Short staple variety demonstrations were conducted in Pinal County in 1989 at the Prechel and Benedict Farms near Coolidge Az. Twelve varieties were included in the demonstration at Prechel Farms. Results from the analysis showed significant differences among varieties. Seedcotton yields in this test ranged from 4826 to 2844 lbs. acre⁻¹ for STV BR-110 and S-55 respectively. Seven varieties were included in the demonstration at Benedict Farms. Results from the analysis showed significant differences among varieties. Seedcotton yields in this test ranged from 4127 to 3530 lbs. acre⁻¹ for STV BR-110 and DP-50 respectively.

Regional variety tests were conducted at Maricopa, and Marana Agricultural Centers in continuing cooperation with the beltwide testing program. The national standards included in this test were Coker 139, Deltapine 50, and Paymaster 145. Lint yields for each variety, at both locations, are given in Table 1.

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Three methods were used to schedule irrigations during 1989 on replicated plots at the Maricopa Ag Center using DPL 90 cotton. This is a continuation of the research initiated in 1988 using the same field The three methods were; a soil water balance model based on historic consumptive use curves, a soil water balance model based on the Modified Penman Equation and daily weather (AZMET), and infrared thermometry using the C.W.S.I. A potassium- bromide conservative tracer was applied at selected sites in the plots to evaluate leaching characteristics. The irrigation scheduling test was again duplicated at the Safford Experiment Station and is presented in another report. Results from this years data indicate that there was no significant difference in yield among the three methods. However, as in 1988 there was a significant difference in water applied with historic consumptive use (ERIE) the lowest and the Penman equation method (CHECKBOOK) the highest.

Two irrigation scheduling trials were performed in 1989, one for short staple and one for long staple. Yields in the trials were very good with the best treatments yielding over 1700 and 1600 pounds of lint per acre for DP 90 and S-4 respectively. The treatment using Infrared thermometry was the best overall treatment in the short - staple trial, with the highest yield, the highest percent first pick, the shortest plants, the lowest water use and the highest water use efficiency. The two computer methods were very close to the IR treatment in yield and percent first pick, but grew taller plants with more water and were not as efficient with their water use. The trial on long staple cotton was encouraging in that reasonable yields were obtained using short-staple parameters. The computer model using AZMET data yielded significantly lower than the other treatments, indicating that we need to refine the evapotranspiration crop coefficients.

Experiments were performed at the Yuma Valley Agricultural Center to determine how timely harvest of cotton may affect aflatoxin contamination of cottonseed As the cotton was held in the field between the final irrigation and harvest, the quantity of aflataxin in the crop increased. Significant reductions in aflatoxin contents of seed were realized by harvesting in early September.

High population levels of Rhizoctonia solani in a field in Coolidge, AZ which also contained Thielaviopsis basicola failed to cause the expected infection by R. solani in untreated seeds of Gossypium hirsutum. Growth chamber experiments with autoclaved soil amended with inoculum of both R. solani, and T. basicola had a significantly lower infection rate by R. solani than did the control soil with R. solani alone.

In 1988 severe beet armywonn (BAW) infestations resulted in damaged cotton flowers and foliage. Some insecticide applications failed to eliminate larvae in the flowers because applications were applied before the flowers opened. Applications made after flowers were open were more effective. In 1989, tests were conducted to define further these results. Karate™ applied when cotton flowers were open achieved 90% control compared to 9% when flowers were closed in one test, and 97% compared to 13 %, respectively, in a second test (P\0.01). A higher percentage (18 %) of cotton bolls was shed on day 7 following flower infestations than were shed (6 %) when flowers were not infested.

Gossyplure, the pink bollworm, Pectinophora gossvpiella (Saunders), sex pheromone is an excellent tool as a bait in traps for detection, survey, research and monitoring male moth populations. We studied the within - and between-seasonal changes of pink bollworm male moth catches in gossyplure-baited live traps installed in cotton fields each year from 1981 to 1988. Seasonal average number of male moths caught varied from 14/trap/night in 1982 to 148 /trap /night in 1981. Male moths caught/trap/night were highly correlated with the minimum air temperatures. The number of male moths caught from March to June were significantly correlated with those caught from July to August, indicating that early spring trapping can be used to identify potential problem fields.

Studies were conducted to identify potential sources of cotton germ plasm resistant to sweetpotato whitefly (SPW), Bemisia tabaci (Gennadius). Numbers of adult SPW sampled using black pan and vacuum methods showed reduced numbers of SPW on GC-EXP-7007 experimental variety vs. all other entries. However, numbers of SPW pupae on leaf samples in most cases were not different. Pima P-62 had the high numbers of SPW adults per blackpan sample, and highest number of pupae/leaf sample.