US food producers have been warned: insects, molds, and other pests that increasingly resist human control are not yet the masters of cropland and pasture, but the farmer's lines of defense have grown thinner.
The Council for Agricultural Science and Technology (CAST) says the United States should reassess pest-control strategies.
CAST - which represents 25 scientific and technical societies - gave its assessment in a recent report on pest resistance. It notes that fears of a ''superpest'' that is beyond control are groundless. The real problem, the CAST study group says, is that ''pesticides that lose their effectiveness . . . are not currently being replaced by new materials or by alternative means of crop and livestock protection.''
Pesticide development now is very expensive, partly because of extensive safety testing. Thus, CAST says, industry now tends to produce a few ''broad spectrum'' chemicals rather than the wide variety of ''narrow spectrum'' materials needed for the best pest management. A broad-spectrum poison kills many kinds of organisms, whereas narrow-spectrum materials are more specific in their effect.
The most effective control strategies often are those that rely on several different methods. Resistance to disease and insects is bred into crop plants and animals while pests themselves are controlled both by their natural enemies (biological control by so-called 'beneficial'' organisms) and by judiciously selected chemicals. This is integrated pest management.
CAST says shifting toward broad-spectrum chemicals ''could aggravate the resistance problem and could impede the progress of integrated pest management, in which chemicals with a narrow spectrum of activity are needed to reduce harm to beneficial organisms. . . .''
While the situation is serious, it is far from hopeless. To begin with, a few pesticides do not seem to lose effectiveness. Sulfur, for example, has been a useful fungicide since at least biblical times. Also, CAST points out that research indicates that a mixture of pesticides retains its efficacy. While pests may become resistant to each of the chemicals separately, resistance to the combined power of the chemicals does not readily appear.
Likewise, by taking advantage of the strength that also is inherent in a mixture of control measures - including use of biological controls and disease-resistant crops - farmers can keep the pests in check, CAST says. But, since they are facing evolution in action, experts who would help farmers must continuously develop new control strategies. This basic fact, plus the reduced arsenal of chemicals now available, has made the need for such new strategies urgent. Potato alarm
Aphids, like many other insects, have an alarm scent - a pheromone they release to warn each other of danger. A wild potato, Solanum berthaultii, ''cleverly'' uses this signal to fend off aphids.
R.W. Gibson and J.A. Pickett of Britain's Rothamsted Experimental Station have found that the potato's leaves repel the aphid Myzuz persicae (Sulzer) at a distance of 1 to 3 millimeters.
Reporting their finding in Nature, the British entomologists say they believe this is the first discovery of a plant using the aphid alarm to protect itself. They observe, ''If this ability could be introduced into the cultivated potatoes , it might provide some protection against aphids and hence aphid-borne viruses.'' Cosmic ghost
Neutrinos - the most important bit of nothing among material particles - are retaining their status as cosmic ghosts.
Although it carries energy and momentum, a neutrino has no intrinsic mass. It can pass through a mass of other matter as big as a planet as though it weren't there.
In recent years, a number of physicists have wondered if neutrinos may not have a little mass, after all. A few experiments suggested they might. However, after making the most exacting measurements yet attempted, physicists from the California Institute of Technology, the Technical University of Munich, and the Swiss Institute of Nuclear Research report neutrinos do appear to be massless, though more exacting experiments may yield other results.