Whitefly has been a major pest in desert vegetables and melons for two decades, but it remains a controllable pest thanks not only to new chemistry like neonicotinoids and foliar insect growth regulators, but new product delivery technology as well.
John Palumbo, University of Arizona research entomologist at the UA Yuma research station, said the first line of defense in controlling whiteflies is to eliminate as many immatures as practical before they can do serious damage as adults. Applying neonicotinoids as systemics in-furrow at planting or pre-plant is the primary way to do that.
This technology Palumbo helped develop has been bolstered lately with the growing use of drip irrigation in high value desert vegetable and melon crops.
“Drip is the best way to apply soil-applied insecticides. Drip allows optimal placement to get at an optimal target,” he told a group of Pest Control Advisers (PCAs) at a Valent-sponsored seminar prior to California Association of Pest Control Advisers' (CAPCA) annual conference in Anaheim, Calif.
“It is critical to get the systemic on the first leaf of a plant to get the immatures before they become adults and cause problems,” he pointed out.
It is not uncommon to get 45 to 60 days or ever longer control with soil applied systemics.
Drip allows more post-emergence control flexibility. He has applied it when melons are at the 13- to 15-leaf stage and got excellent control.
One of the newest insecticides on the market is a third generation neonicotinoids called Venom from Valent. Palumbo has found it to be effective as a translaminar foliar control method with a quick knockdown of whiteflies, as well as a soil applied systemic.
“Where I think Venom has the best fit and does better than other products is as a post emergence treatment through a drip system because it is highly water soluble, more water soluble than other neonicotinoids,” he explained.
Venom is a SG (soluble granular) formulation, and Palumbo admits he does not like granular pesticides because they often do not dissolve adequately.
“A lot of the time when you pour a granular into a tank it floats to the bottom and does not dissolve very quickly. However, for whatever reason Venom dissolves very quickly and stays in suspension,” he said.
Its low use rate (four to six ounces per acre); a “very clean” toxicological profile; a very short pre-harvest interval, all popular attributes encouraging desert PCAs to recommend it, added Palumbo.
This high water solubility makes Venom “probably a better fit than other soil applied products,” he said. This trait allows the product to quickly move through the plant's root system to the growing points to protect against whiteflies and other sucking insects like the flea beetle, which is a growing problem in the desert. Beetles were once a secondary pest, but with improved control for lepidopterous pests, it has become a primary pest.
Palumbo added that Venom foliar spray has also has given “very consistent” results as a foliar at very low water volumes, especially in leafy vegetables and melons.
The array of products for control of whiteflies is impressive, but one more doesn't hurt, said Palumbo, because it adds another alternative for resistance management.
Although Venom is a neonicotinoid, recent studies have shown the third generation neonicotinoid binds itself to a target site in insect nerve cords unique from other neonicotinoids. According to Valent, this means Venom “may still provide some level of control where resistance or tolerance to other neonicotinoids is based on a change or difference in the target site of action.”
Venom is also registered as a soil applied systemic for control of grape and vine mealybugs in grapes, according to Valent rep Monte Peckinpah of Visalia, Calif. This is a new registration to control a pest, vine mealybug, that is quickly rising to the No. 1 pest position for grape growers. High populations of vine mealybugs can deposit honeydew on vines and bunches, rendering a crop non-harvestable.
Venom also controls thrips and glassy-winged sharpshooter. Although not registered for control of phylloxera, data has shown it is also effective against the soil louse.
California growers will have available for the first time this season a new post emergence grass herbicide from Valent, Select Max with Inside Technology, a parent-pending formulation of clethodim. It was registered last season in Arizona, and Valent's Arizona representative Art Anderson said it was widely accepted.
It is registered for use on alfalfa, including the new Roundup Ready alfalfa, and most vegetable crops.
Anderson said the new technology makes it 25 percent more active with a 25 percent lower rate than Valent's other clethodim herbicide.
“It is also an excellent tank mix partner,” Anderson added.
It provides good control on a wide array of grassy weeds, including sprangletop, bermudagrass and johnsongrass.
One of the most exciting products from Valent is a plant growth regulator called ReTain, which has proven to dramatically increase yields of Serr variety walnuts.
For decades growers have experienced a malady commonly known as Serr drop, which can dramatically reduce yields. Researchers have been frustrated in trying to solve the problem, officially known as pistillate flower abscission (PFA). Kings County, Calif., University of California Cooperative Extension farm advisor Bob Beede discovered that treating Serr trees with the Plant Growth Regulator ReTain at 5-30 percent bloom temporarily inhibits ethylene production during bloom.
This has shown to dramatically increase Serr yields and may have a similar, but less dramatic impact on other walnut varieties.
Treating Serr trees with ReTain increased percent nut set from 49 to 84 percent and increased yields by as much as 1,500 pounds per acre. At 76 cents per pound for walnuts, that is a very significant increase income to a walnut producer.