Cotton cultivars and germ plasm lines were screened for resistance to pink bollworm. Sixteen advanced strains were selected for resistance to pink bollworm and/or high yield potential. In a regional early maturing germ plasm lines test, only the short- season check had less seed damage caused by pink bollworm than did the long-season check. Five lines yielded more lint than both checks. In a Pima test, Pima S-6 nectariless had 14% less seed damage than Pima S-6. Seven pink-bollworm-resistant germ plasm lines will be released in the near future.

Ethephon applied at rates of 0.50 or 0.75 lb AI/acre removed early-season squares and delayed initiation of pink bollworm, Pectinophora gossvpiella (Saunders) infestations and reduced the number of infested bolls on early-season fruiting branches, without affecting yield except for ethephon at 0.751b AI /acre at one location. Higher rates of application reduced yields. In most cases, ethephon treatments delayed flowering but plants compensated for removal of early- season squares and equalled or surpassed accumulated flowering of untreated control plants later in the season.

No description available.

A single field experiment was conducted in 1990 on a grower cooperator field to evaluate the response of a full season maturity type of Upland Cotton (DPL 90) to three dates of irrigationtermination. The crop was planted 26 and 27 of March, managed uniformly in all respects until August 1 when earliest irrigation termination wsa imposedThe dates for the second and final irrigationtermination treatments were 15August and 15 September. Each irrigationtermination treatments were given an additional 8 acre inches of water (approximate). Harvest results revealed no significant differences in lint yield on the first two dates but the last date yielded 110 pounds more. All plots received a 2 inch rain 18 August.

Five field experiments were carried out in several representative cotton producing areas of Arizona to evaluate the effectiveness of a number of defoliation treatments on Pima cotton. Variable conditions were encountered among the experimental locations in 1990 for treatment comparisons. However, it appears that consistencies in the effectiveness of several treatments for Pima defoliation offer a basis for recommendations across the state.

A short staple variety trial was conducted on the demonstration farm, at the Maricopa Agricultural Center in 1989. Nineteen varieties, received from various seed companies, were entered into the test. Yields ranged from 829 to 1428 lbs. lint acre⁻¹ for STY 110 and STV 1324 respectively. Results from the statistical analysis showed significant differences among varieties. Those varieties that were medium to short - season maturity types yielded higher than long, full season maturity types. This difference in yield was most probably due to the hot and humid weather conditions experienced in the 1990 growing season and the varietal differences associated with heat tolerance.

Short staple variety trials were grown in two locations in Graham county in 1990, Thatcher in the central part of the valley and Eden on the west end Acala Prema from the San Joaquin Valley in California had the top seed cotton yield in both locations with yield of 3789 and 3162 pounds per acre, at the two locations, respectively. The average lint yield in the Thatcher site was down more than 200 pounds per acre from 1989, whereas the average at the Eden site was about the same as in 1989. 1990 is characterized by its record setting heat spell in the end of June, even though fewer heat units were received in 1990 than in 1989. HS 46, a variety first seen in Graham county in 1989, performed well in both sites and in fact, topped both trials with lint yield Data on yields, percent first pick, plant height and plant populations are presented for each variety in each location.

Seven New Mexico acala varieties and one non-acala short staple variety were evaluated for yield and other agronomic variables. 1517-88 produced the most seed cotton but HS 46, the non-acala produced slightly more lint. Both varieties yielded slightly less than three bales of lint per acre. Yields of most of the varieties in the trial were 100 to 200 pounds less than in the previous year. It is felt that the yield reductions were probably more due to lack of heat units during the growing season than the heat spell in June.

Fourteen short staple varieties were evaluated in Greenlee county in 1990 in two separate trials. Average yields were higher in 1990 than in 1989 in both locations. The highest yielding variety in the acala trial was a new variety from California, C-37, with a yield of 1271 pounds of lint per acre. The highest yielding delta variety in the trials was DP 20 with a yield of 1116 pounds of lint per acre.

Three methods were used to schedule irrigations during the 1990 growing season on replicated plots at the Maricopa Ag Center using DPL 90 cotton. This is the final report of the research initiated in 1988. The three methods were: a soil water balance model based on historic consumptive use curves (ERIE), a soil water balance model (AZSCHED) based on the Modified Penman Equation and daily weather (AZMET), and infrared thermometry using the Crop Water Stress Index (CWSI). 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 between the 3 methods. Also, there was no significant difference in the amount of applied irrigation water. The AZSCHED and ERIE methods will be developed into Extension educational tools and released for use by growers.