2018 Cotton Crop Proceeding Well

Late Season Pests Can Be a Challenge

By Patrick Cavanaugh, Editor

The 2018 cotton harvest will be starting in the southern part of the Central Valley later this month, and some growers will be facing pressure from pests.

California Ag Today recently spoke about the topic with Dan Munk, a UC Cooperative Extension Farm Advisor in Fresno County specializing in irrigation crop nutrient management and cotton production systems.

“The crop looks very good and loaded with cotton bolls. We don’t have a lot of boll losses, and that’s a real positive thing, so very excited about the potential for fairly high yields in the 2018 season. The biggest concern right now is pest management, press pressures as we approach the latter part of the season,” Munk explained.

The main issue this time of year is the honeydew that pest leave on the cotton. Honeydew is the exudate extracted by the insect as it feeds on the leaves.

“Because we have the bolls on the plant that have opened, we now have exposed lint and need to protect that lint from stickiness that’s created from whitefly and the aphid honeydew, which is basically the added sugars that those insects that feed on the leaves of the plant, and they excrete them and deposit them on the lint,” Munk said.

Munk explained that the big concern right now is dealing with pest pressures in terms of whitefly and aphid—both sucking insects. “The problem right now [is] where we’re seeing pest pressures—particularly from whitefly as we get later in the season—will build in many fields.

There are several approaches to controlling whitefly and aphids. One is to deal with the eggs that they produced. And then there’s a certain class of materials to deal with the eggs.

“There’s another class of materials that deal with the juveniles—that early form of the insect—and then there are ways to control the adults,” Munk said.

“A number of insecticides have been applied to deal with those various levels of insect populations based on the individual field situation,” he explained.

ACP Spread in Bakersfield Area, Ingenious Research Proceeds

Ingenious Research Effort to Fight ACP Spread with Natural Predators

By Joanne Lui, Associate Editor

Beth Grafton-Cardwell, Cooperative Extension specialist, University of California, Riverside Department of Entomology

As we have reported in-depth before on California Ag Today, the Asian Citrus Psyllid (ACP) is a tiny, mottled brown insect that poses an ever-increasing threat to the state’s robust citrus industry, as well as to residential citrus trees. The pest can spread a bacterium known as Huanglongbing (HLP) that is fatal to citrus trees. The disease has nearly shut down Florida’s citrus industry.

Beth Grafton-Cardwell, cooperative extension specialist in integrated pest management, UC Riverside Department of Entomology, explained the significance of the recent ACP spread to Bakersfield. “That is really problematic because it’s mostly in the urban areas. It’s very difficult to find, to control and to stop that spread. It’s going to move out from that region into the local citrus orchards, and so there are lots of meetings and discussions right now to mobilize growers to get treatments to help protect their citrus orchards against the psyllid.”

#CitrusMatters

To contain the ACP problem, Grafton-Cardwell stated, “There are traps everywhere, but the traps are not terribly efficient. So, we really need to carefully examine groves and flush [new leaf growth] for the nymph form,” she said.

According to Agriculture and Natural Resources, University of California’s Statewide Integrated Pest Management Program:

Adults typically live one to two months. Females lay tiny yellow-orange almond-shaped eggs in the folds of the newly developing “feather flush” leaves of citrus. Each female can lay several hundred eggs during her lifespan.

ACP (Source: ACP UC IPM)

The eggs hatch into nymphs that are wingless, flattened, yellow or orange to brownish, and 1/100 to 1/14 inch long. Nymphs molt four times, increasing in size with each nymphal stage (instar), before maturing into adult psyllids. The nymphs can feed only on soft, young leaf tissue and are found on immature leaves and stems of flush growth on citrus.

The nymphs remove sap from plant tissue when they feed and excrete a large quantity of sugary liquid (honeydew). Each nymph also produces a waxy tubule from its rear end to help clear the sugary waste product away from its body. The tubule’s shape—a curly tube with a bulb at the end—is unique to the Asian citrus psyllid and can be used to identify the insect.

Grafton-Cardwell and other experts are concerned because once the ACP becomes established in urban areas, it is difficult to eradicate. “It starts spreading into the commercial citrus, and we’re off and running,” she commented.

In a ingenious effort to control the spread of the psyllid, trained teams of entomologists have imported Tamarixia radiata, a tiny wasp that naturally preys on ACP, from Pakistan to research and release in California. A cooperative effort of the University of California Riverside, Citrus Research Board, United States Department of Agriculture and California Department of Food and Agriculture, researchers are also exploring the effectiveness of another beneficial insect called Diaphorencyrtus aligarhensis to assist Tamarixia with control of the Asian citrus psyllid. To see where Tamarixia and Diaphorencyrtus have been released, visit this University of California’s website map at, “Distribution of ACP, HLB and Parasites in California,” and turn on the parasite layers.
Grafton-Cardwell said, “They’re going to inundate that area,” with natural ACP predators, “so hopefully that will push back a little bit.”