(Reprinted by permission California Farmer. Copyrighted August 2001 Farm Progress Companies, Inc.)
By T.J. Burnham
Striving to create a more environmentally friendly almond production industry, the Almond Board of California's (ABC) three Almond Pest Management Alliance (PMA) demonstration sites are forging new alternatives.
"The ABC projects can also save growers substantially in their chemical costs," says Joe Connell, University of California (UC) Cooperative Extension farm advisor in Butte County. "But we must monitor our orchards carefully and make sure you don't get into trouble with pests for which you do not spray."
BioScope's Richard Greger, a Hughson pest control advisor and PMA partner, works hard to bring new "soft" pest management practices to almonds. He says trapping and monitoring is one of the most important aspects of alternative pest control strategies.
"Sanitation [removing mummy nuts] to control navel orangeworm (NOW) is one of the most important issues," he adds. "That is very important whether you are using chemicals or soft approaches."
His recommendation for peach twig borer (PTB) is to monitor using "bucket" traps rather than wing types, to avoid excessive work in changing and scrapping. He also recommends the San Jose scale and NOW traps to promote effective monitoring.
"Mostly, watch what the parasites are doing in your San Jose traps," he says.
"Get these traps out early to get a good bio-fix, and watch the degree days closely."
He uses few dormants but does apply Bt (Bacillus thuringiensis) such as Confirm, which he reports works well. "It helps expand your soft approach," Greger says.
"Watch kernel progression," he urges. "Knowing how their development is progressing helps you know what stage the almonds are at and where the pests may be."
Beneficial insects, such as green lacewings and trichogramma, are an integral part of his control program, along with ant baits, which he considers to be a highly effective PTB-control method.
"Baits allow us to control ants without 'nuking' [sterilizing] the ground, and promote the ability to maintain beneficial populations," he says.
DOWNSIDE
But soft materials are short-lived, perhaps the greatest disadvantage to their use, Greger notes. "This is another reason to consider sanitation as a very important ingredient to your program," he says. "Some people feel sanitation to be costly, but it will pay off in the long run in your pest control costs."
Using dormant sprays can also cut expenses, and when coupled with sanitation can put growers "dollars ahead" on the pest control ledger, he says.
In the winter, Greger urges growers to spend time monitoring for eggs of pests like European red mites, which can be effectively controlled using oils. "Monitoring goes on through more than one or two seasons," he says.
COVER STORY
Think also about ground covers, since vegetation can play a helpful role in pest control.
"Insects like the green lacewing are nectar feeders, and must have a plant source of food," he explains. Because it may be difficult to get a dollar value from the cover crop, having another reason for planting the seeds, such as providing an insectary, makes the option more palatable. Hedgerows are extensively used in San Joaquin Valley almonds to augment the beneficial environment.
MITE CONTROL
"Our main use of hedgerows is along roadways near orchards to reduce dust, and cut down on mite populations," he says. "We have been successful in reducing the amount of miticides that are used as we see fewer mite outbreaks."
Mites are always difficult to control because of the large number of factors that determine whether there will be an outbreak (water stress, disease, human dust-raising activity near the orchard). If the leaf becomes covered with dust and photosynthesis reduces plant activity, mites can quickly become a menace, Greger says.
"This is where chemical augmentation helps," he says. "These materials are still necessary in an orchard, despite your soft approach." Predator mites can be an effective alternative, however, in cases where outbreaks are mild. But these do not work well against European red mites.
Knowing the rules of mite management can help, according to Carolyn Pickel, Northern California area extension integrated pest management advisor. "The most important rule is tree health," she says. "If you over- or underfertilize, you can cause mite problems to worsen."
Using University of California guidelines for almond fertilization is a good way to avoid these problems. Since mites like high-nitrogen leaves as well as stressed leaves, erring on either side can result in a pest buildup.
"Be sure not to stress trees with irrigation," she adds.
"One of the main things is to cut down on dust when mowing, cultivating and driving through the orchard."
MITE HIT
Using a broad-spectrum insecticide that takes out beneficial populations is another reason for mite buildup, Pickel says. "Use lower rates, and delay broad-spectrum material use until late in the season when it will have less affect on beneficial populations."
Mite monitoring is essential. "This is something that isn't done much," she says. Do this by looking at a minimum of four trees, taking 15 leaf samples from each. A quick examination with a large field of vision hand lens will reveal their presence or absence.
Two or more mites per leaf will result in economic damage, she says.
Using University of California guidelines for treatments that vary upon whether predators are present can result in effective control. This information is available through local cooperative extension offices.
WEB AID
For help in identifying mites, check out the photos on a UC Web site at www.ipm.ucdavis.edu.
In his program, Greger says to watch for brown leaves that do not fall off the tree in winter. Upon close hand lens checking, they may reveal the presence of San Jose scale.
"A lot of the success of soft approaches is linked to farmer activity," he says, "whether in use of sanitation, control of dust, assuring trees are vigorous. The grower plays the most important role in making these things work."
One benefit of switching to a soft approach is the shift toward higher beneficial populations once hard chemical use is reduced, he adds.
"Growers will have a hard time backing out of their conventional pest control programs like dormant spraying," Greger warns. "But if you look at the problems you face in the almonds, you can change successfully. Understanding what is going on in the orchard biological system is vital to success with soft pest management."
The soft approach was successful last year in dealing with the buildup of European fruit lecanium scale in orchards not dormant sprayed, and the subsequent control of many of these pests by parasites, Connell says.
"A July application of 1.5% narrow- range oil did a very good job getting control of these pests," he says. A second August application helped, but wasn't as helpful as the July spray, he adds. "Where we did not spray, a lot of biocontrol has moved in to prevent them from becoming a major problem, it appears."
Greger observes lecanium throughout the California almond-growing area. "They are an oddity of not spraying dormant applications and seeing this unusual pest build up," he says. "While they drop honeydew, we have not found any significant damage as a result of this pest."
Heavy populations on leaves can result in yellowing and defoliation on the twig under attack, Connell says.
But there are other pests that can become a problem when switching away from normal pesticide programs, he warns. "Things like the oblique banded leafroller, which you usually would not see in almonds, can become more prevalent in the early spring and early summer. This pest can build up to a point where you can lose an economic level of almonds."
Occasionally, forest caterpillars can move into the orchards to heavily consume leaf tissue, he adds. u