Stripe rust of wheat, Puccinia striiformis f. sp. tritici, was found to oversummer in the Sierra Nevada at altitudes of 6000 ft or above on wild grasses belonging to Elymus spp., Hordeum spp., and Sitanion spp. The similarity of infection types of stripe rust isolates from various locations and hosts on a differential set of wheat cultivars suggests that only one race of P. striiformis f. sp. tritici occurs in California.Stripe rust on Poa spp. should be considered as P. striiformis f. sp. poae f. sp. nov. because of its entirely different host range and temperature requirements.A mean temperature of 22.3 °C or mean maximum temperature of 32.4 °C measured over a 10-day period is lethal to P. striiformis f. sp. tritici, thus accounting for the absence of this fungus during the summer in all regions of California but the Sierra Nevada and the coastal area. In late autumn, recurrence of the rust in the wheat-growing areas is initiated when east winds carry uredospores from the Sierra Nevada into the central part of the Sacramento – San Joaquin Valley, infecting volunteer wheat plants and early sown wheat. In late winter, a shortening of the latent period because of rising daily temperatures results in a rapid development of stripe rust at these infection sites and consequently in secondary spread of the rust to previously uninfected areas.

In central California, neither fungal infections nor aflatoxins are significant problems in cottonseed during the receiving and storage seasons. However, in southern California, the 1967 harvest contained a relatively high percentage of seed which were invaded before harvest by fungi, includingAspergillus flavus. Seed infection and concentrations of aflatoxins in seed increased significantly during the time between harvest and storage in southern California. For a short time during storage, seed infection byA. flavus increased because of the moisture the seed received late in the season; however, aflatoxin concentrations in seed did not increase in storage. The aflatoxin content of the seed removed from storage was a reflection of the relative amount of aflatoxins the seed contained when they were received for storage. In 1967, the conditions that existed in the large, densely packed seed pile did not favor accummulation of aflatoxins in seed, even thoughA. flavus was active.

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Synopsis Punjab 53, which is a composite of wilt resistant selection; of flax stemming from a single plant of Punjab, is resistant to some clone; of wilt because of two complementary genes FUA and FUB—A and B for convenience. The original plant of Punjab apparently had the genotype AaBB or AABb. A third gene FuC was found in Dakota 48–94 that would account for much of its resistance to one clone of wilt highly pathogenic on Punjab 53.