Two studies were conducted investigating the efficacy of Prozap (zinc phosphide), Ramik Green, and Ramik Brown (diphacinone) rodenticides on woodrats infesting citrus. Based primarily on using feeding activity as an indication of population density, Zinc phosphide (ZP) provided a rapid knockdown of the rat population, and offered 60 to 75% control. However, this product is known to cause "bait-shyness" following the initial application so additional control with subsequent applications of ZP targeting the same rat population would not likely result in a significant increase in control. Ramik Green and Ramik Brown are slow acting anticoagulant rodenticides, and performed similarly to each other. Anticoagulant rodenticides are not known to cause bait-shyness. In this study, these products only offered 20 to 38% control, but it is possible that these values may be artificially low since the rats may have been preferentially feeding on stored oat groats used to gauge feeding activity rather than consuming the anticoagulant baits.

Lemons were treated with several plant growth regulators for the 2006-07 season, with the hope of improving fruit size. These PGR’s included Bluestim, Accel, Maxim and MT1350. Although there were some increases in yield, these were just trends, and were not statistically significant. Similarly, there was no improvement in fruit size with application of the treatments.

In a rootstock evaluation trial planted in 1993, five rootstocks, 'Carrizo' citrange, Citrus macrophylla, 'Rough Lemon', Swingle citrumelo and Citrus volkameriana were selected for evaluation using 'Limoneira 8A Lisbon' as the scion. 1994-2006 yield and packout results indicate that trees on C. macrophylla, C. volkameriana and ‘Rough Lemon’ are superior to those on other rootstocks in both growth and yield. C. macrophylla does not consistently outperform C. volkameriana. 'Swingle' and Carrizo’ are performing poorly.

Four 'Lisbon' lemon selections, 'Frost Nucellar', 'Corona Foothills', 'Limoneira 8A' and 'Prior' were selected for evaluation on Citrus volkameriana rootstock. Yield was extremely low for 2006-07, but these results do not change the fact that that 'Limoneira 8A Lisbon' and 'Corona Foothills Lisbon' are superior to the other two selections tested.

Three lemon cultivar selection trials are being conducted at the Yuma Mesa Agriculture Center in Somerton, AZ. Data from these trials suggest that 'Limonero Fino 49' and 'Cascade Eureka' selections may be a suitable alternative for the varieties most commonly planted in Southwest Arizona today. 'Femminello' and 'Villafranca' might also be planted on an experimental basis

Mechanical (disk and Perfecta cultivator) and chemical weed control strategies were compared in a Yuma, AZ lemon orchard. In addition, an optical weed sensing sprayer (WeedSeeker) was evaluated for making post-emergence Roundup Ultramax herbicide applications. The use of pre-emergence herbicides in conjunction with the WeedSeeker spray units has the potential to significantly reduce the amount of post-emergence herbicide and water needed to spray flood irrigated citrus orchards. There was a relationship between weed ground cover and the area sprayed by the WeedSeeker units that indicated the maximum herbicide saving will occur a low weed densities. The use of the Kawasaki Mule with its superior suspension system allowed for faster spraying speeds than were possible with the tractor mounted sprayer and this also reduced spray volume per plot. Weed control was similar for the conventional and the WeedSeeker sprayers. Future investigations will include efforts to improve the estimation of percent weed groundcover, the use of higher rates of pre-emergence herbicides and the development of crop budgets based on experimental operations.

Surround WP and Snow were evaluated for their ability to manage citrus thrips populations in lemons on the Yuma Mesa, and their impact on lemon yield, fruit quality, and packout. Both Surround and Snow effectively controlled citrus thrips and prevented fruit scarring, but their ability to manage Yuma spider mite was inconclusive. Preference tests indicated that both Surround and Snow act primarily by repelling the thrips, but also induce some mortality. Surround produced higher yields than Snow at the first harvest (#8 ring), but did not differ from the commercial standard. There were no differences in yield among treatments for the strip harvest, nor were their any differences in total yield. These data suggest that Surround may have some yield or increased fruit earliness enhancement qualities and that Snow may be slightly detrimental. There were no statistical differences among any of the treatments in fruit size frequency or quality for any of the harvests, and there was no apparent benefit from applying an additional application of Surround or Snow post thrips season solely for quality, fruit size, or yield enhancement.

Higher nutrient and water use efficiency are possible with microsprinkler-irrigated citrus compared to flood-irrigated citrus. Therefore, new N and P fertilizer recommendations are needed for microsprinkler-irrigated citrus. The objectives of these experiments were to i) determine the effects of N applications on tree growth, fruit yield, fruit and juice quality, and N and P removal in fruit for microsprinkler-irrigated navel oranges; ii) determine the effects of P applications on tree growth, fruit yield, fruit and juice quality, and N and P removal in fruit, and iii) develop Best Management Practices for N and P fertigation of microsprinkler-irrigated citrus. Field experiments were conducted at the University of Arizona Citrus Agricultural Center in separate blocks of 'Newhall' and 'Fukumoto' navel oranges, both on 'Carrizo' rootstock. In each block, ten treatments, consisting of all possible combinations of 5 N rates (0, 0.2, 0.4, 0.6, and 0.8 lb N/tree/yr) and 2 P rates (0, 0.2 lb P/tree/year) were applied to five replicate trees per treatment. Maximum yields of the ‘Newhall' trees were 132 lb fruit/tree at a N rate of 0.5 lb N/tree/yr. Maximum yield of the 'Fukumoto' trees was119 lb fruit/tree at 0.5 lb N/tree/yr. Both varieties maintained appropriate leaf N and P concentrations at the yield-maximizing N rates. Total N in the fruit accounted for about 60 % of the N applied at the yield-maximizing N rates in both varieties. The results confirmed that microsprinklers effectively reduced the amounts of N fertilizer needed while maintaining adequate N status in the trees, with excellent N use efficiency.

We proposed creating a user-friendly web site that would provide independent, research-based, integrated pest management information to Arizona’s citrus growers and PCAs. This citrus IPM website, located at http://cals.arizona.edu/crops/citrus/ was created and integrated within an existing web site, the Arizona Crop Information Site (ACIS) http://cals.arizona.edu/crops. The Citrus IPM web site was launched on April 15, 2004.

First year yield and packout data from a trial containing 'Fina', 'Fina Sodea', 'Sidi Aissa', 'Oroval', 'W. Murcott Afourer', 'Fremont', and 'Gold Nugget; selections were collected in 2004-05. For the year, 'Fremont' had the greatest yield, but the smallest fruit size, while 'Fina' had the smallest yield, and 'W. Murcott Afourer' had the largest fruit size.