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.

Initial studies of Fuller rose beetle (FRB) biology have found some adult emergence in late June and early July. No adults woe found in foliage in May or early June, nor was activity noted in August and early September. FRB were not found in early October, but they began expected major emergence in mid-October. Several FRB collected did not have fused wings, atypical for this species. This finding suggests flight ability in FRB, currently unknown to occur.

Two rates of Avermectin were mound- applied; one treatment of Avermectin B one of Carzol were applied by air to citrus in April for control of citrus thrips. Plots were sampled by beating new terminal growth and counting thrips. Ground applications had fewer thrips than applications made by air. Avermectin B1 treatments had significantly fewer thrips than Carzol at all sample dates.

No description available.

During the last 15 years, the Yuma County Citrus Pest Control District (YCCPCD) has twice eradicated infestations of California Red Scale within the district. A third infestation, found in late 1984 is currently being fought with eradication as the goal.

Effects of 12 rootstocks on yield, yield efficiency, bearing potential and quality of 'Redblush' grapefruit were measured and potential rootstocks recommended for the arid climate of southwest Arizona. Trees on 'Palestine' sweet lime and 'Volkamer' lemon produced high cumulative yield but small fruit. Trees on Macrophylla (Alemow) produced higher yields after 5 years of planting and had significantly higher mean yield efficiency than trees on other rootstocks. Thus, Macrophylla rootstock could be a good choice for 'Redblush' at the standard spacing and perhaps at high density spacing in southwest Arizona. Fruit of trees on 'Carrizo' and 'Troyer' citranges were largest. Trees on 'Savage' citrange had lowest yield thinnest peel and highest levels of total soluble solids and soluble solids /acid ratio. Fruit of trees on 'Swingle' citrumelo or C.P.B. 4475 rootstock consistently had higher percentage acid than those on other rootstocks. Considering yield and /or various quality factors, 'Volkamer' lemon, rough lemon , 'Palestine' sweet lime, 'Oklawaha' sour orange and particularly 'Carrizo' citrange are suitable for 'Redblush' grapefruit in the arid Southwest. 'Savage' citrange, 'Ichang' pummelo , 'Cleopatra' mandarin, and 'Swingle' were poor yielding rootstocks for 'Redblush ' grapefruit, and therefore undesirable for planting under the standard spacing of this experiment. 'Savage' and 'Swingle' might be good choices at higher densities because they have yield efficiency, high maximum bearing potential and quality.

Long term comparisons of 8 types of lemons (Citrus limon Bunn. F.) on Macrophylla (Alemow) (C. macrophylla) rootstock regarding yield, tree growth, and quality under the arid conditions of the Southwest were studied. 'Foothill Lisbon' showed significantly higher cumulative yield and total acid than 'Monroe Lisbon', 'Prior Lisbon', Eureka strains, and Villa Franca, and had larger fruit than other Lisbon strains. 'Prior Lisbon' produced larger tree canopy than all other strains. Overall, Eureka strains and 'Villa Franca' had lower relative cumulative yield, yield efficiency, canopy volume, soluble solids, total acid and fruit seed content , but higher soluble solids to acid ratio than Lisbon strains. All factors considered 'Foothill Lisbon' and 'Prior Lisbon' have good potential for planting in the arid climate and sandy soil of Southwest, when Macrophylla rootstock is to be used.