Insecticides and insecticide mixtures were evaluated for sweetpotato whitefly (Bemisia tabaci Gennadius) control on cotton in the Imperial Valley, CA in 1992. Seasonal average number of large immatures was 1.6/cm² leaf disk from plots treated with a mixture of Danitol and Orthene as compared to 4. 5/cm² on leaf disks from untreated control plots. Lint yield was 1232 lbs/ac compared to other treatments which ranged from 551 to 976 lbs /ac.

The repellency to adult SPW of 1% Saf -T -Side and 1% Natur'1 Oil was enhanced by the addition of Butracide + Pounce, Butracide + Pyrellin, or a pyrethrum + diatomaceous earth. Several materials containing pyrethrum appeared to improve the repellency of 2% Saf -T -Side. The number of eggs laid was correlated with the number of adults observed on the plants, thus emphasizing the importance of the repellency of SPW adults. Three oils at 1% concentration gave a high mortality of SPW nymphs. Several materials killed nymphs when applied with a fine spray, simulating the deposit of a mist blower.

The edges of one of each of five pairs of long staple cotton fields were treated for sweetpotato whiteflies. Treated fields had 61% fewer eggs and 53% fewer nymphs than untreated fields. Adult populations were reduced 64% in the treated fields at the edges. In the center of treated fields adult populations remained low and unchanged but in untreated fields there was a 70% increase. According to minicard tests, cotton from treated fields was not sticky but cotton from untreated fields was sticky. Thus, populations of whiteflies and their damage can be significantly reduced by treating only the periphery of cotton fields at the onset of infestation. The treating of only 12 to 15% of the acreage greatly reduces costs and preserves the untreated center for beneficial insects.

Deltapine 50 (DP -50) and Stoneville 506 (ST -506), short season cultivars of upland cotton, Gossvpium hirsutum L., were grown under weekly or biweekly irrigation schedules in 0.2 ha plots in a split plot design at Maricopa, AZ. The seasonal average numbers of sweetpotato whitefly eggs and nymphs were 24% greater on leaves of plants irrigated biweekly. The leaves of ST-506 had 26% greater numbers of eggs and nymphs than did leaves of DP -50. Samples of lint from the two cultivars irrigated biweekly had 32 % more sugar than did lint from the cultivars irrigated weekly (weekly = 0.28 ± 0.02% , biweekly = 0.41% ± 0.03% sugar). Our results indicate that the numbers of immature sweetpotato whitefly on cotton plants can be reduced by 47% by selecting a less susceptible cultivar and avoiding plant water stress.

Surveys for adult sweetpotato whitefly parasites on ornamentals in urban areas and in cultivated cotton fields show high parasite activity in urban areas vs. activity in cultivated cotton fields. A previously unreported Drapetis spp. fly was identified and found to occur in cotton fields in several areas in the state.

RAPD -PCR was used to detect differences at the DNA level between the A and B forms of B. tabaci. All twenty of the RAPD primers tested distinguished readily between the forms. These primers also distinguished between the forms at the egg and nymph stage. Genetic similarity statistics indicate that these two forms of B. tabaci were no more closely related to each other than to bayberry whitefly (Parabemisia mvricae) or bandedwinged whitefly (Trialeurodes abutilonea). DNA from B. tabaci collected from 11 locations around the world was also analyzed. These insects could be classified into six distinct groups, suggesting there are more than two variant forms of B. tabaci. A comprehensive examination of all variant types of B. tabaci will have to be conducted before a concise definition of the taxonomic relationship between the 'A' and 'B' forms can be determined.

Surveys of whitefly parasites in cotton showed few or none were present during July and October in some areas, preliminary observations of sticky traps show that large numbers of parasites were present in some fields during October.

Whitefly management has become a complex objective in Arizona in the past several years. A tremendous amount of research and extension effort is now focused on this significant pest. The purpose of this paper is to describe the position and guidelines of the University of Arizona's Cotton Team regarding the Sweetpotato Whitefly. The information presented is credited to no single source, but represents a collection of information from numerous research and extension scientists within and outside of the U of A system and careful analyses of the presently available data on whitefly management dynamics. Where possible, only the results of research are reported and suggestions based only on experience or speculation are duly noted.

Trap crops were employed against the pink bollworm (PBW) as a part of a community-wide IPM program in Pima County, AZ. Levels of PBW larvae in the early squares of the trap crops were extraordinarily high, indicating that the trap crops were drawing overwintered PBW moths in from wide areas. This concentrated the overwintered moths in small areas where they could be easily and economically destroyed.

Insect damage impacts tremendously on the value of the Arizona cotton crop. As traditional pesticides become increasingly less useful, due to insect resistance and regulatory problems, new methods for insect control are needed. For these reasons, we engineered genes encoding protease inhibitors (PIs) from Manduca sexta (tobacco hornworm), for expression in cotton, with the hope that these inhibitors would have insecticidal activity. Transgenic plants containing PIs have been generated: 22 fertile lines of the duplicated 35S promoter anti-elastase, 4 fertile lines of the anti -chymotrypsin and 5 fertile lines of the anti -trypsin. Over 3,000 T-1 seeds have been collected and T-2 generation seeds are in production. Many crosses have been made into Delta Pine 16, 90 and 5415 respectively. No significant effect of the PIs on boll number or seed yield was observed. Insect tests have been conducted and the results indicate that plants expressing the protease inhibitors (PI's) have decreased emergence of whiteflies compared to control plants. We believe this research is a significant step towards a bio- pesticide producing Arizona cotton variety.