Ag Alert May 5, 2021

New lettuce aphid biotype causes concern for farmers ByBob Johnson

at 21 locations in the Salinas Valley, from Castroville toKing City. “We still need to confirm that this new aphidbiotype ishere, but itwas first report- edin2018that therewereinfestationsof let- tuce aphids on varieties that are supposed to be resistant,” said Daniel Hasegawa, a U.S. Department of Agriculture research entomologist based inSalinas. Hasegawa made his remarks during theCalifornia LeafyGreens BoardAnnual Research Conference, as researchers dis-

cussed their efforts todevisemanagement strategies for this newest aphid problem. “We are monitoring the population of this new biotype on the Central Coast,” Hasegawa said. “We have sticky cards out therethatweswitchweekly,andpost there- sultsontheUCCooperativeExtensionweb- site for aphidand thripsmonitoringdata.” Genetic resistance is particularly im- portantwith the lettuce aphid, because its preferredresidencedeepintheheartof the plant contaminates the crop andmakes it

difficult to reachwith insecticides. A group of USDA researchers in Salinas has already begun the process of trying to identify sources of genetic resistance to this newest version of the aphid, should it be confirmed inMonterey County. “With the likely emergence of a new biotype of the lettuce aphid in the Salinas Valley, we are trying to establish this new biotype 1 in the greenhouse,” said Jim McCreight, a USDA crop improvement research leader at the Salinas station. Because there are extensive collections of lettuce-typematerial at both the USDA Salinas facility and at the University of California, Davis, researchers said they shouldhaveaheadstart infindingeffective genetic resistance to the newaphid pest. “This could affect variety resistance, al- thoughwemayalreadyhavematerialwith resistance toboththebiotype0and1of the lettuce aphid,”McCreight said. According to Hasegawa, the first let- tuce varieties with resistance to the let- tuce aphid were introduced in 1997, after farmers had spent a few years living with unmanageable crop damage. A decade later, a resistance-breaking biotypeof the lettuceaphidwasdiscovered in Europe; a decade after that, the resis- tance-breaker was reported inAustralia. Then, threeyearsago,someSalinasValley farmers began reporting that the aphid re- sistanceof their lettucewasno longer effec- tive,andresearchersbegantryingtoconfirm theirsuspicionthat theresistance-breaking biotypehadreachedCalifornia. Resistant varieties are particularly im- portant for organic growers. Those farmers have the added problem that one of their most widely used insecticides, spinosad, canmake lettuce aphid infestations worse becauseit ishardonbeneficial syrphidflies. Organic farmers generally relyonplant- ing flowering varieties that attract the syr- phid flies, which in turncontrol the aphid. One silver lining is that although the let- tuceaphidwas a tremendous challenge to control when in first appeared in Salinas Valley fields three decades ago, the pest does not carry viral diseases to the crop. ( Bo b J o hn s o n i s a r e p o r t e r i n Sacramento. He may be contacted at bjohn11135@gmail.com.) State Apiary Board seeks newmember Avacancyhasoccurredontheboardthat advises theCaliforniaDepartment of Food and Agriculture onmatters pertaining to beekeeping. CDFA said it is accepting ap- plications for theCaliforniaApiaryBoard. Boardmembers serve a four-year term. CDFA said individuals interested in being considered for the board appointment should email a brief resume byMay 21 to Patricia.Bohls@cdfa.ca.gov with “Apiary Board” in the subject line. For more informat ion about the board, see www.cdfa.ca.gov/plant/ pollinators/apiaryboard.html or contact Patricia Bohls of the Bee Safe Programat the email address above.

Ahandful of SalinasValley lettucegrow- ershave reportedcropdamage tovarieties that had previously been resistant to the lettuce aphid, which takes up residence in theheart of theplant, shielded frominsec- ticide applications. Researchers are closely monitoring aphid infestations, to confirm whether a new pest has arrived. They use sticky cards that are swappedoutweekly in traps

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10 Ag Alert May 5, 2021