Four 'Lisbon' lemon selections, 'Frost Nucellar', 'Corona Foothills', 'Limoneira 8A' and 'Prior' were selected for evaluation on Citrus volkameriana rootstock. 2005-06 results indicate that the 'Limoneira 8A Lisbon' and ‘Corona Foothills Lisbon’ are superior to the other two selections tested.

Two orange cultivar trials have been established in Arizona, one at the Yuma Mesa Agricultural Center, Yuma, AZ and one at the Citrus Agriculture Center, Waddell, AZ. For the navel orange trial in Yuma, all the selections had improved yields in 2005-06. ‘Fisher’ navel continues to have the greatest yield, but is quite granulated. Of the rest in the Yuma trial, ‘Lane Late’ had the best quality and yield. For the Waddell trial, the fourth year data has been collected, and suggests that ‘Fisher’, ‘Beck-Earli’, ‘Chislett’ and ‘Lane Late’ are outperforming the other cultivars tested to date.

Phytophthora 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.

Gummosis 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.

For 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.

The 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.

Activity 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.

With 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.

Chilling 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.

Sodium tetrathiocarbonate (STTC) releases carbon disulfide when added to water and applied to soil. Laboratory tests were conducted to determine the effect of this chemical on growth and sporulation of Phytophthora citrophthora and P. parasitica, which cause Phytophthora gummosis and mot rot of citrus in Arizona Zoospore motility, zoospore cyst viability, sporangia production, and mycelia' growth were significantly reduced in the presence of STTC Results of laboratory tests suggest that application of S7TC as a soil drench could reduce inoculum production and subsequent new infections by P. citrophthora and P. parasitica.