptibility of Citrus Rootstocks to Phytophthora
- Trunk Application of Phosphorous Acid and Two Other Fungicides for Control of Phytophtora Gummosis of Citrus
- Control of Insects and Mites Associated with Citrus in Yuma, Arizona
- Evaluation of Materials for Control of Citrus Thrips
- California Red Scale Eradicated in Yuma County Again
- Influence of Rootstocks on Yield and Quality of "Redblush" Grapefruit
- Arizona Cooperative Citrus Registration-Certification Program Anticipates Increased Activity
- Evaluation of Citrus Front Protectant Materials
- Adaptation of Deciduous Fruit to the Desert Climate
Adaptation of Deciduous Fruit to the Desert ClimateChilling requirements and maturity of several varieties of peaches and apples were studied at the University of Arizona, Yuma Mesa Agricultural Center (Southwest Arizona) in 1985-1986. Flordared, Flordabelle, Flordabeauty, Flordagold, Desert Gold and Suwanee peaches broke their dormancy earlier than other cultivars and showed full bloom between mid-to-late January. Suwanee and Desert Gold matured earlier than other tested varieties, but they produced small size fruit with low sugar content. Anna and Dorsett Golden apples showed extended blooming period due to insufficient chilling.
Evaluation of Citrus Front Protectant MaterialsWith the high cost of maintaining and operating wind machines, growers are increasingly interested in alternative methods of freeze protection. Several possible frost protectant materials were applied to Valencia oranges at the Yuma Mesa Agricultural Center. Although temperatures reached the mid-to-upper 20s at the test site during the winters of 1984-1985 and 1985-1986, no frost damage occurred. As a result, it was impossible to evaluate the effectiveness of the materials.
Arizona Cooperative Citrus Registration-Certification Program Anticipates Increased ActivityActivity under the Arizona Cooperative Citrus Registration- Certification Program was at a new low during 1984 and 1985; no trees were budded under the program during that period. however, increased budding and bud sales during 1986 herald increased activity in the future. Because the program has continued to receive the support of the citrus industry, services have been provided uninterrupted. The program continues to maintain the foundation blocks insuring the industry with sources of budwood that have successfully met all requirements for: 1) freedom from known viruses or virus-like disorders, 2) freedom from injurious pests and diseases, and 3) trueness to horticultural type.
Influence of Rootstocks on Yield and Quality of "Redblush" GrapefruitThe influence of 12 different rootstocks on yield and quality of "Redblush" grapefruit was studied for several years. Rootstocks consisted of: macrophylla, volkameriana, rough lemon, Palestine sweet lime, sour orange, Carrizo citrange, taiwanica, Savage citrange, Citrumelo, Ichang pummelo, Troyer citrange and Cleopatra mandarin. Trees on volkameriana, Palestine sweet lime, rough lemon, and sour orange had higher yield than other rootstocks, while trees on Savage citrange had lowest yield. However, soluble solids and acid /sugar ratio were relatively low in the fruits on volkameriana but high in fruit on Savage citrange rootstocks.
California Red Scale Eradicated in Yuma County AgainFor the second time in two decades, the Yuma County Citrus Pest Control District has been successful in eradicating an infestation of California Red Scale in a commercial citrus grove within its boundaries. The first infestation, found in 1973, was declared eradicated in 1980. The latest infestation was found in 1984 and will be eradicated in record time. Eradication can be declared early next year after the third series of three sprayings each.
Evaluation of Materials for Control of Citrus ThripsThe control of citrus thrips is a major concern for citrus growers in the Yuma area. Five materials were evaluated for control of citrus thrips on Lisbon lemons at the Yuma Mesa Agricultural Center during July and August of 1985. Although there was no statistically significant differences between treatments, Mavrik appeared to provide the best control of the materials tested. Dimethoate (Cygon) and formetanate hydrochloride (Carzol) were not tested.
Control of Insects and Mites Associated with Citrus in Yuma, ArizonaA variety of insecticides have been tested during the last three years to keep pace with the ever-present demand for effective materials to control mites and thrips on citrus. This need is particularly acute with the recent loss of dicofol (Kelthane), which for years was an industry standard for mite control. Some of the more promising new compounds include Avermectin and NC 21314. Comments are included concerning the registration status of some of the compounds we tested. Cautions are given concerning the development of resistance to compounds which are soon to be available.
Trunk Application of Phosphorous Acid and Two Other Fungicides for Control of Phytophtora Gummosis of CitrusGummosis caused by Phytophthora parasitica and P. citrophthora is a serious problem in Arizona citrus groves. In a 15-year-old Orlando tangelo planting at the Yuma Mesa Agricultural Center, a 20 cm section of trunk on each tree was painted with phosphorous acid, metalaxyl or fosetyl-Al. After treatment, pieces of bark were periodically removed from within, as well as below, the treated area and inoculated with P. parasitica and P. citrophthora. After 117 days, both Phytophthora species were inhibited on bark treated with phosphorous acid, metalaxyl or fosetyl-Al. Canker development was also reduced on bark tissue sampled 10 cm below the site of treatment. The results suggest that trunk application of phosphorous acid, metalaxyl or fosetyl-Al can provide effective protection against Phytophthora gummosis of citrus.
Seasonal Variation in Susceptibility of Citrus Rootstocks to PhytophthoraPhytophthora parasitica and P. citrophthora are routinely recovered from diseased citrus groves in Arizona. Stem sections were collected monthly from Citrus macrophylla, rough lemon, .sour orange, Cleopatra mandarin, Troyer citrange and Citrus volkameriana. Stem pieces were wounded, inoculated with mycelium of P. parasitica or P. citrophthora, then incubated for 7 days at 21° C in moist chambers. For all tested rootstocks, the smallest cankers were produced on tissue collected in December, January and February, the winter dormancy period for citrus in Arizona. The period of higher susceptibility ranged between March through November, depending on the rootstock tested. Apparently, these six citrus rootstocks possess seasonal differences in their susceptibility to P. parasitica and P. citrophthora.