The hills ringing the San Joaquin Valley are not alive with the sound of lygus — whatever sounds lygus make.
However, the tiny plant bug may be singing a troublesome tune elsewhere: “Ain't no valley low enough…To keep me from getting to you.” You in this case being cotton.
Limerick-prone University of California IPM Coordinator and entomologist Pete Goodell has not changed his colors from early musing: “If green in May, prepare to pay; If hills are brown, hope abounds.” He has just change geography.
Goodell, buffing his crystal ball at what valley crop pests might munch on this year, particularly cotton, told growers and pest control advisers at San Joaquin Valley seminars sponsored by Valent, that rains starting early last October greened the hills with grasses and continued rain bolstered that early growth through the winter and into spring. That means grasses basically choked out many of the broadleaf weeds that are hosts for lygus and other pests. Goodell has found very few lygus in the foothills, but has found densities as high as 15 per 50 sweeps in the valley floor.
“I am more concerned about local sources of lygus as opposed to what may be coming out of the foothills,” he said.
He is finding overwintering adults and third and fourth instars of the first generation in valley greenery. If green weeds are available for an extended period time into May, this generation can build and produce large populations of lygus to damage susceptible cotton. That was made very likely with a series of early May Pacific storms that dumped large amounts of rain throughout the valley.
Tarweed, small-pod mustard and London rocket are preferred hosts for lygus. Tarweed, reports Goodell, is very abundant along I-5 from Avenal to Kettleman City and along Maricopa Highway in Kern County. Small-pod mustard is generally found along the shoulders of highways. The May rains will keep them vital longer into the season when cotton is most susceptible.
Early cotton risk
If the second generation develops into these weeds, the earliest squares of cotton will be at risk in June.
There also are weedy farm fields, and Goodell is encouraging growers to get them down as quickly as possible to avoid migration from weeds to cotton. However, that has become problematic with the May rains.
“There are a lot of internal sources for lygus in the valley. Abandoned fields from land retirement are one. It has been wet all winter long and growers have not been able to get into many fields to knock down weeds,” said Goodell. May rains only served to give the fields another soaking.
Those valley floor weeds are also hosting other potential crop pests, particularly armyworm and looper populations as well as false chinch bugs. Thrips also are common in grain, alfalfa and weedy fields.
“I have never picked up loopers and armyworms in these weeds before and many PCAs are telling me the same thing,” said Goodell, who surmised that they likely came into the valley due to the huge populations of Painted Lady butterflies that were spawned in Death Valley and other California desert areas with the heavy winter rains.
Goodell said it will be a “challenging insect year.” The amount of trouble will be dependent on how much rain falls in May and the host susceptibility to lygus early.
Some avoid lygus
“I do not think there will be major widespread lygus problems, but lygus will be worse than in years past. Lygus will be heavy in some places and light in others. Some cotton will definitely be hurt by lygus,” he predicted.
“Not all areas will have problems — at least with lygus — so don't treat unless your sampling says you need it,” said Goodell. “Managing budgets will be more difficult this year due to more challenging production conditions.”
“This would be a good year to leave uncut strips of alfalfa to preserve habitat for lygus and mitigate movement into susceptible crops,” added Goodell.
If there is good news, it is Goodell's noting that new products to manage worms, mites and aphids have become available since the last major outbreak of lygus in 1995.