Monday, July 2, 2018

Patience, Second Look Pays Off for the Pocketbook and Environment in the Valley

The pest numbers were up. The grower was worried.

His dilemma at this crucial stage in the development of his cotton plants:
Should he move ahead and treat his field with pesticides to control the potentially crop-damaging bugs? Or should he wait a bit longer, hope the pests go away and avoid treating the field – a move that could risk a population explosion that ultimately could damage his yield at harvest.

Growers weigh decisions on treating their field for pests.
This is real life drama in the Valley – no mocked up reality TV show. 

 What should he do?
First, let’s set up the situation. Earlier pest monitoring reports indicated a higher than desired count for lygus bugs populating his field. Lygus, as many cotton growers know, can cause big-time damage to developing cotton bolls.

“He wanted to spray for the pests,” field scout Damien Jelen says.
But before making that final decision, the grower and Damien rendezvoused at the field. Damien pulled out his trusty sweep net and canvassed the field.

Sweep. Sweep. Sweep….

“I found one count,” Damien recalled. Translated: Out of 50 passes of his sweep net, Damien snared only one lygus bug – way below the numbers from previous field visits and well below the threshold UC Integrated Pest Management recommends for treating for lygus in cotton.

The decision: Hold off spraying.

Yes, patience does pay off. And having Damien provide another set of eyes to supplement monitoring by the grower’s pest control adviser can certainly yield dividends. As in this case, it can avoid an expensive pesticide treatment while keeping chemicals out of the environment.
Sweep nets will catch pests populating a field.

For field scouts like Damien, the key tool of his field scouting practice is no fancy high-tech gadget. It’s a sweep net – akin to a heavy-duty, oversized butterfly net.

Using it in the field to collect pest samples takes practice to ensure results from different practitioners produce comparable results.

In cotton, for example, sampling for lygus starts when the cotton plant develops its first square. Samples should be taken twice a week. UC IPM recommends sampling each quarter of a field and taking even more samples in fields larger than 8 acres. Do 50 sweeps across one row of cotton to sample for lygus, making sure the sweeps don’t overlap. Lygus monitoring can end when acala plants have 5 nodes above white flower and Pima has 3.5.

It’s common for people to sweep from right to left and then step forward and sweep again left to right. After 5 sweeps, you pull the net through the air to push the bugs into the bottom of the net bag. UC IPM recommends taking a sample in four different spots in a field.

If it’s hard to count the bugs while in the field, place the insects in a bag and cool the contents to slow done pest movement.  UC IPM provides information about treatment thresholds for various pests.

While lygus counts jumped up as the early summer heat took hold, Damien says the numbers leveled out in the past week. So far, Damien hasn’t seen many signs of a large number of damaged cotton squares on the ground.

 Of course, there are still some four months – and a long summer – left until the harvest. You can be sure Damien and growers will remain vigilant until then.

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