DVac General Observations August 8 & 9
Kern County BASIC Pilot Program
General observations to all growers:
Defining and implementing Ecologically Based Pest Management, EBPM, as an alternative strategy to IPM requires more information and cooperative action regarding
(a) ecology of the growth patterns of the crop, and
(b) insect pests and their sets of natural enemies, including beneficial predators, parasites, diseases and antagonistic competitors of pests.
The interconnected biodiversity and biocomplexity of the above is working even at the level of those saprophytic organisms that live on such food as insect honeydew, cast insect skins and sooty mold that grows on insect honeydew. In other words, biological control works to control pest organisms and the exudates and detritus left by organisms.
This sounds overwhelming, but the Five Features of EBPM
avoid use of disruptive pesticides,
boild beneficial refuges,
monitor all of the insects,
develop alternative cultural practices, and
release beneficial organisms
is a program that favors the processes of biological pest control over a very broad range of beneficial results. The main goals, of course, are safety, profitability and durability. Programs must seek ways to ensure that pests in the plantscape (the agroecosystem) can be managed over the long term with less environmental, economic, or safety consequences.
Pest management practices that rely on repeated applications of conventional broadspectrum pesticides encourage the selection of resistant pest species. Compare this to ecologically based management that can be accomplished through small changes in the way we farm. What we are seeing follow two fundamental principles about functions of organisms that food drives all of these systems and that they work best where biodiversity and biocomplexity of life works to regulate pest problems.
We are step by step projecting our experiences of the ecology of the farm in ways that fit your particular cotton production system. Our reports and discussions hopefully give you confidence to take advantage of the sets of natural enemies that appear naturally with little or no implementation. Small, costeffective colonizations of beneficial insects: trichogramma, green lacewings, ladybugs and the whitefly parasitic wasp Eretmocerus spp. have been included in the program to assure their presence in spots where they may reproduce along with the naturally occurring populations of beneficials. We do not think of them as a treatment but as another small adjustment to favor the complexity of the beneficials.
We have suffered little or no loss of cotton yield or quality in the process of living with cabbage loopers and a few other worms. The natural enemies have increased in diversity and complexity and numbers relative to pests until now. Cabbage looper is a leaffeeding worm that has many effective beneficials. It was predictable that they would disappear before harvest and have no effect on quality and yield.
The cotton fields actually benefited from the reproduction of natural enemies feeding on the worms. Food drives these systems! The general predators that increased feeding on worms, lygus, mites and flower thrips are now feeding on other food pests such as the increasing populations of cotton aphids and whitefly. This benefit from not spraying for worms not only saved the cost of the pesticide application but it bought what appears to be suppression of these pests: cotton aphids, mites and, perhaps, whitefly. This will depend upon foraging by the general predators like ladybugs and bigeyed bugs. They both are reproducing and increasing their numbers by feeding on the new food the cotton aphids and whitefly pests and their honeydew exudate. The predation appears to be sufficient to control the aphids.
The whitefly, however, continues to increase, but more slowly than would be the case without the predators. Green lacewing larvae feed on immature whitefly as well as aphids. Other insects forage on whitefly but do not reproduce on this prey (food source). Green lacewings reproduce on whitefly honeydew. But the whitefly do not have any resident parasitic wasps like the aphids do. Adult Eretmocerus wasps have been released experimentally but have not been seen in any samples and the numbers available for release are very limited due to insectary production problems. The most that we can expect is for them to become established on weed species and other habitat enhancement plantings.
The experiment with the hedge at Roger Sanders’ farm is planned to carry the whitefly parasites through the winter so they will naturally suppress whitefly the same way the naturally occurring parasites of cotton aphid control this pest. It appears that the parasitic wasps are not able to survive the conventional chemical pesticides and the widespread use of herbicides eliminates any weedy sites where they would winter over. We will meet at this newly installed perennial hedge for our next meeting on Thursday August 23 from 8 to 10 A.M. Growers, foremen and workers are all welcome to this training in English and Spanish.
The next few weeks are critical because these two peststhe cotton aphids and whiteflyare pests that will definitely affect quality of the cotton at picking time. They have potentially high rates of reproduction. The tolerance for whitefly and aphids can be higher on farms that have natural enemies. The published ratings are derived from experimenting in conventional sprayed cotton fields where natural enemies are known to be few in number due to the pesticide treadmill and lack of habitat for natural enemies. These pests explode in monoculture fields that are regularly treated with pesticides, so the thresholds have to be low under those conditions.
The entomologists for the Dietrick Institute are not your PCA’s and you will have to help judge or decide for yourselves with your PCA, if or when you want to protect your crop with chemical controls.