A Wet Spring Does Not Lead to Disease and Pests at the Levels Anticipated

This spring has brought record level moisture to the Central Valley and made for a messy start to the growing season. With all the water, the anticipation was we would also see record levels of disease organisms and pests, however that does not seem to be the case.

“There is some indication of rust and alternaria, but not nearly to the degree we would imagine with the extremely wet weather we had in May,” commented Holloway Ag’s Director of Agronomy, Steve Lenander. “Most operations are taking no chances and doing preventative sprays, especially as we dry out and pests become more prevalent.”

The trees that Holloway Ag is involved with in Kern County seem to have weathered without much damage from the storms. That’s not necessarily the case for all growers. According to Nick Groenenberg, Independent PCA in Hanford, some fields sustained hail damage in mid May and in certain places, the hail knocked off 20 to 60 percent of the nuts. “The block I examined was 640 acers. The storm that moved across that block caused pretty severe damage,” Groenenberg observed in an interview with AgFax on June 3rd.

The biggest concerns when it comes to pests this time of year are mites, but with all the rain they have largely been washed off the trees, or not had the chance to develop. As the weather heats up, this could change as mites tend to appear in hot spots within orchards and along dusty roads. Sixspotted thrips are the natural enemies of mites and you can use yellow sticky cards to monitor thrips in the orchards. “This period of cooler temperatures slowed down mite development, so the thrips might be enough to control mites even later into the season,” said Jhalendra Rijal, Area IPM Advisor to the Northern San Joaquin Valley.

The other pest this could be the year for is lygus bugs. Lygus bugs especially pray on crops like cotton and black eyed beans as the weather warms and those crops get dryer. “I am warning growers of these crops to be especially aggressive when checking their fields, because when the lygus come, they will come in droves,” Lenander cautions. “Now is the time to be proactive in treatment and diligently checking fields weekly for any sign of lygus development.”

As for disease organisms and why we are not seeing more of them as a result of dampness, there is no one explanation. “It has us all a bit baffled,” said Lenander. In order for a disease organism like rust or alternaria to thrive, you need three sides of a triangle to come together: One side is the host (the tree or crop); the other is the disease organism; and the final side is the environmental conditions. “The environment seems to be right, but disease is not taking hold as we would have expected. It could be that the band of environment diseases need is more narrow than we thought.”

Groenberg agrees saying, “Trees look really clean as far as disease goes but we did include a fungicide because of all the rain. Just because you don’t find any problems doesn’t mean they can’t develop. This would be the year for it.”

While it has thankfully been a slow start to any disease issues, most agronomists and PCAs in the area are anticipating diseases like alternaria to be a problem by harvest. “Alternaria is getting worse in places where we typically have it,” commented Tony Touma, PCA at Bio Ag Consulting in Bakersfield. “You can see it moving and it looks like it will be a problem by harvest. At least right now, we don’t have terrible disease issues, but rust and alternaria will likely advance with this heat and humidity.”

It is overall good news for what has started out as an unseasonably wet spring. At Holloway Ag, we will continue to partner with our growers as the season progresses and work to provide solutions and expertise to soil problems that may arise.

Source: Some of the quotes and commentary were provided by the AgFax June 3^rd edition.